One Anastomosis Gastric Bypass (OAGB)

Possible Complications After Surgery (Short-Term)

While most patients recover smoothly, some may experience early complications, including:

• Bleeding
• Infection at incision sites
• Leakage at the surgical join (anastomosis)
• Blood clots (deep vein thrombosis or pulmonary embolism)
• Nausea or vomiting, especially during the adjustment phase

These are typically managed promptly with medical or surgical intervention if needed.

Long-Term Complications (Months or Years Later)

While rare, some complications may occur well after surgery:

• Bile reflux – stomach bile flowing into the oesophagus, causing discomfort
• Nutrient deficiencies – especially in iron, vitamin B12, calcium, and vitamin D
• Dumping syndrome – a rapid shift of food into the small bowel causing nausea, diarrhoea, or dizziness
• Ulcer formation at the site of the bypass
• Weight regain – particularly if lifestyle changes aren't maintained

Lifelong follow-up, including regular blood tests and nutritional support, is essential to reduce the risk of long-term issues.

The Risk of the Anaesthetic

Anaesthetic risks are extremely low because when you come to your operation any conditions which might increase your anaesthetic risk such as high blood pressure, diabetes or sleep apnoea will have been brought under control. All of our anaesthetists are experienced with dealing with the specific problems of patients with excess weight and have full access to all of the tests and information gathered during your preoperative assessment.

Bleeding

Although uncommon, bleeding can occur during an otherwise routine operation and could require blood transfusion and possibly abandoning the laparoscopic (keyhole) approach for a major incision in the abdomen. Occasionally, after a routine operation, bleeding can commence some hours after an operation and require a return to the operating theatre.

Infections

Again these are uncommon with laparoscopic surgery, but occasionally one of the small keyhole wounds can become infected and require antibiotics or drainage. Uncommonly, an infection inside the abdominal cavity or the chest can occur.

Damage to Other Organs

Although uncommon, during laparoscopic surgery it is possible to inadvertently damage another organ such as the spleen or the bowel. Normally this can be diagnosed and repaired during the operation but very rarely this damage may not be obvious until some hours or even days after the procedure and will then require appropriate management.

Conversion to Open Operation

Rarely, it is not possible to complete an operation with keyhole surgery and a full abdominal incision may be necessary. This is more likely to be the case if you have had previous surgery on your stomach such as a gastric band or stomach stapling.

Blood Clots to the Legs or Lung (Pulmonary Embolus)

Blood clots to the legs or the lungs are a very serious complication. At LapSurgery we use the maximum protection against this occurring. Shortly before the operation you will be given a blood thinning injection and have stockings placed on your legs. A further device will also be placed on your legs which keeps pumping blood through your legs whilst you're asleep to minimise the chance of a clot forming whilst you are on the operating table.

Using these precautions and the early mobilisation after the surgery that is possible with the keyhole operation, these complications have been uncommon in our patients.