The role of functional urodynamic disorders in the pathogenesis of urolithiasis.

Objective: The aim of this study was to analyze the functional urodynamic parameters, which affect renal function and can promote stone formation.
Materials and Methods: We examined sixty consecutive patients with renal and ureteral stones and indication to urinary diversion by nephrostomy tube or indwelling catheter In upper urinary tract, urodynamics was assessed with the help of electromanometry and multichannel impedance ureterography. To measure ureteral peristalsis, a probe equipped with 9 successively incorporated electrodes was indwelled retrogradely into distal ureter through a urethroscope. The documented data included renal pelvic pressure (RPP) and the number of ureteric contractility parameters such as peristalsis amplitude, peristalsis rate, the ureteral wall tone, the characteristics of contractile waveform and its direction (antegrade or retrograde). Urinary biochemistry and enzymuria were studied in order to characterize the lithogenic activity and renalfunction. The patients were divided into three groups: group 1 included patients with acute pyelonephritis caused by unilateral stone obstruction (n = 24), group 2 patients with stones and non-acute latent chronic pyelonephritis (n = 31) and group 3 unobstructed patients without signs of inflammation (n = 5).
Results: In the three groups of patients, the mean baseline RPP values were, respectively 28.7 +/- 2.6 (range 20.0-32.4); 15.6 +/- 1.9 (range 3.5-29.0); and 3.6 +/- 1.4 (range 0-8) cm H2O. The ratio of GGT to urinary creatinine changed similarly: it was elevated during acute inflammation, moderately enhanced during the chronic process, but significantly decreased after stone removal and resolution of inflammation (11.5 +/- 3.2; 8.1 +/- 2.0, and 1.6 +/- 0.5 unit/L). Biochemical evaluation revealed 54% patients with enhanced lithogenic activity assessed by elevated calcium and oxalates in the urine (4.95 +/- 0.25 mM and 504 +/- 35 microM, correspondingly) and low level of citrates (2.5 +/- 0.1 mM). In a subgroup of 11 patients with urolithiasis the baseline RPP values were assessed in relation to ureteral contractile activity in the distal region of ureter. Low RPP was found in a patient (9%) with strong ureteral contractions and a low tone while RPP was moderately higher in another patient (9%) with moderate mean peristaltic amplitude value but with elevated tone of ureteral wall. In the majority of examined patients with significantly elevated mean RPP value (45%), peristalsis of distal ureter was characterized by weak long-term and frequent contractions as well as increased tone with respect to the patients with normal RPP. The patients (36%) with moderately increased RPP demonstrated strong frequent contractions in the distal ureter and low ureteral wall tone. Changes in urodynamic parameters in patients examined before and immediately after ureteroscopy and lithotripsy procedures were observed. Factors affecting the ureteral wall tone were duration of stone disease, location and disposition of stones.
Conclusions: Our clinical observations obtained with the help of physiological methods revealed various factors modulating the urodynamic disorders in renal pelvis: temporary or persistent elevation of pelvic pressure; peculiarities of contractile function in distal ureter manifested by the tonic changes and variations in contractile amplitude, and certain abnormalities in propagation of contractile wave in the upper urinary tract. The reported urodynamic changes in patients with stone disease can be supplementary pathogenic factors causing deterioration of renal function probably followed by stone formation.