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In vivo cystometric evaluation of progressive bladder outlet obstruction in rats
L T O'Connor1, E D Vaughan, D Felsen
1Department of Urology, James Buchanan Brady Foundation, New York Hospital-Cornell Medical Center, New York 10021, USA.
Purpose:
Bladder outlet obstruction in man is a common medical disorder that may result from benign prostatic hyperplasia, urethral stricture disease, or congenital anomaly. The functional changes that develop in response to obstruction include detrusor instability, elevated voiding pressures, and the presence of a residual urine. The aim of this study was to document the development of progressive bladder outlet obstruction over time in a rat model using conscious, in vivo urodynamics.
Materials And Methods:
Infravesical bladder outlet obstruction was created in female rats by placing a jeweler's jump ring loosely around the proximal urethra. Gradual development of outlet obstruction was followed urodynamically in awake animals at 3, 7, 14, 21, and 28 days post obstruction using a subcutaneously implanted mediport. For each group n = 5-8 animals.
Results:
Animals developed large capacity bladders with increased compliance, a high residual urine volume, and spontaneous activity. Bladder capacity increased from 0.20 + 0.02 ml. to 6.30 + 1.59 ml. at 28 days post obstruction (p < 0.05). Residual volume increased from 0.06 + 0.01 ml. to 5.95 + 1.54 ml. (p < 0.05). Percent void decreases from 72 + 3.7% in sham controls to 6.7 + 2.5% at 28 d (p < 0.05). Voiding pressure increased from 12 + 1.6 mm. Hg in sham animals to a maximum of 42 + 6.1 mm. Hg at 21 d (p < 0.05). Compliance was significantly higher at 28 d when compared to all other time points. 89% of obstructed animals developed bladder instability.
Conclusions:
This study provides clear evidence of the progressive change in bladder function which occurs following outlet obstruction. Implantation of a subcutaneous mediport allows in vivo recording of both the filling and voiding phases of micturition in awake animals that have intact neural responses. This is a precise and easily reproducible method for producing obstruction in a small animal which can provide a continuum of tissue and urodynamic data that may be used to further study the pathophysiologic changes underlying bladder outlet obstruction or other models of bladder dysfunction.