Balloon topography. A simple method of evaluating anal function

Correlations of anatomical parameters in dynamic pelvic CT and conventional defecography for patients with rectal prolapse

PURPOSE

To evaluate the correlations of anatomical parameters between dynamic pelvic CT (D-PCT) and conventional defecography (CD) for patients with rectal prolapse.

MATERIAL AND METHODS

Anatomical parameters in multislice CT scanning of the pelvis performed at rest and during simulated defecation (D-PCT) were studied with those of CD to evaluate the correlations in both methods for 10 patients with rectal prolapse.

RESULT

The correlation coefficients of the pubococcygeal line and the pubosacral line were r=0.6 and r=0.8 respectively. The length from anal verge to pubococcygeal line and to the pubosacral line showed a good correlation of r=0.7. The length of puborectal muscle showed a good correlation of r=0.8. Anorectal angle was significantly well correlated between two methods (r=0.9, p<0.05). The lengths of anococcygeal length and anosacral length showed a good correlation.

CONCLUSION

The anatomical parameters measured by D-PCT were well correlated with those by CD. D-PCT might be an alternative tool for anatomical evaluation of the anorectal region in patients with rectal prolapse.

Constipation of anorectal outlet obstruction: pathophysiology, evaluation and management

Constipation is a subjective symptom of various pathological conditions. Incidence of constipation fluctuates from 2 to 30% in the general population. Approximately 50% of constipated patients referred to tertiary care centers have obstructed defecation constipation. Constipation of obstructed defecation may be due to mechanical causes or functional disorders of the anorectal region. Mechanical causes are related to morphological abnormalities of the anorectum (megarectum, rectal prolapse, rectocele, enterocele, neoplasms, stenosis). Functional disorders are associated with neurological disorders and dysfunction of the pelvic floor muscles or anorectal muscles (anismus, descending perineum syndrome, Hirschsprung's disease). However, this type of constipation should be differentiated by colonic slow transit constipation which, if coexists, should be managed to a second time. Assessment of patients with severe constipation includes a good history, physical examination and specialized investigations (colonic transit time, anorectal manometry, rectal balloon expulsion test, defecography, electromyography), which contribute to the diagnosis and the differential diagnosis of the cause of the obstructed defecation. Thereby, constipated patients can be given appropriate treatment for their problem, which may be conservative (bulk agents, high-fiber diet or laxatives), biofeedback training or surgery.

Clinical applications and techniques of cinedefecography

BACKGROUND

Cinedefecography is of value in routine examination of functional disorders of the pelvic floor. Interest in this technique has rapidly expanded owing to the increased availability of colorectal physiologic testing and better understanding of the multifactorial pathophysiology involving evacuation disorders.

METHODS

A summary of the available techniques, methodology, and indications for cinedefecography was undertaken. In addition, information was provided on interpretation of these images particularly in the context of anatomic abnormalities and clinical applications.

RESULTS

Cinedefecography can be rapidly and easily performed using standard radiographic equipment. Effective radiation dose is significantly lower than for other intestinal contrast studies. The technique has been found most useful for measurements of perineal descent, puborectalis length, and ascertaining the function of the puborectalis muscle and pelvic floor. Common diagnoses that can be made by this test include nonrelaxing puborectalis syndrome, perineal descent, rectocele, enterocele, sigmoidocele, and rectoanal intussusception.

CONCLUSION

Cinedefecography provides a wide range of information to assist the surgeon with the evaluation and management of patients with evacuatory and other associated pelvic floor disorders.

Patient position during cinedefecography. Influence on perineal descent and other measurements

PURPOSE

This study was undertaken to assess the reproducibility of cinedefecography measurements and abnormal findings between the left lateral decubitus and seated positions.

