Gastroenterology Grand Rounds

BCM Gastroenterology Grand Rounds - Discussion

Final Diagnosis: Pelvic floor dysfunction

Important points regarding the History of patients with this condition include:

Chronic constipation is a common disorder affecting about 3% to 5% of the US adult population. Among the subtypes of constipation, obstructed defecation is fairly common, occurring in about 10% of persons with chronic constipation. In most people with obstructed defecation, there is an inappropriate contraction (or failed relaxation) of the puborectalis muscle and of the external anal sphincter during attempts to defecate. This paradoxical contraction of the pelvic floor muscles during straining at defecation is considered a form of maladaptive learning and is called pelvic floor dysfunction or pelvic floor dyssynergia (PFD).

Hallmark symptoms of PFD are straining at stools and feelings of incomplete evacuation. The need for perineal or vaginal pressure to allow stools to be passed or direct digital evacuation are very strong clues. The diagnostic criteria were elucidated in the Rome II report and include those for functional constipation plus at least two out of three investigations (among manometry, electromyography and defecography) showing inappropriate contraction or failure to relax the pelvic floor muscles during attempts to defecate. (Visual 1)

Important points regarding the Physical Examination in patients with this condition include:

A thorough rectal exam is critical to make the diagnosis of PFD.

The anal reflex tested by light touch should be intact. The anal verge should be inspected during simulated defecation to observe for prolapse of the rectal musoca.

The digital examination should evaluate resting tone of the sphincter segment, and its augmentation by a squeezing effort. The voluntary external sphincter will be tightened by squeezing; sphincter tone should be normal. The puborectalis muscle should be palpated and compressed between the rectal forefinger and external thumb; acute localized pain along the border of the muscle is a feature of the puborectalis spasm syndrome which may accompany PFD. Finally, the patient should be instructed to integrate the expulsionary forces by requesting that she/he “expel my finger.” In the presence of normal sphincter tone, failure to expel the finger should be a strong clue to PFD.

An examination should then be made to look for a rectocele, or consideration be given to gynecologic consultation.

Important points regarding the Laboratory Tests in patients with this condition include:

Laboratory tests are not helpful in making a diagnosis of PFD. A thyroid level and calcium level should be checked as part of the evaluation for chronic constipation.

The Imaging Studies demonstrated the following features:

Imaging studies may be useful in making a diagnosis of PFD.

Colonic transit studies using radiopaque markers such as Sitz-Marks are useful in differentiating slow transit constipation or colonic inertia from obstructed defecation. This is particularly useful in patients with suspected PFD because these two conditions may coexist up to 10% of the time. If more than 80% of markers are expelled by day 5, colonic transit is grossly normal. If remaining markers are scattered around the colon, the most likely diagnosis is colonic inertia. If the remaining markers are accumulated in the rectum, there is a functional outlet problem. (Visual 2)

The other useful imaging study to diagnose PFD is defecography.

Of the observations possible with these techniques, the most relevant are (1) the failure of the anorectal angle to open (i.e., become more obtuse) during defecation and (2) the degree of pelvic floor descent during defecation. Decreased descent is a component of impaired pelvic floor relaxation (“anismus”), and, conversely, excessive descent (“descending perineum syndrome”) can also be a pathophysiologic mechanism of constipation. In this instance, excessive straining, internal intussusception, solitary rectal ulcers, and prolapse may also occur. A representative defecographic sequence of a patient with PFD showing insufficient opening of the anal canal and of the anorectal angle during straining is shown in (Visual 3)

The anorectal manometry demonstrated the following features:

Anorectal manometry provides information on the pressures generated in the rectum and anal canal. A catheter placed into the rectum can measure pressures generated in the rectum as well as across the anal canal. EMG of the external anal sphincter to measure muscle activity is performed by placing electrodes at the anal verge. A balloon in the rectum is used to measure relaxation of the internal anal sphincter in response to rectal distension. It may also be used to test if the balloon can be passed during simulated defecation. (Visual 4)

