RESULTSAcute retention of urine occurred in 78% of patients, urethral anatomical pathology in 6% and posterior urethral calculi in 88%. The urethral stones, solitary in each patient, consisted of calcium oxalate in 86%, struvite in 6%, mixed stones in 4%, calcium phosphate in 2% and uric acid in 2%. A methodical approach to therapy was used which aimed to clearly define the circumstances in which a given procedure was used, and the resulting success rate. CONCLUSIONThe common belief that most urethral calculi in patients in developing countries originate from the bladder does not seem to be generally applicable. Urethral anatomical pathology does not seem to be a necessary condition for most of these calculi.

Synchronous urinary flow and pressure studies were carried out on 51 male subjects of whom 12 were normal subjects and 39 had benign prostatic hypertrophy with varying degrees of bladder outlet obstruction. A urodynamic scoring system was evolved for accurate and objective diagnosis of bladder outlet obstruction. The minimum urethral resistance was found to be the most valuable single urodynamic parameter for the diagnosis of bladder outlet obstruction. Hitherto this urodynamic parameter was determined through tedious calculations. In the course of the present study a new instrument, the Urethroresistance, was devised for the direct recording of urethral resistance during micturition.

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Observations on urethral resistance during micturition in non-obstructed men and in patients with bladder outlet obstruction owing to benign prostatic hypertrophy are presented. The "Urethroresistance", a new instrument, was used for the direct recording of urethral resistance. The upper limit for the minimum urethral resistance during micturition for normal non-obstructed men was 0.5 units. Two patterns of urethral resistance were observed solely in non-obstructed subjects and 3 other patterns, which were found solely in patients with a moderate or severe degree of bladder outlet obstruction, were shown to be characteristic of bladder outlet obstruction. While direct recording of urethral resistance is a better test for bladder outlet obstruction than the recording of urinary flow rate the recording of urinary flow is a simple urodynamic test, which remains a useful screening test for bladder outlet obstruction. With the exception of severe obstructive symptoms none of the other clinical methods for the assessment of bladder outlet obstruction--the size of the prostate gland, the volume of post-micturition residual urine and the degree of bladder trabeculation--is reliable to determine the degree of bladder outlet obstruction.