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.