Weight Loss Surgery (Obesity Surgery) Risks & Complications

As with all surgery there are risks involved with weight loss surgery.  It is important for you to be aware of these but also to get them in proportion and balancing these against the possible benefits of the surgery. 

Take time to talk with your surgeon about the potential risks and complications.  It might be a good idea to jot down any questions you have prior to meeting with your surgeon. Each case is different and your surgeon is the person who understands the risks and complications that you as an individual face.

Here is a list of the most common risks and complications, but by no means exhaustive:

Gastrointestinal Leaks

Put simply this is a leak, when something which should be watertight is not.  Your surgeon will ask you to look out for certain symptoms that indicate a gastrointestinal leak:

  • High heart rate
  • Low urine output
  • Abdominal pain
  • High fever
  • White blood cell count rising
  • Kidney function may get worse

A gastrointestinal leek is very frightening, however the chances of a leak are around 1-2 per cent.  It important to act quickly if you experience any of the symptoms, by contacting your GP or surgeon. 

Gastric Distention

In gastric bypass surgery the bypassed stomach can become blown up and leak as a result of the distention.  Again this is fairly rare with approximately 1 per cent of patients experiencing this.  Patients may experience nausea, abdominal pain, sweating, wind and hiccups as a result of gastric distention. 

The problem is solved by a drainage tube being placed in the distended stomach.  Some of the symptoms can be vague so this condition is sometimes difficult to diagnose.  Therefore it is important to report any of the above symptoms as soon as you experience them. 

Deep Venous Thrombosis & Pulmonary Embolism

Deep Venous Thrombosis (DVT) is a blood clot in one of the deep veins of the leg, arm, neck or pelvis.  These clots can break off and go to the lungs, which is called a pulmonary embolism. 

Blood clots can occur during or after any surgery, some patients arrive with blood clots already present due to lack of activity at home.  If you develop a clot in one of your deep veins you will probably be put on a blood thinner.  DVT and pulmonary embolism develop in around 2 – 3 per cent of patients having weight loss surgery.


Bleeding can occur with all major surgery including weight loss surgeries.  Bleeding from the spleen is a risk in weight loss surgery as the spleen is next to the stomach area.  You many need a blood transfusion if this was to occur.   

Heart attacks

A heart attack can occur after surgery, however they are not common.  If you are considered high risk you will be asked to undergo an echocardiogram or cardiac catherization, which is a dye study of the blood vessels that supply oxygen to the heart.


An arrhythmia is an abnormal heart rate i.e. your heart rate is too fast or too slow.  Different medications are available to treat the arrhythmia, sometimes shock therapy is necessary to shock the heart rhythm into a normal pattern.

This sounds very frightening, however if you are morbidly obese the chances of sudden death if you do not undergo surgery is 20 times higher than the general population.

Respiratory issues

Breathing difficulties can occur after weight loss surgery, usually resulting in having a ventilator until the complication is resolved.  A tracheotomy may be necessary if you are still experiencing breathing difficulties, which means breathing through a tube in your trachea.  Another complication is pneumonia, which is an infection of the lungs.  Antibiotics usually cure pneumonia, however it is condition, which requires hospitalisation and results in chest pain, cough, fever and shortness of breath.

Wound infection 

A wound infection is less common with weight loss surgery as it is not an open surgery however it is possible.  Gastric bypass and duodenal switch procedures are mostly associated with wound infection.  Stomach and intestines are opened in these procedures, which increases the risk.

The infection is usually treated with antibiotics and on average will take around 2-4 weeks to heal.

Intrabdominal abscess

An abscess is basically a collection of pus that remains when the white blood cells fight infection.  If you have an abscess you will be put on antibiotics and there is a chance you may require more surgery to drain the abscess.  The chances of developing an abscess are about 2 per cent and it is most common with gastric bypass.


Stricute is a narrowing caused by scar tissue.  Commonly this occurs where the intestine meets the new stomach.  A stricute can occur around three weeks to three months after surgery.  As the stricute narrows you will be less able to tolerate solid food and will probably experience digestion type pains.  Repeat surgery will be necessary, if you have any abdominal pain or problems eating small amounts of solid food you should contact your consultant immediately.


You body will need fluids after weight loss surgery, to flush out waste products and maintain body systems.  It is important that you drink enough and do not become dehydrated, this will lead to: dark urine, constipation, fainting, dry mouth and light-headedness.

Gastric Prolapse (or Band Slippage)

This occurs when part of the stomach below the band slips through above the band resulting in obstruction.  The common outcome is vomiting, pain and discomfort.  Gastric Prolapse occurs in about 5 per cent of patients and is corrected by repeat surgery.


An ulcer is a breakdown of tissue cased by inflammation.  Following weight loss surgery (obesity surgery), they usually occur on the stomach lining resulting in nausea, pain and discomfort.  All ulcers are treated with medication, which can decrease the acid production by the stomach.  An untreated ulcer can lead to further more serious complications so it is important to contact your consultant as soon as you notice any symptoms.

Bowel Obstruction 

Scar tissue can develop around the intestines or bowels and can block the bowels.   Symptoms include nausea and vomiting and a bloated stomach.  Contact your consultant as soon as you experience any of these symptoms.  The obstruction can be corrected by repeat surgery.

Some lesser serious side effects of weight loss surgery include vomiting, sweating, bloating, feeling weak or faint, diarrhea and hiccupping.  These symptoms are less distressing than the more serious side effects, however they can cause a great amount of discomfort.  Some times these symptoms are an indication of something more serious, so they should not be ignored.  Some patients experience these side effects after eating and this could be for many reasons such as; eating too much, drinking too much water, eating foods that are high in fat and sugar.  If you are worried about any of these side effects it is always best to contact your surgeon or GP.

The best thing you can do to prevent any possible side effects or complications post surgery is to do your best to look after yourself post surgery.  Keep to all the guidelines and advice that your surgeon, dietitian and GP might give you.  Take all the vitamin supplements that you have been advised or prescribed to take.  Not following the nutritional advice and not taking all the vitamin supplements you have been advised to take could lead to gallstones, anemia or osteoporosis.

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