BMI, type 2 diabetes associated with an increased risk of kidney stones


Dr. David Samadi provides his opinion on a recent study showing a positive correlation between BMI, hemoglobin A1C and an increased urinary excretion of oxalate with the development of kidney stones.

A poster session that was published in the Journal of Urology and presented at the 2017 American Urological Association annual meeting in Boston has found a positive association between both obesity and diabetes and the formation of kidney stones.

“This information ties in with past studies that have looked at the elevated risk of kidney stones among patients with type 2 diabetes and obesity,” stated Dr. David Samadi.  “From those studies we know that patients with hyperglycemia and glycosuria have a higher risk of being stone formers due to the fact of having an increased excretion of urinary oxalate (Uox).  This condition is known as hyperoxaluria which is an excessive urinary excretion of oxalate that can lead to calcium oxalate kidney stones.”

Patients with high body mass index (BMI) and who also have type 2 diabetes are known to have a higher association of kidney stone risk.  There is also a known correlation between the higher a person’s BMI is, the higher the amount of the excretion of urinary oxalate.  Researchers wanted to find out if there was also an associated link to a person’s hemoglobin A1C.

“The researchers began by analyzing 1,428 twenty-four hour urine collections that were from two urologists from the years of 2004 to 2015,” explained Dr. Samadi.  “They then analyzed 665 unique non-cystinuric adult stone formers looking to see if there were an association between urinary oxalate excretion and their BMI, age, gender, and A1C levels.”

The makeup of the participants out of the 665 non-cystinuric stone former group was an average age of 49.9 years, with 46% female.  The average BMI was 29.2.  The breakdown of BMI among the group was those underweight – 1.4%; normal weight – 26.5%; overweight – 35.8; obese- 27.7%; and morbidly obese – 8.6%.

“Results from the study showed a significant positive correlation among participants with a high A1C and oxalate excretion and a high BMI and oxalate excretion,” said Dr. Samadi.  “What was also interesting was that the results were the same regardless it the participant was male or female or Caucasian or African American.”

Dr. Samadi further stated, “Like the researchers have said, to clarify the mechanisms involved of why a high BMI and hemoglobin A1Care related to urinary oxalate synthesis, there will need to be controlled dietary studies validating these findings.  In the meantime, it would be pertinent for any urologist working with patients who have a high BMI and type 2 diabetes to help them achieve a healthier body weight and better A1C number to help reduce their risk of forming kidney stones.”