An 84-year-old man with Parkinson disease presented to the emergency department with a 10-day history of watery, nonbloody diarrhea. He reported about 15-20 bowel movements per day, accompanied by urgency, episodes of incontinence and nocturnal diarrhea, but no pain. He reported substantial weakness and light-headedness when moving from lying to sitting or standing. He had no fever, vomiting or nausea, and no risk factors for infectious diarrhea (e.g., recent antibiotic use, sick contacts, travel history, relevant food exposures).
The patient's symptoms began within 24 hours of his first dose of entacapone, an inhibitor of catechol-O-methyltransferase used in patients with Parkinson disease to inhibit the peripheral metabolism of levodopa. His neurologist had prescribed entacapone several years earlier, but the patient had developed diarrhea during therapy and the drug was stopped, with symptom resolution within days. In contrast, during this second trial of treatment, the patient took only 1 dose and diarrhea persisted for 10 days before his presentation to the emergency department.
On examination, the patient appeared hypovolemic, with flat jugular veins, a blood pressure of 110/70 mm Hg and a postural increase in heart rate of 32 beats/min. His abdomen was soft, with no notable tenderness or signs of peritonitis but hyperactive bowel sounds. Examination was otherwise unremarkable, except for features of Parkinsonism.
Blood tests showed a normal complete blood count and C-reactive protein level, severe hypokalemia at 1.8 (normal 3.5-5) mmol/L and mild renal insufficiency (creatinine 135 [normal 62-106] mol/L, urea 7 [normal 2.5-10.7] mmol/L). At this point, the differential diagnosis for acute diarrhea included infectious or ischemic colitis, as well as an adverse drug reaction. An assay for Clostridium difficile toxin and cultures from stool samples were negative. To rule out a surgical cause for his presentation, the emergency department team ordered a computed tomography scan of the abdomen, which showed a fluid-filled colon with no bowel wall edema or stranding (Figure 1). The patient received fluid and electrolytes and was admitted to our general internal medicine service.
To provide symptomatic relief, we prescribed maximum doses of antidiarrheal and antisecretory medications (loperamide and octreotide) for 1 week while he waited for inpatient colonoscopy. He did not respond to these treatments.
Colonoscopy showed a mildly edematous right colon, with no other abnormalities. The results of colonic biopsy specimens were available 2 days after colonoscopy; they showed prominent lymphoplasmacytic infiltrates with intraepithelial lymphocytosis and focal acute inflammation, but no notable architectural distortion, granulomas or thickening of the subepithelial collagen band (Figure 2).
We diagnosed lymphocytic colitis and treated the patient with oral budesonide (9 mg/d). Within 24 hours, his bowel movements decreased to about 2 per day, and he was discharged shortly thereafter. Unfortunately, however, owing to his Parkinson disease, the patient fell a month after discharge and subsequently died.
Discussion
Acute-onset diarrhea (i.e., < 2 wk duration) is a common presenting complaint to the emergency department, with a wide differential diagnosis including infection, ischemia and adverse drug reactions.1 When stool studies are negative for infectious causes, endoscopic evaluation may...