Detrusor glycogen reflects the functional history of bladders with partial outlet obstruction

OBJECTIVE: To assess the relationship between glycogen content in bladder detrusor tissue and historical bladder function in a guinea-pig model of partial bladder outlet obstruction (PBOO). MATERIALS AND METHODS: In male immature guinea pigs PBOO was created with a silver ring around the proximal urethra; a control group had a sham operation for comparison. Longitudinal individual urodynamic data were obtained weekly, so that guinea pigs were killed at different levels of bladder dysfunction. Bladder sections were stained with periodic acid-Schiff (PAS) to assess overall morphology and glycogen granule density, scored from 0 (no glycogen) to 3. Glycogen scores were related to both the end-stage and historical extremes of bladder function values. RESULTS: Glycogen granules were seen only in the detrusor; as their number increased their location expanded from only close to the serosa (glycogen score 1), through the detrusor (score 2) up to the urothelium (score 3). A glycogen score of 0 correlated with normal values for all urodynamic variables. Compared with a glycogen score of 0 a score of 1 correlated with significant (P < 0.05) changes in end-stage compliance (decrease) and contractility (increase) and significantly higher historical values for contractility, pressure and number of unstable contractions (NUC). In the group with a glycogen score of 2 there were significant changes in both the end-stage values and historical extremes for compliance, pressure, contractility and NUC (all P < 0.05). In the group with a glycogen score of 3 all these changes were even more dramatic, except for the end-stage contractility, for which the increase was not significant. From glycogen score 0 to score 3 all changes increased in magnitude. CONCLUSION: A high glycogen content reflects a history of abnormal urodynamic function. This finding exemplifies the added value of structural analysis to urodynamic studies. Further studies are needed to relate bladder structure to the potential for functional recovery.

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