Text Size: A- A+ Facebook Twitter LinkedIn YouTube

Related Classes & Events

Bariatric Surgery

Risks and Complications of Bariatric Surgery

Surgical treatment of obesity and obesity-related health problems is considered major surgery. The risks and complications of surgical treatment of obesity are most often due to the patient’s obesity-related health problems. That is why we stress quitting smoking and losing weight prior to surgery to decrease these risks as much as possible. Also, complications can occur if patients do not follow all of their instructions after surgery.

If you think you may be experiencing a problem:

  • Call us (tell the person answering the phone you have had surgery and are having a problem)
  • Go to the Allegheny General Hospital Emergency Department 

Risks and Complications of Bariatric Surgery


The risk of death at experienced bariatric surgery centers is less than 0.3% (1 per 300 patients). Death is usually due to a patient’s health problems such as heart or lung disease. Surgical causes of death can be related to pulmonary embolism (blood clots to the lungs) or a gastrointestinal tract leak. Patients with a very high BMI, male patients, and patients with severe medical conditions are at the highest risk, but death can occur in any patient.

Back to top

Pulmonary Embolism

Pulmonary embolism occurs when a blood clot in the leg (deep venous thrombosis or DVT) breaks off and travels to the lungs. Sometimes pulmonary embolism causes sudden death, but most times, patients develop sudden shortness of breath and chest pain.

Pulmonary embolism occurs in fewer than 1% of cases (fewer than 1 per 100 patients). To help prevent pulmonary embolism, patients are put on blood thinner therapy (heparin) and given compression stockings while in the hospital. Patients are also encouraged to get out of bed and walk as soon as possible after surgery.

Patients on birth control pills or hormone replacement therapy should stop these medications 3 weeks prior to surgery. If birth control pills are stopped, another form of contraception should be used.

Patients who are at a higher risk of pulmonary embolism because they have had DVT in the past or are immobile may need to be checked before surgery by a hematologist.

Most patients with a previous history of DVT or pulmonary embolism will need 3 to 4 weeks of a daily blood thinner injection after they are discharged from the hospital.

Rarely, the surgeon or hematologist may decide that a filter needs to be inserted in the inferior vena cava (the large vein carrying blood from the legs to the heart) to catch blood clots traveling from the legs. If needed, the filter will be inserted during an interventional radiology procedure (through a catheter inserted into the vena cava under X-ray guidance). These patients may also be discharged on blood thinners at home for 3 to 4 weeks.

Smoking increases the risk of pulmonary embolism so it is essential that patients quit at least 2 months before surgery, if not sooner.

Back to top

Gastrointestinal Tract Leak

Leaks from the gastrointestinal tract can occur where the bowel and stomach are connected or stapled. If a complete seal does not form, bowel contents can leak into the abdomen, causing a serious infection. This occurs in about 1% of patients.

Leaks usually happen within the first 2 weeks after surgery. Symptoms of a leak can include fast heart rate, abdominal pain, fever, shortness of breath, or “just feeling sick”.

The severity of the leak and the infection that might develop vary from patient to patient. In case of small leaks, a drain may be placed by X-ray. Often a temporary tube is placed in the gastric remnant (disconnected stomach). Patients receive nutrition through the vein or through the tube that is inserted in the stomach. Small leaks typically heal within 2 weeks.

Patients with sepsis (severe infection) due to a leak may need to be in the intensive care unit for an extended period of time. Some patients require emergency surgery (laparoscopic or open) to wash out the area of the leak and place drains.

Placement of a drain at the time of initial surgery does not prevent a leak. We may place a drain at the time of initial surgery in patients who are at high risk, those having revisional surgery, patients with a very high BMI, or for other patients at the discretion of the surgeon.

Back to top

Conversion to Open Procedure

In fewer than 1 in 200 patients, the surgery may need to be converted from the laparoscopic approach to the traditional open surgical approach.

Patients are encouraged to diet before surgery to help decrease the amount of fat in the abdomen and to increase the likelihood that surgery can be performed laparoscopically.

