Diarrhea (Case 24)
David Rudolph DO and James Thornton MD
Case: A 22-year-old man was referred to gastroenterology with intractable bloody diarrhea. His past medical history was unremarkable until last month, when he first noted the development of crampy abdominal pain, multiple daily bloody, mucus-filled stools, rectal urgency, and tenesmus. He also reported progressive fatigue, intermittent light-headedness, diminished appetite, and a subsequent 7-lb weight loss since symptom onset. He initially didn’t seek medical attention, because he thought the symptoms would just go away and, frankly, “just didn’t want to describe it to anyone.” He denied any recent travel, antibiotic use, close sick contacts, or high-risk sexual behaviors. On physical examination, he was somewhat ill-appearing with conjunctival pallor. Left lower quadrant abdominal tenderness was elicited with deep palpation, but no rebound or guarding was detected. The remainder of his physical examination was unremarkable.
Differential Diagnosis
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Infectious diarrhea
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Inflammatory bowel disease (IBD)
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IBS, functional diarrhea
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Malabsorption
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Ischemic colitis
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Speaking Intelligently
When we encounter a patient with diarrhea, our investigation always begins with a thorough history and physical examination. The differential diagnosis for diarrhea is extremely broad, but by asking appropriate questions we can usually narrow the differential considerably. In addition, a complete physical examination helps differentiate which patients are currently stable and which patients are in need of more urgent medical attention. Volume depletion, a common sequela of secretory diarrhea, will be manifested by dry mucous membranes, poor skin turgor, and, if severe, tachycardia and hypotension. Anemia, a potential consequence of inflammatory diarrhea, should be suspected in the patient with diffuse pallor, fatigue, light-headedness, and exertional dyspnea.
• Determine the duration of the diarrhea. Acute diarrhea is typically defined as lasting ≤14 days and is often due to infections with viruses or bacteria. Chronic diarrhea is a decrease in fecal consistency and an increase in frequency lasting for 4 or more weeks and has a much broader differential diagnosis.
• Patients with sudden onset of watery diarrhea who provide a history of recent travel, close sick contacts, or ingestion of suspicious foods can be presumed to have acute infectious diarrhea, which is usually self-limited and often (in the absence of clinical volume depletion) requires no further workup or treatment.
• Pus or blood in the stools should alert the clinician to an invasive infectious or inflammatory etiology, which necessitates further workup. In this instance, initial evaluation should include checking stools for routine culture, leukocytes, and occult blood and, in the appropriate clinical setting, performing a Clostridium difficile assay and examination for ova and parasites.
• Oily, foul-smelling stools that float are suggestive of steatorrhea. Workup for disorders of malabsorption or maldigestion should be undertaken in patients who present with steatorrhea.
• Patients with clinical evidence of volume depletion and/or symptomatic anemia should be admitted to the hospital for IV fluid resuscitation and/or transfusion of packed RBCs.
• Factitious diarrhea, often secondary to surreptitious laxative use, should be considered in patients with chronic diarrhea with no identifiable etiology after extensive workup.
• A detailed history should include the duration of the diarrhea, the frequency and volume of stools, as well as associated symptoms (abdominal pain, vomiting, fever, myalgias, arthralgias, rash, diminished appetite, weight loss).
• Ask patients about any recent travel history, close sick contacts, day care exposures, or ingestion of undercooked foods. Recent antibiotic use is suggestive of C. difficile infection.
• Diarrhea that awakens a patient from sleep is worrisome for a pathologic etiology. Patients with IBS are much less likely to report a history of nocturnal symptoms.
• The presence of blood or mucus in stools suggests an inflammatory or invasive infectious etiology. Large-volume watery stools are consistent with secretory diarrhea. Oily, foul-smelling stools that float are suggestive of fat malabsorption or maldigestion.
• Ask patients about a family history of IBD, lactose intolerance, celiac disease, or other malabsorption syndromes.
• Inquire about any other significant medical history. Disordered motility can result from uncontrolled hyperthyroidism or long-standing diabetes mellitus.
• Review current prescribed and over-the-counter medications. Diarrhea can be precipitated by a multitude of commonly used medications including selective serotonin re-uptake inhibitors, colchicine, metoclopramide, antibiotics, laxatives, magnesium-containing antacids, NSAIDs, antiarrhythmics, and antihypertensive agents.
• Review surgical history. Short-bowel syndrome can result in patients who have undergone previous bowel resections. Bile salt diarrhea can occur in patients who have undergone ileal resection.
• Dry mucous membranes, sunken eyes, poor skin turgor, tachycardia, and orthostatic hypotension are signs concerning for volume depletion. Pallor is suggestive of anemia.
• Oral aphthous ulcers or episcleritis may be seen in patients with IBD.
• Close attention should be paid to the dermatologic examination. Erythema nodosum or pyoderma gangrenosum suggests underlying IBD. Dermatitis herpetiformis is suggestive of celiac disease.
• Abdominal examination should include inspection for surgical scars, palpation to assess for tenderness, masses, and/or hepatosplenomegaly, and auscultation for bowel sounds and abdominal bruits.
• Perianal fissures, fistulas, or abscesses provide support for a diagnosis of Crohn disease.
• Visible blood or pus on digital rectal examination (DRE) suggests an inflammatory or invasive infectious etiology.
• Palpable mass on DRE should raise suspicion for rectal neoplasm or fecal impaction.
• Fecal incontinence should be excluded with evaluation of anal sphincter tone to assess sphincter competence.
• Thyromegaly, exophthalmos, fine resting tremor, and hyperactive reflexes suggest uncontrolled hyperthyroidism.
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• Diagnostic testing is NOT indicated for most patients with acute diarrhea, as the disease process is usually self-limited.
Diagnostic evaluation is indicated when any of the following are present: profound volume depletion, fever (temperature ≥ 38.5° C), blood or pus in stools, severe abdominal pain, and/or symptoms lasting ≥48 hours. Those patients who are hospitalized, 70 years of age or older, immunosuppressed, or who have recently used antibiotics also warrant further evaluation.
• CBC with differential should be obtained. Leukocytosis is suggestive of an infectious or inflammatory etiology.
Anemia may be present in patients with chronic inflammatory diarrhea or a colonic neoplasm.
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$11
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• CMP may reveal electrolyte derangements, azotemia, or hypoalbuminemia.
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$12
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• Elevated erythrocyte sedimentation rate and C-reactive protein levels are suggestive of inflammation.
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$11
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• Thyroid function tests may detect hyperthyroidism.
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$24
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• Fecal leukocytes and occult blood help differentiate inflammatory vs. noninflammatory diarrhea.
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$11
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• Routine stool cultures identify the most common pathogens, including Salmonella, Shigella, and Campylobacter. Clinical history often dictates the need for testing for less common pathogens.
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$13
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• C. difficile toxin assay, or another test to evaluate for C. difficile infection, should be checked in those patients who report a history of antibiotic use within the past 3 months.
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$16
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• Ova and parasites should be checked in immunocompromised patients, travelers, men who have sex with men, or in patients with exposure to day care facilities.
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$13
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• Endoscopic evaluation (flexible sigmoidoscopy or colonoscopy
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