Jejunoileal bypass

Last revised by Yaïr Glick on 27 Jul 2022

Jejunoileal bypass is an older form of bariatric surgery that was developed to be an improvement on jejunocolic bypass. It is no longer performed due to severe side effects.

For this bypass, the proximal small bowel (jejunum) is divided ~35 cm past the ligament of Treitz, and the proximal end is anastomosed to the terminal ileum, ~10 cm proximal to the ileocecal valve.

This has been performed with both end-to-side and end-to-end anastomoses. In the end-to-end anastomosis, the excluded small bowel is anastomosed to the colon.

The bypass was designed to treat obesity by malabsorption of ingested food.

Treatment and prognosis


Although the end-to-end anastomosis is effective in achieving short-term weight loss 2, the procedure has several side effects:

  • bacterial overgrowth in the blind loop anastomosed to the colon ("bypass enteritis")
    • lactose intolerance
    • absorption of bacterial toxins leading to polyarthralgia and hepatic failure
  • continuous diarrhea
    • anal excoriation and hemorrhoids
  • short gut syndrome with nutrient malabsorption and multiple systemic side effects from malnutrition
    • paradoxically resulted in increased carbohydrate absorption, leading to regain of weight

Mortality rate in the first two years is ~4%, mostly from liver failure 3.

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