However, conversion to an open procedure may be necessary for patient safety. Reasons could include bleeding, injury to other organs, excessive scar tissue from previous surgeries, or a very large liver.

Back to top

Bowel Obstruction

Bowel obstructions (blockages) can be caused by scar tissue in the abdomen or kinking of the bowel. This occurs in 1% to 3% of patients.

Bowel obstructions can happen early after surgery but also late (months to years) after surgery. Symptoms of bowel obstruction include severe abdominal pain, nausea, and vomiting. An emergency operation is typically necessary. It is important to call our office or come to the emergency room if you develop any of these symptoms.

Back to top


Excessive scar tissue formation (stricture) can occur where the stomach pouch is connected to the bowel. This occurs in about 2% of patients.

Symptoms of stricture usually occur within the first 2 months after surgery, during the time of healing. Symptoms include vomiting and decreased tolerance to food, even liquids. Patients typically do not have any pain.

A stricture is corrected by a procedure called upper endoscopy and balloon dilatation. This procedure involves inserting a tube (endoscope) through the mouth into the stomach, passing a balloon down the tube to the area of stricture, and inflating the balloon to dilate (stretch) the scar tissue.

Usually 1 or 2 dilations are necessary, although some patients require more dilations or, rarely, surgery may be needed to revise the connection.

Another area of potential stricture is where the small intestine passes under the colon. These strictures are rare and occasionally require surgical treatment.

Back to top


Bleeding can occur anywhere a stapling device was used. This includes the following:

  • where the bowel and stomach are connected,
  • where the intestines are connected,
  • at the stapled stomach,
  • where scar tissue is ‘cut’,
  • within the gastrointestinal (GI) tract (symptoms are vomiting blood or passing blood clots with bowel movements), or
  • inside the abdominal cavity.

Bleeding occurs in about 2% of patients. In most cases, bleeding stops with stopping of the medication (heparin) used to prevent blood clotting and pulmonary embolism. In rare cases, an endoscopic exam or surgery may be needed to stop the bleeding.

Back to top


An ulcer may develop in the area where the new stomach pouch is connected to the small bowel.

Symptoms of an ulcer include pain with eating, bleeding (noted as dark or bloody stools), vomiting blood, and nausea. An ulcer occurs in about 2 % of patients.

Ulcers are typically diagnosed by an upper endoscopy examination. They are treated by long-term use of an anti-ulcer medication.

Patients who smoke or take anti-inflammatory medications (such as ibuprofen [brand names such as Advil, Motrin], naproxen [brand names such as Aleve], indomethacin [brand names such as Indocin], nabumetone, Relafen, and aspirin) for arthritis or pain are at increased risk of developing ulcers. Patients taking corticosteroid medications (such as prednisone) are also at increased risk.

Patients are discharged home from the hospital with a prescription for a strong antacid (omeprazole [brand name Prilosec]), and they should keep taking this medication for at least 2 months. Patients at higher risk for ulcers (those who smoke or take anti-inflammatory medications) may need to be on anti-ulcer medications for life. Patients on Plavix will need ranitadine (brand name Zantac) instead of a proton pump inhibitor.

Ulcers may lead to stricture, especially if there are multiple ulcers or ulcers recur.

Back to top


About 1 in 3 patients who follow a diet for rapid extreme weight loss will develop gallstones during the period of rapid weight loss. To decrease this risk after bariatric surgery, patients are given supplemental bile salts (ursidiol/Actigall) for 6 months after the procedure. This treatment decreases the risk of gallstone formation after bariatric surgery to 3%.

Even with this treatment, patients may develop gallstones. Symptoms of gallstones include pain under the ribs on the right side that spreads to the back, chest pain, nausea, or vomiting, especially after a meal high in fat.

About 7% of patients who undergo bariatric surgery need to have their gallbladders removed at a later time (see Research publications)

In rare cases, a patient may develop an acute infection of the gallbladder or develop pancreatitis (if the gallstones migrate into the main bile duct).