METHODS

Prospective patient evaluation included all patients who had lateral radiographs of the pelvis taken at rest, during squeezing, and pushing in both positions. Anorectal angle, perineal descent, and puborectalis length measurements were calculated for each set of radiographs. Pelvic floor dynamics during evacuation were measured as the changes between rest and pushing. Abnormal findings included both increased dynamic and fixed perineal descent, nonrelaxing puborectalis, and premature evacuation.

RESULTS

One hundred five consecutive patients underwent cinedefecography. There were statistically significant differences between the positions with regard to anorectal angle (P < 0.0001), perineal descent (P = 0.0001), and puborectalis length (P = 0.0001). Dynamic changes of the anorectal angle, perineal descent, and puborectalis length were not significantly different (P > 0.05). However, 6 of 22 (27 percent) patients with fecal incontinence had premature evacuation severe enough to impede measurement only when seated (P = 0.05).

CONCLUSION

Because of the statistically significant differences between the two positions, centers should always employ the same position for a given diagnostic group.

Etiology and management of fecal incontinence

Fecal incontinence is a challenging condition of diverse etiology and devastating psychosocial impact. Multiple mechanisms may be involved in its pathophysiology, such as altered stool consistency and delivery of contents to the rectum, abnormal rectal capacity or compliance, decreased anorectal sensation, and pelvic floor or anal sphincter dysfunction. A detailed clinical history and physical examination are essential. Anorectal manometry, pudendal nerve latency studies, and electromyography are part of the standard primary evaluation. The evaluation of idiopathic fecal incontinence may require tests such as cinedefecography, spinal latencies, and anal mucosal electrosensitivity. These tests permit both objective assessment and focused therapy. Appropriate treatment options include biofeedback and sphincteroplasty. Biofeedback has resulted in 90 percent reduction in episodes of incontinence in over 60 percent of patients. Overlapping anterior sphincteroplasty has been associated with good to excellent results in 70 to 90 percent of patients. The common denominator between the medical and surgical treatment groups is the necessity of pretreatment physiologic assessment. It is the results of these tests that permit optimal therapeutic assignment. For example, pudendal nerve terminal motor latencies (PNTML) are the most important predictor factor of functional outcome. However, even the most experienced examiner's digit cannot assess PNTML. In the absence of pudendal neuropathy, sphincteroplasty is an excellent option. If neuropathy exists, however, then postanal or total pelvic floor repair remain viable surgical options for the treatment of idiopathic fecal incontinence. In the absence of an adequate sphincter muscle, encirclement procedures using synthetic materials or muscle transfer techniques might be considered. Implantation of a stimulating electrode into the gracilis neosphincter and artificial sphincter implantation are other valid alternatives. The final therapeutic option is fecal diversion. This article reviews the current status of the etiology and incidence of incontinence as well as the evaluation and treatment of this disabling condition.

How reliable are currently available methods of measuring the anorectal angle?

A prospective study was undertaken to compare two different methods of measuring the anorectal angle (ARA), balloon proctography (BP) and cinedefecography (CD), as well as to evaluate the reproducibility of this measurement using each technique. One hundred four consecutive patients (75 women and 29 men) with constipation (63 patients), fecal incontinence (25 patients), or rectal pain (16 patients) underwent both BP and CD. The ARA was measured by taking lateral radiographs of the pelvis during rest (R), squeeze (S), and push (P). The same interpretation process was performed 2 to 12 months later by the same observer, blinded as to diagnosis and initial measurements. There were highly significant differences in each measurement category, R (P less than 0.0001), S (P less than 0.0001), and P (P less than 0.0004) between BP and CD. However, the correlation between the first and second measurements was excellent (P less than 0.0001). BP was consistently more difficult to interpret because of balloon configuration. Although BP and CD have poor correlation with each other, each examination can be reliably interpreted. CD appears to be a superior examination because of the added ability to delineate rectoceles, intussusceptions, and other structural defects.

