A 55-year-old woman is evaluated in the emergency department for a 3-day history of diarrhea. She reports seven to eight stools daily without vomiting. She also notes abdominal cramping without vomiting and has been able to maintain adequate fluid intake. Medical history is significant for metastatic malignant melanoma, for which she recently completed the third of four planned doses of ipilimumab therapy. She has no history of inflammatory bowel disease, recent antibiotic use, recent travel, or consumption of uncooked foods. The remainder of the medical history is noncontributory, and she takes no other medications.
On physical examination, temperature is 37.5 °C (99.5 °F), blood pressure is 125/85 mm Hg, pulse rate is 90/min without orthostatic changes, and respiration rate is 14/min. The abdomen is soft and nontender with increased bowel sounds. The remainder of the physical examination is normal.
Hemoglobin | 12.2 g/dL (122 g/L) |
Leukocyte count | 9300/μL (9.3 × 109/L) with normal differential |
Alanine aminotransferase | 120 U/L |
Aspartate aminotransferase | 160 U/L |
Creatinine | 1.2 mg/dL (106.1 μmol/L) |
Fecal occult blood test | Negative |
A chest radiograph is normal and abdominal films show nondilated bowel loops with no free air.
In addition to discontinuing the ipilimumab and providing supportive care, which of the following is the most appropriate next step in treatment?