Textbook of Maritime Medicine

In this chapter a review is presented on the epidemiology of gastrointestinal (GI) diseases in seafaring and of the initial treatment of some serious GI conditions prior to evacuation. The special features of lay medical care at sea are taken into account.

Dental disorders, motion sickness, alcohol (mis-)use, obesity, diabetes, and infections (except norovirus) will be mentioned only briefly since these subjects are covered elsewhere in the Textbook.

10.10.1   Epidemiology of GI disorders

Seafarer mortality and morbidity have been extensively studied, especially in British and Danish seafarers, and for many years diseases of the digestive system have been shown to be a major cause of morbidity and death [1]. Most studies on mortality and morbidity are based on statistics from government agencies and insurance companies, reports from Tele-Medical Advice Services (TMAS), and studies on passenger vessels by cruise doctors. The US Centers for Disease Control and Prevention (CDC) have published many series on outbreaks of acute gastroenteritis on passenger ships. 

In mortality studies [1-4], liver cirrhosis, peptic ulcers and pancreatitis dominate in seafarers, and there is a high overall relative risk of all cancers associated with tobacco smoking and alcohol [5-7]. 

Morbidity studies show that diseases of the digestive system are second only to accidents - and gastritis and ulcers occur as the most frequent GI disorders [8, 9]. Thus, the excess gastrointestinal morbidity in seafarers may be related to their work and lifestyle and may to some degree be caused by stress and/or stress-relieving measures [9,10].

 It is noteworthy that in Britain a significant reduction in mortality from gastrointestinal diseases and alcoholism has been demonstrated since the 1970s, which is in contrast to the general British population. Shorter contracts, improved work conditions aboard, stricter policies regarding alcohol use at sea, and a shift from European to Asian seafarers are some factors that may influence future series. There are also important limitations to longitudinal mortality studies in seafarers [1].

 Tele-Medical Advice Services (TAMS) report that abdominal complaints  (e.g. pain, nausea, vomiting and/or diarrhea) account for 10 - 25% of the maritime radio-medical contacts [11-17]:

Studies from cruise ships [18-21] – with doctor(s) aboard – show that the most frequent GI cause of:

• sick leave aboard is acute gastroenteritis,
• hospitalization ashore is ’abdominal pain’ and appendicitis,
• medical sign-off and repatriation is inguinal hernia, and
• referral to a specialist ashore is dental disorders.

 Further epidemiology details can be found in the studies referred to below, a selection based on the author’s maritime-medical library and PubMed searches. The quality of the studies varies widely, from small reports comprising a few cases to large statistical series based on official records from insurance companies and government agencies:

10.10.2      Studies of morbidity and mortality

In a mortality study among seafarers in British merchant shipping 1976-1995 gastrointestinal disease was the second largest cause of death (after cardiovascular diseases), with 9% out of a total of 600 deaths,  largely due to liver cirrhosis and stomach ulcers (14 each) and acute pancreatitis (7) [2]. Many were linked to lifestyle factors, and several of these diseased were also suffering from delirium tremens and other alcohol-related problems. A large proportion of fatal gastrointestinal disease (42%) was found in catering crew and stewards, a rank previously identified with frequent alcohol use [22]. However, Roberts [2] pointed out that heavy alcohol consumption at sea has declined in recent years; in particular following the implementation of screening after the grounding of the tanker Exxon Valdez resulting in a major oil pollution disaster off Alaska in 1989.

 Studying work-related mortality among British seafarers employed in flags of convenience shipping 1976-95, Roberts [3] found that out of a total of 200 deaths, illnesses caused 68 deaths, of which seven were from gastrointestinal disease (liver cirrhosis, acute pancreatitis, peptic ulcer, kidney failure, ruptured gall bladder and hepatitis [two]).

 In a study on work-related mortality among seafarers who were employed in British merchant shipping from 1939 to 2002, with a population of 7.29 million seafarer-years at risk, 864 deaths were from gastrointestinal diseases and 72 from alcoholism [1]. Overall mortality from gastrointestinal diseases fell from 18.4 per 100,000 in 1939-49 to 9.3 in 1970-79 and 0.3 in 1990-2002. Mortality from alcoholism, and from alcohol-related diseases such as liver cirrhosis and diseases of the pancreas, increased up to the 1960s or 1970s, but fell thereafter. At the time of the last censuses of seamen in 1961 and 1971, compared with the general British male working aged population, mortality among British seafarers was greatly increased for peritonitis and alcoholism but not for most other gastrointestinal diseases. The author concluded that sharp reductions in mortality from gastrointestinal diseases and from alcoholism since the 1970s contrasts with increases among the general British population, and are largely because of the “flagging-out” of most British deep sea ships, and consequent reductions in long voyages, as well as reduction in alcohol consumption among seafarers at work. Largely because of the healthy worker effect, seafarers were usually only at increased risks from particularly acute diseases, like peritonitis. Mortality from gastrointestinal diseases was similar among British and Asian seafarers in the British fleet during the 1940s, but it was almost twice as high among Asian seafarers from 1950-72, particularly for peptic ulcer, liver disease and peritonitis. Roberts speculated that this may be related to a higher prevalence of heliobacter pylori and hepatitis infections among Asian seafarers.

However, an important limitation of longitudinal mortality studies is that death certification would have improved over time, but it may be quite unreliable in the earlier years of the studies when sea burials were quite common, particularly on long inter-continental voyages, and at a time when more deaths occurred in foreign countries with less chance of an autopsy being undertaken [1]. There have also been substantial improvements in diagnostic techniques over time, and pre-employment medical examinations have become more apprehensive.

 In a Danish study, overall mortality was increased among seafarers compared to the population ashore, and mortality from cirrhosis of the liver was increased in deck and engine crew and in deck officers [4].

 In a British pathology study of 111 cases of primary hepatic malignancy collected in the Liverpool region [23], Cruickshank noted that “although the incidence in the region as a whole was not unusually high, most of the cases were found in the vicinity of two ports, and the relatively large number of seafarers may give an indefinite hint of some etiological relationship between seafaring and the disease”.

 Increased risks for primary liver cancer were observed in Sweden for occupations with high consumption of alcohol and/or high prevalence of smoking, like seamen, waiters and cooks [5].

 Another Danish series showed that the standardized incident ratio (SIR) of all cancers combined was higher than expected in seafarers: Male Danish seafarers have a high overall relative risk of cancer that is related to all cancers associated with tobacco smoking and alcohol (including mouth, pharynx, esophagus, and pancreas cancer), and a borderline increased excess of colon cancer, while female Danish seafarers have an excess of rectum cancer [6].

 An analysis of 2.8 million cancers among 15 million people, aged 30-64, in Denmark, Finland, Iceland, Norway and Sweden showed that the occupations with the highest SIR for all cancers combined included waiters, workers producing beverage and tobacco, seamen and chimney sweeps [7]. It was noted that exposure to the known hepatocarcinogens, the Hepatitis B virus and aflatoxin, is rare in the Nordic countries, and a large proportion of the primary liver cancers can therefore be attributed to alcohol consumption. The highest risks of liver cancer were seen in occupational categories with easy access to alcohol at the work place or with cultural traditions of high alcohol consumption, such as waiters, cooks, beverage workers, journalists and seamen [7]. However, in a serological study of 523 volunteers during compulsory health control before embarkation from the port of Oslo, the prevalence of hepatitis B markers was 9.4% which was significantly higher than in the general Norwegian population. The prevalence increased with the number of years of occupation, and was associated with frequent casual sexual contacts in foreign countries [24]. The prevalence of antibodies against hepatitis A (HAV) was 36% in seamen born in 1945 and earlier and 5% in younger individuals, an age-dependent pattern which is essentially similar in the general Norwegian population [24]. The authors’ conclusion was that the incidence of viral hepatitis infections in the occupation was noticeably high, suggesting that vaccination of seamen in certain areas of trade should be considered.