Back to top


Patients have a very low risk of developing infections.

  • Pneumonia is very rare (<1% of patients) if patients do breathing exercises and get back to normal activity soon after surgery. Patients who smoke are at increased risk of breathing problems and complications after surgery and need to quit smoking at least 6-8 weeks prior to surgery.
  • Abscess (pus collection) formation in the abdomen is also very rare (<1%). This can usually be drained without the need for an operation.
  • Urinary catheter insertion at the time of surgery poses a risk for a urinary tract infection. This is uncommon and usually can be readily eradicated with antibiotic treatment without any additional hospital stay.
  • Wound infections are very uncommon as the small (½” and ¼”) incisions heal well. The skin stitches are usually absorbed by the body, but occasionally the wound “spits it out”. Any wound infection that does occur is similar to a big pimple and is usually treated by opening the wound.
  • C. difficile colitis is a type of colon infection caused by antibiotics. C. difficile colitis is very rare in patients undergoing Roux-en-Y gastric bypass surgery. Usually it responds well to treatment with antibiotics but may, rarely, require surgical treatment.

Back to top

Chronic Nutritional Problems

Protein deficiency or vitamin and mineral deficiency can occur after gastric bypass surgery. More information about each type of deficiency follows:

Protein Deficiency
Protein is an essential nutrient for the body. Patients need to eat about 4 ounces (60 to 80 grams) or more of protein each day to maintain healthy organ function. If protein is eaten in 2 meals a day, a deficiency is very unlikely to occur. Protein supplements (shakes, bars, etc.) are usually not necessary as long as your dietary protein intake is adequate. Simply remember, protein first at mealtimes. See the Dietary Guidelines section for more information.

Vitamin and Mineral Deficiency
After a gastric bypass, adequate amounts of vitamins and minerals may not be consumed. Also, certain vitamins and minerals are not absorbed as easily. Therefore, after surgery, patients need to take the following supplements:

  • Multivitamins (2 times a day)
  • Iron supplement (once a day) – (in addition to the iron in multivitamins with iron)
  • Calcium with vitamin D supplement (2 times a day)
  • Vitamin B12 (once-a-day pill or daily/weekly B12 lozenges that dissolve under your tongue or once a month injection)

Following is information about why these supplements are needed:

  • Iron. Iron deficiency is one of the most common deficiencies seen following gastric bypass surgery. This is a particular concern for patients who have chronic excessive menstrual flow or bleeding hemorrhoids. Iron deficiency or anemia occurs in about 15% of patients after gastric bypass surgery.
         The amount of iron included in a multivitamin is usually not enough to prevent iron deficiency - a daily iron supplement is needed to prevent iron deficiency. The addition of vitamin C to iron supplements may help iron absorption.
         Rarely, patients who develop iron deficiency anemia that does not respond to iron by mouth may require parenteral iron (injection through an IV). Young women of child-bearing age will develop iron deficiency anemia, causing fatigue, if they do not take iron.

  • Calcium and Vitamin D. Vitamin D deficiency is very common in the United States. Vitamin D is needed to help absorb calcium. Malabsorption of calcium can lead to osteoporosis (metabolic bone disease that can result in bone pain, loss of height, humped back and fractures of the ribs and hip bones).
         Women are already at increased risk for osteoporosis after menopause. Calcium absorption is decreased after gastric bypass surgery because the portion of the small bowel being bypassed (the duodenum and proximal jejunum) is where calcium is maximally absorbed. Low calcium may stimulate the production of parathyroid hormone (PTH), which can increase release of calcium from the bone.
         We recommend that patients take 1000 to 2000 mg of calcium with vitamin D (1000 IU) every day. It is important to take the calcium and iron supplements at different times of day, because if taken together, less of each is absorbed.