Intraobserver variation in the radiological measurement of the anorectal angle

Seven experts drew the rectal axes of 18 representative proctographic images on two occasions, with a 1-year interval, in order to assess intraobserver variation in the determination of the anorectal angle (ARA). Intraobserver variation (6%) and interobserver variation (17%) were smallest when the central rectal axis was used to determine the ARA. A strong relation was found between inter- and intraobserver variation (r = 0.77). Intraobserver variation tended to be rather small for pictures made during straining, but a relation with the magnitude of the ARA was not found. Although none of the seven experts could reproduce the rectal axes with less than or equal to 10% variation in all 18 pictures, redrawing of the central rectal axis delivered less than or equal to 10% variation in 86% of determinations. It is concluded that intraobserver variation is influenced by the expertise of the investigator, the method of analysis, and the anorectal configuration to be analyzed. Radiologic assessment of the ARA may yield reliable data on the dynamics of the anorectum if performed by a single investigator on x-ray films that allow confident analysis.

How reliable is measurement of the anorectal angle by videoproctography?

The anorectal angle can be determined either by constructing a straight line along the lower border of the rectum (Method A) or by using the central longitudinal axis of the lower rectum (Method B). We have used a computer program to derive the centroid of the rectum for Method B. The coefficients of variation for angles measured at rest, during maximum pelvic floor contraction, and during attempted defecation were 0.616, 0.351, and 0.358, respectively, compared with 0.993, 0.972, and 0.968 for Method B. The presence of a rectocele had no influence on the measurement of the anorectal angle in incontinence, but there was a significant difference in assessment of the angle between constipated patients (P less than 0.05) and controls (P less than 0.05). Posterior indentation of the rectum had no significant influence on measurement of the angle in any group. These data indicate that a computer-derived centroid is more reliable for measurement of angles, but a correction factor for anterior rectocele is needed in constipated patients and controls.

Anorectal physiology testing. A survey of availability and use

Survey forms were sent to all members of the Coloproctology Section of the Royal Society of Medicine and the American Society of Colon and Rectal Surgeons to obtain their opinions of the availability, actual use, and perceived helpfulness of different methods for the evaluation of the physiology of the colon and rectum. Responses revealed a similarity in age and practice patterns in both groups. Of the 19 methods surveyed, greater than 90 percent of respondents in both groups rely on three traditional methods of patient evaluation: patient history, digital examination, and sigmoidoscopy. Four other methods have gained acceptance by the majority of respondents in both groups: colon transit studies, defecography, perfused-catheter manometry, and rectal compliance. The three methods ranked lowest in availability, actual use, and helpfulness by both groups were single-fiber electromyography, use of a perineometer, and evoked potential studies. Our study provides a baseline for future surveys on the investigative efforts of physicians studying the physiology of the colon, rectum, and anus.

Chronic constipation in adults. How far should evaluation and treatment go?

In all patients who present with constipation, a history should be taken and physical examination and proctosigmoidoscopy performed. Structural evaluation of the entire colon by barium enema should be considered when constipation is of recent onset, is severe, or does not resolve with simple measures. A colonic transit study should also be considered in the latter two situations. Anorectal manometry, defecography, and electromyography are helpful in patients with diagnosed or suspected outlet delay. Treatment is most often empirical. Simple, helpful measures include education, dietary fiber supplementation, adequate fluid intake, and regular physical activity. When laxatives are necessary, they should be used sparingly. Pelvic floor retraining may be helpful in the management of patients with outlet delay. Select patients with intractable constipation may benefit from surgery, although results are variable.

