Blind loop syndrome refers to the overgrowth of bacteria into the small intestine. While small intestinal bacterial overgrowth (SIBO) can occur in several populations, patients who have had surgery resulting in the creation of a blind intestinal loop (ie, Roux-en-Y anastomosis) are at high risk for intestinal stasis and retained food products, which predispose to bacterial overgrowth. Patients with delayed gastric or intestinal motility, celiac disease, irritable bowel syndrome, Crohn disease, cirrhosis, chronic kidney disease, and pancreatitis are at increased risk for SIBO. The prevalence of SIBO also increases with advanced age.

Patients present with bloating, abdominal pain, and diarrhea. Diarrhea is typically nonbloody and can be associated with nutritional deficiencies due to malabsorption.