Increased duration of simulated childbirth injuries results in increased time to recovery

• Published in: American journal of physiology. Regulatory, integrative and comparative physiology integrative and comparative physiology, 2007-04, Vol.292 (4), p.R1738-R1744
• Main Authors: Pan, H. Q, Kerns, J. M, Lin, D. L, Liu, S, Esparza, N, Damaser, M. S
• Format: Article
• Language: English
• Subjects: Animals; Births; Computer Simulation; Delivery, Obstetric - adverse effects; Disease Models, Animal; Female; Histology; Obstetrics; Parturition; Pregnancy; Random Allocation; Rats; Rats, Sprague-Dawley; Rodents; Time Factors; Urinary Catheterization; Urinary incontinence; Urinary Incontinence, Stress; Urodynamics; Urology; Vagina - physiology
• ISSN: 0363-6119; 1522-1490
• DOI: 10.1152/ajpregu.00784.2006

1 Cleveland Clinic and 2 Louis Stokes Cleveland Department of Veterans Affairs (VA) Medical Center, Cleveland, Ohio; and 3 Rush University Medical Center, Chicago, 4 Hines VA Hospital, Hines, and 5 Loyola University of Chicago Stritch School of Medicine, Maywood, Illinois Submitted 9 November 2006 ; accepted in final form 22 December 2006 Stress urinary incontinence (SUI) development is strongly correlated with vaginal childbirth, particularly increased duration of the second stage of labor. However, the mechanisms of pelvic floor injury leading to SUI are largely unknown. The aim of this study was to determine the effects of increased duration of vaginal distension (VD) on voiding cystometry, leak point pressure testing, and histology. Sixty-nine virgin female rats underwent VD with an inflated balloon for either 1 or 4 h, while 33 age-matched rats were sham-VD controls. Conscious cystometry, leak point pressure testing, and histopathology were determined 4 days, 10 days, and 6 wk after VD. The increase in abdominal pressure to leakage (LPP) during leak point pressure testing was significantly decreased in both distension groups 4 days after distension, indicative of short-term decreased urethral resistance. Ten days after VD, LPP was significantly decreased in the 4-h but not the 1-h distension group, indicating that a longer recovery time is needed after longer distension duration. Six weeks after VD, LPP was not significantly different from sham-VD values, indicating a return toward normal urethral resistance. In contrast, 6 wk after VD of either duration, the distended rats had not undergone the same increase in voided volume as the sham-VD group, suggesting that some effects of VD do not resolve within 6 wk. Both VD groups demonstrated histopathological evidence of acute injuries and tissue remodeling. In conclusion, this experiment suggests pressure-induced hypoxia as a possible mechanism of injury in vaginal delivery. rat; urodynamics; leak point pressure; histology Address for reprint requests and other correspondence: M. S. Damaser, Dept. of Biomedical Engineering, Cleveland Clinic, 9500 Euclid Ave. ND20 Cleveland, OH 44195 (e-mail: damasem{at}ccf.org )