Mike B. Siroky

The flow rate nomogram: I. Development.

In normal individuals the flow rate depends on the initial bladder volume in a non-linear fashion. A flow rate nomogram taking this relationship into account was developed as an aid in the interpretation of urinary flow rate data. With this approach excellent differentiation of normal from obstructed individuals was achieved. In addition, the variability in a single individuals flow rate over time was estimated to be relatively small and, thus, uroflowmetry may be used to identify changes in outflow resistance after medical or surgical therapy.

The Flow Rate Nomogram: II. Clinical Correlation

Using the previously demonstrated statistical relationship between urinary flow rate and bladder volume we tested 53 patients with clinically evident outflow obstruction by uroflowmetry. Of these patients 32 were tested before and after a successful operation for outflow obstruction. In 98 per cent of the maximum flow measurements in obstructed patients the nomogram values were less than minus 2 standard deviations, indicating a clear separation from the normal population. After operative relief of the obstruction repeat uroflowmetry demonstrated all values to be in the normal range. Furthermore, in each patient the peak flow rate value increased an average of 2.7 standard deviations (minimum increase of 1.5 standard deviations). No significant correlation could be demonstrated between the size of the prostatic resection and the degree of urinary flow impairment. The use of a flow rate nomogram appears to differentiate reliably normal from obstructed individuals and also is highly useful in the postoperative followup of urinary outflow obstruction.

Sacral Signal Tracing: The Electrophysiology of the Bulbocavernosus Reflex

We studied 52 men with electrophysiologic testing of the bulbocavernosus reflex to determine reflex latency. The bulbocavernosus reflex was demonstrated to be a segmental polysynaptic reflex with cross-over in the sacral spinal cord. Excellent correlation was obtained between prolonged latency and clinical evidence of neuropathy. The examination may be useful clinically to evaluate patients suspected to have sacral cord lesions or pudendal neuropathy (for example impotence, chronic back pain and lesions of the cauda equina and peripheral nerves).

Post-Prostatectomy Continence in the Parkinsonian Patient: The Significance of Poor Voluntary Sphincter Control

A retrospective urodynamic study of 50 parkinsonian patients was done to determine the incidence and causes of post-prostatectomy incontinence. At presentation 22 per cent of the patients were incontinent. In 36 patients who underwent transurethral prostatectomy the incontinence rate was 17 per cent preoperatively and 28 per cent postoperatively. There was a clear association between normal voluntary sphincter control and urinary continence. After transurethral prostatectomy 5 of 6 patients continent preoperatively (83 per cent) who had abnormal sphincter control became incontinent compared to 1 of 24 (4.2 per cent) who had normal sphincter control. We conclude that the major risk of incontinence following prostatectomy in the parkinsonian patient is associated with lack of voluntary sphincter control.

Neurologic Aspects of Detrusor-sphincter Dyssynergia, with Reference to the Guarding Reflex

Of 137 patients with neurogenic detrusor hyperreflexia 71 with and 66 without vesicosphincter dyssynergia were analyzed. Intracranial lesions did not lead to vesicosphincter dyssynergia, which occurs only after spinal cord transection. The normal increase in striated sphincter activity with bladder filling (guarding reflex) usually is lost, while vesicosphincter dyssynergia usually appears after complete spinal cord injury. This finding provides evidence of supraspinal mediation of detrusor-sphincter interaction. Vesicosphincter dyssynergia is hypothesized to be an abnormal flexor response of the perineal musculature to bladder contraction, which is peculiar to humans.

Vasculogenic Impotence: Role of the Pelvic Steal Test

A new dynamic pelvic flow test is described that measures differential right and left corporeal artery blood pressure changes with exercise. Previous penile blood flow measurements have been made at rest. It is well known that exercise may unmask vascular pathological conditions not apparent at rest. Furthermore, cases have been reported that document potency at rest and impotence following exercise. As a result exercise was used to stress the pelvic vasculature in 97 patients chosen from vascular and urology clinics. A decrease of 0.15 or more in penile-brachial index with exercise was found to be statistically abnormal. A total of 23 patients (27 per cent) fulfilled the criteria for positive pelvic steal testing. In this group there were high incidences of smoking (52 per cent), hypertension (52 per cent) and diabetes (30 per cent). Although 70 per cent of these patients had at least occasional morning erections 78 per cent complained of loss of erection with exercise. The pelvic steal test detected vascular pathological conditions in 17 patients (20 per cent) previously missed by resting penile-brachial index measurements. Nocturnal penile tumescence studies in these patients demonstrated poor quality erections and correlated with the intermediate penile-brachial index values. Angiographic data performed in 5 of 23 patients corroborated the pathophysiology of a pelvic steal condition in each case. The pelvic steal test is simple to perform and markedly improves the sensitivity and yield of penile blood pressure measurements. The test appears to have better results in patients with suspected vasculogenic impotence and intermediate resting penile-brachial index values.