 In a large Danish series, SIR for hepatitis A was 1.77 for male seafarers compared with the general population, and SIR for hepatitis B was 3.02, the main risk factors being intravenous drug use and casual sex aboard [25]. The authors recommended that merchant seamen should be vaccinated against hepatitis A according to general recommendations for travelers [26]; thus seamen from low-endemic areas who eat and drink ashore in endemic areas should be recommended vaccination. Prophylaxis against hepatitis B should primarily be directed against blood-borne and sexually transmitted diseases in general, as HIV infection also has been found among seamen. Vaccination against hepatitis B should be reserved for special categories of personnel, such as ship officers who perform medical treatment as part of their duties on board, and therefore have a well-established, but limited risk of blood-borne disease [27].

 In a study comprising 24,765 male offshore workers, a four-fold excess risk of esophageal adenocarcinoma was found in upstream operators, who are assumed to have the most extensive contact with different phases of crude oil. The authors noted that a major limitation of the study was the lack of data on other risk factors of esophageal adenocarcinoma, such as prevalence of gastro-esophageal reflux and the lifestyle factors body mass index, smoking and alcohol consumption [28].

 Occupational associations with gastric cancer were investigated in a multicenter case-control study in Italy [29], and the only significantly increased risk was observed for ‘men who ever worked as sailors, seamen and allied groups (OR=2.9). The risk increased slightly to 3.1 among those employed for 21+ years.’ This was consistent with an earlier study which indicated an increased gastric cancer risk among Icelandic seamen, which the authors speculated might be due to consumption of home-smoked foods [30]. Also British Columbia and Singapore fishermen are reported to have an increased gastric cancer mortality and incidence [31, 32].

 In a review of diseases and accidents among European seafarers (663,290 diagnoses from a total of15 countries from 1976 to 1990), accidents took first place with 18.5%, but diseases of the digestive system were those occurring most often (14.8%), ‘exactly as 10 years previously’ [8]. Italian seafarers were affected most frequently (25.6%), followed by Germans (20.7%) and Greeks (18.7%). Gastritis and gastric and duodenal ulcers occurred as the most frequent disorders;  it was noted that seafarers suffer twice as often from digestive complaints as does the corresponding male population on land, and that a number of factors have a synergistic effect on chronic gastritis and gastric ulcers, like unphysiological rhythm during working time, monotony on board, seasickness, macro- and micro-climatic factors, excessive use/consumption of tobacco, alcohol and other stimulating beverages, stress and mental strain.

 In a gastroscopy study from 1986, morbidity of peptic ulcer was found to be higher in Chinese seafarers compared to controls {33], and in a Japanese analysis of 51,641 reported seafarer cases of accidents and disease that required more than 3 days off work, the most prevalent were diseases of the digestive system (33.5%); the proportions of disorders in the digestive system varied from 21.4% in passenger vessels to 39.8% in specialized  ships, equally high for officers and ratings [34].

 In a report from Vietnam [35] there were more cases of diseases of the digestive system among 865 seafarers (12%) than in 881 controls (2%).

 In a Danish study of hospitalizations among seafarers on merchant ships [9], it was noted that despite pre-employment selection and biennial health examinations, a large proportion of the seafarers showed evidence of poor health. Hospitalizations because of diseases of the digestive system were second to only injuries. They were particularly high among ratings aboard passenger ships, a group dominated by catering crew and cooks. This may again reflect lifestyle factors including alcohol, active and passive smoking, and non-daytime work, and a similar hospitalization rate is found among people employed in the Danish hotel and restaurant industry [9, 10].

 In a  another study of hospital contacts for chronic diseases among Danish seafarers and fishermen, high standardized hospital contact ratios were found, among others, for alcohol-related liver diseases in male officers[6].  

 Hansen et al. [9] also found a high ratio of seafarer hospitalizations in Denmark due to inguinal hernia and commented that this finding is likely to be iatrogenic: “The seafarers are checked for hernia at biennial mandatory health examinations, which have almost certainly caused many referrals for surgical repair of hernia”.

10.10.3      Telemedical contacts for abdominal complaints

Abdominal complaints (e.g. pain, nausea, vomiting and/or diarrhea) accounted for 25% of the maritime radio-medical contacts in a report from Singapore[11], 24.4% in a 12-year Japanese report [12] and 24.3% in a 10-year Japanese report [13], 19% in a report from the Italian Telemedical Maritime Assistance Service[14], 15% in a report from Swedish Radio Medical 1997-2009 [15]  and  10% in a report from US telemedicine services  [16]. Sixteen percent of telemedical advice to passengers and 22% to crew on long-distance ferries from Radio Medical Denmark concerned the digestive system [17].

10.10.4     Gastrointestinal diseases on passenger ships and oil rigs - with physicians aboard

In three World Cruise studies lasting 90-106 days, 9-14 % of the crew and 9-16 % of the passenger consultations were because of gastrointestinal disorders [20,36,37], but in the first study [36], gastroenteritis was included in ‘infectious diseases’, which was the largest group (18% of crew and 12% of passenger consultations).

 In a descriptive 1-year study about crew sick leave aboard a cruise ship [18], 137 crew were isolated for a total of 268 days (= 32% of all sick leave) to prevent spreading of acute gastroenteritis. Out of 7 crew members admitted to ward observation aboard and/or hospitalized in port, 3 cases were related to GI: acute abdominal pain (1) and acute appendicitis (2). Two crew members were referred to gastroenterologists during scheduled vacation at home.

 In a study of crew referrals to dentists and medical specialists ashore from three cruise ships during one year, only 10 crew members were hospitalized in port prior to repatriation, of which four were classified as gastrointestinal [19]. All 4 were acute appendicitis, which made this the most frequent reason for hospitalization in port. In earlier years, appendectomy was done aboard  when convenient [36], but ship’s doctors are now only required to have minor surgical skills, according to the Health Care Guidelines for Cruise Medical Facilities, issued by the American College of Emergency Physicians [38]. Most crew referrals to services in port (50-70%) concerned dentistry, reflecting the fact that the ship’s doctors are neither trained nor equipped to do elective dentistry aboard [19]. This study also confirms earlier studies that suggested that seafaring constitute a risk factor for oral health [39, 40]. It is in agreement with a large study from 1984 of 201 voyages of Polish cargo ships having doctors aboard: The majority (67%) of all 1868 cases referred for consultation and treatment in foreign ports concerned diseases of teeth, pulp and peri-apical tissue [21].

 In a study from 2 cruise ship in the Caribbean in 1989 and 1990 among 1,360 medically related passenger and crew presentations 9% were gastrointestinal [41].

 A study of 232 passenger consultations aboard an Antarctic cruise ship during the summer season 2004/2005 the most common reason for presentation to the ship’s physician was motion sickness ( 41%), whereas  6% were listed as ‘gastrointestinal” [42].

