CUA 2018: Impact of Percutaneous Nephrolithotomy (PCNL) on Renal Function

Halifax, Nova Scotia ( Percutaneous nephrolithotomy (PCNL) remains the gold standard treatment for large kidney stones (>2cm). Patients with large and staghorn stones often experience renal functional deterioration due to chronic obstruction of the collecting system. Infectious stones with chronic pyelonephritis tend to even further decrease renal functional outcomes. When it comes to less invasive management of kidney stones, urologists nowadays have two or three options depending on the stone size and patients characteristics. PCNL is probably most invasive compared to ureteroscopy and shock wave lithotripsy. In order to establish a surgical tract to the kidney, tubes must be placed percutaneously into the renal calyces. This often damages renal parenchyma which is mostly responsible for adequate clearance of variety of blood toxins. Measurement of renal function after PCNL procedure is important in order to keep the patients in check for their eGFR. 

Luke Reynolds, MD, reported a study that examined the impact of PCNL on renal function and complications in patients with normal and reduced renal function. Authors retrospectively reviewed prospectively maintained database of patients who underwent PCNL between 2012 and 2017 at St. Michael’s Hospital in Toronto. Patients creatinine and eGFR were measured before, immediately after the procedure and at the time of the follow up. Patients were divided into two groups based on their pre-op eGFR. Group 1 included patients with eGFR of less than 50ml/min and the second group included patients with eGFR of greater than 50ml/min. 

The study included a total of 220 patients who underwent PCNL. Of these, 25 patients had less than 50ml/min of eGFR and 195 had eGFR of greater than 50ml/min. There was no difference in gender distribution between the two groups. Patients with less than 50ml/min of eGFR were significantly older than the other group. Similarly, body mass index (BMI) was greater in older patients with less eGFR. Baseline creatinine was also higher in patients with higher BMI and age. 

Dr. Reynolds concluded that patients with reduced baseline renal function often have more complex and obstructing stone disease, requiring more pre-operative drainage tubes and greater need for multiple tracts. PCNL can be performed safely, with no increased risk in complications and minimal impact on renal function in patients with pre-existing renal dysfunction. 

Findings in this study are consistent with previous studies reporting on renal functional outcomes. Although PCNL is considered minimally invasive modality for stone removal it does have an impact on renal function within the 3-6 months after the procedure. Studies have shown that patients with normal eGFR will drop their renal function significantly after the procedure but recover to the baseline function at about 6 months period after the procedure. This time can be prolonged with baseline renal functional abnormalities, multiple tracts during the procedure, multiple staged procedures, inadequate drainage after the procedure and finally, postoperative complications such as bleeding and sepsis. 

Presented by Luke Reynolds, MD
Co-Authors: Jason Lee, Michael Ordon, Kenneth Pace

Written by Zhamshid Okhunov, Twitter: @OkhunovZham, Department of Urology, University of California-Irvine, medical writer for at the 73rd Canadian Urological Association Annual Meeting - June 23 - 26, 2018 - Halifax, Nova Scotia