Ultrastructural features of detrusor myohypertrophy (muscle fascicle derangement, collagenosis, variation in myocyte size and shape) have been seen in males with bladder outlet obstruction and associated with worse voiding outcomes following transurethral resection of the prostate. Initial studies have suggested similar detrusor ultrastructural features in females with bladder outlet obstruction. This study further examines ultrastructural features in female patients with bladder outlet obstruction and correlates these features with functional information from clinical and urodynamic studies to explore the role of bladder biopsy as a diagnostic tool for female bladder outlet obstruction.

Sixteen patients (twelve female and four male) with known bladder outlet obstruction on urodynamic study and two control patients (both female) with normal urodynamic studies underwent cystoscopy and detrusor muscle biopsy. The detrusor muscle biopsy specimens were processed for transmission electron microscopy. Previously established diagnostic criteria were used for ultrastructural analysis (such as, muscle fascicle derangement, myocyte irregularity, myocyte cell separation, collagenosis, and cellular degeneration). Severity of the ‘myohypertrophy pattern’ was assessed and correlated with clinical and functional features.

Features of myohypertrophy (muscle fascicle derangement, collagenosis, variation in myocyte size and shape) were present in the detrusor specimens of all female and male patients with bladder outlet obstruction but absent in the detrusor specimens of control patients. Features of degeneration were present in varying degrees in all patients, consistent with previous studies showing that degeneration correlates with age rather than degree of obstruction. Myohypertrophy features were less marked in females with bladder outlet obstruction compared to males with bladder outlet obstruction, except in one female with prolonged voiding dysfunction after colposuspension. Myohypertrophy features were also seen in one patient with four months history of an obstructive sling. Semi-quantitative analysis of ultrastructural features showed severity of myohypertrophy correlated with duration and degree of obstruction in female bladder outlet obstruction.

There are similar ultrastructural features using a standardized protocol in detrusor biopsies of female patients with bladder outlet obstruction compared to detrusor biopsies of male patients with bladder outlet obstruction, however the myohypertrophy pattern that is present in female bladder outlet obstruction is less marked than in the male, but appears to correlate with duration and severity of obstruction.

Given the uncertainty in diagnosis of female bladder outlet obstruction on urodynamic parameters, we have shown that the use of detrusor biopsy and its electron microscopy ultrastructural analysis may add further information and assist in the diagnosis of female bladder outlet obstruction.