 Peake et al. [43] evaluated 7.147 passenger consultations on 4 cruise ships during 1 year, of which 8.9% were ‘digestive system diseases’

 Inguinal hernia, back pain and accidents were the most common reasons for repatriation from HAL (Holland America Line) ships 2000-2004. HAL provides health care to > 5000 active sea-based crew from all over the world [20].

 Prina et al. [44] evaluated emergency air evacuation of 104 patients, apparently all passengers, from cruise ships in the Caribbean to Fort Lauderdale. Seventeen evacuations (16%) were because of gastrointestinal conditions (gastrointestinal bleeding 9, infection/peritonitis 3, pancreatitis/cholecystitis 3, hepatitis 1, intestinal occlusion 1), and two of these patients developed complications during the air transport (1 required endotracheal intubation because of respiratory failure following sepsis secondary to diverticular abscesses, 1 sudden hypotension because of gastrointestinal hemorrhage, responding to fluid administration).

 In a 1-year study of injuries and diseases on an American oil rig in the Mediterranean 12.2 % of 518 consultations concerned gastrointestinal disorders, mostly acute and chronic gastritis [45].

10.10.5   Acute Abdomen and ‘surgical’ Gastrointestinal Emergencies at Sea

 All seafarers with abdominal pain are potential ‘surgical emergencies’ and need special attention. Never leave port with a person aboard who - because of abdominal pain - is unable to work or needs analgesics to be able to work!

 Of special interest is diagnosis and treatment of acute GI conditions at sea as they are to be handled initially by a seafarer, usually the captain or chief officer, with limited medical knowledge and experience.

 Most gastrointestinal cases that lead to telemedical consultations present with the general symptom ‘abdominal discomfort / abdominal pain’. The initial challenge is to decide whether the patient is acutely unwell. With a little experience it is relatively simple to differentiate between the extremes; the patient who is comfortable, sitting up and talking, is not seriously ill and a more measured approach can be adopted, but some early signs of impending deterioration can be subtle [46].

 Some of the conditions are life-threatening and may require urgent transfers to medical facilities ashore. This may not be possible when the ship is far from land and outside helicopter range, and in such cases alternative, suboptimal solutions may buy time or provide temporary help.

Bed rest Reverse ‘Trendelenburg position’: Elevate head end of the bed by placing a life vest under  
the mattress at the head end of the bed (or bricks/books under the head end of the bed ) and
add pillows under the patient’s head, neck and upper chest – for easier breathing. 

• No medication by mouth, especially not tablets that can cause hyperacidity or bleeding, like non-steroid anti-inflammatory drugs (NSAIDS) and aspirin.
• Painkillers (analgesics) by rectum (suppositories), intramuscular injection (im) or slow intravenous (iv) injection. The hypothesis that analgesia may mask the pain and result in an incorrect diagnosis has no evidence base, so all patients should be given appropriate analgesia, e.g. morphine 4-6 mg [47].
• Antiemetic in case of nausea caused by ship movements, medication (morphine) or the GI condition as such. Metoclopramid can be given by rectum, im and iv, while Promethazine should not be given intravenously.
• Fluids:
• If thirsty and not nauseated: clear fluids/water by mouth.
• Nothing by mouth if unstable.
• If available: saline and/or glucose solution intravenously  2-3 liter/day.
• If intravenous fluid is not available and there are signs of dehydration when nauseated or vomiting: physiological (normal) saline solution (NaCl 0.9%) as an enema.
• No solid food until the situation has been stabilized.
• Call Telemedical Advice Services (TMAS)
• If signs of infection (temperature >37.7^oC/100^oF), consider broad-spectrum antibiotics in
  cooperation with TMAS
• Consider evacuation possibilities to next port by helicopter, ship deviation, increased ship
     speed, - or possibility to transfer to closest cruise or naval ship carrying a physician.

Acute GI bleedings are emergencies and require medevac. GI bleeding can originate anywhere from the mouth to the anus and can be overt or occult, but is for practical reasons usually divided into upper and lower GI bleeding.

Often taken over-the-counter analgesics like NSAIDs and aspirin may cause or contribute to ongoing bleeding. Note that doses taken aboard often exceed recommended ones (‘a hand-full’), and some seafarers may take prophylactic low-dose aspirin without being aware of harmful side effects.

The patient usually vomits fresh or altered (coffee-ground) blood and may pass dark tarry or black stool (melena) after as little as 50-100 ml of blood loss. While the passage of red blood per rectum is more commonly associated with lower GI bleeding, this can also be seen in a massive upper GI bleed (> 1000 ml). Upper GI bleeding is self-limited in 80%. Risk factors are esophageal varicose veins and non-steroid anti-inflammatory drugs or aspirin.

The most common cause is peptic ulcer (1/3), and the bleeding is often preceded by dyspepsia (1/5). The majority of peptic ulcer bleeding will stop spontaneously, as will bleeding associated with small tears in the stomach lining caused by retching or vomiting, irritation of the esophagus (esophagi is), vascular malformations or an underlying cancer.

The other important cause of upper GI bleeding is bleeding from esophageal or stomach varicose veins, usually from liver cirrhosis after alcohol misuse.  Such bleeding is often severe, and > 50% of these patients will die in connection with the first bleed episode - even under optimal hospital care [48].

 At sea prior to evacuation: strict bed rest, stops all medications that can contribute to bleeding, and monitor hourly pulse rate and blood pressure:

A systolic blood pressure 100 beats/min and blood pressure > 100 mm Hg means moderate acute blood loss [49].

If the blood pressure is rapidly dropping, raise the patient’s legs (place pillows under the patient’s lower legs – or even better: put a life vest under the mattress at the foot end of the bed). If available:

• give intravenous fluid replacement (normal 0.9% saline solution, up to 2000 ml/day) fast through two venous cannulas (venflons);
• try acid suppression: High dose proton pump inhibitors (e.g. omeprazole, esomeprazole or pantaprazole 80 mg at once, followed by infusion 8 mg hourly for 72 hours).

Lower GI bleeding is defined as arising from the bowels distal of the duodenum (95% from the colon) and presents with either fresh blood or melena  by  rectum (see above: Upper GI bleeding). Brown stools mixed or streaked with blood predict a source in rectum or anus. Painless large-volume bleeding usually suggests diverticular bleeding. Bloody diarrhea associated with cramping abdominal pain and urgency suggests colitis. Occult (‘hidden’) bleeding is slow and chronic, frequently leading to anemia (low blood count) as the first sign of blood loss. The patient is pale and may easily faint. There are many possible causes, few of which can be dealt with while at sea. Most lower GI bleedings (>85%) stop spontaneously with supportive treatment over several days.

Supportive treatment

 The supportive treatment is similar to that of Upper GI bleeding: Bed rest, raise the patient’s legs, and give fluids. However, clear fluids can be given by mouth. Note that hemorrhoids are a common (5-10%) source of fresh lower GI bleeding. Hemorrhoid bleeding is usually intermittent, associated with bowel movements, is rarely significant and will usually stop with conservative measures (steroid cream and/or suppositories). In cases of rectal prolapse and palpable hemorrhoids, proper analgesia should be given and reduction attempted (by gently compressing the prolapsed tissue and pushing it back inside the anal channel).

