Part of the TeachMe Series

Consent: Gastric Bypass

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Last updated: December 9, 2021
Revisions: 5

Last updated: December 9, 2021
Revisions: 5

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This article is for educational purposes only. It should not be used as a template for consenting patients. The person obtaining consent should have clear knowledge of the procedure and the potential risks and complications. Always refer to your local or national guidelines, and the applicable and appropriate law in your jurisdiction governing patient consent.

Overview of Procedure

A gastric bypass procedure works via both a restrictive and malabsorptive mechanism.

Most of the stomach is divided and a small gastric pouch formed.  This is joined on to the small bowel approximately 0.75-1 metre from the caecum.  Bile flow is restored via a Roux-en-Y anastomosis.

Fig 1 – A gastric bypass procedure



Complication Description of Complication Potential Ways to Reduce Risk
Haemorrhage Damage to any of the surrounding structures can cause significant haemorrhage.
Injury to surrounding structures including bowel, liver and spleen Damage can occur to any surrounding organ during the surgery.
Anaesthetic risks Includes damage to the teeth, throat and larynx, reaction to medications, nausea and vomiting, cardiovascular and respiratory complications. Forms a part of the anaesthetist assessment before the operation


Complication Description of Complication Potential Ways to Reduce Risk
Infection Superficial wound infection or intra-abdominal collections are both possible as is chest infection due to the body habitus and reduced mobility of these patients. Early mobilisation, breathing exercise, or incentive spirometry can help
Leak from the staple line (1 in 20) Leakage from the staple line or either of the anastomoses may occur.  As with any anastomotic leak, this is potentially serious and frequently requires further surgery, tube feeding, and a prolonged hospital stay
Blood Clots DVTs and PEs are a possibility in any operation. The risk is increased in patients with a raised BMI, on the pill, recent flights, previous DVT, pregnancy, smokers, cancer, and prolonged bed rest. The patient will be given anti-embolism stocking and low molecular weight heparin peri-operatively to minimise this risk as deemed appropriate.
Stroke, MI, Kidney Failure, Death Although small, this is always a risk in any major surgery; the mortality risk is around 1 in 200


Complication Description of Complication Potential Ways to Reduce Risk
Metabolic and endocrine disturbances This is potentially life-threatening. Changes to absorption and gastric secretions of the alimentary canal can affect nutrition considerable post-operatively The involvement of a specialist bariatric dietician in the management of bariatric patients is essential
Anastomotic stricture The anastomosis may narrow over time.  This can be a serious complication, leading to malnutrition and require revisional surgery
Ulceration of the stomach pouch (1 in 100) This is rare but potentially serious as they can bleed or perforate
Internal hernia Patients can develop internal hernias which can lead to obstruction.  This is either due to adhesions or protrusion into the mesenteric defect (Peterson’s space) Closure of the mesenteric defect prophylactically can reduce this risk
Failure to lose weight or weight regain Sleeve gastrectomy is highly effective, but inevitably a minority of patients ultimately fail to lose or regain weight.