Gastric bypass surgery is a term that describes variations of a standard surgical procedure, in which, the stomach and small intestine is reconfigured, so that food no longer passes through the stomach and upper intestine, with digestion starting further down the small intestine, beyond the duodenum.


In practice there are two types of gastric bypass, the original Roux en-Y gastric bypass and the newer one anastomosis gastric bypass, also known as the mini gastric bypass or loop gastric bypass, as described below. In addition to the two basic procedures, particularly with the Roux en-Y gastric bypass, the procedure can be modified for an individual patient, by lengthening the segment of small intestine bypassed or placing a ring around the pouch to prevent stretching of the gastric pouch. 


Individualising the surgery, may offer potential benefits in terms of weight loss and better management of metabolic illnesses, such as diabetes, but may also cause increased risk of side effects, such as diarrhoea and malnutrition, which is why the surgery needs to be discussed in detail, with each patient, in clinic. 


The one anastomosis gastric bypass and Roux en-Y gastric bypass, are both performed using laparoscopic (keyhole) surgery, with one or two nights in hospital

Laparoscopic Roux en-Y Gastric Bypass


For many years, laparoscopic Roux en-Y gastric bypass (LRYGB) has been the gold standard operation, against which all other obesity operations were compared. First performed in the USA in 1967, it has stood the test of time providing reliable long-term weight loss. Globally it was the most commonly performed procedure, but recently has been overtaken by the sleeve gastrectomy. First performed as an open operation, it is now performed laparoscopically, reducing hospital stay to between one and three nights, with an earlier return to normal activities.

The Loop Gastric Bypass


Also known as the mini-gastric bypass or the one anastomosis gastric bypass, the loop gastric bypass is a newer variant of the original Roux en-Y gastric bypass.


A longer narrow gastric pouch, similar to a sleeve gastrectomy is formed. Depending on the patient’s body mass index, between 100cm and 250cm of the small intestine is bypassed, joining the small intestine to the gastric pouch at that point.


This form of the gastric bypass may give better weight loss, than the original Roux en-Y gastric bypass, with increased resolution of T2DM, but there may be an increased incidence of diarrhoea and increased risk of nutritional deficiencies.

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