Study of Etiologic Relationship of Arterial Atherosclerosis to Corporal Veno-Occlusive Dysfunction in the Rabbit

PURPOSEnThe aim of this study was to explore the possible etiologic relationship of hypercholesterolemia and atherosclerosis to corporal veno-occlusive dysfunction.nnnMATERIALS AND METHODSnIn the New Zealand White rabbit, the competence of the corporal veno-occlusive mechanism was examined at various intervals after exposure to control diet, high cholesterol diet, or aortoiliac atherosclerosis.nnnRESULTSnInitially, all animals showed normal erectile function and corporal veno-occlusion. After 8 weeks and 16 weeks, the control animals preserved normal erection and corporal veno-occlusion, while most of the hypercholesterolemic and atherosclerotic animals developed corporal veno-occlusive dysfunction. The incidence of corporal veno-occlusive dysfunction in the hypercholesterolemia and atherosclerotic animals increased with time.nnnCONCLUSIONSnThis study suggests that a close relationship exists between prolonged atherosclerotic occlusion of major penile arteries and the development of corporal veno-occlusive dysfunction. Ischemia-induced corporal veno-occlusive dysfunction may be the result of alterations in corporal smooth muscle relaxation or changes in the structure and fibroelastic properties of erectile tissue.

The Phentolamine Test in Neurogenic Bladder Dysfunction

In an attempt to improve the selection of patients with neurogenic bladder dysfunction likely to benefit from phenoxybenzamine therapy, the effect of intravenous phentolamine (Regitine) on the urinary flow rate was determined in normal and abnormal subjects. A nomogram relating mean flow rate to volume voided was constructed to aid in the interpretation of results. In 16 patients with neurogenic bladder dysfunction it was found that a response of more than 0.8 nomogram units indicates a likelihood of clinical improvement with phenoxybenzamine therapy. The clinical applications of this test are discussed.

Hemodynamics of Penile Erection: III. Measurement of Deep Intracavernosal and Subtunical Blood Flow and Oxygen Tension

Previous studies have shown that intracavernosal blood flow increases during penile erection, but little is known about intracavernosal hemodynamics. Using a previously developed canine model of erection, we measured intracavernosal blood flow and oxygen tension at 2 sites within the corpus cavernosum: directly beneath the tunica albuginea and deep within the cavernous tissue. We chose to measure oxygen tension as an indicator of arterial blood flow. Penile erection was induced by pelvic nerve stimulation as well as by injection of papaverine and phentolamine. In the flaccid penis, blood flow measured directly under the tunica albuginea was significantly higher than deep intracavernosal blood flow. Subtunical oxygen tension in the flaccid penis was consistent with a largely arterial circulation. These observations provide physiological evidence of an important subtunical circulation that carries most of the intracavernosal blood flow when the penis is flaccid. With pelvic nerve stimulation, deep intracavernosal blood flow increased significantly followed by an increase in oxygen tension. Oxygen tension deep within the corpus cavernosum increased during penile erection from a level consistent with venous blood to a level consistent with arterial blood. Injection of papaverine and phentolamine caused a significant increase in intracavernosal pressure and a significant decrease in subtunical blood flow but did not cause statistically significant change in intracavernosal blood flow or oxygen tension. In contrast to nerve-induced erection, pharmacologically induced erection appears to depend more on intracavernosal shunting of blood than on increased total arterial blood flow to the penis. Hypogastric nerve stimulation during established erection caused detumescence by contracting cavernosal smooth muscle, reducing deep cavernosal blood flow and reestablishing blood flow through the subtunical space. Our observations suggest that the subtunical space contains an important circulation that may play a role in the hemodynamics of the flaccid, as well as the erect, penis.

The Urodynamic Aspects of the Guillain-BarrÉ Syndrome

A total of 7 patients with the Guillain-Barré syndrome and voiding dysfunction, large post-voiding residuals or urinary retention underwent urodynamic evaluation. Of the patients 4 had detrusor areflexia with a positive bethanechol supersensitivity test, including 3 with electromyographic evidence suggestive of neuropathy. This is the expected pattern in the Guillain-Barré syndrome. However, 3 patients had detrusor hyperreflexia with appropriate sphincteric relaxation, which was associated with Babinskis sign in 2. The presence of detrusor hyperreflexia suggests the possibility of Guillain-Barré pathological conditions involving the central nervous system, although the Guillain-Barré syndrome typically is a disease of the peripheral nervous system. Long-term urodynamic studies may help clarify such issues in future patients.