Blind loop syndrome occurs when part of the small intestine becomes bypassed as a complication of abdominal surgery or as a consequence of gastrointestinal disorders which impede effective motility. Digested food slows or stops moving through part of the small intestines (blind loop). This causes bacteria to grow too much in a portion of the small intestine that is unintentionally bypassed and leads to problems in absorbing nutrients.

Sometimes called stasis syndrome or stagnant loop syndrome, blind loop syndrome is often a complication of stomach (abdominal) surgery. But blind loop syndrome can also result from structural problems and some diseases. Sometimes surgery is needed to correct the problem, but antibiotics are the most common treatment.

Clinical signs of blind loop syndrome include bloating, abdominal pain, diarrhea and weight loss. If untreated, the clinical course progresses to malabsorption of fats, vitamin B12 and calcium, the latter which predisposes to nephrolithiasis (kidney stones) and osteoporosis).