Key Clinical Updates in Diarrhea
Immune checkpoint inhibitor therapy for malignancies may cause mild to severe GI side effects in 8–27% of patients.
Patients with severe diarrhea or dysentery and a known history of IBD or prior immune checkpoint inhibitor therapy require expedited evaluation with stool studies and possible sigmoidoscopy or colonoscopy with biopsy to exclude infection prior to therapy with intravenous corticosteroids.
Shiga-toxin–producing Escherichia coli infection should not be treated with antibiotics due to an increased risk of hemolytic-uremic syndrome, especially in children.
Dougan M et al. Gastroenterology. [PMID: 33080231]
Siciliano V et al. Rev Recent Clin Trials. [PMID: 32598272]
Elevated fasting levels (> 48 ng/mL) of the bile acid precursor 7aC4 are strongly predictive of bile acid diarrhea.
Borup C et al. Am J Gastroenterol. [PMID: 32740083]
Diarrhea can range in severity from an acute self-limited episode to a severe, life-threatening illness. To properly evaluate the complaint, the clinician must determine the patient’s normal bowel pattern and the nature of the current symptoms.
Approximately 10 L/day of fluid enter the duodenum of which all but 1.5 L/day are absorbed by the small intestine. The colon absorbs most of the remaining fluid, with less than 200 mL/day lost in the stool. Although diarrhea sometimes is defined as a stool weight of more than 200–300 g/24 hours, quantification of stool weight is necessary only in some patients with chronic diarrhea. In most cases, the physician’s working definition of diarrhea is increased stool frequency (more than three bowel movements per day) or liquidity of feces.
The causes of diarrhea are myriad. In clinical practice, it is helpful to distinguish acute from chronic diarrhea, as the evaluation and treatment are entirely different (Tables 15–5 and 15–6).
Table 15–5.Causes of acute infectious diarrhea. ||Download (.pdf) Table 15–5. Causes of acute infectious diarrhea.
|Noninflammatory Diarrhea ||Inflammatory Diarrhea |
Noroviruses, astrovirus, adenovirus, rotavirus, sapovirus, SARS-CoV-2
1. Preformed enterotoxin production
2. Enterotoxin production
Enterotoxigenic Escherichia coli (ETEC)
Vibrio cholerae, Vibrio vulnificus
1. Cytotoxin production
Enterohemorrhagic E coli O157:H5 and O157:H7 (EHEC)
2. Mucosal invasion
Enteroinvasive E coli (EIEC)
3. Infectious proctitis
Table 15–6.Causes of chronic diarrhea. ||Download (.pdf) Table 15–6. Causes of chronic diarrhea.
CLUES: Stool volume decreases with fasting; increased stool osmotic gap
Medications: antacids, lactulose, sorbitol
Disaccharidase deficiency: lactose intolerance
Factitious diarrhea: magnesium (antacids, laxatives)
CLUES: Large volume (> 1 L/day); little change with fasting; normal stool osmotic gap
Hormonally mediated: VIPoma, carcinoid, medullary carcinoma of thyroid (calcitonin), ...