Intrarectal Pressure Research Articles

Evidence from dynamic integrated proctography to redefine anismus.

The role of anismus in the aetiology of defective rectal evacuation was investigated by dynamic integrated proctography in 20 controls and 71 constipated patients. Normal parameters were defined and compared between 21 constipated patients with poor evacuation during proctography (< 40 per cent of contrast evacuated; group 1) and 50 who evacuated fully (> 90 per cent of contrast evacuated; group 2). Nine patients in group 1 failed to evacuate. Radiological abnormalities of the rectum were recorded in all groups but obstructed evacuation was not observed. Anismus (defined as a recruitment of puborectalis electromyogram (EMG) activity of > 50 per cent) was significantly more common in group 1 than group 2 patients (14 of 21 versus 12 of 50, P < 0.01) and present in seven of those unable to evacuate. Eight patients in group 1 failed to raise intrarectal pressure > 50 cmH2O compared with two in group 2 (P < 0.001). Six patients in group 1 demonstrated both anismus and inability to raise intrarectal pressure, which may combine to cause defective evacuation. EMG recruitment alone is insufficient to diagnose anismus. Definition should be based on three criteria: demonstration of puborectalis EMG recruitment of > 50 per cent; evidence of an adequate level of intrarectal pressure (> 50 cmH2O) on straining; and presence of defective evacuation.

New method for the dynamic assessment of anorectal function in constipation.

A new dynamic technique for the investigation of anorectal function has been developed. This involves radiological visualization of the rectum during voiding of a semisolid radio-opaque contrast medium, and simultaneous measurement of the intrarectal pressure and electrical activity of the external anal sphincter. The method has been used to study patients (n = 16) with profound difficulty passing formed stool. It has demonstrated an abnormal increase in the activity of the puborectalis and superficial and sphincter muscles during voiding in these patients, compared with normal subjects (n = 6). The inability to void was associated with failure to widen the anorectal angle on straining.

Functional and histological effects of intravaginal electrical stimulation on the pelvic muscles: a study in the rat

We studied functional and histological effects of electrical stimulation (ES) on pelvic muscles of the rat. With intravaginal electrodes, the musculus pubococcygeus and musculus iliococcygeus in the awake animal were stimulated three times 6 min per day with 5 min of rest in between, 5 days per week, 7 consecutive weeks with a biphasic rectangular symmetrical current of 25 Hz, 400-mus pulse duration, on/off time of 5/10 and with an amplitude of 2-4 mA. A "sham group" received the same handling but no stimulation. Contraction measured with intra-rectal pressure during stimulation increased more in the stimulated than in the sham group, but did not reach statistical significance probably due to low power. The 2A fast fibres increased with 14% in the musculus iliococcygeus and with 6% in the musculus pubococcygeus. Type 1 slow fibres did not change. Increased capillary density was found after stimulation. Repeated intravaginal ES has mainly an influence on the fast fibres in the pelvic muscles. To influence slow fibres, another stimulation program or current parameters would seem necessary.

Investigation of the Pathophysiology of Fecal Seepage

Unintentional seepage of stool without awareness is common but its pathophysiology is poorly understood. Our aim was to examine the underlying mechanism(s) for fecal seepage. We evaluated prospectively 25 patients with fecal seepage, by performing anorectal manometry, balloon expulsion, saline infusion, pudendal nerve latency tests, and symptom assessments and compared their data with 26 fecal incontinence patients and 43 healthy controls. Predisposing factors for fecal seepage were back injury (7), obstetric injury (6), hemorrhoidectomy (3), pelvic radiotherapy (1), and unknown (8). In the seepage group, the resting and squeeze sphincter pressures were lower (p < 0.02) than healthy controls, but higher (p < 0.002) than incontinent group. During straining, the intrarectal pressure and defecation index were lower (p < 0.05) in the seepage group compared to controls; 72% showed dyssynergia and balloon expulsion time was prolonged (p < 0.01). Threshold for first rectal sensation was impaired (p < 0.002) in the seepage group compared to controls and incontinent group. The seepage group retained more (p < 0.001) saline than the incontinent group but pudendal nerve latency time was impaired (p < 0.05) in both patient groups compared to controls. Anal sphincter function and rectal reservoir capacity were relatively well preserved but most patients with seepage demonstrated dyssynergia with impaired rectal sensation and impaired balloon expulsion. Thus, incomplete evacuation of stool may play a significant role in the pathogenesis of seepage.

