Effects of gastric bypass surgery on kidney stone disease

March 09, 2010: Obesity is associated with comorbidities like type II diabetes, heart disease, hypertension, pregnancy complications and other health problems. While dietary changes and physical exercises are prescribed for weight reduction, morbidly obese patients are often advised to undergo bariatric (weight-loss) surgery. Currently weight-loss surgery is the only therapy that results in a sustained and significant weight loss in the majority of the morbidly obese patients.

Jejunoileal (JI) bypass, an early form of gastric bypass surgery was banned as it led to serious postoperative consequences such as osteomalacia (softening of bone due to loss of mineral from bone), nephrolithiasis (process of forming a stone in the kidney) and kidney failure. The Roux-en-Y gastric bypass (RYGB) overcame many of the problems associated with JI bypass. In the RYGB surgery, the stomach is made smaller and a length of small intestine is bypassed. This reduces the absorptive surface area and oral intake of calories leading to malabsorption and weight loss. However, malabsorption of fat soluble vitamins and calcium may lead to increased absorption of dietary oxalate (chemical that combines with calcium to create the most common type of kidney stone) which may lead to severe hyperoxaluria (too much oxalate is present in the urine) and kidney stones.