THE UPS AND DOWNS OF BARIATRIC SURGERY: A CASE OF REVERSIBLE OXALATE NEPHROPATHY

A GALLAGHER1, B RYAN2, P SNELLING1, S CHADBAN1

1Royal Prince Alfred Hospital, Sydney, NSW; 2Sydney Bariatric Clinic, Sydney, NSW

Background: Obesity related morbidity and mortality are growing concerns as the incidence of obesity continues to rise. There is a burgeoning body of evidence on the benefits of bariatric surgery on cardiovascular, metabolic and now renal outcomes with signal of reversibility of progression of renal impairment. With emergent numbers of patients undergoing bariatric procedures, the deleterious renal effects of these surgeries must also be considered.

Case Report: A 43-year old obese female with type one diabetes mellitus and associated nephropathy underwent laparoscopic gastric banding in 2008. This resulted in 30kg of weight loss, as well as reducing proteinuria and stabilising her renal function. A pregnancy in 2012 upturned her weight loss successes and was associated with progressive decline in creatinine and proteinuria. The patient then went onto to have a roux en Y gastric bypass in 2015, successfully restoring weight-loss targets and partially reversing her diminishing renal function. In early 2016 despite a normal microalbumin to creatinine ratio of less than 3.5mg/mmol, good glycaemic control and a stable weight, the patient’s renal function began to deteriorate reaching a nadir estimated glomerular filtration rate of 13mL/min. A 24-hour urinary oxalate confirmed suspicions of oxalate nephropathy resulting from her altered gastrointestinal anatomy. A conversion of her gastric bypass to a gastric sleeve succeeded in reducing her enteric hyperoxaluria and restored her renal function. Conclusion: Malabsorption through surgical manipulation of the gastrointestinal system is the basis of bariatric intervention and is an effective tool to stabilise the significant metabolic and renal sequelae of obesity. This case serves as a caveat of some of the negative ramifications that bariatric surgery can have such as enteric hyperoxaluria and associated nephropathy.

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