Follow-up

 Before next seafarer contract GI bleeding episodes must be properly investigated, and when ano-rectal disease is suspected, ano/rectoscopy should be done to rule out cancer and to avoid re-bleeding at sea.

Esophageal damage is an emergency and requires in most cases medevac. Caustic (strong acids and alkalis) ingestion burn upper GI tissue and sometimes resulting in esophageal or gastric perforation. Common sources are solid and liquid drain and toilet bowl cleaners. Symptoms include drooling, pain in the mouth, chest, or stomach, difficulties swallowing, and strictures may develop later.

Supportive treatment

 Fluids by mouth are started when tolerated.

If perforation is suspected (fever!), broad-spectrum antibiotics are given iv or im.

• Do not try to empty the stomach (by vomiting or lavage) as this can re-expose esophagus to the caustics. 
• Do not try to neutralize a caustic acid by correcting pH with an alkaline substance (and vice versa) as severe exothermic reactions may result.
• Do not administer activated charcoal as it may infiltrate burned tissue and interfere with later endoscopy.

Note that different tablets, especially if taken without sufficient fluid and while lying down, can injure the esophagus, like NSAIDs, potassium chloride, quinidine, iron, vitamin C and antibiotics.

Gastro esophageal reflux (GERD) means that reflux of stomach contents (most often acid) causes troublesome symptoms, like heartburn, which may be worse after meals or when bending or reclining.

Treatment

 Relief is often achieved by taking antacids or baking soda. Against symptoms at night: Sleep with the head end of the bed elevated (See Bove: Supportive treatment for abdominal pain).

 Uncomplicated GERD should be treated with a once- or twice-daily proton pump inhibitor for 4-8 weeks, but investigate further by having endoscopy done by a gastroenterologist in the next port if ‘alarm features’ (difficulties or painful swallowing, weight loss, persisting symptoms despite acid reduction).

Strong suspicion of an ulcer requires GI specialist evaluation and most likely medical sign-off in the next port. Smoking is believed to be one of the most important etiological factors for peptic ulcers, especially in the young, and increases the risk tenfold in both women and men, while the use of non-steroid anti-inflammatory drugs (NSAIDs) increases the risk by 5-8 times [50]. Other risk factors for seafarers may include alcohol and stress. Current evidence shows that eradiation of heliobacter pylori significantly reduces the peptic ulcer recurrence rate. Patients should be encouraged to eat balanced meals at regular intervals. There is no justification for bland or restrictive diets [49].

Treatment  

 H2-receptor antagonists (cimetidine 800 g, ranitidine 300 mg, famotidine 40 mg – by mouth once a day at bedtime) or proton pump inhibitors (omeprazole 20 mg, lansoprazole 30 mg, pantoprazole 40 mg, or esmeprazole 40 mg) twice a day for 6-8 weeks (or  - to be on the safe side - for the rest of the seafarer’s present contract).

Perforated ulcer is an emergency and requires medevac. The initial symptom is sudden, sharp pain in the upper mid-region (epigastric) of the abdomen, sometimes associated with pain in the lower abdomen, and subsequently diffusely over the abdomen due to inflammation of the peritoneum (peritonitis). The abdomen is rigid and very tender to touch.

Perforated ulcer can mimic acute pancreatitis, cholecystitis, any perforated bowel (appendicitis, diverticulitis), and myocardial infarction.

Monitor pulse rate, blood pressure and temperature.

Supportive treatment

 Up to 40 % of ulcer perforations seal spontaneously. While at sea, conservative management (analgesics, antibiotics and nothing by mouth) can be effective:

 Appropriate analgesics (morphine subcutaneously or intramuscularly: 5-20 mg/70 kg every 4 hours; intravenously 2.5-15 mg/70 kg over 3-5 minutes every 4 hours).

Broad-spectrum antibiotics (preferably intravenously, alternatively intramuscularly).

• If available: Give oxygen by mask or catheter, intravenous fluids (normal saline solution, > 3000 ml/day) and an intravenously proton pump inhibitor (See Upper GI bleeding). Very helpful to avoid spillage of gastric contents into the abdominal cavity: pass a naso-gastric tube through a nostril into the stomach and keep the stomach empty by aspiration of stomach contents with a 10-20 ml syringe every 10-15 minutes 

 Increasing temperature and pulse rate and falling blood pressure (systolic < 100 mm Hg) are danger signs; consider then fluids by rectum (enema with physiologic saline solution = 0.9%NaCl).

Follow-up

 After successful treatment of the perforation, eradiation of Helicobacter pylori must be done, etiological factors (smoking, NSAIDs, alcohol, stress) should be eliminated, and the patient should be without symptoms on a normal diet for at least 3 months before further work at sea.

Acue appendicitis is an emergency and requires medevac. The clinical presentation consists of a relative short history (hours – 2 days), pain migration (often start in upper mid-abdomen or around the navel, moving toward lower right quadrant), malaise, loss of appetite, nausea and vomiting after the pain started, and constipation (- but occasionally diarrhea).

On examination the patient has often low-grade fever (temperature 37.7^o -38.3^oC / 100^o-101^oF), is flushed and lying still, has the right hip (or both) flexed and complains of pain when the examiner is trying to stretch out the knee and hip (passive hip extension). Pain increases with cough and motion. There is direct and rebound tenderness and guarding in the right lower quadrant, or if the appendix is perforated, the abdomen may be tender all over and rigid (peritonitis). Additional signs are pain felt in the right lower quadrant with palpation of the left lower quadrant (indirect pain).

Unfortunately, these classic findings appear in less than 50% of patients.

Some other conditions may mimic acute appendicitis such as

Surgical: Perforated colon cancer, pancreatitis, perforated peptic ulcer, intestinal obstruction, mesenteric adenitis, diverticulitis, acute cholecystitis

Gynecological: Ruptured ovarian follicle, salpingitis (usually less nausea), torted ovarian cyst, ectopic pregnancy (usually no fever, positive pregnancy test, last menses > 5 weeks ago

Urological: kidney stone on the move (ureteric colic – colicy pain, usually no fever), pyelonephritis, urinary tract infection

Medical: Diabetic ketoacidocis (high blood sugar), gastroenteritis (diarrhea), terminal ileitis, pneumonia.

Preferred treatment for appendicitis is evacuation and emergency surgery within 24 hours. After the first 36 hours after the onset of symptoms, the risk of perforation is 16-36% and increases by approximately 5% per 12-hour period [47].

Supportive treatment

 Bedrest in Fowler’s position (= elevated upper body, both hips and knees bent, and body turned to the right).

• Analgesics.
• Water by mouth.
• No solid food.
• Start broad-spectrum antibiotics (preferably third-generation cephalospirins) intravenously or intramuscularly if fever and/or suspicion of appendicitis is strong

In the developed world, by the age of 50 years, approximately half of all individuals will have colonic diverticulosis. Of the 25% of them who have symptoms, three quarters will have at least one presentation of diverticulitis. Diverticulitis appears to be more virulent in young patients (30-50 years of age), linked to obesity, and up to 80% may need surgery during their initial attack, with a high risk of recurrence.

The most common presentation is of fever and localized left-sided lower abdominal pain with or without guarding, often associated with nausea, or altered bowel habit (diarrhea or constipation).

Colonic diverticulosis is the cause of major lower gastrointestinal bleeding in about 40% of instances and is for most patients (80%) self-limited [51].

