It's a stormy day, yet the ED is furiously busy. As you pick up your next patient's chart, you glance at the chief complaint—diarrhea. “Why would anyone come out on a day like this, for something like that?” you wonder. Then your eye catches the patient's age (60) and vital signs—temperature, 38.7°C (101.7°F); pulse, 124 beats per minute; respiratory rate, 24 breaths per minute; blood pressure, 102/50 mmHg. This man seems a bit sicker than the run-of-the-mill diarrhea patient. A quick glance into his room confirms your suspicion; he's pale, sweaty, ill-looking. He clearly needs help. But is an extensive work-up really going to be cost-effective—and won't it keep you from treating other patients in a timely manner? Besides, don't most of these cases run their course with a little help from fluids and symptomatic treatment?