One hundred and seventeen males over the age of 55 were investigated for possible prostatic obstruction. About half of the cases in this series could have been objectively classified as unobstructed or obstructed from the maximum flow rate alone. In about two-thirds of the cases obstruction could be satisfactorily assessed from the maximum flow rate together with the detrusor pressure at maximum flow. It was not helpful to combine these 2 measurements into a single urethral resistance factor. In the remaining one-third of the cases, obstruction could be objectively assessed only from a plot of detrusor pressure against flow rate throughout micturition. In many of these cases both the pressure and the flow rate were low and the main peculiarity was that the contractile power of the bladder was weak. Residual urine is a sign of an abnormality of bladder function rather than the direct result of urethral obstruction.

The Assessment of Prostatic Obstruction from Urodynamic Measurements and from Residual Urine

In pressure/flow studies of adult voiding the behaviour of the urethra can be distinguished from that of the bladder, and quantified separately, as follows. Different degrees of urethral obstruction can be quantified and ranked using a group-specific resistance factor (URA) that is based empirically on the pressure/flow plots obtained in a large number of voidings of adult patients. Different detrusor contractions can be similarly quantified using a physiologically based measure (WF, abbreviated from power [W] factor) of the contraction strength. Both URA and WF can be calculated by computer from measurements of detrusor pressure, voiding flow rate, and the residual volume in the bladder after voiding. For other groups of patients, e.g., children, different group-specific resistance factors are appropriate.

In men with obstructed voiding due to benign prostatic hyperplasia (BPH), “chemical castration” with cyproterone acetate or buserelin caused a substantial, reversible reduction in the size of the prostate. The effect on the degree of urethral obstruction and the voiding bladder contraction has been studied using the above-mentioned methods. There was an increase in peak urinary flow rate, a reduction in residual urine, and a decrease in daytime voiding frequency. Surprisingly, however, there was on average no decrease in urethral resistance but only an increase in the average detrusor contraction strength. In individual patients large increases and decreases of urethral resistance and detrusor contraction strength occurred, which largely cancelled each other out. These large changes masked the relatively modest urethral resistance decrease caused directly by prostate size reduction.

Quantification of urethral resistance and bladder function during voiding, with special reference to the effects of prostate size reduction on urethral obstruction due to benign prostatic hyperplasia

The treatment of benign prostatic hyperplasia and the definition of bladder-outlet obstruction has preoccupied urologists and researchers in recent years. Bladder-outlet obstruction can be defined only by pressure-flow measurement. Various methods of analysis of pressure-flow data have been proposed. The Abrams-Griffiths nomogram is an easy method of classifying these data to distinguish between the presence or absence of obstruction. Using the values for the maximal flow and the corresponding voiding detrusor pressure a point can be plotted on the nomogram that determines whether the bladder outlet is obstructed, unobstructed, or equivocally obstructed. For those that fall in the equivocal zone, further criteria for the mean slope of the pressure-flow plot and the minimal voiding detrusor pressure are used to determine whether there is obstruction or not. The nomogram's prognostic value in predicting the outcome of prostatectomy has been studied and found to be excellent. The Abrams-Griffiths nomogram can be modified by assigning an Abrams-Griffiths number to each set of pressure-flow data. This number is easy to calculate and use and gives a continuous variable that can be used to evaluate the effects of therapy. Although the Abrams-Griffiths nomogram and number are somewhat simplistic, none of the more complex methods of pressure-flow analysis have been shown to be better predictors of treatment outcome to date.

The Abrams-Griffiths nomogram

Urodynamic Evidence of Vesical Neck Obstruction in Men with Misdiagnosed Chronic Nonbacterial Prostatitis and the Therapeutic Role of Endoscopic Incision of The Bladder Neck

Pseudodyssynergia (Contraction of the External Sphincter During Voiding) Misdiagnosed as Chronic Nonbacterial Prostatitis and the Role of Biofeedback as a Therapeutic Option

There is no dispute that there exists, in men, a condition of obstruction at the bladder neck in the absence of fibrous stricture or prostatic enlargement. The condition was clearly described by Guthrie (1836) and Young (1913) reported the results ff punch resection operation in over 50 cases. The large measure of success now achieved following resection of the bladder neck in these patients has perhaps been allowed to mask our ignorance of the nature of the abnormality and thus discourage studies of its cause. It is perhaps most often thought to result from fibrosis but a number of studies--for example Baadenoch (1949)--have shown no associated increase in fibrous tissue. Certainly the condition is in no way similar to the hard fibrous stricture seen more often in the distal urethra, or at the bladder neck as an occasional complication of prostatectomy. Our study shows that the obstruction if functional in nature and is due to the tightening of the bladder neck as the detrusor contracts.

E. P. Arnold

Papers

The nature of the abnormality in bladder neck obstruction.