Small localized perforations may cause localized abscesses and focal pain, while large perforations can present with peritonitis or sepsis and can be life-threatening.

Treatment

 Mild attacks are treated with rest, analgesia, antispasmodic medication if available, and, sometimes, antibiotics by mouth.

More severe symptoms (fever, increasingly unwell, tender abdomen) require hospitalization in the next port / medevac. In the meantime, bed-rest, intravenous fluids and antibiotics against anaerobic and gram-negative bacteria from the colon (cephalosporin + metronidazole) are recommended.

If intravenous administration is not possible, consider intramuscular administration of antibiotics, and bowel rest with only clear fluids at first. Oral intake is gradually increased through clear fluids, free fluids to soft diet and eventually full diet at variable pace depending on the patient’s condition.

In patients who are going to respond to conservative management, an improvement is generally seen within the first 2-3 days, but even then a surgical consult and medical sign-off – or hospital admittance - should be arranged in the first port [51].

A bowel obstruction is an emergency and requires medevac

Postoperative adhesions and strangulated hernias are the most common causes of small bowel obstruction, while a variety of conditions, like cancer, diverticulitis, volvulus, constipation and inflammatory bowel disease, can cause large bowel obstruction.

The common symptoms are pain (colicky at first), abdominal distension, vomiting, - and after some time absence of flatus and stool, vomiting and dehydration. It is essential to identify the patient with threatening or actual strangulation of the bowel. This is suggested by a sharper, more constant and more localized pain, and the patient have often fever and signs of peritonitis (diffuse tenderness, guarding).

A history of abdominal surgery is important, and the groins must be examined closely for tender lumps (hernias), as about ¼ of intestinal obstructions are cause by strangulated hernias. Redness, tenderness, and non-reduction over a hernia suggest strangulation. A hernia becomes strangulated when the blood supply of the contents within the sac becomes impaired and gangrene is imminent. Fever is not typical for simple obstruction and suggests compromised circulation and perforation, or may be associated with the cause if this is connected with an inflammatory process [52].

Supportive treatment

 Bed rest, analgesics, nothing by mouth (‘bowel rest’), intravenous fluids if available, - and if possible: decompression of the bowel by inserting a nasogastric tube (through a nostril into the stomach) and a rectal drainage tube (gentle insertion 10-20 cm through the anus). Naso-gastric tubes are not available on most vessels, but efforts should be made to introduce them. Once inserted, keep the tubes in place, and aspirate contents with a 10-20 ml syringe at hourly – or more frequent – intervals. Record aspiration volumes, color and smell. Consider intravenous, alternatively intramuscular broad-spectrum antibiotics (see diverticulitis).

A hernia of the abdominal wall is a protrusion of the abdominal contents, mostly bowel, through a weakness or defect in the wall. The most common ones are found in the groin (inguinal and femoral hernia) and in the umbilicus. Incisional (ventral) hernias stem from abdominal operations where insufficient closure or postoperative wound infection have resulted in a wall defect. Most hernias present with only a visible bulge and only vague or no discomfort, whiles some become incarcerated or strangulated, causing pain and symptoms of mechanical obstruction and/or peritonitis, and requiring immediate operation. Before the symptoms have become severe (< 12 hours), manual reduction by gentle compression and persistent pressure while the bed end is elevated may be successful. Even if reduction was successful, the seafarer should be signed off medical in the next port. No further seafaring until successful surgical hernia repair and complete recovery to prevent future strangulation.  If the reduction fails, an obstruction is imminent and evacuation may become necessary

Strangulation and incarceration of incisional and umbilical hernias are unusual. If incarceration happens in an umbilical hernia, the content is usually omentum rather than intestines; this may be painful but not dangerous. 

Persistent bright red blood from the anus, slimy anal discharge, persistent itchy rashes or signs of local infection in the anal area should be evaluated by a doctor in the next port.

Patients often attribute a variety of complaints near the anus as ‘hemorrhoids’. The area should be carefully inspected and examined for other signs of disease, like fistulas, fissures, skin tags, or dermatitis. It is particularly important to rule out tumors (cancer) when the patient reports bright red blood from anus.

Hemorrhoids are dilated veins, ‘cushions’ characterized by bright red blood from anus following stools, protrusion of ‘lumps’ from anus, anal discomfort, and sometimes a feeling of incomplete evacuation. Itching is usually not a symptom. They are very common and may become symptomatic as a result of activities that increase venous pressure in the region, resulting in distention and engorgement. Straining at stool, constipation, prolonged sitting, pregnancy, obesity, and low-fiber diet all may contribute.

Straining at stool, constipation, prolonged sitting, obesity, pregnancy and low fiber diets all may contribute.

External (outside) hemorrhoids are covered by skin and easily seen. Prolapsed hemorrhoids are visible as protuberant purple nodes; they are firm to touch and quite tender. Non-prolapsed internal (inside), covered by hemorrhoids are not visible but may protrude through the anus with gentle straining while the examiner spreads the buttocks. Uncomplicated internal hemorrhoids are neither palpable nor painful on digital rectal examination.

Supportive treatment

 At sea, most patients with early stage hemorrhoids can be treated conservatively with high-fiber diet, increased fluid intake and stool softeners/laxatives. Recurrence is unfortunately common, especially if the patients don’t alter their diet.

Swollen, prolapsed hemorrhoids should be gently manipulated, preferably by the patient, into the anal canal, supplemented with hemorrhoid suppositories (with or without hydrocortisone). Warm sit baths (i.e., sitting in a tub of tolerably hot water for 10 minutes) after each bowel movement may give some relief. 

Thrombosed external hemorrhoids are characterized by relatively acute onset of an exquisitely painful, tense and bluish node that may be up to several centimeters in size. Pain is most severe within the first few hours, but gradually eases over the next 2-3 days when the swelling subsides. Warm sit baths, analgesics (NSAIDs), and anesthetic ointments may give some relief. If rapid pain relief is necessary, simple incision and evacuation of the blood clot can be done: after infiltration with 1% local anesthesia, the hemorrhoid is cut open and the clot expressed or extracted with forceps. Bleeding afterward is stopped by gentle manual pressure on a dressing.

Ano-rectal abscess is a localized collection of pus near anus. Symptoms are local pain, swelling, redness, and often fever.

Supportive treatment

 Treatment of superficial abscesses is incision and drainage, which is simple when ‘the abscess points’: a superficial stab wound (1-1.5 cm) through the skin at the most pointed area releases the pus and the pain subsides. After incision and pressure relief, antibiotics are rarely needed. However, ano-rectal abscesses may be the first sign of more serious conditions, like immunodeficiencies, Crohn’s disease etc, and even when the initial treatment results in satisfactory relief, a GI specialist evaluation should be arranged in the next port.

Jaundice is yellow discoloration of skin and sclera  (‘white of the eye’), usually associated with dark urine, pale stools and general itching, and can be caused by a variety of conditions involving the liver and gallbladder.

Action

 Jaundiced seafarers with or without abdominal pain should be signed off for expert evaluation in the next port.

Most people with gall stones have no or mild symptoms, but gallstones can present suddenly with a combination of abdominal pain, mainly in the upper right quadrant, nausea, loss of appetite, and sometimes fever and jaundice.

