Clinical Pearls on Infectious Diarrhea
Clinical Pearls on Infectious Diarrhea
A presentation on October 11, 2013, at the 2013 American College of Gastroenterology Annual Scientific Meeting by Christina M. Surawicz, MD, MACG (University of Washington), covering the session:
Surawizc CM. Infectious Diarrhea and Clostridium difficile Colitis: Underlying Mechanisms and Appropriate Therapy
Christina Surawicz, MD, lectured as part of the pathophysiology sequence that the ACG Scientific Meeting always includes, and these sessions usually have a research focus that generalists might find less useful. As such, Dr Surawicz’s discussion included plenty of research-oriented material on infectious diarrhea and C difficile colitis, but her session also included some very practical pearls—there’s a lot here for general internists, family physicians, and pediatricians.
Hydrate first and foremost: 75% of acute diarrhea is viral, and it’s rarely severe in adults. So this form of the disease doesn’t require antibiotics—supportive care is all that’s needed. The most important complication is dehydration, and Dr Surawicz provided a formula for a currently preferred oral rehydration solutions (ORS), based on rice cereal. Although she didn’t provide any research data on this in today’s lecture, Dr Surawicz referenced better results (improved survival in severe dehydration) with this new version of ORS. It has lower osmolarity (245) compared with the old standard (311), with less sugar and salt. The formula is simple and inexpensive: it’s just ½ cup rice cereal, ¼ teaspoon salt, and 2 cups of water, and in children and adults who are not vomiting, it can substitute for expensive intravenous fluids. She notes that salty snacks such as pretzels or crackers can be consumed with water to approximate an ORS; chicken broth is always a good choice, as are salty yogurt drinks (Indian-style lassi). She recommends against sports drinks, which are designed to replace sweat, not the fluid lost with diarrhea, and even more emphatically against sodas and coffee, which have zero osmolarity once sweetener is absorbed and metabolized and which can contain diuresis-inducing caffeine.
Does your patient have zinc deficiency? This is common in the third world—zinc is found in animal products such beef, seafood, and dairy, which are lacking in impoverished diets. The deficiency impairs immune response, disrupts intestinal mucosa, and impairs mucosal water and electrolyte transport—this worsens acute diarrheal illnesses and makes them more difficult to treat. While this is mainly a problem for third-world children and infants, Dr Surawicz recommends that we screen our patients with chronic diarrhea for zinc deficiency, especially those with inflammatory bowel disease, who malabsorb the mineral and lose it through their recurrent diarrhea. In third-world children with zinc deficiency, supplementing an ORS with zinc decreases the severity and duration of diarrhea. The dosage is 20 mg/d for 10 to 14 days in children older than 6 months, and 10 mg/d for infants under 6 months. It’s unclear whether this will become standard in the US, where zinc deficiency is much less common—but patients may ask about it, much as they did when zinc was proposed as beneficial for upper respiratory tract infections (on the basis of less compelling data).
When acute diarrhea isn’t viral, the most common US invasive bacteria are Campylobacter, Salmonella, Shigella, and Shiga toxin–producing Escherichia coli (STEC, ie, 0157:h7 and others). The diarrhea can be watery or bloody. These pathogens cause diarrhea two ways: through invasion and cellular destruction of the mucosa, and through cytotoxins. Salmonella penetrates the brush border and tight junctions, allowing access to the bloodstream and distant infection of bones, joints, and gallbladder.
Some clinical pearls:
Does your patient have bacterial or parasitic diarrhea? Who needs stool cultures? Dr Surawicz recommends stool cultures for all patients with bloody diarrhea, those with severe disease, those with diarrhea persisting longer than a week, those presenting in the context of an epidemic, those with immune deficiency or suppression, and those appearing toxic.
Who needs empiric antibiotics? Those with traveler’s diarrhea, which is usually caused by enterotoxigenic E coli (ETEC); those with suspected epidemic cholera; and those with suspected Giardia infestation (travel to an are where the organism is endemic with more than 10 days of diarrhea).
Which bacterial diarrheas should be treated with antibiotics? Always treat Shigella, severe Campylobacter, C difficile, and severe Salmonella (treatment of mild Salmonella may promote a carrier state). The research base is unclear on whether Yersinia, Aeromonas, Plesiomonas, and non-cholera Vibrios should be treated, but any pathogen should be treated in the immunosuppressed.
Antimotility agents: Data from the 1970s suggested they were dangerous, but more recently they have been shown to be safe in the setting of adult diarrhea (even for dystentery), decreasing the duration of illness. However, Dr Surawicz recommends avoiding them for children, for C difficile, and for severe dysentery.