Kidney stones develop in approximately 2% of first-time kidney transplant recipients within 3 years following transplantation, a rate that is “not rare,” according to investigators.
“Kidney stone events in patients who receive a kidney transplant are consequential,” Calyani Ganesan, MD, MS, of Stanford University in Palo Alto, California, and colleagues wrote in the Clinical Journal of the American Society of Nephrology. “Patients may not experience renal colic due to a denervated kidney allograft, which could lead to the development of larger stones or undetected urinary tract obstruction.”
Using the US Renal Data System (USRDS), Dr Ganesan’s team studied 83,535 recipients of their first kidney transplant during 2007-2018. Of these, 1436 (1.7%) were diagnosed with kidney stones within 3 years of transplantation. A history of kidney stones in the recipient was the strongest risk factor for post-transplantation stone occurrence. Kidney stone risk significantly increased 4.7-fold among those with vs without a history.
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Longer dialysis vintage was another predisposing factor. Compared with patients on dialysis for less than 2.5 years, those on dialysis for at least 2.5 years but less than 5 years had a significant 1.2-fold increased risk for kidney stones. Those on dialysis for 5 to 9 years and more than 9 years had significant 1.3-, and 1.5-fold increased risks for kidney stones, respectively. Peritoneal dialysis was significantly associated with a 1.2-fold higher risk of stones compared with hemodialysis. The investigators suggested that post-transplantation hyperparathyroidism and hypercalcemia may underlie this association.
Gout and hypertension significantly increased the risk for stones by 1.5- and 1.3-fold, respectively. Older age and female sex were other contributing factors. The investigators found no association between prescription of cinacalcet, thiazide and thiazide-type diuretics, or allopurinol and the risk of a kidney stone event.
The proportion of deceased-donor and living-donor transplant recipients diagnosed with a kidney stone was 1.8% and 1.5%, respectively.
Overall, a kidney stone event occurred in 7.8 per 1000 person-years. An earlier USRDS study documented a rate of 0.69 per 1000 person-years from 1994-1998. The investigators suggested that higher rates of imaging or monitoring might account for the increase, or the finding may correlate with the rise in kidney stone incidence in the general US population.
The investigators explained that kidney transplant recipients are immunosuppressed and therefore more susceptible to stone-related urinary tract infections, complicated pyelonephritis, and urosepsis. Such infections may force clinicians to decrease immunosuppression, which raises the risk for allograft rejection, they noted.
Dr Ganesan’s team recommended that new kidney transplant recipients be evaluated for kidney stone risk factors, particularly in the first year. This could include metabolic testing with 24-hour urine collection, dietary counseling, prescription of stone-related medications, periodic imaging, and medical or surgical treatment for post-transplant hyperparathyroidism.
Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.
Reference
Ganesan C, Holmes M, Liu S, et al. Kidney stone events after kidney transplant in the United States. Clin J Am Soc Nephrol. Published online April 18, 2023. doi:10.2215/CJN.0000000000000176
