Chronic Diarrhea: Diagnosis and Management

Lawrence R. Schiller; Darrell S. Pardi; Joseph H. Sellin


Clin Gastroenterol Hepatol. 2017;15(2):182-193. 

In This Article

How Can Symptom Clusters and Settings Focus the Differential Diagnosis?


3. Consider comorbid symptoms and epidemiologic clues when constructing a differential diagnosis. (2c)

The main distinction in patients with chronic diarrhea is between functional and organic etiologies. The functional category includes irritable bowel syndrome (IBS), when abdominal pain accompanies the diarrhea, and functional diarrhea, when abdominal pain is absent.[3] IBS can be prospectively characterized by symptoms such as those defined by the Rome IV criteria (recurrent abdominal pain at least 3 days per month in the last 3 months, associated with a change in stool frequency or form, and improvement with defecation).[3] Functional diarrhea is defined as similar stool changes without prominent pain.[3] However, many patients with organic causes of chronic diarrhea such as microscopic colitis often fulfill these criteria.[5] Therefore, these criteria are not sufficiently specific to rule out organic etiologies. However, for patients with relatively mild symptoms and no alarm features such as gastrointestinal (GI) bleeding, fevers, or significant weight loss, those meeting the Rome IV criteria for IBS or functional diarrhea can be managed with empiric therapy. If empiric therapy fails, then further diagnostic testing may be considered.

Other symptom clusters can also be helpful in suggesting a specific diagnosis. Significant abdominal pain, fever, or GI bleeding suggests an inflammatory cause for diarrhea. Gas and bloating suggest carbohydrate malabsorption. Substantial weight loss suggests malabsorption, maldigestion, or a malignancy (particularly in an older person). Fatigue and night sweats suggest lymphoma, whereas anemia or change in stool caliber suggests colorectal malignancy. The positive predictive values of these symptoms for the underlying problems causing chronic diarrhea are unknown but likely are low. Physical findings can indicate the impact of diarrhea on nutrition and sometimes suggest a specific diagnosis (Supplementary Table 1).

The characteristics of the stool also help. Small, frequent bowel movements with tenesmus and bleeding suggest proctitis, whereas larger volume, less frequent stools suggest a small bowel source of diarrhea. Steatorrhea indicates either fat maldigestion or malabsorption.

Epidemiologic associations and patient characteristics also help limit the differential diagnosis[6] (Supplementary Table 2). Immunosuppressed patients with human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome are at increased risk for common and uncommon, opportunistic infections. Recent travelers and migrants from endemic areas with chronic diarrhea should be tested for protozoa, atypical infections, Strongyloides, and tropical sprue. In patients with a history of constipation, the possibility of overflow diarrhea due to obstipation should be considered, especially if diarrhea worsens despite antidiarrheal therapy. Patients with diabetes or those attempting to lose weight should be questioned about consumption of diet foods containing poorly absorbed sugar alcohols.