Observer variation in the radiological measurement of the anorectal angle

Determination of the anorectal angle (ARA) and the position of the pelvic floor is, theoretically, very important in understanding the mechanisms of anorectal continence and defaecation. The variability in the measurement of the ARA was analyzed. Nine experts drew ther rectal axis either as a line along the posterior wall of the distal rectum or as the central axis of the rectal lumen on the outlines of 18 representative proctographic images. The standard deviations and ranges of the mean values of each ARA were comparable but large in both methods. On average, the S.D. was 8 degrees and the range value about 23 degrees. Inter-observer variation was not related to the magnitude of the ARA, but rather to the anorectal configuration. Drawing a line along the posterior distal rectal wall is difficult when it is irregular or when the puborectalis impression is indistinct. The central rectal axis is difficult to draw when the junction between the upper and lower rectum is ill defined or when the outlines of the distal rectum are asymmetric e.g. by the presence of a rectocele. Thus, the variability of both methods was not strongly interrelated (r = 0.68 for the median values). It is concluded that, in general, radiologic assessment of the ARA is not reliable enough for comparative investigation of the dynamics of the anorectum.

Scintigraphic assessment of the anorectal angle in health and after ileal pouch-anal anastomosis

To determine whether the anorectal angle was preserved after ileal pouch-anal anastomosis, a simple, safe, low-radiation, real-time method of imaging the anorectum was developed. A cylindrical balloon was placed in the neorectum and anal canal and filled with a solution of 99mTc in water. A gamma camera then imaged the angulation of the balloon while the subject was at rest, during sphincteric squeeze, and during a Valsalva maneuver. Thirteen healthy volunteers and six patients were studied after ileal pouch-anal anastomosis. An angle was identified in all controls and patients. In the lateral decubitus position at rest, the mean anorectal angle in controls (102 +/- 18 degrees; SD) and anopouch angle in patients (108 +/- 19 degrees) were similar (p = 0.3). Sitting straightened the angle in both groups (p less than 0.03), whereas sphincteric squeeze and a Valsalva maneuver sharpened the angle in both the sitting and standing positions (p less than 0.03). In the lateral decubitus position, however, the pouch group was less able to sharpen the angle than were the controls (p = 0.04). In controls, the anorectal junction descended during sitting and elevated during squeeze (p less than 0.03), but this did not occur in the pouch group. In conclusion, maneuvers favoring or stressing continence (squeeze, Valsalva) sharpened the anorectal angle and elevated the pelvic floor, whereas a maneuver favoring defecation (sitting) straightened the angle and caused the pelvic floor to descend. After ileal-anal anastomosis, the angle and its movements (except those while lying) were similar to controls. Elevation of the pelvic floor during squeeze, however, was decreased, indicating a decreased mobility of the pelvic floor after operation.

Balloon sphincterography. Clinical findings after 200 patients

There are two muscular mechanisms of fecal continence. The anal sphincter squeezes the anal canal, thus lengthening it and increasing its resistance. The puborectalis kinks the distal rectum, preventing the transmission of intra-abdominal pressures into the anal canal. Balloon sphincterography simultaneously records the shape of the anal canal and distal rectum and measures the strength of the puborectalis and anal sphincter muscles. This allows the physician to evaluate the function of these important muscles in patients with symptomatic defecation disorders such as constipation, incontinence, and rectal prolapse. A cylindrical balloon is connected by a hose to a fluid reservoir filled with liquid barium. The deflated balloon is placed into the anal canal and inflated by raising the fluid reservoir in increments. Fluoroscopy visualizes the balloon's shape and video records the results. Quantitative sphincterogram measurements in patients with defecation disorders include (the three measurements in each category refer respectively to incontinent patients [N = 87], prolapse patients without incontinence [N = 26], and constipated patients [N = 65]); anorectal angle (degrees + S.D.): 114 + 28, 103 + 18, 95 + 19; anal canal length (mm + S.D.): 33 + 11, 38 + 10, 39 + 10; squeeze pressure (cm H2O + S.D.): 68 + 23, 80 + 16, 91 + 22, and opening pressure (cm H2O + S.D.): 52 + 25, 67 + 22, 81 + 24. The method is useful in identifying specific defects, such as paradoxic puborectalis contractions, that can cause constipation, and injuries to the sphincters that can cause incontinence. In over 280 patients with a wide variety of defecation disorders, sphincterography has yielded information not available by standard manometric techniques. It augments the findings of defecography.