STONE DISEASE

Acute Effects of Percutaneous Tract Dilation on Renal Function and Structure
Handa RK, Matlaga BR, Connors BA, Ying J, Paterson RF, Kuo RL, Kim SC, Lingeman JE, Evan AP, Willis LR
Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana, USA
J Endourol. 2006; 20: 1030-40

• Background: Percutaneous nephrolithotomy (PCNL) is performed on a routine basis for the rapid and efficient removal of large caliceal stones. After percutaneous puncture, rigid dilators or an inflatable balloon are used to dilate the nephrostomy tract to allow access to the collecting system for stone removal. Little is known of the acute impact of tract dilation procedures on renal function.
• Materials and Methods: We compared renal hemodynamic and excretory function in female pigs immediately before and up to 5 hours after percutaneous nephrostomy (PCN) using sequential Amplatz dilators (N = 8) or Nephromax balloon inflation (N = 7) and control pigs with no PCN access (N = 8). We also examined renal function in patients undergoing PCNL.
• Results: The two PCN procedures produced a renal lesion of comparable size and morphology, as well as similar changes in renal function. Glomerular filtration rate (GFR), renal plasma flow (RPF), and urinary sodium excretion (U(Na)V) were significantly reduced in Amplatz- and Nephromax-treated kidneys throughout the 5-hour observation period, by about 50%, 60%, and 80%, respectively. In control pigs, GFR and RPF remained stable and U(Na)V declined progressively to about 50% of baseline over the course of the experiment. The contralateral kidney showed changes in renal function similar to those in the PCN-treated or control kidney in all three groups. A retrospective analysis of 196 adults with normal renal function who underwent unilateral PCNL using the Nephromax balloon dilator revealed a significant increase in serum creatinine of 0.14 mg/dL at 1 day.
• Conclusion: Both animal and human studies show that PCN is associated with an acute decline in renal function.
  
  
• Editorial Comment
  This study raises concern regarding transient decrease in ipsilateral and contralateral renal function during PCNL. The authors did not have a control group where percutaneous access was gained with a puncture needle, but the tract was not dilated. Such a group would help delineate whether the insult to the kidney leading to hemodynamic and functional changes is the percutaneous access or tract dilation. Renal obstruction may have confounded the results obtained during the evaluation period - it is possible that the 8F Cope catheter and ureter may have been blocked by clots associated with the tract dilation. Indeed the authors report a marked decrease in urine output in these animals, with 2 animals experiencing complete cessation of urine formation from the treated kidney. Future studies evaluating the relative changes in function with regards to maximum diameter of tract dilation may help support or refute the concept of a mini-PCNL. As such, these findings are critical for the practicing urologist to appreciate, as the impact on ipsilateral and contralateral renal filtration, perfusion and excretory function suggests a need to monitor the use of nephrotoxic medications, such as ketorolac or gentamycin, during the immediate post-PCNL period.

Dr. Manoj Monga
Professor, Department of Urology
University of Minnesota
Edina, Minnesota, USA