On the pathogenesis of rectocele: the concept of the rectovaginal pressure gradient.

Coughing or straining evokes reflex bulbocavernosus (BCM) and puborectalis (PRM) muscle contraction, which apparently transforms the vagina into a closed high-pressure cavity. This elevated vaginal pressure counteracts the increased intra-abdominal pressure and the tendency of the uterus to prolapse, and also supports the rectovaginal septum against the high straining-induced intrarectal pressure and possible consequent rectocele (posterior vaginal prolapse) formation. We investigated the hypothesis that a weak BCM and PRM share in the genesis of rectocele by changing the rectovaginal pressure gradient. Twenty-three women with rectocele (mean age 43.2+/-6.6 years) and 12 healthy women volunteers (mean age 41.6+/-6.2 years) were studied. The response of the intrarectal (intra-abdominal) and intravaginal pressure, as well as the EMG activity of the BCM and PRM to straining or coughing, was recorded. In the healthy volunteers the rectal and vaginal pressures showed a significant increase on coughing or straining, with no significant difference between the rectal or vaginal pressures. Also, the BCM and PRM EMG activity exhibited a significant increase. Rectocele patients showed a significantly low resting vaginal pressure. The increase in rectal and vaginal pressure, as well as of the EMG activity of the BCM and PRM on straining or coughing, was significantly lower and the latency of the EMG response was significantly longer than those of the healthy volunteers. A difference in the rectovaginal pressure gradient showing a significant increase in the rectal against the vaginal pressure, particularly on coughing or straining, is suggested to be the basic factor in the genesis of rectocele. This pressure difference appears to be caused by diminished BCM and PRM contractile activity. A disrupted rectovaginal septum is not a prerequisite for rectocele formation, as the septum appears normal in obstructed defecation despite the common occurrence of rectocele. A histopathologic study of the septum in rectocele seems necessary.

Study of the effect of straining on the bulbocavernosus muscle with evidence of a straining-bulbocavernosus reflex and its clinical significance.

The bulbocavernosus muscle (BCM) surrounds the vaginal introitus and covers the vestibular bulb. Its role in erection is known. However, as it surrounds the vaginal introitus, it may also have a role in intravaginal pressure regulation and in the pathogenesis of uterovaginal prolapse. We investigated the effect of increased intra-abdominal pressure (IAP) on the BCM, aiming to assess its possible function in supporting the uterus, vagina and anorectum. The intrarectal (representative of the IAP) and intravaginal pressures were measured by manometric catheters in 19 healthy women volunteers (mean age 46.2 +/- 10.4 years). The EMG activity of the BCM and its response to straining at different pressures were recorded by a concentric needle electrode. Two types of straining were tested: sudden momentary and slow sustained. The procedure was repeated in 11 of the women after individual anesthetization of the BCM, rectum and vagina. Sudden straining (coughing) produced a significant increase in intrarectal ( P<0.0001) and intravaginal ( P<0.0001) pressure as well as BCM EMG activity. Slow straining effected a similar but lower response: the BCM responded gradually with pressure elevation, whereas the latency exhibited a gradual decrease. The BCM did not react to straining after individual anesthetization of the BCM, vagina and rectum, but did respond to saline administration. The results were reproducible. BCM contraction on straining postulates a reflex relationship, which we call the 'straining-bulbocavernosus reflex'. We hypothesized that this reflex is evoked by straining and results in BCM contraction and closure of the vaginal introitus. The vagina is believed to become a closed cavity, counteracting the increased intra-abdominal pressure and the uterine tendency to prolapse. The high pressure in the closed vaginal cavity presumably supports the rectovaginal septum against the high intrarectal pressure, and is suggested to share in the prevention of rectocele. The role of BCM in the pathogenesis of uterovaginal prolapse and rectocele needs further study.

On the adequate stimulus for rectal mechanoreception and perception: a study in cat and humans.

The adequate stimulus that is specific for both rectal mechanoreceptor excitation and rectal perception is still undefined. Using a visual analogue scale, healthy male volunteer subjects rated the intensity of the non-noxious 'pressure sensation evoked by slow balloon-induced distensions of the rectum. In a parallel study, the responses of spinal afferents originating from intramural mechanoreceptors of the rectum to the same stimulus were recorded in decerebrate cats. Both receptor activity and sensation intensity were linearly related to the diameter of the rectum, which is in turn a linear function of the tangential length of the rectal wall. In contrast, both saturated when expressed as a function of intrarectal pressure or rectal wall tension. It is concluded that the perception associated with rectal dis tensions in the non-noxious range is mediated by intramural mechanoreceptors that linearly encode tangential wall length, and that the underlying information is linearly transmitted throughout the CNS.