  • Vitamin B12. Vitamin B12 deficiency occurs in 25% to 75% of gastric bypass patients after surgery, with the majority of reports citing deficiency of approximately 35%. Because long-term vitamin B12 deficiency can cause irreversible neurological damage, we recommend B12 supplementation in all patients. B12 can be supplemented with a monthly shot or by mouth (on a daily or weekly base).

  • Folic acid (folate). For most patients, taking a daily multivitamin is enough to prevent folic acid deficiency. However, taking a folic acid supplement (1 mg per day) may be advised for pregnant women or women expressing a desire to become pregnant.

  • Thiamine. Thiamine deficiency may occur after gastric bypass surgery due to reduced acid production, restriction of food intake, and frequent episodes of vomiting. Thiamine deficiency may lead to nerve problems and memory loss. To avoid thiamine deficiency, patients are advised to take a multivitamin supplement daily.

Patients who need to be admitted to the hospital due to frequent vomiting will be given vitamins and thiamine through an IV.

Back to top

Failure of Weight Loss - Chronic Symptoms

Patients may have unrealistic expectations about weight loss after surgery. Counseling before surgery is essential to set realistic goals for health and weight loss after bariatric surgery.

About 1 in 10 patients fail to lose adequate weight (50% or more of excess body weight) after gastric bypass surgery (although health problems such as diabetes usually improve). Failure may be due to "not following all the rules" following the prescribed diet, exercise, activity, office follow-ups), or just to poor metabolism: some patients seem to be destined to be overweight no matter what they do.

Patients who “graze” on food all day or constantly eat to the point of stretching their pouch can gain weight again. Also, patients who do not exercise regularly may not achieve their goal weight.

Surgery is not a "quick fix" for weight loss. Patients must be motivated and committed to changing their lifestyle - the surgery is a tool to help them lose weight. It doesn’t work by magic and it does not work alone.

Many patients will start to gradually gain weight 2 to 3 years after their surgery for one or both of these reasons:

  • The gastric pouch may dilate (enlarge) over time, allowing patients to tolerate a larger meal.
  • The small intestine becomes more efficient in absorbing calories (less dumping syndrome).

The weight gain occurs in most cases when patients eat many small portions of high-calorie foods. Patients will gain weight after surgery if they don’t follow the rules for a healthy diet, exercise, etc. Patients often say that it is more difficult to lose the 10 to 30 lbs they regain than the 150 lbs they initially lost with surgery.

Morbid obesity is a complex problem that is not easily fixed, even when surgery is technically successful. It is vital that patients obtain nutrition counseling, psychological counseling, and expert opionion about bariatric surgery.

Back to top

Too Much Weight Loss - Chronic Nausea, Vomiting, Abdominal Pain

Rarely, excessive weight loss (BMI less than 19 kg/m2) occurs after bariatric surgery.

Each patient’s metabolism is different, so post-surgery weight loss varies from patient to patient. In the great majority of patients, metabolism reaches equilibrium at the end of the first year and they stop losing weight. However, a few patients develop excessive weight loss due to very poor food intake.
This may be due to one or more of the following:

  • Depression
  • Food fear
  • Anorexia
  • Chronic abdominal pain
  • Chronic nausea
  • Untreated chronic stricture

About 1 in 200 patients (0.5%) develop chronic abdominal pain or nausea after surgery. Multiple X-ray tests, endoscopies, and surgeries may be required to evaluate these cases, yet often no cause is found. These patients need to have a feeding tube inserted into their disconnected stomach to improve nutrition or may need intravenous fluids for nutrition. These interventions almost always lead to improvement within one year.

Very rarely, patients may require reversal of the surgery.

Back to top

Body Image - Emotional Loss - Depression

Patients may experience psychological turmoil the first year after surgery.

Rapid weight loss may cause body image distortion, in which patients have a hard time adjusting to their new body image and develop anxiety or depression. They may say, “I look at the mirror and I don’t recognize the person I see” or "I feel fat” even though they have lost a great deal of weight. Body image distortion can be very stressful and cause anxiety and depression.

