The scale for the evaluation of the renal parenchymal injury degree in patients with nephrolithiasis

Background. The absence of scale that allows us to assess the degree of renal parenchymal injury by renal calculi and traumatic impact of the surgical methods of treatment has made this research relevant. The purpose of the study was to improve the efficiency of renal parenchymal injury diagnosis and to optimize the surgical management of urolithiasis. Material and methods. For the period from 2014 to 2017, 158 patients with nephrolithiasis were examined. The level of cystatin C in the blood serum of patients with nephrolithiasis was determined by the enzyme immunoassay method in the preoperative period and in the first 48 hours after surgery. The test system BioVendor (Germany) was used. Patients were divided into five groups. Group I was formed of 31 patients, who underwent micropercutaneous nephrolithotripsy. The second group included 31 individuals, who underwent ultra-mini-percutaneous nephrolithotripsy. Group III consisted of 35 patients treated with standard percutaneous nephrolithotripsy. Group IV included 30 persons with staghorn calculi, in this group the combination of a single standard access with multiple ultra-mini-percutaneous access was used. Thirty one patients in group V underwent nephrolithotripsy using multiple standard accesses. Group VI (control) included 32 apparently healthy volunteers with normal serum cystatin C level. To determine the adequacy of the proposed scale of the degree of renal parenchyma injury distribution, Receiver Operating Characteristic curve analysis was applied. Statistical studies were performed using the Statistica 6.0 package. Results. A serum marker of renal parenchymal injury degree — cystatin C in patients with nephrolithiasis is proposed. Based on its assessment, it was proved that in patients with calculi up to 2 cm in diameter, micropercutaneous nephrolithotripsy and ultra-minipercutaneous nephrolithotripsy have a statistically identical degree of renal parenchymal injury. The above noted degree of renal injury was lesser in comparison to standard percutaneous access. In patients with staghorn calculi, according to the serum cystatin C level, percutaneous nephrolithotripsy with multiple standard accesses is the most traumatic endoscopic surgical intervention. The coefficient of renal parenchymal injury was developed, which is determined by the ratio of the difference in serum cystatin C levels (before and after the surgery) to the serum level of this biomarker before surgery. A scale of its use has been created that makes it possible to establish three degree of renal parenchymal injury: mild — with a coefficient of ≤ 0.15; average — from 0.15 to 0.35 and severe — more than 0.35. This scale allows us to assess the traumatic effect of renal calculi in patients with urolithiasis, the efficacy of applied surgical technique and the success of conservative therapy. Conclusions. Based on evaluation of the renal parenchymal injury biomarker (cystatin C) in patients with nephrolithiasis with calculi up to 2 cm in diameter, it was proved that micropercutaneous nephrolithotripsy and ultra-minipercutaneous nephrolithotripsy have statistically equal degree of renal parenchymal injury but lesser than with a standard technique. Regardless the diameter of the calculus, nephrolithotripsy using one standard access or combined application of one standard and multiple ultra-minipercutaneous accesses, according to the serum cystatin C levels, have the same traumatic impact on the renal parenchyma (p > 0.05). In patients with staghorn nephrolithiasis, according to the levels of cystatin C, percutaneous nephrolithotripsy using multiple standard access is the most traumatic endoscopic intervention. A scale for predicting the extent of renal parenchymal injury has been developed for various clinical forms of urolithiasis and methods of nephrolithotripsy.