Use of the Hagen-Poiseuille Law: A New Mathematical Approach for the Integration and Evaluation of Anorectal Physiological Testing in Patients with Faecal Incontinence and Pelvic Dyschezia and in Normal Controls

This work was done in order to study the possibility of using the Hagen-Poiseuille law for flow of fluids through tubes to integrate and quantitate the anorectal physiological parameters in patients suffering from faecal incontinence and functional pelvic outlet obstruction compared to normal controls. The Hagen-Poiseuille law was intended to be used in the explanation of the role played by different sensory and motor functions of the anorectal segment in maintaining continence and normal rectal evacuation. The intrarectal pressures during rest, coughing, attempted defaecation, rectal sensation, and rectal compliance at the point of first rectal sensation were measured using anorectal manometry. Anal canal length and diameter were measured using lateral defaecographic views during rest, squeeze, and attempted defaecation, and the anal sphincteric reflex contraction in response to coughing or Valsalva’s manoeuver was measured using plug or needle electromyography. These factors were analyzed using the Hagen-Poiseuille law in order to determine anal canal resistance and flow to air, water, and BaSO₄ during rest, coughing, and attempted defaecation in controls, during attempted defaecation in patients with functional pelvic outlet obstruction, and during rest and coughing in patients with faecal incontinence. The Hagen-Poiseuille law could detect anal continence in all controls and could also detect and quantitate functional pelvic dyschezia in all patients. The equation could detect and quantitate faecal incontinence in 8 of 14 patients (57.14%) during rest, in 11 of 14 (78.57%) during coughing, and in all 14 patients after correction for sensory and reflex deficits. Both the Hagen-Poiseuille law and the law of Laplace and their proposed hybrid law were successful in explaining some facts concerning factors affecting normal continence and defaecation. The Hagen-Poiseuille law is a useful new mathematical approach for the integration and quantitation of normal and abnormal continence and defaecation. It can be used to plan for treatment and to determine the outcome of patients suffering from functional anorectal disease.

Obstructive defecation: a failure of rectoanal coordination

Objective: The pathophysiology of obstructive defecation is unclear. We investigated whether impaired rectoanal coordination causes obstructive defecation and if this dysfunction can be corrected by biofeedback therapy. Methods: We prospectively studied 25 healthy subjects and 35 consecutive patients with constipation (>1 year) with anorectal manometry and balloon expulsion test. Symptoms were assessed from diary cards. Patients found to have obstructive defecation were offered biofeedback therapy. After treatment, their defecation dynamics and symptoms were reassessed. Results: Eighteen patients had obstructive defecation and 17 had normal defecation dynamics (nonobstructive). Five normals (20%) exhibited obstructive pattern but only one failed to expel balloon. In the obstructive group, during straining, the intrarectal pressure and defecation index were lower ( p < 0.05), and anal residual pressure was higher ( p < 0.01) when compared with the nonobstructive group or normals. After biofeedback therapy, the intrarectal pressure and defecation index increased ( p < 0.02) and anal residual pressure decreased ( p < 0.001); stool frequency, degree of straining, and bowel satisfaction scores improved ( p < 0.05); 67% stopped laxatives and 11 patients discontinued stooling with digitation. Conclusion: Patients with obstructive defecation showed impaired rectal contraction, paradoxical anal contraction, or inadequate anal relaxation. These features suggest that rectoanal coordination was impaired. Biofeedback therapy rectified these pathophysiological disturbances and improved constipation.

Discharge patterns of intramural mechanoreceptive afferents during selective distension of the cat's rectum.

