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What are the long-term side effects of a Gastric Bypass?

When moving from sloppy foods to solids, a small number of patients experience excessive vomiting due to a narrowing (stenosis) at the join up between the stomach pouch and the food channel. This is an easy problem to fix by stretching the join up under sedation using a small inflatable balloon. Sometimes the stenosis can result from ulcers causing a build-up of scar tissue around the join up. Ulcers like this can also cause stomach pains on eating. It is important to avoid smoking and NSAIDs (anti-inflammatory painkillers like ibuprofen, diclofenac and aspirin etc) after bariatric surgery as these are major risk factors for ulcer formation.

Gastric bypass patients need to take vitamins long-term because the bypass reduces the body’s ability to absorb nutrients somewhat, particularly iron, vitamin B12 and calcium. This can lead to anaemia and occasionally other problems. It’s not uncommon to have to take top-up courses of some of these minerals or vitamins for a few months from time to time in addition to your regular multivitamin supplements. Having said that, if you follow our advice and stick to a balanced diet it is very unlikely (in the absence of other complications) that you will run into serious nutritional problems.

Bypass patients occasionally suffer with low blood sugar (especially if they skip meals – see our FAQ about dumping syndrome) that can cause dizziness and tiredness. In the longer term, weight regain can also occur in about 10-15% of patients, particularly if they over-eat and stretch the stomach pouch. There are treatments we can offer for this, but it’s better to avoid the need for such complex revisional surgery if you can!

A year or more after surgery 1-2% of patients may experience abdominal colic due to the development of an internal (or ‘Petersens’) hernia. This happens when a knuckle of bowel gets trapped behind the food channel draining the gastric pouch. It seems to be more common after laparoscopic bariatric surgery and so most surgeons now routinely close off this area with sutures at the time of the original bypass to prevent it happening.

Rapid weight loss after a gastric bypass can cause 3 things to happen. Firstly, it increases the chance of you developing gallstones – if these are painful (about 1 in 10 risk), you may need to have your gallbladder removed at a later date. Rapid weight loss can also cause temporary hair thinning lasting 3-6 months. Keeping your protein intake high and using preventative measures such as biotin supplements may help reduce this. Finally, weight loss results in some loose skin in most people. This can be on your tummy, at the tops of your arms and thighs or over the breasts. Plastic surgery is often the most effective way of dealing with this. Some patients experience psychological distress because of the loose skin or perhaps to other changes in their relationships (both with food and with people).


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The clinical information expressed in these video clips is for general information only, and not intended to be a substitute for a detailed discussion with your bariatric surgeon. For further information please contact one of our team on 03452 515 515 to discuss your individual case.

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