Diarrhoea Flashcards
What time frame distinguishes acute and chronic diarrhea?
Diarrhea is the frequent (> 3 times per day) evacuation of liquid feces. Acute diarrhea is often self-limiting and lasts for a few days. Diarrhea is considered chronic when lasting > 3 weeks.
What is the most common cause worldwide of epidemic diarrhea?
Norovirus. These single-stranded RNA viruses are believed to be responsible for at least 50% of all gastroenteritis outbreaks worldwide and a major cause of foodborne illness. With the widespread use of rotavirus vaccination, norovirus has become the most common cause of medically attended acute gastroenteritis in children
What are other common causes of acute diarrhea?
- Viral (others include rotavirus, enterovirus)
- Bacterial (e.g ., Escherichia coli, Shigella, Salmonella, Yersinia, Campylobacter, Clostridium difficile )
- Protozoal
- Allergic
- Medication side effect (e.g., antibiotic usage)
- Extra-intestinal infections (e.g., respiratory, urinary, sepsis)
Which historical questions are key when seeking the cause of diarrhea?
- Recent medications, especially antibiotics
- History of immunosuppression (e.g., recurrent major infections, history of malnutrition, acquired immunodeficiency syndrome, immunosuppressive medications)
- Illnesses in other family members or close contacts
- Travel outside of the United States
- Travel to rural or seacoast areas (i.e., involving the consumption of untreated water, raw milk, or raw shellfish)
- Attendance in day care
- Recent foods particularly focus on juice and fructose consumption
- Presence of family pets
- Food preparation and water source
In what settings can diarrhea be a severe, life-threatening illness?
- Intussusception
- Salmonella gastroenteritis (neonatal or compromised host)
- Hemolytic-uremic syndrome
- Hirschsprung disease (with toxic megacolon)
- Pseudomembranous colitis (classically due to C. difficile )
- Inflammatory bowel disease (with toxic megacolon)
Why is true diarrhea during the first few days of life especially concerning?
In addition to the greater potential for dehydration in a newborn, diarrhea in this age group is more commonly associated with major congenital intestinal defects involving electrolyte transport (e.g., congenital sodium- or chloride-losing diarrhea), carbohydrate absorption (e.g., congenital lactase deficiency), immune-mediated defects (e.g., autoimmune enteropathy), or those characterized by villous blunting (e.g., microvillus inclusion disease). Although viral enteritis can occur in the nursery, any newborn with true diarrhea warrants thorough evaluation and possible referral to a tertiary center.
What are the most useful stool tests for diagnosing fat malabsorption?
Measurement of 72-hour fecal fat is the gold standard test for fat malabsorption. The patient must ingest a high-fat diet for 3 to 5 days (100 g daily for adults), and all stool is collected for the final 72 hours. A complete and accurate dietary history should be obtained concomitantly so the coefficient of fat absorption can be calculated. Steatorrhea is present if more than 7% of dietary fat is malabsorbed. In normal infants, up to 15% of fat can be malabsorbed. Other tests include Sudan staining of stool for fat globules (a qualitative test that, if positive, indicates gross steatorrhea), the steatocrit, and monitoring absorbed lipids after a standardized meal.
What stool test is most useful for helping diagnose GI protein loss?
Fecal α 1 -antitrypsin measurement is the most useful stool marker of protein malabsorption. It is important to concomitantly measure serum α 1 -antitrypsin to ensure that the patient does not have α 1 -antitrypsin deficiency, which could result in a false-negative stool study.
How do patterns of secretory or enterotoxigenic and inflammatory diarrhea vary?
Secretory or enterotoxigenic disease is characterized by watery diarrhea and the absence of fecal leukocytes. Inflammatory disease is characterized by dysentery (i.e., symptoms and bloody stools), as well as fecal leukocytes and red blood cells.
What is the primary pathophysiologic difference between secretory and osmotic diarrhea?
In osmotic diarrhea , undigested nutrients increase the osmotic load in the distal small intestine and the colon leading to decreased water absorption. In secretory diarrhea , a noxious agent causes the intestinal epithelium to secrete excessive water and electrolytes into the lumen.
How can osmotic diarrhea be distinguished from secretory diarrhea?
In true osmotic diarrhea, symptoms should cease when the patient is made NPO. In addition, a fecal osmotic gap can be calculated. In osmotic diarrhea, the fecal electrolyte content becomes lower than the serum. Stool electrolytes should be collected and compared with a normal serum osmolality, 290 mOsm/kg. The fecal osmotic gap is [290 − 2(Na + K)].
How should children with secretory diarrhea be managed?
After the child is taken off feeds, a vigorous attempt must be initiated to maintain fluid and electrolyte balance. If this is successful, the child should be evaluated for proximal small bowel damage, enteric pathogens, and a baseline malabsorption workup. If abnormalities of the mucosal integrity are suspected, a small bowel biopsy is performed; if the findings are significantly abnormal, the patient may be given parenteral alimentation and gradual refeeding. Electron microscopy may reveal congenital abnormalities of the microvillus membrane and the brush border. Hormonal causes of secretory diarrhea (e.g., a VIPoma, hypergastrinoma, or carcinoid syndrome) must be considered if initial studies are negative
What rare tumors can cause true secretory diarrhea?
- Gastrinoma : Children present with typical ulcer pain, hematemesis, vomiting, and melena. High acid output into the proximal small bowel leads to precipitation of bile salts and steatorrhea.
- VIPoma: Children present with profuse watery diarrhea with marked fecal losses (20 to 50 mL/kg/day) due to high levels of vasoactive intestinal peptide (VIP).
What features characterize “toddler diarrhea”?
Toddler diarrhea , which is also known as chronic nonspecific diarrhea , is a clinical entity of unclear etiology that occurs in infants between 6 and 40 months of age, often following a distinct identifiable enteritis and treatment with an antibiotic. Loose, nonbloody stools (at least two per day but usually more) occur without associated symptoms of fever, pain, or growth failure. Malabsorption is not a key feature.
What is primary lactose intolerance?
In more than 50% of the population, beginning at the age of 5 years, lactase levels decline progressively after having been normal in infancy. These levels decline at different rates for different people depending on their genetics. Most adults with primary lactose intolerance have lactase levels of about 10% of those seen during infancy. Symptoms of lactose intolerance (e.g., bloating, nausea, cramps, diarrhea after dairy foods) may develop if excessive lactose loads are ingested.