During normal defecation, the intrapelvic pressure is raised by contraction of the diaphragm and abdominal musculature, while at the same time the pelvic floor is relaxed. The rectal contents are expelled by striated muscular activity with little or no assistance from colonic or rectal propulsive waves. The internal anal sphincter generates approximately 85% of the resting anal canal pressure, whereas the external anal sphincter is solely responsible for the voluntary squeeze pressure. Passage of a stool is associated with relaxation of the smooth muscle forming the internal anal sphincter, of the striated muscles forming the puborectalis (which maintains the anorectal angle), and of the external anal sphincter. During manometric recording, this is manifest by increased rectal pressure during straining and decreased internal and external anal sphincter pressures. The external anal sphincter EMG will show low voltage as it relaxes during straining. (Visual 5)

The striated muscle of the pelvic floor is tonically contracted in the resting state, and there is reflex contraction when intra-abdominal pressure rises, as during a cough. Unconscious relaxation of the striated pelvic floor muscles accompanies straining during defecation in normal subjects. However, in certain people the striated muscles of the pelvic floor contract, rather than relax, on straining causing pelvic floor dyssynergia. Manometry will demonstrate normal relaxation of the internal anal sphincter in response to rectal balloon distension. However, during straining, there will be inappropriate contraction of the external anal sphincter that will manifest as increased activity on EMG and increased external anal sphincter pressures.

Relaxation of the internal anal sphincter is a reflex initiated by rectal distention or by passage of a peristaltic wave down the left colon. Aganglionosis of the colon, as in Hirschsprung’s disease, leads to failure of relaxation of the internal sphincter on rectal distention. This is shown manometrically in (Visual 6)

AGA Position Statement: “Anorectal manometry is clinically useful in relatively few patients with chronic constipation. The technique has potential value in exclusion of Hirschsprung's disease and in assessment and treatment of constipated adults who exhibit pelvic floor dyssynergia, especially if this is corroborated by anal sphincter EMG and by impaired expulsion of contrast with defecography.”

Points about treatment of pelvic floor dysfunction using biofeedback:

Techniques:

Sensory training was the first biofeedback technique to be used in clinical practice. It entails simulated defecation by means of a water filled balloon introduced in the rectum; this is then slowly withdrawn, while patients are asked to concentrate on the sensations evoked by the balloon and to try to ease its passage. Variations of this technique involve defecation of a balloon or simulated stools to improve defecatory dynamics.

Electromyography consists of recording a patient's averaged electromyographic activity from the pelvic floor muscles for training. Measurements may be obtained from intraluminal probes or from surface electrodes taped to the perianal skin. By watching the recording, the patient first learns to relax the pelvic floor muscles during attempts to defecate, and then gradually increases straining efforts to increase intra-abdominal pressure while keeping the pelvic floor muscles relaxed.

Manometry—Anal canal pressures are measured to detect the contraction and relaxation of the pelvic floor muscles. The training procedures are almost identical to those described above for electromyographic training.

Effectiveness of biofeedback in treating pelvic floor dysfunction:

Literature reviews conclude that more than 70% of patients with pelvic floor dysfunction are likely to benefit from biofeedback training. Because of its safety, and lack of other good treatments, it is probably the treatment of choice. However, the overall quality of studies is not good; they are mostly small uncontrolled trials, with different patient selection criteria. A comparison of these trials are shown in (Visual 7). Long term follow-up after biofeedback training shows a fading effect over time. However, up to 50% will have continued improvement up to 12 months after treatment.

There seem to be no physiologic, anatomic, or demographic variables that influence treatment outcome or predict the type of patient who will benefit from biofeedback therapy for constipation. The number of treatment sessions was identified as a possible variable-effecting outcome, but this requires further investigation. Although psychologic and behavior problems often are observed in subjects with constipation, there is question as to whether this is a cause or consequence of being constipated. Providing psychological counseling is recommended by several researchers and may prove helpful, especially in cases in which patients with PFD do not respond to biofeedback training.