“ Whether CKD due to surgical removal of kidney tissue (nephrectomy) is as significant as CKD due to other etiologies remains unclear,” explains Robert J. Ellis, MD, PhD. “The general rationale behind this uncertainty is that CKD due to surgical causes is a ‘one off’ event, in which the loss of kidney tissue happens only during the surgery but the remaining kidney tissue after surgery remains healthy. This perspective contrasts with medical causes of kidney disease, which are characterized by progressive and ongoing loss of kidney tissue. However, no strong evidence supports this perspective, and it is difficult to undertake studies that compare surgical and non-surgical etiologies of kidney disease since the causes are so different.”
Dr. Ellis emphasizes the importance of understanding the differences in CKD incidence and progression among patients who developed CKD after nephrectomy so that clinicians may guide follow-up and long-term CKD screening and provide accurate information before surgery about possible adverse outcomes.
Testing a CKD Progression Hypothesis
For a study published in International Urology and Nephrology, Dr. Ellis and colleagues tested the hypothesis that CKD progression is less aggressive in patients with nephrectomy as their primary cause of CKD and not non-surgical causes. The researchers utilized a large multicenter cohort of patients (N=5,983) already known to a specialist nephrology service with CKD ranging from stage 1 to 5 to compare clinically significant outcomes of patients with CKD due to nephrectomy and CKD due to other causes.
The cause of CKD was determined by the patient’s physician and grouped as acquired single kidney (nephrectomy), glomerulonephritis, polycystic kidney disease (PCKD), diabetic neuropathy, or other.
Likelihood of Kidney Failure Equivalent to Other Etiologies
Among the 5% of patients with an acquired single kidney as their primary cause of CKD, 10% and 17% developed kidney failure or died at median follow-up times of 12.9 and 33.6 months following recruitment. Among patients with an eGFR <45 mL/min per 1.73m2 at baseline, those with PCKD and diabetic nephropathy had the highest rates of kidney failure, while those with glomerulonephritis and an acquired single kidney had lower rates. Among patients with an eGFR ≥45 mL/min per 1.732, those with diabetic nephropathy had the highest rates of kidney failure, whereas those with glomerulonephritis, acquired single kidney, and PCKD had a lower risk.
“The main takeaway from our research is that among patients with CKD due to an acquired single kidney who have been referred to a nephrologist, the likelihood of developing kidney failure was essentially equivalent to other etiologies of CKD, which are generally considered medical,” Dr. Ellis says. The secondary outcomes of CKD progression and mortality, he adds, were also similar between etiologies. “While there was a slight male predominance among the 10% of patients who developed kidney failure and a link between hypertension and kidney failure, low eGFR was the strongest predictor of kidney failure (Table).”
CKD After Nephrectomy Linked With Real Risk for Kidney Failure
Dr. Ellis and colleagues emphasize that these data suggest that eGFR, rather than etiology, should be used to stratify risk for kidney failure and CKD progression, and that patients who develop CKD after nephrectomy have a similar risk for CKD progression, kidney failure, and death compared with patients who have CKD due to other causes.
“While CKD after nephrectomy is not the most aggressive cause of kidney disease, it is not a benign condition,” Dr. Ellis explains. “It is linked with a real risk for kidney failure and death, which is comparable to other major causes of CKD.”
The study team would like to see further research focus on developing pragmatic approaches for postoperative CKD screening and developing evidence-based criteria for identifying patients at risk for CKD progression so that early referral to specialist nephrologist services can be made.