The afferent input from the rectum to the central nervous system (CNS) has yet to be thoroughly characterized. The characteristics of mechanoreceptive rectal afferents have been studied in unanaesthetized decerebrate cats. Following lumbo-sacral laminectomy, single-unit activity (occasionally multi-unit activity) was recorded from centrally cut filaments of the sacral dorsal roots (predominantly S2), while a balloon was inflated in the rectum. Starting from their background activities (mean 15.1 imp sec-1, SD 7.6 imp sec-1), afferent discharge rate increased with increasing balloon pressure (mean threshold 6.3 mmHg, SD 3.6 mmHg). The dependence of firing rate on intrarectal pressure began to flatten out at 25 mmHg (mean; SD 10 mmHg). For 22 out of 29 units (76%) complete saturation occurred at 35 mmHg (mean; SD 15 mmHg) with a maximum discharge rate of 31 imp sec-1 (mean; SD 12.6 imp sec-1). In a number of recording sessions, cyclical rectal contractions were observed. In these cases, changes in firing of the units were closely related to changes in intrarectal pressure. Pressure-related afferent activity could be enhanced by parasympathomimetic drugs which augmented rectal contractions. We conclude that sacral dorsal roots contain afferents from low-threshold mechanoreceptors located in the rectal wall, and that these afferents monitor the filling state and contraction level of the rectum.

Examination of Voiding in Seated Women Using a Remote-Controlled Ultrasound Probe

Background: A remote-controlled steering arm was developed that allows the ultrasound probe to be held on the perineum under ultrasound image guidance with the woman seated on a commercially available bedside commode. Technique: The arm’s servomechanism monitors contact pressure between the scanning head and the perineum, keeping constant gentle pressure on the perineum so that the transducer follows perineal movement. Experience: Twenty patients with urinary incontinence and ten normal volunteers were examined during two voiding episodes, one without perineal ultrasound and one with ultrasound. Ultrasound images and intrarectal pressure measurements were displayed simultaneously on a video monitor. Bladder and urethral visibility and behavior were analyzed during bladder emptying. Of the 30 women, 28 were able to void, with and without the ultrasound probe applied. Two women were not able to urinate under observation either with or without sonography. The bladder base, bladder neck, and upper two-thirds of the urethra were visible throughout voiding in the 28 women able to void. Bladder neck opening could be observed in all of the 28 women. Bladder neck descent during initiation of voiding occurred in 17 women, whereas 11 voided without bladder neck descent. Conclusion: The use of this device facilitates ultrasound evaluation of micturition in the physiologic sitting position and allows bladder neck behavior to be seen during bladder emptying.

Effects of biofeedback therapy on anorectal function in obstructive defecation.

Biofeedback therapy improves symptoms in patients with constipation and obstructive defecation. Whether it also improves anorectal function is unclear. Our purpose was to investigate prospectively the effects of biofeedback therapy on subjective and objective parameters of anorectal function in 25 consecutive patients with obstructive defecation. Biofeedback therapy consisted of pelvic floor relaxation exercises (phase I) and neuromuscular conditioning of rectal sensation and rectoanal coordination, with a solid state manometry system and simulated defecation maneuvers (phase II). The number of sessions was customized for each patient. Clinical improvement was assessed from the changes in anorectal manometry, balloon (50 cc) expulsion test, and the symptom and stool diaries. The number of therapy sessions varied [mean (range) = 6 (2-10)]. After therapy, when straining as if to defecate, the percentage anal relaxation, intrarectal pressure, and defecation index increased (P < 0.001). The balloon expulsion time, laxative consumption, and straining effort decreased (P < 0.001). Before therapy, 16/25 (64%) patients had impaired rectal sensation, and after therapy this improved (P < 0.001). After therapy, 15/25 (60%) patients reported > or = 75% satisfaction with bowel habit and 8/25 (32%) reported > or = 50% satisfaction (P < 0.001); 15/16 (94%) patients discontinued digital disimpaction. Biofeedback therapy not only improves subjective but also objective parameters of anorectal function in at least 76% of patients by rectifying the underlying pathophysiologic disturbance(s). Sensory conditioning and customizing the number of sessions may offer additional benefits.

The discovery and a study of the adventitia rectalis, a fibrous layer of the rectal wall

In sacral anoplasty, it is frequently found that an outer layer of the rectal wall, which resembles the structure of the taenia bands of the colon, limits the elasticity of the rectum making it different from the small intestine, hence preventing the rectal stump from being advanced to reach the perineum. Results of autopsy studies on 40 human babies and 40 dogs showed that a special collagenous fibrous layer called adventitia rectalis was found to limit the free expansion of the rectal wall. This was responsible for keeping the rectum a straight tubular shape with a fixed volume. This tissue plays an important role in bowel movement by defining a threshold of intrarectal pressure in the bowel reflex of defecation and by transmitting the expulsive force from the abdomen above down to the anal opening. This discovery may explain why (1) in Hirschsprung's disease, the preservation of the rectal wall in Soave's or Rehbein's procedure or partial preservation in Duhamel's operation will preserve better bowel function; (2) in atresia ani, rectal tapering results in better bowel control than rectal pouch amputation; and (3) in sacral anoplasty, multiple releasing incisions of adventitia rectalis at different levels will lengthen the rectal stump to about double its original length to reach the perineal incision, and the divided fibers will soon regenerate.

