Gastric Bypass

Gastric Bypass: Surgery, Risks, Side Effects & Results

Intra-abdominal abscess

Occasionally an abscess can develop without any evidence of leak. This may be due to some intra-abdominal fluid from the time of surgery becoming infected, and it usually presents 5 to 14 days postoperatively.

This type of situation usually responds to antibiotic treatment but may require drainage of the abscess under x-ray control and occasionally further surgery which is again usually performed laparoscopically.


The stomach pouch outlet is purposely made small in order to limit the amount of food that can get of the pouch at any one time.

If the outlet is too large, food passes through the pouch quickly and you fail to gain the sensation of feeling full, resulting in you feeling hungry all the time and consuming more food and thus, not losing weight. Natural healing of this new joint results in some scar formation and some contraction of the opening.

For some people this scarring of the anastomosis can cause it to become too small, leading to a stricture. This usually occurs four to eight weeks after surgery.

It leads to difficulty in eating and can cause prolonged nausea or vomiting. This is usually treated via a gastroscopy and burn dilatation as a day case.

In 80% of cases only one dilatation is necessary, but a small number of patients may require two or more dilatations. Very rarely a further operative procedure is required to resolve this issue.


Ulcers can occur in the pouch but occur most often on the small bowel side of the outlet. These ulcers can cause significant problems including perforation, bleeding or the need to revise your bypass with an additional operation.

There are three basic causes of ulcers:

  1. Anti-inflammatory medications such as ibuprofen or aspirin
  2. Smoking
  3. Helicobacter pylori infection

As a result it is recommended that you avoid anti-inflammatory medications as much as possible after surgery, stop smoking prior to surgery and to test for (and treat) Helicobacter pylori infections at your pre-operative gastroscopy.

Vitamin mineral deficiencies

As the laparoscopic gastric bypass does involve a degree of alteration in the normal gut anatomy and some malabsorption, this can result in deficiency of a number of vitamins and minerals.

It is therefore important that you take regular multivitamins and that you have your blood checked on a regular basis.

It is possible for patients who are compliant with their diet and take supplements to develop vitamin deficiencies.

The most common would be iron deficiency anaemia or deficiencies in calcium. More rarely vitamin B deficiency can occur along with vitamin A deficiency.

We recommend that your GP perform regular blood tests to check for vitamin deficiency.

Hair loss

It is not uncommon to have some thinning or loss of hair in the first few months after bariatric surgery. This is mainly temporary and can be related to inadequate protein intake.

Hiatus hernia

A hiatus hernia occurs when part of the stomach slips up through the diaphragm into the chest.

It is very common in the obese patient and will probably have been noted at your gastroscopy. At the time of your gastric bypass surgery your hiatus hernia may be repaired with simple sutures to the hiatus.

Generally the symptoms associated with a hiatus hernia of heartburn and reflux respond best to weight loss, rather than anti-reflux surgery.

Failure to lose weight

As has been discussed previously, as this is a restrictive procedure it is possible to cheat the operation and not lose weight.

Diarrhoea or constipation

Diarrhoea is unusual following laparoscopic gastric bypass but as has been described earlier, can be associated with ‘dumping’ syndrome, describe above.

Constipation is common after bariatric surgery, as patients tend not to drink enough liquid. As your liquid and fibre intake improves your tendency to constipation will settle. If necessary, a gentle laxative can be taken.

Large folds of skin

This is always a possibility with significant weight loss. There is no reliable way to determine before surgery to what extent this will occur in your case. Age, exercise, speed of weight loss, elasticity of skin all play a role. Plastic surgery procedures are available to correct excess skin problems and you can be referred to an appropriate plastic surgeon if necessary.


Whilst your surgical team will always attempt to complete your operation laparoscopically, as this is easier on you and certainly easier from a surgical point of view, it is occasionally necessary to convert to an open procedure. This is a rare procedure but obviously if it occurs will lead to prolonged time in hospital and a longer postoperative recovery.

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