BERKELEY, CA (UroToday.com) - We continue to find the penile cuff device an excellent adjunct to the clinical assessment of men with lower urinary tract symptoms and suspected bladder outlet obstruction. We continue to use it and to teach its application to our nursing and junior medical staff. There is, of course, a learning curve involved! Our nurses are generally responsible for performing the test, which is performed in a separate consultation before the patient is seen for specialist urological review. In this commentary, I outline some things to be mindful of when conducting the test.
A brief explanation to the patient is required prior to performing the test. There are two key pieces of information that must be delivered. Firstly, the man should feel as though he is ready to void normally: that is to say, his bladder is full and, should he be at home, he would normally choose to pass urine. The second piece of explanation that is important for the pressure-flow curve to be reliable is that the patient must be advised not to void by abdominal straining. It is, therefore, particularly important that the first piece of advice is adhered to: we find that men who have a full bladder and are ready to void are much more likely to comply with the test and void without abdominal straining. On the other hand, men who are trying to please you or need to “get home in a hurry” are more likely to force a suboptimal void by abdominal straining. Abdominal straining will give artificially high urethral closure pressures, the surrogate for bladder pressure, and therefore make an incorrect diagnosis of outlet obstruction more likely.
Another implication of a suboptimal void is that the voiding time is shorter. This allows less opportunity for three to four cycles of penile cuff inflation and deflation, which gives less opportunity for an optimal pressure-flow graph to be procured. Without an optimal graph, the allocation of an incorrect diagnosis of obstruction, or otherwise, (based on the modified ICS nomogram) may occur.
We have on rare occasions found men who have a particularly short penile length to have difficulty accommodating the smallest penile cuff. This is particularly pronounced when the short penis is found in association with a prominent suprapubic fat pad. On occasion, a nurse holds the cuff in position manually whilst the patient voids. Fortunately, in our local population, this is rare! For a very small group of men, the test proves technically impossible and must be abandoned.
As in conventional urodynamics, the patient must be asked to ensure that he does not occlude the distal penile urethra when holding his penis – usually a transverse grasp is most effective rather than an antero-posterior grasp. The presence of the cuff should, in fact, make the transverse grasp easier. Artefact from an incorrect penile grasp is seen, just as in conventional urodynamics, as a sudden burst of urine flow.
There are several reasons when the graph provided should be excluded from analysis due to technical reasons. Firstly, if there is no recovery of urine flow after cuff inflation, this indicates that the void finished at some point during the inflation cycle. In normal circumstances, a brief surge of urine should be seen when the cuff releases, relating to the urine which has been stored in the proximal urethra. Secondly, an erratic tracing makes it difficult to establish the exact moment of flow interruption. Thirdly, if flow does not stop at the instrument’s maximum pressure of 200 cmH2O, the trace should not be interpreted, as flow termination was not achieved. This situation would usually still reassure the clinician about the absence of bladder hypo-contractility. Finally, if a tracing is inconsistent with other tracings by the same patient, as with all clinical tests, it should be regarded with suspicion and generally discarded. Despite these caveats, this remains a highly useful clinical test that is simple and inexpensive to perform. There continues to be a scattering of publications in the literature about various alternatives to ‘non-invasive’ urodynamics. Only time will tell us which ones are here to stay.
Written by:
Giovanni Losco, MB, ChB(Dist), FRACS(Urol) as part of Beyond the Abstract on UroToday.com. This initiative offers a method of publishing for the professional urology community. Authors are given an opportunity to expand on the circumstances, limitations etc... of their research by referencing the published abstract.
Department of Neurourology, Royal National Orthopaedic Hospital, Stanmore and Department of Urology, University College Hospital, London
Non-invasive urodynamics predicts outcome prior to surgery for prostatic obstruction - Abstract
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