Defecation Disorders

Diagnostic criteria for functional constipation

1. Must include two or more of the following:

(a) Straining during at least 25 % of defecations

(b) Lumpy or hard stools in at least 25 % of defecations

(d) Sensation of anorectal obstruction/blockage for at least 25 % of defecations

(e) Manual maneuvers to facilitate at least 25 % of defecations (e.g., digital evacuation, support of the pelvic floor)

(f) Fewer than three defecations per week

2. Loose stools are rarely present without the use of laxatives.

3. Insufficient criteria for irritable bowel syndrome

Functional defecation disorders

Diagnostic criteria^a

1. The patient must satisfy diagnostic criteria for functional constipation**

2. During repeated attempts to defecate, must have at least two of the following:

(a) Evidence of impaired evacuation, based on balloon expulsion test or imaging

(b) Inappropriate contraction of the pelvic floor muscles (i.e., anal sphincter or puborectalis) or <20 % relaxation of the basal resting sphincter pressure by manometry, imaging, or electromyography

Dyssynergic defecation

Inappropriate contraction of the pelvic floor or <20 % relaxation of the basal resting sphincter pressure with adequate propulsive forces during attempted defecation

Inadequate defecatory propulsion

Inadequate propulsive forces with or without inappropriate contraction or <25 % relaxation of the anal sphincter during attempted defecation

^aCriteria fulfilled for the past 6 months, with symptom onset at least 6 months before diagnosis

^**As described here above

While the exact prevalence of constipation of the outlet delay type is unknown, it is recognized as a common health problem. In several population surveys, the prevalence of symptoms compatible with outlet obstruction has been as high as 30 %. It is accepted that about one-third of patients who present to their physician complaining of constipation demonstrate evidence of outlet obstruction [1]. Studies from referral centers also show a higher incidence of outlet delay than slow-transit constipation (60 % vs. 30 %, with the two types of constipation combined in 5 % of cases).

Defecation disorders occur significantly more frequently in women than in men. Prevalence increases with advancing age in both sexes, and the elderly, especially women, are frequently affected. The reasons for the female predisposition toward evacuation problems include pelvic floor alteration related to childbirth through vaginal delivery, long-lasting and excessive straining when passing stool, postmenopausal hormonal estrogen deprivation, previous hysterectomy, and association with urogenital prolapse and urinary incontinence. A genetic predisposition to pelvic organ prolapse is also recognized as a predisposing factor.

11.2 Etiology – Pathophysiology

Impaired defecation may result from various functional and/or anatomic disorders combined in a complex syndrome that is still not completely understood.

11.2.1 Functional Anal Obstruction

Inappropriate contraction of the pelvic floor or ineffective relaxation of striated muscles on the pelvic floor during attempted defecation impedes the passage of stool. Anal dyssynergia or anismus refers to this situation. Neurologic disorders such as spinal cord lesions and multiple sclerosis may also be responsible. In rare instances the functional obstruction is due to the ineffective inhibition of the internal anal sphincter with failure of the rectoanal inhibitory reflex, as occurs in Hirschsprung disease, Chagas disease, and hereditary myopathy of the internal anal sphincter. This feature may be encountered in association with pelvic organ prolapse [2].

11.2.2 Rectal Inertia – Rectal Hyposensitivity – Megarectum

The failure to increase intra-abdominal/intrarectal pressure to a level sufficient to allow defecation frequently occurs in elderly or debilitated patients and accumulates stool in the rectum, leading to fecal impaction (or fecaloma). In some conditions, defined as “rectal inertia” or “megarectum” and occurring in young patients, the rectum and often the distal sigmoid colon dilate and attempts to evacuate are ineffective. Abnormal rectal sensation during rectal filling, termed rectal hyposensitivity (blunted rectum), may be present and is caused by diabetes mellitus, multiple sclerosis, cerebrospinal disease, or direct injury to the pelvic nerves during hysterectomy or following disc (L5–S1) surgery.

11.2.3 Excessive Perineal Descent

Perineal descent during defecation that exceeds 4 cm is associated with evacuation difficulties. It is caused by weakness of the pelvic floor support as a consequence of stretching of or stress on the nerves, ligaments, and muscles of the pelvis during childbirth. Perineal descent may be associated with sacral nerve damage, secondary muscular atrophy, and eventually fecal incontinence, leading to the so-called descending perineum syndrome. It is, however, unclear whether perineal descent itself induces dyschezia.

