Patient-Friendly Explanation

Jejunoileal bypass was an early weight-loss operation that skipped most of the small intestine. It caused serious complications and is no longer performed.

Clinical Definition

Jejunoileal bypass anastomosed the proximal jejunum to the distal ileum, leaving a long segment of bypassed bowel. It produced substantial weight loss but caused intractable diarrhoea, electrolyte loss, oxalate kidney stones, liver failure and bacterial overgrowth, and was abandoned during the 1970s.

Why It Matters

Its failure defined the safety requirements of modern bariatric surgery: nutrient absorption must be preserved and metabolic effects, not simple malabsorption, should drive weight loss.