Weight Loss Surgery: Understanding the Risks

Common Complications of Bariatric Surgery

If you are thinking of having weight loss surgery, it is essential that you consider the risks that accompany the procedure. Some potential risks are minor and are resolved soon after the weight is lost, while others can be more serious and/or long-term.

In addition to the general risks of surgery that apply to patients undergoing any surgical procedure, there are additional concerns that those considering weight loss surgery need to be particularly aware of.

  • Anemia
    Anemia is common with all types of malabsorptive surgeries (procedures that surgically change the intestines).  These procedures decrease the body's ability to absorb nutrients. Anemia is a deficiency of hemoglobin (protein in red blood cells that carries oxygen) frequently caused by iron and/or B12 deficiency. This can typically be managed with supplements, which may be prescription strength.
  • Osteoporosis and Bone Degeneration
    Calcium deficiency is another risk of malabsorptive procedures. Too little calcium can cause weak and brittle bones and stooped or "humped" back posture. When caught early, supplements can manage the deficiency and help head off serious problems. However, medication may be required if the condition progresses.
  • Malnutrition
    In addition to the above conditions, vitamin and mineral deficiencies that can result from weight loss surgery can cause malnutrition. Low levels of vitamins and minerals can happen very quickly in patients who have had malabsorptive surgeries that limit the digestion of food. Supplements are typically an adequate defense.
  • Excess Skin
    When significant amounts of weight are lost, skin may begin to hang off of the body regardless of the type of weight loss surgery. This is because skin loses its elasticity when stretched and cannot spring back after significant weight loss.  

  • Dumping Syndrome
    When patients who have had a gastric bypass procedure, specifically Roux-en-Y, eat too much or consume a meal high in sugar, the stomach contents rapidly “dump” into the small intestine. This causes cold sweats, diarrhea and feelings of faintness. The symptoms are distressing, though not life-threatening, and they typically improve within a few hours. Eliminating or decreasing sugar intake and eating smaller meals can prevent dumping syndrome.
  • Erosion
    When a surgery introduces a foreign object into the body, one runs the risk that that object may wear away healthy tissue, causing damage. This can occur, for example, when someone eats an excessively large meal after weight loss surgery, or when a gastric band is fitted too tightly. This problem happens after weight loss surgeries that require an implant, specifically a gastric band appliance.
  • Spleen Injury
    In rare cases, the spleen must be removed during weight loss surgery to control bleeding, a procedure called a splenectomy. In some cases, the spleen can also be injured during surgery due to its close proximity to the structures being operated on, though it does not need to be removed.
  • Suture Line Disruption (SLD) When there is an interruption in an area that is stapled or sutured in the digestive tract, known as an SLD, food can pass into areas that are no longer intended for food. For example, if part of the stomach is stapled to prevent food from entering a section of the stomach, but the staples do not actually prevent food from entering, food becomes trapped; the area it's resting in no longer moves food into the rest of the digestive tract. Severe abdominal pain, infection, abscess and local and body-wide infections called sepsis can result. SLD is a life-threatening condition.
  • Hernia
    A hernia occurs when an organ begins to protrude through a weakened area of muscle. Any type of abdominal surgery can weaken the muscle walls enclosing the abdomen, but as many as one out of every five weight loss surgery patients requires a second surgery to fix a complication such as a hernia, especially at incision sites.
  • Long-term Nausea and Inability to Tolerate Food
    In some instances, weight loss surgery can work too well, leaving patients unable to tolerate eating without experiencing symptoms ranging from severe nausea to vomiting. The food intolerance may be so severe that the patient must be hospitalized.
  • Migration
    With band surgeries, the band can shift out of position, decreasing or eliminating the effectiveness of the band.
  • Narrowing of Stomach Outlet (Stenosis)
    After bariatric surgery, scarring of the area where food leaves the stomach can occur, causing it to narrow and restrict the flow of food. In serious cases, where the narrowing causes severe vomiting and inhibits digestion, an outpatient procedure is necessary to enlarge the area.
  • Leaking
    After weight loss surgery, it is possible for the suture or staple lines created during the surgery to leak. The most common type of leak can cause stomach contents (including digestive acid) to seep into the abdominal cavity. Leaks require additional surgery to repair and, depending on the severity of the leak, may be considered an emergency.
  • Ulcers
    An ulcer occurs when the area of the stomach that has been cut during surgery erodes when exposed to stomach acid. Many surgeons prescribe medication to prevent stomach acid from harming the tissue.
  • Gallstones
    As many as one in three patients develops gallstones after having weight loss surgery. Rapid weight loss and low calorie intake are risk factors for gallstones, and both of those conditions are met in the weeks immediately after surgery when patients are eating tiny meals as they adjust to their new stomach size. Gallstones can be minimized with medication prescribed by your surgeon.
  • Constipation
    The abrupt and major change in eating habits can leave many patients constipated after surgery. In addition to the discomfort, the “bearing down” that is done when trying to have a bowel movement can cause extreme stress on incisions that are healing. Your surgeon should have recommendations for treatment; over-the-counter treatment is not recommended.


Bariatric Surgery For Severe Obesity. Consumer Information Sheet. National Institute of Diabetes and Digestive and Kidney Diseases. March 2008. http://win.niddk.nih.gov/publications/gastric.htm

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