A 24-year-old woman comes to the office due to a 6-week history of abdominal cramps, loose stool, and bloating. The patient has 4 or 5 watery, foul-smelling stools each day and night. She has also lost 2.5 kg (5.5 lb). The patient has had no fever, vomiting, or blood in the stools. She has no prior medical problems and takes no medications. The patient works in a day care center and has not traveled recently. Temperature is 37.1 C (98.8 F), blood pressure is 110/72 mm Hg, and pulse is 80/min. The abdomen is soft with active bowel sounds and mild distention; there is no tenderness. The remainder of the examination shows no abnormalities. Which of the following is the most appropriate next step in management of this patient?
Giardiasis | |
Risk factors |
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Pathogenesis |
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Clinical features |
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Diagnosis |
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Treatment |
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CF = cystic fibrosis; CVID = common variable immunodeficiency. | |
This patient has chronic diarrhea, which can be due to either a functional disorder (eg, irritable bowel syndrome) or an organic disorder (eg, inflammatory bowel disease [IBD], malabsorptive disease, chronic infection).
An organic cause should be suspected when any of the following features are present:
Because this patient has weight loss and episodes of diarrhea overnight, she requires further work-up for organic pathology, including malabsorptive conditions (eg, celiac disease) and chronic infections (eg, Giardia, Cryptosporidium) (Choice C). An organic inflammatory disorder is less likely given her lack of fever or bloody stools.
This patient's exposure to a day care setting raises concern for infections that can be transmitted fecal-orally and cause chronic symptoms, such as giardiasis. Giardia is a protozoan parasite that classically presents with prolonged, foul-smelling, oily, nonbloody stools due to malabsorption and bloating/flatulence, as seen in this patient. Most cases resolve within a month, but some patients may develop chronic symptoms, leading to weight loss and vitamin deficiencies (eg, B12). The preferred test for giardiasis is a stool antigen assay (direct immunofluorescence, enzyme-linked immunosorbent assay) or PCR; stool microscopy can identify Giardia oocysts and trophozoites but is less sensitive.
(Choices A and B) Initial evaluation of patients with chronic diarrhea is typically noninvasive (eg, stool studies). Acutely worsening or progressive abdominal pain, not seen in this patient, often warrants CT scan of the abdomen, which may identify conditions such as malignancy or mesenteric ischemia; colonoscopy is typically warranted in patients with rectal bleeding or signs of systemic inflammation concerning for malignancy or IBD. This otherwise healthy patient has watery stools and a benign abdominal examination.
(Choice E) Bacterial enteropathogens typically cause acute diarrhea; chronic infection rarely occurs in otherwise healthy, immunocompetent patients, and this woman's lack of abdominal tenderness and fever makes bacterial gastroenteritis unlikely and stool culture unnecessary. Giardia is a parasite that does not grow on culture.
Educational objective:
Chronic diarrhea due to organic causes should be suspected when there are nocturnal symptoms, systemic findings, or rectal bleeding. Patients with chronic giardiasis often have risk factors for exposure (eg, day care setting), weight loss, and foul-smelling, oily, nonbloody stools. Diagnosis is with stool antigen or PCR testing.