Objectives: To establish the contribution of the anterior fibromuscular stroma to the urethral resistance in an ex vivo human prostate model. The anterior fibromuscular stroma constitutes the anterior portion of the prostatic surgical capsule. Methods: An intact bladder and prostate were obtained from 10 patients who had undergone cystoprostatectomy. The bladder was filled at a predetermined flow rate through a catheter inserted into the bladder dome. The incoming flow was allowed to drain freely through the urethra. The bladder pressures were recorded after a steady state had been reached. The prostatic anterior fibromuscular stroma was incised longitudinally from the prostatic base to its apex. The bladder pressures were recorded before and after the incision was made and again after suture approximation of the cut edges of the anterior fibromuscular stroma. Results: The median patient age was 72 years (range 52-81). The median prostatic volume was 46 cm3 (range 30-260). A statistically significant decrease in bladder pressure was observed after division of the anterior fibromuscular stroma. The mean pressure decreased from 12.5 cm H2O to 10.6 cm H2O, with a flow rate of 6 mL/s, and from 16.4 cm H2O to 13.7 cm H2O, with a flow rate of 12 mL/s (P < .0001). This corresponded to a 15% reduction in bladder pressure. A return to the baseline pressure or greater than baseline was recorded after approximation of the anterior fibromuscular stroma. Conclusions: The anterior fibromuscular stroma plays a significant role in maintaining urethral resistance. Its longitudinal division reduced the bladder pressure an average of 15% across flow rates of 6-12 mL/s.
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