Pelvic Floor Disorders: Surgical Approach

9. Obstructed Defecation Syndrome

Kim J. Gorissen  and Martijn P. Gosselink

(1)

Department of Colorectal Surgery, Churchill Hospital, Oxford University Hospitals NHS Trust, Oxford, UK

Kim J. Gorissen

Email: kgorissen@yahoo.com

Abstract

Obstructed defecation syndrome (ODS) is a term used to describe the whole complex of mechanical and functional disorders leading to difficult or inadequate rectal emptying. ODS or anorectal outlet obstruction is typically seen in middle-aged, multiparous women. Prevalence ranges from 3.4% in the general population up to 23% in middle-aged women [12]. ODS and slow-transit constipation (STC) are two subgroups of constipation, as defined in the Rome III criteria for functional bowel disorders [3]. Strictly speaking, ODS is confined solely to the evacuation disorder and differs from STC because in patients with isolated ODS the fecal stream reaches the rectum without delay. However in around 30% of patients both conditions occur simultaneously [4] and their strong association leads to a suspicion of interaction. Differentiation between both subtypes of constipation requires a specialized pelvic floor work-up because treatment approaches are different.

9.1 Introduction

Obstructed defecation syndrome (ODS) is a term used to describe the whole complex of mechanical and functional disorders leading to difficult or inadequate rectal emptying. ODS or anorectal outlet obstruction is typically seen in middle-aged, multiparous women. Prevalence ranges from 3.4% in the general population up to 23% in middle-aged women [12]. ODS and slow-transit constipation (STC) are two subgroups of constipation, as defined in the Rome III criteria for functional bowel disorders [3]. Strictly speaking, ODS is confined solely to the evacuation disorder and differs from STC because in patients with isolated ODS the fecal stream reaches the rectum without delay. However in around 30% of patients both conditions occur simultaneously [4] and their strong association leads to a suspicion of interaction. Differentiation between both subtypes of constipation requires a specialized pelvic floor work-up because treatment approaches are different.

9.2 Symptoms

Patients with ODS typically report straining, incomplete emptying, need for manual support of the perineum, vaginal/rectal “digitation”, and pain. Prolonged and repeat visits to the toilet may develop in substantial daily rituals with severe impact on quality of life. Dependence on laxative and/or enema use is common. In contrast, patients with isolated STC report the absence of urge or call to stool. Their main complaint is abdominal heaviness and bloating.

Patients with ODS and/or STC are not uncommonly also troubled by varying degrees of fecal incontinence. Postdefecatory soiling might be caused by residual stool trapped in the anal canal or rectocele. Both overflow-diarrhea and excessive laxative use can aggravate existing borderline incontinence. Clinical scoring tools such as the Cleveland Clinic Constipation Score [5] and, more specific for ODS, the Altomare Obstructed Defecation Scoring tool, are essential to assess severity of initial symptoms and audit treatment outcomes [6].

9.3 Etiology

Defecation is a complex process composed of several essential factors. After propulsion into the rectum, bowel content is sensed and sampled by the anorectal mucosa. Afferent signals are processed in the cerebral cortex under the influence of environmental stimuli. If regarded safe and appropriate, the internal and external sphincter, together with the pelvic floor muscles, are allowed to relax. Relaxation of the puborectal sling leads to alteration of the angulation of the rectum, and rectal motility needs to expel the contents in the right vector towards the anal canal. Problems can occur on all levels of this process.

9.3.1 Anorectal Hyposensitivity

Decreased perception of the rectum has been described in about one-third of patients with ODS [7]. The tonic response of the rectum to evoked urge to defecate seems to be absent or significantly blunted in ODS patients with or without STC [8]. The most likely cause is impairment of afferent sensory pathways due to pelvic nerve injury such as during childbirth, pelvic surgery (hysterectomy), or excessive perineal descent and prolapse.

9.3.2 Relaxation of Sphincter and Pelvic Floor Muscles

Several terms (anismus, dyssynergia, spastic pelvic floor, and puborectalis syndrome) are used to reflect the inability to relax the pelvic floor muscles in order to open the anal canal and facilitate defecation. This might be related to subconscious cortical inhibition, as it is more common after sexual abuse. The currently popular “safe toilet syndrome” is a more subtle variant of anismus, demonstrating the influence of various psychological components [9].

