Background and purpose: In men with lower urinary tract symptoms of hesitancy or poor flow rate, an enlarged prostate may be suspected, for which a surgical reduction of the prostate is appropriate. However, in some men the symptoms are due to bladder weakness, and these men may gain no benefit from surgery. Bladder pressure/flow studies allow an objective diagnosis, but such studies are invasive and uncomfortable. We have proposed a method for non-invasive measurement of bladder pressure using an inflatable penile cuff [1]. Here we present the results of a 1-year trial of the new 'cuff test', comparing the new measurements with those from simultaneous invasive pressure/flow studies.
Methods: In the cuff test, a paediatric blood pressure cuff is placed round the penis before the subject voids. When flow is established, the cuff is inflated at 10 cm H2O s-¹ until flow interruption. We believe the cuff pressure required to stop flow (Pcuff,int) reflects the isovolumetric pressure in the bladder (Pves.isv). Once flow has stopped, the cuff is rapidly deflated and, when voiding resumes, the inflation cycle is repeated. Typically, 2 or more measurements can be performed during each void.
We recruited 151 consecutive men attending our prostate assessment clinic with lower urinary tract symptoms. Bladder pressure (Pves) was recorded simultaneously with the cuff test, using a fluid-filled line and external pressure transducer, zeroed at the level of the symphysis pubis. This method is in accordance with the International Continence Society guidelines on assessment of bladder pressure [2]. For each inflation of the cuff, we determined the point at which flow was reduced to zero. At this point, we measured cuff pressure (Pcuff,int), and the simultaneous isovolumetric bladder pressure (Pves,isv).
Results: Of 151 patients recruited, 31 could not perform a satisfactory cuff test, one was unable to void and two sets of data were lost due to computer failure. For the remaining 117 subjects, Pcuff,int overestimated Pves,isv by 16.4 ± 27.5 cm H2O.
The relation of Pcuff,int with simultaneous Pves,isv for 117 subjects. For voids with two or more cuff inflations, the inflation with highest Pcuff,int was taken as the best indication of bladder contractility.
Conclusions: While Pcuff,in~ generally over-estimates the invasively recorded Pves,isv, this is largely due to the position of the cuff 9 ± 2 cm below symphysis pubis, the standard baseline for pressure recording [2]. Figure 2 shows greater variability than anticipated. We previously demonstrated good pressure transmission from the cuff to the urethra in the absence of flow [3]. We have reason to suspect the presence of the bladder catheter affects the cuff measurement, and are planning a further investigation using. supra-pubic catheters. Nevertheless, we believe the test provides useful information in the assessment of men with lower urinary tract symptoms.
References: [1] Griffiths CJ, Rix D, MacDonald AM et al. Non-invasive measurement of bladder pressure by controlled inflation of a penile cuff. Journal of Urology 2002; 167: 1344-47.
[2] Schafer W, Abrams P, Liao L et al. Good urodynamic practices. Neurourology and Urodvnamics 2002: 21 261-74.
[3] Drinnan MJ, Robson W, Reddy M, et al. Transmission of penile cuff pressure to the penile urethra. Journal of Urology 2001; 166: 254.5-9.
Drinnan MJ, Brown J, Ramsden P, Pickard R, Griffiths CJ. Non-invasive estimation of bladder pressure using a penile cuff technique. In: Morgan HM, Starritt HC, Duck FA, eds. Proceedings of the 9th Annual Scientific Meeting, IPEM 2003; 104.
Clive J. Griffiths or Dr. Michael J. Drinnan, Freeman Unit, Newcastle upon Tyne. Tel: +44 (0)191-223-6161.
Regional Medical Physics Department, Freeman Hospital, Newcastle upon Tyne, NE7 7DN, UK.
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