What is your approach to working up diarrhea in an immunocompromised patient?

Tough question and very common in clinical and research management. The approach is going to mirror any new complaint and start with a history. Diarrhea means many things to many patients/clinical trial subjects, so characterizing duration, frequency in a day, nocturnal events (diarrhea that occurs during sleep is almost always pathologic), and associated symptoms/signs such as blood, fever, abdominal pain, weight loss, nausea and vomiting (to name a few) are all critical to the next step. Short-lived diarrhea after attending a picnic is going to have a different approach than progressive diarrhea with worsening weight loss. I next review the past history as some of our disease states, such as the spondyloarthropathies, as well as SLE, have...