Electrical stimulation of sacral spinal nerves for treatment of faecal incontinence

Summary Functional deficits of the striated anal sphincteric muscles without any apparent gross defect often result in a lack of ability to postpone defaecation by intention or in faecal incontinence in response to increased intra-abdominal or intra-rectal pressure. We applied electrostimulation to the sacral spinal nerves to increase function of the striated muscles of the anal sphincter. Of three patients followed for 6 months, two gained full continence and one improved from gross incontinence to minor soiling. Closure pressure of the anal canal increased in all. Preliminary data indicate that anal closure pressure increases with the duration of stimulation. Continuous stimulation of sacral spinal nerves can help some patients with faecal incontinence. It may be possible to promote continence with intermittent stimulation.

Is barium trapping in rectoceles significant?

This study was designed to determine whether rectocele size and contrast retention are significant. Evacuation proctography and simultaneous intrarectal pressure measurements from a small, noncompliant balloon catheter were performed in three matched groups of 11 constipated female patients with rectoceles, rectoceles and contrast trapping of > 10 percent, and no rectocele. Computerized image analysis was used to measure rectocele area and evacuation. In the two groups with rectoceles, there was no significant difference in rectocele area or width pre-evacuation. The anorectal angle, pelvic floor descent, maximum anal canal width, evacuation time or completeness, maximum and distal intrarectal pressure, or need to digitate did not differ significantly between the groups. In seven patients with barium trapping (64 percent) the intrarectal pressure dropped abruptly as the balloon entered the rectocele, suggesting that trapping results from sequestration into the vagina, closing part of the rectocele from the normal intrarectal pressure zone. Because no impairment of evacuation appears to be associated with either a large rectocele or trapping, these evacuation problems should not be directly attributed to these proctographic findings.

Intrarectal pressures and balloon expulsion related to evacuation proctography.

Seventy four patients with constipation were examined by standard evacuation proctography and then attempted to expel a small, non-deformable rectal balloon, connected to a pressure transducer to measure intrarectal pressure. Simultaneous imaging related the intrarectal position of the balloon to rectal deformity. Inability to expel the balloon was associated proctographically with prolonged evacuation, incomplete evacuation, reduced anal canal diameter, and acute anorectal angulation during evacuation. The presence and size of rectocoele or intussusception was unrelated to voiding of paste or balloon. An independent linear combination of pelvic floor descent and evacuation time on proctography correctly predicted maximum intrarectal pressure in 74% of cases. No patient with both prolonged evacuation and reduced pelvic floor descent on proctography could void the balloon, as maximum intrarectal pressure was reduced in this group. A prolonged evacuation time on proctography, in combination with reduced pelvic floor descent, suggests defecatory disorder may be caused by inability to raise intrarectal pressure. A diagnosis of anismus should not be made on proctography solely on the basis of incomplete/prolonged evacuation, as this may simply reflect inadequate straining.

Are vaginal and rectal pressures equivalent approximations of one another for the purpose of performing subtracted cystometry?