9.3.3 Anatomical/Mechanical Obstruction

Rectocele is a result of weakening of the rectovaginal septum, leading to “herniation” into the posterior vagina. The bulging at straining, together with the entrapment of stool in the rectocele, prohibits efficient evacuation. Isolated rectocele can occur, but often they are a sign of overall pelvic weakness. The complex of rectocele, rectal intussusception, enterocele and anterior compartment prolapse is known as 'descending perineal syndrome'.

In enteroceles, small bowel or sigmoid (sigmoidocele) becomes trapped between the vagina and rectum in a deepened pouch of Douglas. The role of enterocele in ODS is debatable, as two studies found no influence of adequate enterocele repair on symptoms of ODS [1011].

External rectal prolapse can be accompanied by symptoms of ODS, but fecal incontinence is often more pronounced. Bowel mucosa and pudendal nerves can be damaged as a result of stretch. Recurrent or persistent full-thickness prolapse dilates the sphincters and anal canal. Repetitive stimulation of the rectoanal inhibitory reflex can result in insensitivity to the reflex. In addition to this, the intussusseptum occludes the lumen of the rectum causing mechanical obstruction. Internal prolapse or intussusception seems to be the precursor of external prolapse, and is increasingly recognized as a cause of ODS [12]. Early studies demonstrating internal intussusception in asymptomatic volunteers [13] have been contradicted by others [14] showing that high-grade full-thickness intussusception is confined to symptomatic patients. The good results of laparoscopic ventral rectopexy in both external and internal intussusception, where anatomical correction is achieved without resection of the hyposensitive mucosa, argues in favor of the important role of prolapse in ODS.

9.4 Investigations

9.4.1 Anamnesis

Anamnesis should identify patients who are mainly worried about underlying (malignant) pathology and are satisfied by reassurance only, instead of further treatment. A subgroup of patients has unrealistic views of “normal” bowel patterns. A common, but easily negated, misbelief seems to be that if defecation fails to occur for a few days, toxins arise that “poison the body”.

9.4.2 Physical Examination

Inability to relax, and especially paradoxical contractions on straining, can raise suspicion of anismus, although digital examination alone gives a high rate of false-positives results [15]. Perineal descent and rectocele have to be assessed. Sometimes internal prolapse can be felt touching the fingertip on straining.

9.4.3 Flexible Sigmoidoscopy/Colonoscopy

Flexible sigmoidoscopy/colonoscopy should be used with a low threshold to exclude anorectal malignancies and strictures.

9.4.4 Colon Transit Studies

Colon transit studies are an easy, safe, and inexpensive way to diagnose whole-gut slow-transit constipation where the radiopaque markers are found mainly proximal in the descending and transverse colon. Left-sided retention can sometimes be seen in obstructed defecation.

9.4.5 Defecating Proctography

Defecating proctography gives very valuable functional dynamic information. Inability to void any contrast can be indicative of anismus, but the clinician has to be aware that embarrassment can mimic the disorder and lead to a high rate of false-positive results. Defecating proctography is the preferred tool in assessing anatomical causes of obstruction such as enterocele, rectocele, and intussusception, although incomplete emptying can lead to underdiagnosis of the latter. An examination under anesthetic is used to diagnose these initially missed prolapses.

9.4.6 Anorectal Physiology

Anorectal physiology with rectal balloon distension is used to examine rectal sensory perception and rectal wall contractility, sensory threshold volume, urge to defecate volume, and maximum tolerable volume. Paradoxical contractions or pelvic dyssynergia can be detected. The rectal anal inhibitory reflex is absent in congenital Hirschsprung’s disease and systemic sclerosis.

9.4.7 Endoanal Ultrasound

A thickened internal sphincter can be seen in anismus, rectal intussusceptions, and solitary ulcer of the rectum syndrome. Congenital myopathy/hypertrophy of the internal anal sphincter is a rare cause of ODS. Diagnosis is made by observation of inclusion bodies on biopsy specimens. Successful treatment with nitrates, calcium-channel blockers, and strip myectomy has been reported [16]. A balloon expulsion test is mandatory when considering colectomy.

