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 .
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.
Supportive treatment for abdominal pain
- 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 .
- Antiemetics in case of nausea caused by ship movements, medication (morphine) or the GI condtion itself. Metoclopramid can be given by rectum, im and iv, while Promethazine should not be given intravenously.
- If thirsty and not nauseated: clear fluids/water; otherwise nothing by mouth.
- 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 >37.7oC/100oF), 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 Bleeding
Acute severe 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 taking 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.
Upper GI bleeding
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 varices 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 (esophagitis), vascular malformations or an underlying cancer.
The other important cause of upper GI bleeding is bleeding from esophageal or stomach varices, 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 .
At sea prior to evacuation: strict bed rest, stop all medications that can contribute to bleeding, and monitor pulse rate and blood pressure hourly:
A systolic blood pressure 100 beats/min and blood pressure > 100 mm Hg means moderate acute blood loss .
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 cannulae (venflons);
- try acid suppression: High dose proton pump inhibitors (e.g. omeprazole 40 mg twice a day by mouth, or - if available - 80 mg iv[jc1] ).
Lower GI bleeding
Lower GI bleeding is defined as arising from the bowels distal of the duodenum (95% comes 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 (49).
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 (thrombozed) hemorroids, proper analgesia should be given and reduction attempted (by gently compressing the prolapsed tissue and pushing it back inside the anal channel).
Before next seafarer contract GI bleeding episodes must be properly investigated, and when anorectal disease is suspected, anorectoscopy should be done to rule out cancer and to avoid re-bleeding at sea.
GI conditions causing acute abdominal pain
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.
- 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 esophageus 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.
Gastroesophageal reflux disease
Gastroesophageal 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.
Relief is often achieved by taking antacids or baking soda. Against symptoms at night: Sleep with the head end of the bed elevated (See above: 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).
Gastritis and gastric and duodenal ulcers
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 . 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 .
See Upper GI bleeding.
Perforated peptic ulcer
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.
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 nasogastric 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 (51).
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).
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.
Acute 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 37.7o -38.3oC / 100o-101oF), 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), torsion of 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 .
Bedrest in Fowler’s position (= elevated upper body, both hips and knees bent, and body turned to the right).
- 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
Diverticulosis and diverticulitis
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 .
Small localized perforations may cause localized abscesses and focal pain, while large perforations can present with peritonitis or sepsis and can be life-threatening.
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 .
Mechanical bowel obstruction / Ileus
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 .
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). Nasogastric 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 a 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 the 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.
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 sitz 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 sitz 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.
Anorectal abscess is a localized collection of pus near anus. Symptoms are local pain, swelling, redness, and often fever.
Treatment of superficial abscesses is incision and drainage, which is simple when ‘the abcess 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, anorectal abscesses may be the first sign of more serious conditions, like immunodeficits, 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.
Liver, gallbladder and pancreatic conditions
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.
Jaundiced seafarers with or without abdominal pain should be signed off for expert evaluation in the next port.
Gallstones and acute infection of the gallbladder (cholecystitis)
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.
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 consultation – 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 is often a serious condition that requires medevac
The condition is easily confused with other acute abdominal pain conditions and cannot 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 .
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.
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!
Diarrhea / Acute Gastroenteritis
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 . 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 foodborne or waterborne 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 . 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 . 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.
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, cholecystis, 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 (yougurt with a ctive cultures), is generally safe and can relieve symptoms.
Antimotility 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 ) .
Proper procedures for handling and preparing food and beverages must be followed, and seafarers should avoid potentially contaminated food (‘peel it, cook it or leave it’) and drink carbonated beverages without ice cubes served in sealed bottles. Hot buffets, fast food restaurants and street vendor food pose an increased risk.
Outbreaks of acute gastroenteritis on cruise ships
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 . 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 . 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  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 .
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 . 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 .
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 . 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.  for a European view of public health and passengers ships.