About 1% of patients find that they are depressed after surgery, even though they have good weight loss and have not suffered any complications. Some patients develop depression because they can’t use food to satisfy their psychological needs any more. These feelings are generally felt within the first 4 to 8 weeks after surgery. Patients are not always aware how important food was to them. It may have been the only bright part of their day.

Surgical weight loss may affect personal relationships for the better or worse. Single patients have found new partners and started families, but some married patients have divorced. Because of these dramatic changes, we think that postoperative psychological support is very important. The West Penn Allegheny Health System Bariatric Surgery Center Program offers postoperative psychological support meetings in small groups of patients.

Back to top

Nerve Problems

Nerve problems (neuropathy) may occur during the hospital stay or at the time of surgery. This occurs in fewer than 1 in 200 obese patients. An obese patient’s own weight in an unfamiliar bed or on the operating room table can compress a nerve and lead to symptoms like “foot drop” or leg or hand numbness or tingling.

Another cause of nerve problems is low levels of the vitamin thiamine. Patients who do not take their vitamins may develop irreversible memory loss and other nerve problems. This tends to occur if patients are vomiting a lot.

Back to top

Low Blood Sugars (Hypoglycemia)

Low blood sugar (hypoglycemia) can occur after weight loss surgery. Symptoms can include shakiness, nervousness, tremor, palpitations, tachycardia, sweating, clamminess, nausea, vomiting, abdominal discomfort, abnormal thinking, confusion, fainting, and seizures.

Low blood sugars can occur if the patient has not eaten for a few hours. It may be a signal that it's time to eat.

"Late dumping syndrome" can cause hyperglycemia. This typically occurs about 1 hour or so after a meal if starches (bread, potatoes, pasta) were consumed. The starch is digested, turned to sugar, and causes an initial high blood sugar. The pancreas then releases too much insulin, resulting in the episode of hypoglycemia. Patients should keep a diary of their foods, meal times, and time of symptoms. If this is the case, starches should be avoided. The medication Precose, which helps prevent the conversion of starch to sugar, can also be used to help prevent these episodes of hypoglycemia. Precose should be taken just prior to meals to offset the hypoglycemic episodes.

Rarely, some patients may need to eat a little sugar or glucose tablet to treat these episodes, but have to be careful not to eat too much as to regain weight. There have been a few reported cases of elevated insulin levels after gastric bypass surgery requiring the removal of part of the pancreas. We have not seen this complication in our series of over 2000 patients, but are always on the look-out.

Back to top

Kidney Problems

Kidney failure or kidney stones may occur after gastric bypass surgery.

Kidney Failure
A rare complication of gastric bypass surgery is kidney failure. Risk factors include prolonged operations (longer than 5 hours) and BMI >55. These may cause injury to muscles and build-up of muscle protein in the kidneys, which can damage the kidneys. Symptoms of kidney failure include muscle pain in the buttocks area and low urine output. The treatment is hydration with IV fluids.

Kidney Stones
Kidney stones may develop after gastric bypass surgery. The most common type of kidney stone is calcium oxalate. If oxalate builds up in the body it can be deposited as calcium oxalate in the urine and form kidney stones. Rarely, this can result in kidney failure.

Back to top

Complications from Anesthesia

Complications can occur with any anesthesia, although they are especially likely in morbidly obese individuals who also have sleep apnea.

The anesthesiologist will discuss possible anesthesia complications with each patient, based on his or her health history and health status.

Back to top

Other Complications

There is a possibility that other complications, unknown at this time, may occur. Although gastric bypass surgery has been performed since 1967, “new” complications may arise that may not have been reported before. To help identify any new complications, it is important for all patients to continue to follow up with us after surgery.

Back to top

West Penn Allegheny Health System
Tell us who you are:

What areas do you use on our website?*
(select more than one if it applies)

Did you find what you were looking for?

Would you refer others to our website?

Can we contact you for future questions?

CAPTCHA math question:* 3 + 2 =

Thank you for completing the West Penn Allegheny Health System website survey.
We value your feedback and comments.