11.2.4 Anatomic Defects and Deformities of the Rectal Reservoir

In addition to functional disorders, anatomic abnormalities may lead to impaired rectal evacuation. Any prolapsing organ pressing on mechanoreceptors adjacent to the rectum may give the patient the perception of impending defecation and disturb the normal evacuation process.

Rectocele is defined as a herniation of the anterior rectal wall into the posterior vagina.
Enterocele is the insinuation of a viscus (the small bowel or sigmoid colon) between the posterior vaginal wall and rectum into a herniated pouch of Douglas.
Rectal intussusception (also known as “internal procidentia” or “occult rectal prolapse”) is defined as an incomplete, nonexteriorized rectal prolapse. Infolding of the rectal wall is a common finding in healthy individuals, but high-grade intussusception reaching the anal canal may contribute to defecation disorders.

11.3 Diagnostics

11.3.1 Symptoms

History-taking is essential in defining what symptom causes the patient the most problems. Questions must assess various factors:

Presence of an urge to defecate (patients with colonic inertia rarely have a need, but patients with defecation disorders have the urge to defecate daily)
Bowel frequency, stool consistency, and size (best assessed using the Bristol stool chart)
Use of laxatives, suppositories, and enemas
Duration of the problem and the circumstances in which it occurs
Maneuvers and digitations that the patient performs to help him-/herself evacuate
- Vaginal digitation suggests a rectocele
- Leaning forward on the toilet seat suggests an enterocele
- Massaging lateral to the anus suggests poor rectal contractility
- Use of enemas and/or suppositories may suggest megarectum
- Supporting the perineum is used in abnormal perineal descent

Typical symptoms of obstructed defecation, with variations according to the type of disorder, are presented in Table 11.2. These symptoms are best assessed using standardized questionnaires specifically designed for this purpose [3] (Table 11.3). A diary of gastrointestinal complaints and defecation habits can be helpful. The presence of fecal incontinence is also established and, if present, scored. Abdominal pain and bloating may be present, as irritable bowel syndrome is frequently associated with defecation disorders. Associated urogynecologic symptoms including urinary incontinence, dyspareunia, and manifestations of urogenital prolapse must also be identified.

Table 11.2

Symptoms to be searched in defecation disorders

Inability to empty the rectum (sometimes even for soft or liquid stool)

Excessive and prolonged straining efforts and time spent in toilets

Feeling of incomplete and/or fragmented, unsatisfactory evacuation

Pain and perineal discomfort in the standing position and/or at defecation

Need for (intra-anal, perineal, or vaginal) stimulation and manual evacuation

Rectal bleeding and mucous discharge

Use of laxatives, suppositories, enemas

Table 11.3

Severity of disease index for obstructed defecation

Variables	Score
Variables	0	1	2	3	4
Mean time spent on the toilet	≤5 min	6–10 min	11–20 min	21–30 min	>30 min
Attempts to defecate per day, n	1	2	3–4	5–6	>6
Anal/vaginal digitations	Never	>1/month, <1/week	Once a week	Two to three per week	Every defecation
Use of laxatives	Never	>1/month, <1/week	Once a week	Two to three per week	Every day
Incomplete/fragmented defecation	Never	>1/month, <1/week	Once a week	Two to three per week	Every defecation
Straining during defecation	Never	<25 % of the time	<50 % of the time	<75 % of the time	Every defecation
Stool consistency	Soft	Hard	Hard and few	Fecaloma formation

This score, ranging from 0 (normal) to 31 points, has been validated and is recommended for the assessment of patients and for research purposes [3]

Any history of proctologic, obstetric, gynecologic, and/or urologic conditions should be carefully established. Obtaining psychological or psychiatric advice is relevant in select cases, particularly if surgery is contemplated. Underlying personal problems are frequently present, and this patient population more likely to have suffered some form of sexual abuse during childhood and is more depressed than a normal population.

11.3.2 Examination – Clinical Findings

After an abdominal examination, the patient is placed in the lithotomy position for a complete perineal and anorectal examination. The following must be clinically assessed: