A qualitative ultrastructural study of the hypocontractile detrusor

It has been proposed that precise and specific ultrastructural patterns exist in the dysfunctional human detrusor. We evaluated ultrastructural changes in the hypocontractile detrusor and examined the technique of detrusor muscle biopsy and its clinical application.

After clinical and urodynamic evaluation 19 male and 2 female patients with severe hypocontractility were entered into this prospective study. All patients had a post-void residual urine volume of consistently greater than 300 ml. and were classified as weak or very weak according to the Schäfer nomogram. Multiple biopsies were obtained with the patient under general anesthesia using the cold cup technique. Subsequent specimens were processed for electron microscopy using standard methods. Biopsies were also obtained from 6 controls with normal voiding parameters.

Cold cup detrusor biopsy provided muscle of sufficient quality for detailed electron microscopic analysis in 26 of the 27 specimens obtained. Previously described criteria of the degeneration pattern were present in all cases of severe hypocontractility. These criteria include widespread disruptive muscle cell profiles with sarcoplasmic vacuolation, disruption of cell organelles and ultimately cell lysis. These features were evident in more than half of the randomly studied fields. In addition, 7 patients had an indistinct muscle fascicle cell arrangement with excessive deposits of collagen and elastic fibers between widely separated muscle cells and in the interstitium. It was suggested that these features represent the hyperelastosis pattern in the chronically over distended bladder. These morphological appearances were not present in any controls.

This early study would appear to support a morphological basis for detrusor hypocontractility and it reinforces the feasibility of electron microscopy as a potential diagnostic tool. The hypocontractile detrusor has distinct ultrastructural appearances that are easily distinguishable from those of the normal age matched detrusor.