Effect of the location and severity of partial ureteral obstruction on urinary system stone disease formation

Abstract

This study aimed to observe the effect of the location and severity of partial ureteral obstruction, based on ureteropelvic and ureterovesical junction strictures, on stone formation. Forty 8-week-old male rats were divided into five groups: control and mild/severe proximal or distal ureteral obstruction groups. A partial ureteral obstruction was created according to the type of obstruction by a surgical procedure. After 5 days of intraperitoneal glyoxylate injection, the urine, blood samples, and kidney tissues of the rats were examined. There were significant differences in urine citrate concentrations, pH values, and oxalate/creatinine, citrate/creatinine, and calcium/creatinine ratios between the groups (all p < 0.05). The mean citrate/creatinine ratio was 21.13 ± 0.44 in the control group, 17.31 ± 3.82 in the distal obstruction group, and 15.48 ± 1.87 in the proximal obstruction group. Regarding the degree of obstruction, urine citrate concentrations, pH values, and citrate/creatinine were lower, and the oxalate/creatinine ratio was higher in severe obstruction than in mild obstruction (p < 0.05). This study represents an initial attempt to evaluate a model of partial ureteral obstruction and urolithiasis. The findings indicate that obstruction alters urinary parameters, such as citrate and pH, indirectly increasing the risk of stone formation. Furthermore, stone formation in an obstructed urinary system appears to be a complex process. However, metabolic evaluation and treatment may help prevent stone formation in patients with ureteral obstruction.

Keywords: Kidney stone; Partial ureteral obstruction; Ureteropelvic junction obstruction; Ureterovesical junction obstruction; Urinary system stone disease.

Fig. 1

Surgical procedures performed on the groups of rats with obstruction at the distal level (mild distal obstruction and severe distal obstruction groups): (a) Dissection of the distal ureter; (b) Knotting of the ureter using steel wire; (c) Appearance after removing the wire and cutting the suture.

Fig. 2

Surgical procedures performed on the groups of rats with obstruction at the proximal level (mild proximal obstruction and severe proximal obstruction groups): (a) Dissection of the ureteropelvic junction; (b) Knotting of the ureter using steel wire; (c) Cutting the suture after removing the wire.

Fig. 3

Histological evaluation of representative rat kidney cortex sections according to the Pizzolato classification ((a) Grade 0; (b) Grade 1; (c) Grade 2; (d) Grade 3). Arrows show crystals in sections of renal cortex (haematoxylin and eosin staining, x100 magnification.

Fig. 4

Evaluation of the right renal crystal score according to the pH ( = 3.031, p < 0.502)