9.5 Treatment

9.5.1 Lifestyle Modification

Physical activity has shown to accelerate colonic transit time [17]. The effect of increased fluid intake and “timed toilet training” are not supported by any trials. However, providing information on different coping techniques in “pelvic floor educational programs” seems logical [18].

9.5.2 Medication

Bulking or fiber laxatives are first line treatment, but they have to be ingested with sufficient water. Soluble fibers can lead to gas formation and bloating through fermentation. Osmotic laxatives, such as macrogol, are supported by level I evidence. Stimulative laxatives are generally used as rescue medication, as doubt of dependence and rebound constipation limits their use on a daily basis. Prucalopride is a high-affinity 5-hydroxytryptamine 4 receptor agonist that has been proven to be effective in severe constipation [19].

9.5.3 Biofeedback

Biofeedback is laborious and time consuming, and requires a highly dedicated therapist as well as a strongly motivated patient. Several randomized controlled trials proved its benefit mainly in pelvic floor dyssynergia [20]. Its use in the presence of anatomical problems such as intussusception seems to be far less helpful.

9.5.4 Retrograde Colonic Irrigation

Retrograde colonic irrigation is simple, noninvasive, and safe. High success rates have been reported by several groups, especially when patients are guided by dedicated nurses [2122]. Normal water is used and provides a mechanic washout, but also triggers colon mass movement. Addition of polyethylene glycol, glycine, bisacodyl, and glyceryl trinitrate solutions can enhance colonic emptying even further.

Antegrade colonic irrigation, for example by a Malone stoma, should in theory be even more effective, as the flow of water and bowel contents is in the same direction as the bowel motor complexes. However this technique is invasive, possibly less effective in adults [2324], and often requires revisions of the appendicostomy because of stenosis or rectraction.

9.5.5 Botulinum Toxin

Botulinum toxin is very effective in the treatment of anismus, especially if underlying (internal) prolapse is excluded [15].

9.5.6 Surgery

Many different surgical procedures have been developed since colectomy and colostomy were the only options. Most surgery is focused on restoration of anatomical abnormalities.

Primary repair of an isolated rectocele can be performed by transperineal, endoanal, or transvaginal repair. The only randomized trial performed to date showed no benefit [25] apart from a possible lower recurrence rate for transvaginal repair. Rectal repair might be associated with (transitory) fecal incontinence due to stretch of the sphincter, and transvaginal correction might cause more dyspareunia.

Stapled transanal rectal resection procedures for ODS seem to be quite successful, with long-term improvement of around 50% in ODS scores [26]. Success seems to be related to the combination of removal of the insensitive part of the rectum and anatomical correction of the rectocele/intussusception.

Postoperative (transient) urgency is often reported, and major complications such as bleeding, anastomotic dehiscence, rectovaginal fistulas, and stenosis illustrate the need for specialized surgical care.

Rectopexy previously had a negative image, as posterior mobilization with division of the lateral ligaments caused worsening of constipation. With modern nerve-sparing laparoscopic ventral rectopexy, significant improvement of over 50% in the short-term and mid-term has been reported [2728]. Prosthetic mesh repair compared with repair by biodegradable meshes might lower recurrence rates of intussusception and rectocele, but long-term follow-up is scarce. Mesh erosion is a severe, but relatively uncommon, complication (< 2%), especially when compared with transvaginally placed meshes.

Sometimes correction of anatomical abnormalities as a treatment on its own does not lead to restoration of normal function. In these cases, hyposensitivity/mobility might be the key.

Sacral nerve stimulation (SNS) can elicit pancolonic pressure waves [29]. Long-term effects of SNS in ODS/constipation varies and SNS might be more effective in adolescent females [30]. Alterations of SNS settings, like suprasensory stimulation, might be helpful in improving success rates [31].

9.6 Summary

Although often coexisting in the same patient, ODS and STC are different entities.

Whether ODS is caused primarily by sensory dysfunction or by anatomical/mechanical obstruction is not clear yet, although there seems to be an increasing awareness of the role of internal prolapse in ODS.

Treatment should be directed to the disorders found at full pelvic floor work-up.

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