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Revista Uruguaya de Medicina Interna

On-line version ISSN 2393-6797


SAN ROMAN, Sofía et al. Lithogenic risk factors in morbidly obese patients in the preoperative period of bariatric surgery. Rev. Urug. Med. Int. [online]. 2022, vol.7, n.1, pp.17-26.  Epub Mar 01, 2022. ISSN 2393-6797.


Morbid obesity is a risk factor for kidney stones. Bariatric surgery achieves good metabolic results, and can generate an increased risk of kidney stones. Target. To study the lithogenic risk factors in obese patients in the preoperative period of bariatric surgery.


Descriptive, cross-sectional study. Patients from the Obesity and Bariatric Surgery Program were included, from February 2019 to March 2020.


68 patients were analyzed, 83.3% women, median age 46 (37-52) years. The median BMI was 46 (43-53) kg/m² with a range of 35 to 70 kg/m². Of the participants, 29 (43%) were super-obese (BMI>50kg/m2), 31 (48%) had metabolic syndrome, 19 (28.7%) were diabetic, and 39 (59%) were hypertensive. The median creatinine clearance measured was 136.5 (100.5-162.5) ml/min, 41 (60%) patients were greater than 120 ml/min. In 16 (23%) patients, a history of clinical-ultrasound manifestation of lithiasis was confirmed. All patients were asymptomatic at the time of the study. We found at least 1 lithogenic factor in 97% patients and 2 in 71%. 60.6% had hyperparathyroidism, 63% with hypovitaminosis D (<20ng/ml). Urinary pH was <6 in 33.3% of patients, 62 (91.2%) had natriuria >100 mmol/24h, 60.3% had hyperuricosuria, 48.5% had hypocitraturia, 42.6% hyperoxaluria, 25% hypercalciuria and 79.4% with hyperammoniuria. No differences were found in the lithogenic variables, between patients with a history of lithiasis and without, in obese and super obese patients, or when comparing diabetic patients and patients with metabolic syndrome vs patients without these alterations.

Discussion and Conclusions:

In our study, the high prevalence of lithogenic risk factors supports the link between obesity and kidney stone disease. It is advisable to carry out a specific clinical evaluation and a lithogenic study prior to bariatric surgery, with its result affecting the choice of surgical technique.

Keywords : Lithogenic Factors; Morbid Obesity.

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