INVESTIGATIVE UROLOGY

Detrusor Quantitative Morphometry in Obstructed Males and Controls
Collado A, Batista E, Gelabert-Mas A, Corominas JM, Arano P, Villavicencio H
Urology Service, Instituto Valenciano de Oncologia, Valencia, Spain
J Urol. 176: 2722-8

• Purpose: We studied the usefulness of computer assisted morphometry for measuring detrusor muscle cell diameter and the connective tissue-to-smooth muscle ratio in patients with bladder outlet obstruction, acute urinary retention and a nonobstructed control group.
• Materials and Methods: A prospective study was done in patients with bladder outlet obstruction undergoing transurethral prostate resection. Patients were divided into 33 with obstruction and 14 in acute urinary retention. A total of 15 males without obstruction undergoing transurethral prostate resection for bladder tumor formed the control group. Detrusor specimens were obtained during transurethral prostate resection. Detrusor muscle cell diameter was measured using light microscopy and a semiautomatic image analysis system. The connective tissue-to-smooth muscle ratio was automatically determined with computer assisted image analysis. Symptoms and urodynamic assessment were performed preoperatively and 6 months postoperatively.
• Results: A total of 62 patients were included. The obstruction and acute urinary retention groups had a statistically higher detrusor muscle cell diameter and more fibrosis than the control group. Patients in acute urinary retention had more intrafascicular fibrosis (higher connective tissue-to-smooth muscle ratio at 40x magnification) than patients with obstruction. There were no differences in detrusor muscle cell diameter or interfascicular fibrosis (connective tissue-to-smooth muscle ratio at 10x magnification) between the obstruction and acute urinary retention groups. Detrusor muscle cell diameter correlated with symptom duration and functional recovery after transurethral prostate resection. Detrusor fibrosis correlated with preoperative detrusor pressure at maximum flow and postoperative compliance. Patients in acute urinary retention had fewer symptoms and higher residual volume. Other urodynamic parameters and their improvement after surgery were similar in the acute urinary retention and obstruction groups.
• Conclusions: Morphometric differences in detrusor muscle cell diameter and the connective tissue-to-smooth muscle ratio were observed between controls and patients with obstruction. There is an increase in detrusor muscle cell diameter and fibrosis in bladder outlet obstruction and more intense intrafascicular collagen deposition in patients in acute urinary retention.
  
• Editorial Comment
  Previous studies suggested that bladder outlet obstruction could produce histological changes in detrusor muscle and extracellular matrix; nevertheless, the results have been contradictory, with some authors reporting increase in smooth muscle and collagen decrease, while others reported collagen increase.
  The authors studied 33 patients with bladder outlet obstruction (BOO) due to benign prostatic hypertrophy (BPH) and 14 patients in acute urinary retention (AUR). A total of 15 males without obstruction undergoing transurethral prostate resection for bladder tumor composed the control group. The present paper reported that the detrusor muscle cell diameter correlated with symptoms. It was found a positive correlation between the increase in cellular diameter and symptoms duration. The authors also studied the urodynamic parameters and found that there was no correlation in the obstructed and acute urinary retention groups with the detrusor muscle cell diameter. The authors found hypertrophy and an increase in fibrosis in patients with BOO. In patients with obstruction, there were slightly morphometric differences between those with an episode of AUR, that is higher intrafascicular fibrosis. There were no urodynamic differences preoperatively and postoperatively.
  In a recent study (1), we analyzed the detrusor extracellular matrix in samples taken from bladders of 10 patients who underwent transvesical prostatectomy for treatment of BPH. Control material was composed of 10 vesical specimens, removed during autopsies performed in cadavers of accident victims, with ages between 18 and 35 years (mean = 26 years). We found that the components of connective tissue (collagen and elastic system fibers) are increased in the detrusor muscle of patients with infravesical obstruction, when compared to controls.

Reference
1. Rubinstein M, Sampaio FJ, Costa WS: Stereological study of collagen and elastic system fibers in the detrusor muscle of bladders from controls and patients with infravesical obstruction. Int Braz J Urol. 2007; 33 (1), In Press.

Dr. Francisco Sampaio
Full-Professor and Chair, Urogenital Research Unit
State University of Rio de Janeiro
Rio de Janeiro, Brazil