Biliary colic occurs when a gallstone obstructs the neck of the gallbladder, and the pain can be triggered by fatty meals. The pain is usually constant, deep and aching in nature, is of short duration and is not associated with fever, but can be strong enough to cause nausea and vomiting. The abdomen is usually soft with only mild tenderness to touch in the right upper quadrant.

Acute cholecystitis occurs when a stone obstructs the gallbladder neck and the gallbladder becomes inflamed. The pain is similar to biliary colic, but usually more severe, and associated with fever and increased pulse rate.

Supportive treatment

 Bed rest, broad-spectrum antibiotics, only clear fluids at first, and an antiemetic (cyclizine, promethazine, metoclopramid)  rectally (suppository) or by injection, as tablets will be thrown up. Arrange a surgical consult – or hospitalization – in the first port. Following a gallbladder pain attack, the seafarer should undergo cholecystectomy and be fully recovered before the next sea contract. 

Acute pancreatitis

Acute pancreatitis is often a serious condition that requires medevac

The condition is easily confused with other acute abdominal pain conditions and can not be diagnosed with certainty without lab facilities and/or imaging. Hence, both diagnostic work-up and treatment should be done at a facility ashore.

The most common causes at sea are gallstones, alcohol misuse, and blunt abdominal trauma.

Pancreatitis is broadly classified as mild or severe. It is characterized by sudden onset of severe pain in upper mid-to left abdomen, radiating through to the back and sometimes to the left shoulder, associated with nausea, vomiting and dehydration. Fever is common. In more severe cases the pulse rate is fast (tachycardia), breathing is fast and shallow (tachypnea), and the blood pressure low (hypotension). The abdomen is diffusely tender with distension and guarding, and rigidity may mimic bowel perforation. However, the abdomen may in early stages be soft despite generalized tenderness. In severe cases there may be discoloration (‘black and blue’) of the skin in the flanks (Grey Turner’s sign) and around the navel (Cullen’s sign).

In the majority of cases, pancreatitis resolves rapidly with simple conservative management, but approximately 20% develop organ failure [53].

Supportive treatment

 Management at sea is limited to bed rest, fluid replacement and appropriate analgesia, usually opiate-based (morphine).  Patients with mild pancreatitis do not usually require dietary restriction or support. Nutrition by mouth is preferred and should be considered early in the disease process. There is no indication for prophylactic antibiotics in mild pancreatitis, and antibiotics do not appear to reduce the incidence of infected pancreatic necrosis or infections of other organs.

Consequences of abdominal trauma may be serious and evacuation must be considered.

The mechanism of injury is critical; broadly divided in blunt and penetrating injuries. Patients with penetrating injuries are more susceptible to infection, especially if the bowel has been injured.

Supportive treatment

 Bed rest and close observation of vital signs (pulse, blood pressure, temperature). Nothing by mouth until the situation is reasonably clear and stable. Give intravenous, alternatively intramuscular, broad-spectrum antibiotics (see above:  diverticulitis) in penetrating and unclear blunt injuries. Fever after injury is a danger sign!

Gastroenteritis is an inflammation of the lining of the stomach and the intestines and can be caused by bacteria, virus, toxins and drugs. Symptoms include nausea, vomiting, diarrhea, loss of appetite, and abdominal discomfort/cramps. There may be fever, and the abdomen may be distended and slightly tender, often with audible bowel sounds.

 Norovirus has become the most common cause of acute GI illness outbreaks in cruise ships calling not only on US ports but worldwide [54]. The number of outbreaks is increasing in parallel with the increase in norovirus infections on land. Symptoms often start with sudden onset of vomiting and/or diarrhea. There may be fever, headache, abdominal cramps, myalgia and malaise. Gastroenteritis caused by norovirus is very contagious, and although outbreaks may begin as food-borne or water-born disease, the virus is easily transmitted by person to person contact. The infectious dose of this virus is less than 100 particles, and it is resistant to many common control mechanisms [55]. This can at least partly explain why CDC’s VSP had less success in preventing GI outbreaks after the millennium. Norovirus illness is difficult to diagnose as the symptoms are similar to those caused by other types of gastroenteritis, and presently there is no fast and sufficiently reliable diagnostic test to distinguish norovirus from other pathogens on board. Outbreaks often affect both passengers and crew, sometimes with very high attack rates. Recurrences of infection on successive cruises are common. Outbreaks may continue because groups of new susceptible passengers are introduced on a regular basis, so that rather than running its course, the outbreak continues over a period of several cruises. Bridging between groups may occur by a reservoir of illness in the crew or by failure to decontaminate the environment [56]. A particular hazard is symptomatic persons moving around in public falsely believing that they are not contagious because they take antibiotics. Travel Medicine Clinics, especially in USA, often give tourists – and seafarers -a prescription for a 3-day-course of antibiotics to take on voyages to exotic place. They should be warned that antibiotics should not be taken on cruise ships without consulting the ship’s doctor – and on merchant vessels without consulting TMAS - as they do not help against viral gastroenteritis and do not exclude preventive measures like isolation.

Treatment

 Gastroenteritis is usually uncomfortable, but self-limited. Hence, treatment is symptomatic, although infections caused by parasites and some bacteria require specific anti-infective therapy. Other GI disorders that cause similar symptoms (e.g. appendicitis, cholecystitis, ulcerative colitis) must be excluded. Bed rest with convenient access to a bedpan or to a toilet not used by others is desirable. Oral glucose-electrolyte solutions (Gatorade), broth, bouillon, or mild, sweetened tea may prevent dehydration. If dehydration is prominent, iv fluids may be useful – if available. If vomiting is severe, give an anti-emetic (promethazine 12.5-37.5 mg im or 25-50 mg per rectum 3-4 times a day; prochlorperazine 5-10 mg iv 3-4 times a day; metochlopramid 10 mg iv, im or by rectum 3 times per day). While intake of fluids is important, solid food should only be (gradually) restarted when the patient feels really hungry, starting with small amounts of the patient’s regular diet. The use of probiotics, such as lactobacillus (yogurt with a active cultures), is generally safe and can relieve symptoms.

Anti-motility agents should only be started after the GI tract ‘is empty’ (e.g. loperamid 4 mg at first and then 2 mg after each loose bowel movement – up to 16 mg a day). Preparations with bismuth subsalicylate are preferred by some.

Antibiotics are generally not recommended except when the suspicion of certain bacterial infections is high (Shigella, Campylobacter). In patients with severe diarrhea (> 3 loose stools over 8 hours) with fever, severe abdominal cramps and/or bloody stools antibiotics may be helpful (ciprofloxacin 500 mg twice a day for 3 days or levofloxacin 500 mg once a day ) [57].

Preventive measures

  Proper procedures for handling and preparing food and beverages must be followed, and seafarers should avoid potentially contaminated food (‘peel it, cook it or….’) and drink carbonated beverages without ice cubes served in sealed bottles. Hot buffets, fast food restaurants and street vendor food pose an increased risk.

