www.kjurology.org http://dx.doi.org/10.4111/kju.2011.52.12.835 Voiding Dysfunction Early Sequential Changes in Bladder Function after Partial Bladder Outlet Obstruction in Awake Sprague-Dawley Rats: Focus on the Decompensated Bladder Yong-Jin Kang, Long-Hu Jin, Chang-Shin Park1, Hwa-Yeon Shin, Sang-Min Yoon, Tack Lee Departments of Urology and 1Pharmacology, Inha University College of Medicine by BK 21 Project, Incheon, Korea Purpose: We investigated bladder function, with special focus on initial functional changes, by objective report of decompensated bladder according to the percentage of residual urine volume to bladder capacity in awake, obstructed rats. Materials and Methods: Thirty rats were randomly subjected to sham operations (n=10) or partial bladder outlet obstruction (BOO, n=20). Cystometric investigations were per- formed without anesthesia 1 or 2 weeks after BOO surgery. To reduce the influence of confounding factors in awake cystometry, we used simultaneous recordings of intra- vesical and intraabdominal pressures. Decompensated bladder was defined as the bladder with more than 20% of residual volume compared with bladder capacity. Results: Compared with that in sham animals, basal pressure was elevated in both BOO groups. Threshold pressure was higher in the 2 week BOO (p＜0.01) group. Compliance was decreased in the 1 week BOO group (p＜0.01) and increased in the 2 week BOO group (p＜0.001). Bladder capacity was not increased in the 1 week BOO group, but was increased in the 2 week BOO group (p＜0.01). Decompensation was found in 62.5% of the 1 week BOO group and in 33.3% of the 2 week BOO group. Conclusions: From the earlier phase, the bladders exhibited serial changes in pressure and volume parameters, and decompensated bladders defined by the percentage of re- sidual volume to bladder capacity could be seen. During the later phase, there was an increasing tendency of compensated bladders, accompanied by the bladders being en- larged and more compliant. Key Words: Detrusor, overactive; Urinary bladder; Urodynamics This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Article History: received 4 June, 2011 accepted 11 October, 2011 Corresponding Author: Tack Lee Department of Urology, Inha University College of Medicine by BK 21 Project, 7-241, Sinheung-dong, 3-ga, Jung-gu, Incheon, 400-711, Korea TEL: +82-32-890-3448 FAX: +82-32-890-3097 E-mail: lt11@inha.ac.kr This study was supported by grants from the Korea Healthcare Technology R&D Project, Ministry of Health & Welfare, Republic of Korea (A090715-1002-0000100). INTRODUCTION Bladder outlet obstruction (BOO) in men is a common clin- ical condition secondary to benign prostatic hyperplasia (BPH). Histologic BPH is a highly prevalent disease, start- ing in men in their 40s, and evidence of BPH can be found in 90% of men in their 80s [1,2]. The lower urinary tract symptoms (LUTS) caused by this BPH develop in men after their 60s [1]. In men older than 50 years of age, 81% will experience those symptoms and 5% to 25% will develop acute urinary retention. Many recent studies have pro- vided strong evidence for the progressive nature of BPH [3,4]. There are still not enough clinical data, however, showing the pathophysiological serial changes in the blad- der caused by BOO. Experimental animal models with BOO have shown sig- nificant alterations in bladder structure and function [5,6]. It is known that the decompensatory changes in the blad- der occur after the compensatory changes. Rabbits sub- jected to BOO will develop a rapid, progressive increase in bladder weight during the first 1 to 2 weeks (initial period) following surgical obstruction. The detrusor function dur- ing this phase shows normal or increased pressure gen- eration, which is referred to as the compensated period. It Korean Journal of Urology Ⓒ The Korean Urological Association, 2011 835 Korean J Urol 2011;52:835-841