Effect of simulated birth trauma on the urinary continence mechanism in the rat

Objectives. To examine the effect of simulated birth injury in an animal model as part of a study on the pathogenesis of stress urinary incontinence (SUI) and the urinary continence mechanism. Methods. A balloon was inflated in the vaginas of rats for 4 hours to simulate prolonged labor. The effect...

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Published in:	Urology (Ridgewood, N.J.) Vol. 52; no. 1; pp. 143 - 151
Main Authors:	Lin, Austin S, Carrier, Serge, Morgan, Daniel M, Lue, Tom F
Format:	Journal Article
Language:	English
Published:	New York, NY Elsevier Inc 01-07-1998 Elsevier Science
Subjects:	Animals Biological and medical sciences Birth Injuries - complications Disease Models, Animal Female Medical sciences Nephrology. Urinary tract diseases Rats Rats, Sprague-Dawley Urinary Incontinence, Stress - etiology Urinary Incontinence, Stress - pathology Urinary system involvement in other diseases. Miscellaneous Urinary tract. Prostate gland Modification Urinary system disease Levator muscle Rat Pathogenesis Rodentia Urinary tract disease Experimental study Pathology Voiding dysfunction Nervous ganglion Vertebrata Abdominal distension Mammalia Histopathology Urethra Animal Bladder disease Delivery Biological effect Urinary stress incontinence
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Summary:	Objectives. To examine the effect of simulated birth injury in an animal model as part of a study on the pathogenesis of stress urinary incontinence (SUI) and the urinary continence mechanism. Methods. A balloon was inflated in the vaginas of rats for 4 hours to simulate prolonged labor. The effect on the continence mechanism was assessed by functional, anatomic, biochemical, and histologic examinations. The functional test consisted of placing chili powder or a clipped whisker into the rat’s nostrils to induce sneezing. Anatomic measurement of the genital hiatus was performed with a caliper. Serum creatine phosphokinase (CPK) and lactate dehydrogenase (LDH) were measured to examine the value of muscle injury in predicting incontinence. c-Fos immunostaining in the spinal cord was used as a marker of nerve injury. These data were then correlated with histopathologic examination of the urethra and pelvic floor tissues. Results. Four weeks after simulated birth injury, SUI was noted in 19 of 48 experimental rats. The genital hiatus was significantly wider in incontinent rats. The serum CPK and LDH levels were markedly elevated, but no difference was noted between the continent and incontinent rats. All experimental rats showed many c-Fos immunostaining neurons in the L6 to S1 spinal cord segments, but none was seen in control rats. Histologic study revealed a marked decrease of ganglion cells in the neural plexuses posterolateral to the vagina in experimental rats. After 4 weeks, muscle necrosis and degeneration, irregular shape and size of muscle fibers, and a change in the type I/II ratio were prominent features in the levator ani. In the urethra, we noted a significant decline in urethral wall musculature (both smooth and striated) in incontinent rats. Conclusions. In this novel rat model, simulated birth injury resulted in SUI in a portion of the animals. Pathologic changes in the urethra, pelvic ganglia, and levator muscles seem to be the contributing factors to SUI.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0090-4295 1527-9995
DOI:	10.1016/S0090-4295(98)00136-8