Gout after living kidney donation: a matched cohort study

Background — In the general population, high serum uric acid concentration is a risk factor for gout. It is unknown whether donating a kidney increases a living donor’s risk of gout as serum uric acid concentration increases in donors after nephrectomy.

Study Design — Retrospective matched cohort study using large healthcare databases.

Setting & Participants — The researchers studied living kidney donors who donated in 1992 to 2010 in Ontario, Canada. Matched nondonors were selected from the healthiest segment of the general population. 1,988 donors and 19,880 matched nondonors were followed up for a median of 8.4 (maximum, 20.8) years. Predictor Living kidney donor nephrectomy.

Predictor — Living kidney donor nephrectomy.

Outcomes — The primary outcome was time to a diagnosis of gout. The secondary outcome in a subpopulation was receipt of medications typically used to treat gout (allopurinol or colchicine).

Measurements — The researchers assessed the primary outcome with healthcare diagnostic codes.

Results — Donors compared with nondonors were more likely to be given a diagnosis of gout (3.4% vs 2.0%; 3.5 vs 2.1 events/1,000 person-years; HR, 1.6; 95% CI, 1.2-2.1; P < 0.001). Similarly, donors compared with nondonors were more likely to receive a prescription for allopurinol or colchicine (3.8% vs 1.3%; OR, 3.2; 95% CI, 1.5-6.7; P = 0.002). Results were consistent in multiple additional analyses.

Limitations — The primary outcome was assessed using diagnostic codes in healthcare databases. Laboratory values for serum uric acid and creatinine in follow-up were not available in our data sources.

Conclusions — The findings suggest that donating a kidney modestly increases an individual’s absolute long-term incidence of gout. This unique observation should be corroborated in future studies.