Gastroenteritis outbreaks on passenger ships have been the subject of numerous studies over the last three decades. Cruising is considered a pleasant and relatively safe way to see exotic areas, but although cruise ships offer the comfortable familiarity of home, they can not entirely remove the risks of international travel [56]. In general, GI conditions seen on ships mirror those on land. The main differences are high population density aboard, high turnover of passengers, and the large number of countries from which the crew and passengers originate. These issues are significant in the transmission of infectious diseases on the cruise vessels, as ships are isolated communities with crowded living accommodation, shared sanitary facilities, and common water and food supplies. The cruise ships’ rapid movement from one port to another, where there may be differences in the sanitation standards and exposure risks, can introduce sightseeing and embarking passengers and crew to communicable diseases, which may result in outbreaks aboard. Shipboard conditions facilitate person-to-person spread of infectious diseases at sea, and disembarking passengers and crew might then contaminate communities ashore [56]. These factors have lead to a keen interest from national and international public health agencies; cruise ships have been like epidemiological laboratories for studies on outbreaks of gastroenteritis (and respiratory infections). Most of the detected gastroenteritis outbreaks associated with cruise ships before 2000 were linked to consumed food or water [58] and were caused by bacteria. Factors contributing to outbreaks included contaminated bunkered water, inadequate disinfection of potable water, potable water contaminated by sewage on ship, poor design and construction of potable water storage tanks, deficiencies in food handling, preparation and cooking and use of seawater in the galley [58].

 Since the early 1970s the US Centers for Disease Control and Prevention (CDC) Vessel Sanitation Program (VSP) has worked with the cruise line industry to prevent, detect, and respond to outbreaks of GI illness on cruise ships calling on US ports [59]. This program has had a marked success in preventing outbreaks of GI illness caused by bacteria: Between 1990 and 2000, the incidence of GI illness per 100,000 cruise ship passenger days decreased from 29.2 to 16.3. Yet, between 2001 and 2005, the overall incidence increased to 25.6, an increase that has largely been attributed to norovirus [60].

Prevention of outbreaks on cruise ships

 Proper surface disinfection, meticulous and frequent hand-washing before entering and leaving toilets and eating facilities (crucial in employees handling food and beverages (ice cubes!), and isolation of patients for 24 hours after the last symptom (48 hours in food handlers!) are important measures. The US CDC consider 3 or more loose stools or vomiting and one additional symptom a ‘reportable

gastroenteritis case’ and have strict guidelines (CDC Vessel Sanitation Program) for reporting and handling gastrointestinal infections at sea: See www.cdc.gov/vsp [59]. See also the chapter on Cruise Medicine in this Textbook of Maritime Medicine.

Public health authorities of ports around the world have followed CDC’s example and have similar programs for ships. See Mouchtouri et al. [54] for a European view of public health and passengers ships.

References  

1.  Roberts SE. Work related mortality from gastrointestinal diseases and alcohol among seafarers employed in British merchant shipping from 1939 to 2002. Internat Marit Health 2005; 56 (1-4): 29-44.

2.  Roberts SE. Mortality from disease among seafarers in British merchant shipping (1976-1995). Internat Marit Health 2002; 53: 43-56.

3. Roberts SE. Work-related mortality among British seafarers employed in flags of convenience shipping, 1976-95. Internat Marit Health 2003; 54:7-25.

4. Brandt LPA, Kirk NU, Jensen OC, Hansen HL. Mortality Among Danish Seamen From 1970 to 1985. Am J Industrial Med 1994; 25: 867-876.

5. Jianguang J, Hemminki K. Variation in the risk for liver and gallbladder cancers in sosioeconomic and occupational groups in Sweden with etiological implications. Int Arch Occup Environ Health 2005; 78: 641-649.

6. Kaerlev L,Hansen J, Hansen HL, Nielsen PS. Cancer incidence among Danish seafarers: a population based cohort study. Occup Environ Med 2005; 62: 761-765.

7. Pukkala E, Martinsen JI, Lynge E, Gunnarsdottir HK, Sparén P, Tryggvadottir L, Weiderpass E, Kjaerheim K. Occupation and cancer – follow-up of 15 million people in 5 Nordic countries. Acta Oncol 2009; 48: 646-790.

8. Vuksanovic P, Low A, Herrmann R. Diseases and Accidents among European Seafarers – A Review. In: Proceedings (eds. Gardner W, Saarni H). The (1st) International Symposium on Maritime Health, Turku, Finland, 5-9 June 1991.pp 187-201.

9. Hansen HL, Tüchsen F, Hannerz H. Hospitalisations among seafarers on merchant ships. Occup Environ Med 2005; 62: 145-150.

10. Hannerz H, Tüchsen F, Kristensen TS. Hospitalizations among employees in the Danish hotell and restaurant industry. Eur J Publ Health 2002; 12: 192-197.

11. Lateef F, Anantharaman V. Maritime Radio-Medical Services: The Singapore General Hospital Experience. Am J Emerg Med 2002; 20: 349-351.

12. Shoda M, Fujiwara K, Obata Y, Kaji K, Sawashima M. Observation of seafarers’ disease on board ships in the past 12 years (11980-1991) in Japan. In: Proceedings of the Second International Symposium on Maritime Health (ed. Ward Gardner A), June 2nd-6th, 1993, Antwerp, Belgium: 295-304.

13. Imanishi H, Shoda M, Watanabe T, Saito M, Fujino M. Radio medical advice for recent 10 years in Japan. In: Book of Abstract (ed. Carter T), 8th International Symposium on Maritime Health, Rijeka, Croatia, 8-13 May 2005; page 24 / Abstract O-0127.

14. Amenta F, Dauri A. Activities of the International Radio Medical Centre (C.I.R.M.) in Rome during the last five years (1996-2000). Internat Marit Health 2001; 52: 68-73.

15. Westerlund K, Nilsson R, Attvall S, Blohm L. Swedish Radio Medicali (RM) 1997-2009. A descriptive study concerning symptoms, action taken, number of evacuations, means of communication and use of digital photos. In: Book of Abstracts (ed. Carter T), 10th International Symposium on Maritime Health, Goa, India, 23-26 September 2009, PS 2/T4, paper 3.

16. McKay MP. Maritime health emergencies. Occup Med 2007; 57: 453-455.

17. Jensen OC, Bøggild NB, Kristensen S. Telemedical Advice to Long-Distance Passenger Ferries. J Travel Med 2005; 12: 254-260.

18. Dahl E. Medical practice during a world cruise: A descriptive epidemiological study of injury and illness among passengers and crew. Internat Marit Health 2005; 56 (1-4): 115-128.

19. Dahl E. Crew referrals to dentists and medical specialists ashore: A descriptive study of practice on three passenger vessels during one year. Internat Marit Health 2006; 57 (1-4): 127-135.

20. Hansson S, Hill C, Jaranilla J, Borbon E, Mariano C. Crew health care on the sea – Holland America Experience. In: Book of Abstracts (ed. Carter T). 10th International Symposium on Maritime Health, Goa, India, 23-26 September 2009, PS 1/T1, paper 2.

21. Tomaszumas S. The work of ship’s doctors of Polish Ocean Lines. Bull Inst Marit Trop Med Gdynia 1985; 36 (1-4): 51-58.

22. Hansen HL, Dahl S, Bertelsen B, Brix J. Lifestyle, nutritional status and working conditions of Danish sailors. Travel Medicine International 1994; 12: 139-143.

23. Cruickshank AH. The pathology of 111 cases of primary hepatic malignancy collected in the Liverpool region. J Clin Path 1961; 14: 120-131.

24. Siebke JC, Wessel N, Kvandal P, Lie T. The Prevalence of Hepatitis A and B in NorwegianMerchant Seamen – A Serological Study. Infection 1989; 17: 77/23-26/80.

