A 30-year-old man presents to the emergency department with diarrhea. He states he has had profuse, watery diarrhea for the past 24 hours. He notes that eating and drinking make him defecate more, thus he has been refraining from drinking. He is otherwise healthy and takes no medications. His temperature is 97.7°F (36.5°C), blood pressure is 84/64 mmHg, pulse is 130/min, respirations are 17/min, and oxygen saturation is 99% on room air. Physical exam reveals dry mucous membranes with an otherwise benign exam. The patient is given 1L of normal saline and drinks 1L of oral fluids. His blood pressure is subsequently 120/70 mmHg and pulse 95/min. Which of the following is the most appropriate next step in management?
Stool PCR
Ciprofloxacin
Stool ova and parasite study
Rest and oral rehydration
Rest and oral rehydration
This patient is presenting with a likely diarrheal illness given he has profuse, watery diarrhea and his vitals normalized with oral and IV hydration. Since the patient is young and healthy, oral hydration and rest are all that is needed for management.

Diarrheal illness is a common chief complaint with variable workups pending on the patient's clinical status. Young, healthy, non-immunosuppressed patients who can tolerate an oral diet require only reassurance and oral hydration, as most cases of viral and bacterial diarrhea will resolve on their own. Moreover, most cases of diarrhea are caused by viral etiologies which simply require supportive therapy. This is even true in bacterial diarrhea as long as the patient's vitals normalize and they can tolerate an oral diet. It is important to consider inflammatory causes of diarrhea (such as ulcerative colitis or Crohn disease) as this would change the workup and management.

Schiller et al. discuss different types of diarrhea. They review the management and diagnosis of diarrhea and its different forms, including chronic forms. They recommend noting the difference between different causes and working up and treating them appropriately.

Incorrect Answers:
Answer A: Ciprofloxacin is an antibiotic that can be used for bacterial/infectious diarrhea. It should not be given in young, healthy patients and would only be indicated in the setting of bacterial diarrhea in ill patients, patients with persistent symptoms, or patients who are immunosuppressed. Bacterial diarrhea would present with fever, abdominal pain, and bloody/purulent diarrhea.

Answer C: Stool culture should not be empirically performed in young, well-appearing patients. It may be performed in hospitalized patients who are more ill or in patients who are going to start antibiotic therapy. It may also be performed in patients with persistent diarrhea.

Answer D: A stool ova and parasite study would not be performed unless there was a suggestive history or exposure (such as drinking unfiltered water) in the setting of fatty, foul-smelling diarrhea. This would raise suspicion for Giardia lamblia which would be treated with metronidazole.

Answer E: Stool PCR for viral etiologies of diarrhea is not useful as the management of viral diarrhea is supportive therapy in most cases. On occasion, it may be performed in critically ill patients to determine the etiology of their symptoms. It should not be performed routinely.

Bullet Summary:
Healthy patients with limited diarrheal illness require supportive therapy only (in particular, oral hydration) and do not need more invasive diagnostic tests.