Blind loop syndrome (or stagnant loop syndrome) happens when part of the small intestine makes a loop of tissue which food cannot pass through during the digestive process. The loop of tissue may be very small or much larger, depending on the cause. This 'blind loop' results in a reservoir of stagnating food that remains trapped in the small intestine. There are a number of causes of blind loop syndrome including:

Complications following abdominal surgery
Scar tissue or adhesions around the small intestine
Diverticulitis
Some medical conditions including Crohn's disease, scleroderma, radiation enteritis, obesity, celiac disease, and diabetes

People born with a structural defect to the small intestine may also be at risk of developing blind loop syndrome in later life.