Pelvic Floor Dysfunction and Refractory Constipation

Vol. 22, Issue 1 (May 2017)

Noemi Baffy, MD, MPH
Division of Gastroenterology and Hepatology, Mayo Clinic
Scottsdale, AZ USA

Lucinda A. Harris, MD
Division of Gastroenterology and Hepatology, Mayo Clinic
Scottsdale, AZ USA

Amy E. Foxx-Orenstein, DO
Division of Gastroenterology and Hepatology, Mayo Clinic
Scottsdale, AZ USA

Introduction

Constipation is one of the most common gastrointestinal complaints with one-third of the general population reporting it during their lifetime. ^(1,2)  Patients use a broad range of symptoms to describe constipation, including being irregular, having hard stools, a feeling of incomplete evacuation, bloating, distention, prolonged time needed to evacuate or time between movements, as well as a need to strain or apply manual pressure.  Physicians often equate constipation with infrequent bowel movements or a functional disorder, yet, less than 3% of the general population report fewer than a normal (<3 times per week) number of evacuations ^(1,2) and testing is often needed to exclude other causes of constipation.  Constipation is defined as a symptom-based disorder characterized by unsatisfactory defecation. ⁽³⁾ The three primary causes of constipation, which are distinguished according to their pathophysiological characteristics, include slow transit constipation (colonoparesis), defecatory disorders (pelvic floor dysfunction, outlet obstruction), and normal transit constipation (functional).

Defecation occurs through a neurologically mediated series of coordinated muscle movements of the pelvic floor muscles and anal sphincters. Failed relaxation or paradoxical contraction of the puborectalis muscle and external anal sphincter to expel the stool completely leads to impaired rectal evacuation and is termed pelvic floor dyssynergy (PFD). Contributing factors include high anal resting pressures, incomplete relaxation of the pelvic floor and external anal sphincters. Patients often have concomitant slow colonic transit that may improve once the PFD is treated. ⁽²⁾

Etiology

The etiology of dyssynergic defecation is unclear. A prospective survey identified the problem beginning in childhood in 31% of patients, and after a particular event like pelvic floor trauma, back injury or pregnancy in 29% of patients, with no cause in 40% of patients. ⁽⁴⁾ This study also noted that 43% of the patients reported frequent passage of hard stools, leading one to believe that straining to expel hard stools may over time lead to dyssynergia. A classic study demonstrated that dyssynergic defecation is a result of the inability to coordinate the abdominal, rectoanal and pelvic floor muscles to facilitate defecation. The failure of rectoanal muscle coordination leads to inadequate propulsive forces, paradoxical contraction of the anal sphincter muscles or inadequate anal relaxation to allow the passage of stool. Approximately half of patients with PFD have also been shown to have impaired rectal sensation which presumably diminishes the urge to defecate. ⁽⁵⁾

Evaluation

Assessment should always start with a comprehensive history focusing on relevant clinical features, including a review of medications. A digital rectal examination and perianal inspection are essential for identifying mass lesions, anal strictures, fissures, and to assess the mechanics of defecation. ^(6,7)  Presence of stool in the rectum is also important to note and a lack of awareness may suggest rectal hyposensitivity. During a digital exam, asking patients to “squeeze” will provide information about the anal sphincter muscle tone while “pushing” should elicit relaxation of the external anal sphincter and lead to perineal descent.  With the aid of these two maneuvers, dyssynergia can be identified with 75% sensitivity and 87% specificity. Certainly, colon cancer screening is recommended for all patients 50 years or older as well as those with alarm symptoms. ⁽²⁾

Current available tests to assess pelvic floor function include anorectal manometry (ARM) with or without balloon expulsion, standard defecography, and dynamic magnetic resonance (MR) defecography.

Four types of dyssynergic pattern have been identified based on manometric findings: ⁽⁸⁾

• Type I: Abdominal pushing force is adequate, but is associated with a paradoxical increase in anal sphincter pressure.
• Type II: Inadequate abdominal pushing force, and a paradoxical anal sphincter contraction.
• Type III: Abdominal pushing force is adequate but, either there is absent or incomplete anal sphincter relaxation.
• Type IV: Inadequate abdominal pushing and absent or incomplete anal sphincter relaxation.

