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| 發表人 | 討論主題 | 發表時間 | 討論數 |
| 盧令一 | 一、以即時磁振造影探討男性正常排尿時之解剖變化；二、排尿啟動時必須有攝護腺前段之收縮 | 2013/3/27 上午 11:33:24 | 0 |
| 原 文 | 題 目 | 1. Real-time magnetic resonance imaging (MRI): anatomical changes during physiological voiding in men. ；2. Contraction of the anterior prostate is required for the initiation of micturition. |
| 作 者 | Hocaoglu Y, Roosen A, Herrmann K, Tritschler S, Stief C, Bauer RM. Department of Urology, Ludwig-Maximilians-University, Munich, Germany. | |
| 出 處 | 1. BJU Int. 2012 Jan;109(2):234-9; 2. BJU Int. 2013 Jan 28. | |
| 出版日期 | Epub 2011 Jul 8. | |
| 評 論 |
男性排尿時，下泌尿道各個解剖構造相互之間的啟動順序及關聯一直沒有定論，以往利用尿動力學檢查的曲線壓力變化來做推測，慕尼黑大學利用一系列的即時磁振造影（rtMRI）檢查針對男性排尿時的解剖變化提供更直接的證據。 Dr. Hocaoglu對16位平均近70歲的男性，利用即時磁振造影對其設定的參數做排尿前後以及只做Valsalva manoeuvre的結果比對，發現男性排尿啟動前，最先發生的動作是骨盆底肌放鬆，接下來是膀胱頸下降呈漏斗型，然後攝護腺會在恥骨聯合處做出旋轉的動作，接著攝護腺的腹側做出垂直收縮（vertical contraction），讓攝護腺變短，才能開始排尿！但是攝護腺縮短的動作到底是攝護腺本身的收縮，抑或是骨盆底肌放鬆加上膀胱頸下降造成攝護腺變短的呢？Dr. Hocaoglu找來8位接受根除性攝護腺切除手術的病患，除了術前以即時磁振造影比對設定參數的變化之外，更將切除的攝護腺分為腹側、背側及尿道三部份，分別以電刺激測量其收縮力，發現攝護腺腹側的收縮力大於攝護腺背側，更遠大於尿道的收縮力，因而肯定攝護腺（尤其是腹側）的收縮對男性啟動排尿的重要性。 |
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| abstract |
1.OBJECTIVE: To investigate the interactions between the bladder, urethra, pelvic floor and the function of the prostate during normal voiding. PATIENTS AND METHODS: In all, 16 men with no history of urinary incontinence, urgency or obstructive voiding dysfunction were enrolled. We analysed the interaction between the bladder, urethra, pelvic floor and changes in the prostate during the Valsalva manoeuvre and voiding using real-time magnetic resonance imaging (rtMRI). The axis through the external sphincter (AES) to pubo-coccygeal line (PC-line) and the angle between the axis of the os pubis (AOP) and ventral prostate (VP) was measured before and at the end of voiding. Additionally, the angle between the AOP and the VP was measured during the Valsalva manoeuvre. Change of position, or contraction, of the VP was measured. RESULTS: The mean age of the men was 69.8 years and mean prostate volume 33.1 mL. Before voiding, the mean AES to PC-line was 10.5 mm. At the end of voiding, the mean AES to PC-line was 20 mm. The mean angle between AOP/VP was 31.6° in the storage phase and increased to a mean of 54.5° during voiding. During the Valsalva manoeuvre, the angle between the AOP/VP remained constant. There was a mean vertical contraction of the VP of 48.25 mm before voiding and a declining of the cranio-caudal distance of the VP with a mean of 33.92 mm during voiding. CONCLUSIONS: All the men in our study showed relaxation of the pelvic floor, followed by a descent of the bladder neck. Voiding could not be initiated unless the prostate rotated around the symphysis. The study suggests that both the rotation and a vertical contraction of the prostate precede voiding. The anatomy of physiological voiding or voiding dysfunction can be investigated non-invasively using rtMRI. 2.WHATS KNOWN ON THE SUBJECT? AND WHAT DOES THE STUDY ADD?: In a recent rtMRI study, we were able to show that, during initiation of voiding, there was both funnelling of the bladder neck and simultaneous contraction of the ventral prostate. We presumed that the vertical contraction of the ventral prostate contributes to the initiation of successful micturition. The question remained as to whether this shortening of the ventral prostate is predominantly caused by contractile elements in the organ itself, or by surrounding contractile elements of the pelvic floor. In our study we provide insight in to anatomical changes, and biometric and functional analysis of the prostate during micturition. A sagittal contraction of the ventral prostate and the longitudinal smooth muscle elements at the onset of voiding, which can be observed on MRI, is likely to shorten and open up the prostatic urethra. OBJECTIVE: To investigate if in vitro contractile strength of the prostate and the prostatic urethra might correlate with the shortening of the ventral prostate seen on real-time magnetic resonance imaging (rtMRI). Micturition is a complex process that includes anatomical and neurological interactions for successful voiding. Recently we described on rtMRI that vertical contraction of the ventral prostate precedes initiation of male micturition and may contribute to the funnelling of the bladder neck. PATIENTS AND METHODS: In all, 10 patients undergoing radical prostatectomy (RP) were enrolled. Approval was obtained from all patients and by the local Ethics Committee. Preoperative rtMRI during voiding was performed as described before in eight patients undergoing RP, measuring the difference of the cranio-caudal distance of the ventral prostate (VP). To roughly estimate the amount of force required to deform the prostate in a vertical direction as seen on rtMRI, we uniaxially compressed the organ immediately after surgery by the same distance, assuming incompressibility and isotropy of prostatic tissue. A muscle strip (3 × 3 mm) from the ventral prostate, dorsal prostate and prostatic urethra was obtained after pathological evaluation. Contraction was elicited by electrical-field stimulation (EFS: 0.1 ms pulses at 2, 4, 8, 16, 32 and 64 Hz for 4 s). RESULTS: There was a mean cranio-caudal contraction of the ventral prostate by 7.6 mm at the onset of micturition on rtMRI (P = 0.002). The mean (sd) contractile force of strips elicited by EFS at 32 Hz was 1472.44 (706.88) mN for the ventral prostate, 1044.24 (894.66) mN for the dorsal prostate, and 639.10 (785.06) mN for the prostatic urethra (P = 0.02). Extrapolating these values to the whole organ diameter, we calculated comparable force as observed in compression experiments. CONCLUSIONS: Our functional and biometric in vitro analyses of prostate tissue showed sufficient contractile strength of the ventral prostate to induce a shortening of the organ as seen on rtMRI. There was significant higher contractile strength in the ventral prostate than in the dorsal prostate or the proximal urethra. The consistency of in vivo and in vitro results underlines the significance of the ventral prostate for the initiation of normal micturition. |
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