Collagen-to-smooth muscle ratio helps prediction of prognosis after pyeloplasty

Purpose: We quantitatively evaluated the collagen-to-smooth muscle tissue m atrix ratio in ureteropelvic junction obstruction, and compared the ratio w ith the degree of obstruction, patient age and postoperative renal recovery . Materials and Methods: We analyzed histological sections from 65 patients w ith ureteropelvic junction obstruction and 6 normal controls. Morphological and functional grading systems were adapted to determine the degree of ren al obstruction. To examine smooth muscle and collagen tissue, sections were stained using Masson's trichrome. Two distinct populations of collagen ver sus smooth muscle were identified and the tissue matrix ratio was calculate d by color image analysis. Results: The mean tissue matrix ratio plus or minus standard deviation was 1.32 +/- 0.79 in all patients with ureteropelvic junction obstruction but o nly 0.30 +/- 0.10 in normal controls (p <0.0001). It appeared that the lowe r the tissue matrix ratio, the better the improvement in postoperative hydr onephrosis (r = -0.50, p = 0.0001). Better recovery of renal function after pyeloplasty was observed with a decrease in the tissue matrix ratio (r = - 0.43, p = 0.0004). We divided patients according to the tissue matrix ratio into groups 1-ratio 1 or less, 2-greater than 1 to 1.5 and 3-greater than 1.5 to determine a more detailed and clinically applicable correlation of t issue matrix ratio with postoperative renal functional changes. Better impr ovement in postoperative renal function was observed in group 1 than in gro up 3 (p = 0.002). Also, the tissue matrix ratio increased with patient age (r = 0.33, p = 0.007). Conclusions: Since our data represent an objective and quantitative paramet er associated with ureteropelvic junction obstruction, we believe that our findings may help to predict the prognosis after pyeloplasty.