Gastroenteritis

recommended for those who have complicated diverticulitis after resolution of their symptoms. This is because an immediate reanastomosis can be performed.

GASTROENTERITIS

Gastroenteritis represents some type of inflammation of the stomach, small and large intestinal linings. The majority of these will be infectious process, although drugs and toxins can lead to similar symptoms. Most of the causes will spread from the fecal-oral route, waterborne infectious organisms, or foodborne infectious organisms. Typical symptoms include nausea, vomiting, anorexia, vague abdominal pain, and diarrhea. This is usually a self-limited disease with fluid losses minimal and well-tolerated in the healthy person. It becomes more difficult and problematic for the very young or very old person, or in those who are immunosuppressed.

The most common organisms are viruses, bacteria, or parasites. The most common virus infections of the GI tract are the norovirus and rotavirus infections. Viruses by themselves cause most cases of gastroenteritis. The viruses enter the enterocytes of the intestines, affecting carbohydrate absorption. The diarrhea will be watery without white blood cells or red blood cells in the feces.

Norovirus is the main cause of gastroenteritis in adults but it can be seen in children as well. It is mainly seen in the winter months and is now more common in children because of rotavirus vaccinations given to babies. This can be a waterborne or foodborne infection and it is highly contagious in crowded facilities. It takes 24 to 48 hours before the symptoms become apparent.

Rotavirus infections remain the most common infectious causes of gastroenteritis in young kids throughout the world but the incidence has dramatically decreased in the US because of vaccinations against the virus given to babies. It is highly contagious and passed through the fecal-oral route. It can also affect adults with an incubation period of 1 to 3 days. It is usually seen in the winter months.

Less common causes of viral gastroenteritis include astrovirus, which is seen in all ages with a 3 to 4-day incubation period. Adenoviruses can also cause infectious diarrhea in

the summertime, also through the fecal-oral route. Enterovirus and cytomegalovirus can cause gastroenteritis in immunosuppressed patients.

There are many causes of bacterial gastroenteritis, including Campylobacter, Salmonella, Shigella, E. coli type O157:H7, and Clostridium difficile. The infection can develop because of enterotoxins, which adhere to the mucosa and block intestinal absorption of nutrients. Look for an enterotoxin being the cause in C. difficile infections, E coli infections, and Vibrio cholerae gastroenteritis. The person will have watery diarrhea as a result.

Other bacteria will produce exotoxins, such as Staphylococcus aureus and Clostridium perfringens. The infection itself does not have to be present; the presence of the toxin is enough to cause the symptoms. The disease is usually foodborne and things like nausea, vomiting, and diarrhea are seen within 12 hours of the toxin ingestion. It resolves spontaneously.

Those bacteria that cause disease through mucosal invasion include Campylobacter, Salmonella, Shigella, C. difficile, and some E. coli infections. There will be ulceration of the mucosa with GI bleeding and bloody diarrhea. The stool will show WBCs and RBCs in the sample. It can be transmitted in several different ways, usually from undercooked poultry, unpasteurized milk, animal-borne disease, undercooked eggs and unwashed vegetables in certain parts of the world.

E. coli represents a unique case because there are many subtypes that can cause gastroenteritis, with differing symptoms. Enterohemorrhagic E. coli is the strain called O157:H7. It is the most common subtype and comes from unpasteurized milk or juice, undercooked ground beef, and contaminated water sources. It can be passed through the fecal-oral route or through water exposure in contaminated bodies of water. Hemolytic-uremic syndrome can develop as a complication in up to 10 percent of cases.

Other E. coli subtypes include enterotoxigenic infections, which cause disease because of toxins. It commonly causes traveler’s diarrhea. Enteropathogenic E. coli leads to watery diarrhea and is seen in nurseries. Enteroinvasive E. coli infections are seen in the developing parts of the world and may lead to bloody or non-bloody diarrhea.

Enteroaggregative E. coli is a milder type of gastroenteritis, which can be a cause of lingering traveler’s diarrhea.

Clostridium difficile used to be causative mainly of hospital-based infections. In the last 20 years, however, a community-acquired strain called the NAP1 strain is in the environment, leading to the most common bacterial cause of diarrhea in the United States. It occurs outside of the hospital setting.

Less common causes of bacterial gastroenteritis include Yersinia enterocolitica, Vibrio cholerae, Vibrio parahaemolyticus, and listeria infections. Aeromonas infections come from brackish water that is consumed or swam in. Plesiomonas infections happen when eating raw shellfish in tropical parts of the world.

Parasitic infections usually involve Giardia or Cryptosporidium infections. Giardia can adhere to the intestinal mucosa, leading to typical gastroenteritis infection symptoms plus generalized malaise. It can be an acute or chronic infection that leads to malabsorption. It can be passed through the fecal-oral route or through drinking contaminated water. Cryptosporidium infections are self-limited in the healthy host and comes from drinking contaminated water. It can be gotten in swimming pools because it doesn’t kill easily through chlorination. Amoebiasis is common in developing countries but not in the US.

Look for a sudden onset of typical symptoms in all cases of gastroenteritis, although some will lead to myalgias, malaise, and prostration. Muscle guarding can be present. Bowel sounds will be hyperactive. Look out for dehydration, which can lead to renal failure, shock, and cardiovascular collapse. Metabolic acidosis is seen with diarrhea, while metabolic alkalosis is seen with prominent symptoms of vomiting. Vomiting and diarrhea both can cause hypokalemia.

Test the patient with stool testing, particularly if the diarrhea is bloody. Stool cultures can be done as well as a stool analysis for WBCs and RBCs. If there has been an outbreak, recent travel, or ingestion of possibly contaminated food or water, suspect gastroenteritis rather than something like appendicitis or ulcerative colitis. There now exists multiplex polymerase chain reaction testing that can get at the causative organism

but these are expensive to do if you don’t have a strong suspicion of one organism over another.

The CBC will be nonspecific but you should get serum electrolytes and kidney function studies. Obtain an acid-base status in the very sick patient. Eosinophilia in the blood points to a parasitic disease process. Kidney function testing can detect hemolyticuremic syndrome in its early stages.

The treatment is supportive in the majority of cases. Rest and oral glucose plus electrolyte solutions can be helpful to treat mild dehydration. If there is more severe infection involved, consider IV fluid replacement. Children become more easily dehydrated than adults. Antidiarrheal agents should not be used for bloody diarrhea but can be used in watery diarrhea. Loperamide is the treatment of choice for diarrhea. Prochlorperazine and promethazine are used for vomiting but they can cause dystonia in some children. Ondansetron is safe and effective for kids. Probiotics are not effective but may shorten the course of the disease symptoms.

Antimicrobial agents are used for some cases of traveler’s diarrhea, or when you suspect Shigella or Campylobacter infections. You should otherwise withhold antibiotics until you have a known agent. Antibiotics will increase the risk of hemolytic-uremic syndrome in E coli infections so they are not often used. Salmonella infections are not aided by antimicrobial agents and antibiotics do not help with toxic infections, such as Staphylococcus aureus or Clostridium perfringens infections. The treatment of choice for Clostridium difficile infections is vancomycin. Stop any contributory antibiotics. Giardiasis is treated with metronidazole or nitazoxanide, while cryptosporidiosis is treated primarily with nitazoxanide.