To determine if rectal and vaginal pressures are clinically equivalent to one another for the purpose of calculating subtracted detrusor pressure during routine filling cystometry and pressure-flow voiding studies. A total of 140 consecutive filling and voiding cystometrograms were performed at separate sessions on 127 female patients undergoing routine clinical cystometry for a variety of clinical indications, usually urinary incontinence. In all cases, intravaginal as well as intrarectal pressures were measured simultaneously using microtip transducer pressure catheters, and two subtracted detrusor pressures were calculated throughout each study. Rectal and vaginal pressure measurements from the same patient were compared with the patient in the supine position with an empty bladder, in the erect position with a full bladder, and in the sitting position during voiding at the point of maximum urinary flow. The mean pressures were similar in all cases. Although there was no statistical difference in the mean differences between the rectal and vaginal pressures in the supine-empty position (P = .5528), significant differences were noted between them in the erect-full and sitting-voiding positions (P = .0016 and P = .0033, respectively). Linear regression analysis of the data obtained in each position was carried out, plotting vaginal pressure on the x axis and rectal pressure on the y axis. The corresponding r values for each position were 0.431 for the supine-empty position, 0.547 for the erect-full position, and 0.478 for the sitting-voiding position, indicating poor correlation between pressures in individual patients. In nine patients (6.5%) with significant vaginal relaxation and large cystoceles, a steady rise in vaginal pressure was noted during bladder filling. In six patients (4.4%), one or more spontaneous vaginal contractions were noted during the course of the study, whereas in 68 (48.9%), spontaneous rectal contractions were present. Of the 68 cases where spontaneous rectal contractions were noted, these contractions faded away in 53 cases (77.9%) as the study progressed. Rectal pressure and vaginal pressure are not the same during filling and voiding cystometry. Although they are reasonable approximations of each other for most qualitative clinical diagnostic purposes, potentially significant differences in subtracted detrusor pressure may occur, depending on which pressure is used as the approximation of intra-abdominal pressure. This may affect clinical management decisions in individual patients. The technique used for approximating abdominal pressure must be stated clearly in any report or publication dealing with subtracted cystometry.

Functional obstructive defaecation

Objective: To study patients with obstructive defaecation to determine quantitatively its pathophysiology and homogeneity. Design: Twenty-two patients with obstructive defaecation were studied by isotope proctography and by conventional methods for quantitative analysis of the pathophysiological factors involved. Methods: Examination of the patients included ano-rectal manometry, the rectal balloon expulsion test, pelvic floor electromyography and isotope proctography. Eleven asymptomatic subjects were studied for comparison. Results: Pelvic floor electromyography revealed increased 'straining electromyographic activity' in all patients (P< 0.001). Patients with obstructive defaecation had impaired rectal sensation and were unable to perform a complete rectal evacuation (54% rectal evacuation) on isotope proctography. The defaecation time was prolonged and was associated with a reduced defaecation rate. Simultaneous recording of intrarectal pressures and external anal sphincter (EAS) electromyography during proctography revealed increased intrarectal pressure (P<0.0001) and EAS electromyographic voltage (P<0.01) during evacuation. The anorectal angles correlated with the pelvic floor movement and the anismus index. The anismus index in these patients correlated with the intrarectal pressure (P<0.02). No increase in the electromyographic voltage of the EAS was observed in any of the control subjects who successfully performed rectal balloon expulsion. Conclusion: Obstructive defaecation is a multifactórial condition involving derangements of rectal sensation and abnormal activity of the pelvic floor and anal sphincter musculature; its homogeneity is affected by the duration of the process.

The Long Head of the Biceps Femoris

Electrical stimulation of the nerve to the gracilis muscle following its transposition around the anal canal creates an artificial sphincter capable of actively opposing intrarectal pressure. Not all patients have an available or suitable gracilis. This paper describes the anatomic basis for the use of the long head of the biceps femoris as a potential electrically stimulated neoanal sphincter. The muscle was found to have an adequate length and a suitable arc of rotation for transposition around the anal canal. In 75 percent of thighs studied the neurovascular anatomy of the long head of the biceps femoris was compatible with its utilization in this manner as an alternative to the gracilis.

Uroflowmetry Combined with Simultaneous Measurement of Abdominal Pressure by Tocodynamometer

We used a guard-ring tocodynamometer to detect abdominal straining simultaneously with uroflowmetry in 19 normal volunteers, 63 patients with benign prostatic hyperplasia and 25 with a neurogenic bladder. The pressure curves obtained by the tocodynamometer were similar to the intrarectal pressure curves simultaneously measured by an intrarectal balloon. The frequency of straining in patients with benign prostatic hyperplasia did not differ significantly from that in normal volunteers and did not decrease postoperatively. In these patients abdominal straining did not produce a synchronously increased flow rate. Patients with a neurogenic bladder frequently voided with straining. Abdominal straining tended to produce a synchronously increased flow rate in patients with lesions in the sacral cord or peripheral nerves but not in patients with neural lesions above the sacral cord. The presence of urinary flow without straining was considered to signify an intact voiding reflex. We believe that this method is simple and provides much more information than uroflowmetry alone to evaluate voiding dysfunctions.