Several studies have found that these patterns were also observed in nearly 90% of asymptomatic controls which is attributed to a non-physiologic position during the test (left lateral position) with an empty rectum. ⁽⁹⁾ The addition of balloon expulsion adds specificity (80-90%) making it a useful screening test for dyssynergic defecation. ⁽¹⁰⁾

Conventional defecography which uses barium paste placed into the rectum provides useful information regarding the presence of anatomic abnormalities that may influence rectal evacuation. ⁽¹¹⁾ However, due to methodological differences and poor inter-observer agreement its role is limited. MR defecography can evaluate the anatomy of the pelvic floor and rectal evacuation in dynamic motion. It can provide information about the integrity of the anal sphincters, pelvic floor muscles and the soft tissue surrounding the rectum all without exposure to radiation. There is no single best test and more than one is usually required for accurate diagnosis.

Treatment

Chronic constipation is associated with impaired quality of life, increased health-care costs and with excess work absenteeism and about half of those who are seen by physicians are not satisfied with their response to therapy, leading to refractory constipation. ⁽¹²⁾

Bowel training can lead to improvement in symptoms so it should be tried as a first-line treatment. It includes keeping a detailed diet log, a diary of stool frequency and consistency along with associated symptoms such as straining, the need for manual or positional maneuvers to facilitate defecation is important to emphasize. ₍₁₃₎  The day should begin with mild physical activity, consumption of a hot and preferably caffeinated beverage and a breakfast that includes a form of soluble fiber to induce high-amplitude peristaltic contractions within an hour of waking, taking advantage of several known factors that stimulate defecation. ⁽²⁾

Biofeedback using pelvic floor rehabilitation is the most effective treatment for PFD. Patients receive education about the process of defecation, how to coordinate abdominal pressure with pelvic floor muscle relaxation during evacuation, and practice simulated defecation with a balloon. ⁽¹⁴⁾  During anorectal biofeedback, patients are trained to use breathing techniques with relaxation of the pelvic floor muscles to produce a propulsive force that facilitates effective evacuation. Biofeedback has been shown to be superior to laxatives, with a durable effect when used in patients with PFD. ⁽¹⁵⁾ Concomitant slow transit constipation frequently requires simultaneous treatment and can improve once the PFD has been rehabilitated.

Supplementation with fiber is a mainstay in the management of chronic constipation and has been shown to be beneficial for mild to moderate constipation. ⁽¹⁶⁾ It facilitates bowel function by increasing the water absorption capacity of stool increasing stool bulk and facilitating its passage resulting in increased stool frequency. ⁽¹⁷⁾ Adequate hydration while using fiber is important. Benefits may not be evident for days and those with PFD may actually note worsening in their symptoms and it may even lead to fecal impaction, thus initiation at low doses and with caution is recommended. ⁽⁸⁾

Laxatives have a common purpose of stimulating defecation or softening the consistency of stool in order to facilitate evacuation and newer agents have been developed to facilitate treatment of refractory cases None of the laxatives nor the newer agents have been evaluated in patients with PFD. ⁽¹⁰⁾  Lubiprostone and lineclotide have both been shown to be effective at increasing the number of spontaneous bowel movements, but neither has been specifically evaluated in patients with dyssynergic defecation. There is promising research investigating the use of bile salt inhibition and a synthetic form of ghrelin receptor analog. ⁽²⁾

Use of sacral nerve stimulation for refractory cases has been described but with conflicting results. Benefit has been found primarily with normal or slow transit constipation. ⁽¹⁸⁾ It is unclear if any additional value would be gained in those with PFD.

Surgery for defecatory disorders should only be considered in those patients who have evidence of retained contrast during a defecography and failed conservative approaches and pelvic floor rehabilitation. ⁽¹⁹⁾ Colectomy with ileorectal anastomosis is the most commonly performed surgery and care has to be taken to rule out pan-intestinal dysmotility and those with pelvic floor dysfunction will have limited success due to the underlying physiology not being corrected.

Finally, botox, a potent neurotoxin that inhibits presynaptic release of acetylcholine has been used to treat defecatory disorders by injection into the puborectalis muscle with mixed results. ⁽²⁰⁾ A recent study used electromyography to guide botox placement with improvement in pelvic floor pain and quality of life measures, but did not evaluate its impact on defecation. ⁽²¹⁾ Targeted therapy may therefore be the key to finding an effect for those with pelvic floor dyssynergy, specifically for those with type I or type II manometric findings.

Conclusions

Constipation is common in the general population and teasing out the underlying etiology is key in order to provide the appropriate therapeutic intervention. Treatment may be as simple as lifestyle modifications or the addition of fiber but may require pharmacologic approach. Often multiple treatment modalities are necessary to improve outcomes.  Biofeedback remains the mainstay of therapy for those with pelvic floor dyssynergy and it has shown to have durable effect. Refractory cases may need repeated evaluation with consideration for surgery or botox injection.   

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