Kidney donors have some of the abnormalities typically associated with mild chronic kidney disease (CKD) six months after donation, researchers concluded.

These abnormalities include a decline in kidney function, increased parathyroid hormone (PTH) and uric acid levels, and lower hemoglobin levels, researchers reported in the American Journal of Kidney Diseases (2013;62:577-586).

The prospective study compared 203 kidney donors with 201 controls, who were healthy individuals with two kidneys and who theoretically would have been suitable to donate a kidney. Donors and controls were comparable with respect to all parameters measured. A team led by Bertram L. Kasiske, MD, of the Hennepin County Medical Center in Minneapolis, measured glomerular filtration rate (GFR), blood pressure, and other variables at baseline (predonation) and at six months.

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Compared with controls, donors had a significant 28% decrease from baseline in measured GFR at six months (94.6 vs. 67.6 mL/min/1.73 m2), a significant 23% increase in PTH level (42.8 vs. 52.7 pg/mL), a significant 8.2% increase in uric acid level (4.9 vs. 5.3 mg/dL), and a significant 3.7% decrease in hemoglobin level (13.6 vs. 13.1 g/dL). The study found no significant difference between donors and controls in blood pressure, urine total protein, urine albumin, body weight, or body mass index.

“The increase in PTH levels is in keeping with the correlation between PTH level and kidney function reported in patients with mild CKD,” the researchers stated.

Additionally, the authors noted that hyperuricemia has long been suggested to cause CKD, hypertension, diabetes, and cardiovascular disease (CVD), but this has been a source of ongoing controversy because it is possible that hypertension, diabetes, and CVD directly or indirectly cause hyperuricemia. “The present study unequivocally shows that a reduction in GFR causes a significant increase in serum uric acid level, even in otherwise healthy individuals,” they wrote. “Thus, whatever other factors may be causing an association between CKD and hyperuricemia, the reduction in GFR itself may explain much or all of the observed association.”

The researchers stated that they are unaware of any previous report of a significant decrease in hemoglobin in donors. “Possible explanations include mild anemia due to surgical blood loss, iron deficiency, and/or reduced erythropoietin due to the reduced kidney function,” they observed.

 “This new knowledge of biochemical changes after donor nephrectomy is welcome,” Amit X. Garg, MD, PhD, of Western University, London, Ont., wrote in an accompanying editorial. “A prospective cohort design, as used in this study, is well suited to describe biochemical, GFR, and blood pressure changes after donor nephrectomy.”