25. Hansen HL, Hansen KG, Andersen PL. Incidence and Relative Risk for Hepatitis A, Hepatitis B and Tuberculosis and Occurrence of Malaria among Merchant Seamen. Scand J Infect Dis 1996; 28: 107-110.

26. WHO. International travel and health. Vaccination requirements and health advice. World Health Organisation, Geneva 1994.

27. Nelsing S, Nielsen TL, Nielsen JO. Occupational blood exposure among health care workers: I. Frequency and reporting. Scand J Infect Dis 1993; 25: 193-198.

28. Kirkeleit J, Riise T, Bjørge T, Moen BE, Bråtrveit M, Christiani DC. Increased risk of oesophageal adenocarcinoma among upstream petroleum workers. Occup Environ Med 2009 (Epub on line October 26, 2009; doi: 10.1136/oem.2009.046953 – accessed from oem.bmj.com on March 24, 2010).

29. Cocco P, Palli D, Buiatti E, Cipriani F, DeCarli A, Manca P, Ward MH, Blot WJ, Fraumeni JF. Occupational exposures as risk factors for gastric cancer in Italy. Cancer Causes and Control 1994; 5: 241-248.

30. Sigurjonsson J. Occupational variations in mortality from gastric cancer in relation to dietary differences. Br J Cancer 1967; 21: 651-656.

31. Gallagher RP, Threlfall WJ, Band PR, Spinelli JJ. Occupational Mortality in British Columbia 1950-1984. Vancouver, BC, Canada: Cancer Control Agency of British Columbia, 1989.

32. Jeyaratnam J, Lee J, Lee HP, Phoon WO. Stomach cancer in a cohort of fishermen in Singapore. Scand J Work Environ Health 1987; 13: 524-526.

33. Jinzhong W. Diseases and Accidents among Asian Sailors – A Review. In: Proceedings (eds. Gardner W, Saarni H). The (1st) International Symposium on Maritime Health, Turku, Finland, 5-9 June 1991.pp 202-208.

34. Ehara M, Muramatsu S, Sano Y, Takeda S, Hisamune S. The Tendency of Diseases among Seamen during the Last Fifteen Years in Japan. Industrial Health 2006; 44: 155-160.

35. Nguyen ST, Quynh CT. Diseases of seafarers in Vietnam – Preliminary report. Internat Marit Health 2004; 55: 53-59.

36. Dahl E. General practice at sea – Medical experiences from a world cruise. Tidsskr Nor Lægeforen 1979; 99 (6): 327-330.

37. Dahl E. Anatomy of a world cruise. J Travel Med 1999; 6: 168-171.

38. American College of Emergency Physicians. Health Care Guidelines for Cruise Medical
    Facilities 2002. www.acep.org/webportal/PracticeResources/ Accessed 18 January 2010.

39. Sandbekk OW. Dental health status and use of dental services among seamen in overseas
    trade (In Norwegian). Nor Tannlægeforen Tid 1977; 87 (6): 275-281.

40. Holltinen T, Saarni H, Murtomaa H, Pentti J, Alvesalo I. Seafaring: a risk for seamen’s oral
    health? Acta Odontol Scand 1995; 53 (5): 275-278.

41. DiGiovanna T, Rosen T, Forsett R, Sivertson K, Kelen GD. Shipboard medicine: A new
    niche for emergency medicine. Ann Emerg Med 1992; 21:1476-1479.

42. Bledsoe GH, Brill JD, Zak D, Guohua L. Injury and illness aboard an Antarctic cruise ship.
    Wilderness Environ Med 2007; 18: 36-40.

43. Peake DE, Gray CL, Ludwig MR, Hill CD. Descriptive epidemiology of injuries and illness
    among cruise ship passengers. Ann Emerg Med 1999; 33: 67-72.

44. Prina LD, Orazi UN, Weber RE. Evaluation of emergency air evacuations of critically ill
    patients from cruise ships. J Travel Med 2001; 8:285-292.

45. Valentic D, Stojanovic D, Micovic V, Vukelic M. Work related diseases and injuries on an
    oil rig. Internat Marit Health 2005; 56 (1-4): 56-66. 

46. Brooks A, Simpson AD. The initial approach to the emergency surgery patient. In: Emergency Surgey (ed. Brooks A et al.), BMJ Books, Wiley-Blackwell, UK 2010.

47. Palser T, Humes DJ, Brooks A. Acute appendicitis. In: Emergency Surgery (ed. Brooks A et
    al.), BMJ Books, Wiley-Blackwell, UK 2010.

48. Hammond JS. Acute upper gastrointestinal hemorrhage. In: Emergency Surgery (ed. Brooks A et al.), BMJ Books, Wiley-Blackwell, UK 2010.

49. McQuaid KR. Gastrointestinal disorders. In: Lange 2010 Current Medical Diagnosis and Treatment (ed. McPhee SJ, Papadakis MA). McGraw Hill, NY 2010.

50. Morris A, Midwinter MJ. Perforated peptic ulcer. In: Emergency Surgery (ed. Brooks A et al.), BMJ Books, Wiley-Blackwell, UK 2010.

51. Luke D, Bowley DM. Colonic diverticulosis. In: Emergency Surgery (ed. Brooks A et al.), BMJ Books, Wiley-Blackwell, UK 2010.

52. Fitzgerald JEF. Small bowel obstruction. In: Emergency Surgery (ed. Brooks A et al.), BMJ       Books, Wiley-Blackwell, UK 2010.

53. Dickson EJ, McKay CJ, Carter CR. Acute pancreatitis. In: Emergency Surgery (ed. Brooks A et al.), BMJ Books, Wiley-Blackwell, UK 2010.

54. Mouchtouri VA, Nichols G, Rachiotis G, Kremastinou J,Riemer T, Hadjichristodoulou C (for the SHIPSAN partnership). State of the art: Public health and passenger ships. Int Marit Health 2010; 61(2): 49-98

55. Neri AJ, Cramer EH, Vaughan GH, Vinje J, Mainzer HM. Passenger Behaviors During Norovirus Outbreaks on Cruise Ships. J Travel Med 2008; 15:172-176.

56. Nikolic N, Dahl E, Rooney R, deBernardis C. Acute Gastroenteritis at sea and outbreaks associated with cruises. In: Ericsson/Dupont/Steffen. Travelers’ Diarrhea. Second edition. BC Decker, Lewiston, NY 2008; chapter 14: 136-143.

57. Anon. Gastrointestinal disorders. In: The Merck Manual of Diagnosis and Therapy (ed. Beers MH et al.), 18th edition. Merck Research Laboratories, Whitehouse Station, NJ 2006.

58. WHO. Sanitation on ships. Compendium of outbreaks of foodborne and waterborne and Legionnaires’ disease associated with ships, 1970-2000. WHO/WSH/01.4; 2001.

59. Centers for Disease Control and Prevention . Vessel Sanitation Program Operations Manual 2005. Atlanta, GA: US Department of Health and Human Services, CDC, 2005 (www.cdc.org).

60. Cramer EH, Blanton CJ, Blanton LH, Vaughan GH, Bopp CA, Forney DL. Epidemiology of    Gastroenteritis on Cruise Ships, 2001-2004. AM J Prev Med 2006; 30 (3): 252-257.