| Background and Objective:Benign prostatic hyperplasia ( BPH ), characterized by chronic progression, is a major aspect of urologic investigations. It had been thought that the patient would recover completely after relief of obstruction. However, clinically, about 40% of these patients will not regain their normal voiding ability after surgery. One of the most important reasons for it is the damaged detrusor. So it is better to treat the obstruction before the inreversible changes in bladder function occur. Currently, the urodynamic studies is the standard methods to evaluate the baldder outlet obstruction ( BOO ) and bladder function. But it is impossible to use it as an routine to monitor the progession of BPH. Recently some reported that the measurements of bladder wall weight or bladder wall thickness may be a useful marker to predict BOO and acute urinay retention. This provided a novel clue in exploring noninvasive methods to evaluate bladder function. However, in the point of clinical research, they had difficulty in answering the following questions : ( 1 ) How to estimate the compensation status of detrusor contractile function? ( 2 ) How to judge whether the damaged bladder function will be reversible or not? ( 3 ) How to determine the ideal time to intervene to prevent deterioration? The first thing must to do to answer it is to investigate the correlation between the bladder wall morphologic changes and bladder function. In this study, we want to use animal model of partial bladder outlet obstruction ( PBOO ) to explore the relationship of bladder wall weight ( BWW), detrusor structural abnormality and bladder function after BOO. Also clinical research will be performed simultaneously.Methods:The study includes two parts : ( 1 ) New Zealand White rabbits were used to establish mild PBOO model. The BWW, bladder wall microscopic and ultrastructure changes, and detrusor contractility were investigated in different prolonged time of obstruction. The statistical analysis were then performed to data. ( 2 ) Ultrasound evalued bladder wall weight ( UEBW ) were measured by B type ultrasonagraphic methods. Our series included 78 cases of BPH, 3 cases urethral stricture, and other 30 cases of age-matched males without BOO were also included as control. The UEBW was measured pre- and post-operatively for each patient. BOO and bladder function was evaluated by urodynamic studies. The correlation of UEBW with BOO and bladder function was statistically analysed.Results:1. In animal modals, As compared with the control, BWW increased dramatically after PBOO. BWW rised rapidly and progressively during week 1, almost reaching the maximum levels and then slight decreased and stabled during week 2～3, thereafter, gradually increased with time. During week 12 BWW was 7 times as that of control.2. Physiologic experiment demonstrated that the detrusor contractility waved with time after PBOO : during week 1 decreased sharply as 1/4 of normal control, then gradually restored nearly to normal during week 2～3, and it was even more powerful than normalcontrol during week 4; thereafter decresed sharply with time.3. BWW correlated negtively with detrusor contractility. Analysis of the rate of tension development among 3 group based upon BWW (≤5g, 5～10g,≥10g ), the rate increased with BWW. This hinted that BWW may predict the bladder function change, that is when BWW > 5g, detrusor may shift from compensation to decompensation.4. Pathomorphology changes in bladder wall after PBOO : ( 1 ) As compared with control, besides the hypertrophy of muscle bundles, serosa significantly thickened. ( 2 ) Smooth muscle cell ( SMC ) experienced hypertrophy, hyperplasia and even endocytoplasmic reticulum and mitochondria dilation to compensate the detrusor contractility (2～4 week ) . After some time of duration, displayed the following : vacuole formation, cell fusion, reduced cell and cell organ number, nuclear fragmentation and cell disruption, enlarged intercellular space contain basal lamina-like material, all these resulted in decompensation (8～12 week ) . ( 3 ) Intermuscullar nerve fiber displayed demyelination and degeneration. ( 4 ) During severe decompensation, degeneration and necrosis was not a rare phenomenon. Some SMC shifted from contractile phenotype to secretory phenotype.5. Clinical research: ( 1 ) When compared with normal, UEBW increased significantly , and was found to be significantly correlated with urodynamic parameters such as LinPURR grade, and was negtively correlated with Qmax. ( 2 ) detrusor contraction strength changed with UEBW, the tendency like a para-curve : UEBW <60～80g, WF rised with UEBW. UEBW>80g, WF reduced with UEBW increasing. ( 3 ) After relief of obstruction, UEBW decreased more than 50 % in the first 3 months. When UEBW greater than 100 g or even 180 g, it is difficult to reduce to normal.Conclusions:1. Based upon animal modal data, BWW increased dramatically after PBOO, and significantly correlated with detrusor contractility. It may have an useful role in predicting the detrusor congtractile function. This will provide an excellent experimental foundation for UEBW to assess compensation status of bladder detrusor in clinical practice.2. PBOO mediated significant morphological changes in bladder wall to enhance the contractile function of detrusor. But this compensation was relatively limited to some extent and was also time-dependent. Prolonged obstruction would bring about inreversible pathomorpholgy change in SMC, combined with fibrosis , and at last resulted in severe decompensation - lost of contractile function. So it is well-advised to relieve the obstruction relatively earlier.3. In clinical research, we found that UEBW increased significantly BOO patients.It correlated positively with the urodynamic obstruction and the grade of obstruction. So it may serve as marker to diagnose BOO quantificationally.4. UEBW was correlated with WF, a urodynamic parameter representing the contractility of detrusors. So it may have a capability to predict the detrusor contractile function. But it should be further confirmed by prospective study with large samples. As an non-invasive methods, The nature of reliability and convenience makes it appear to be a useful marker in evaluating status before operation and in monitoring the effection of surgery for patients with BPH.
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