Obstructed defecation


Obstructed defecation syndrome is a major cause of functional constipation, of which it is considered a subtype. It is characterized by difficult and/or incomplete emptying of the rectum with or without an actual reduction in the number of bowel movements per week. Normal definitions of functional constipation include infrequent bowel movements and hard stools. In contrast, ODS may occur with frequent bowel movements and even with soft stools, and the colonic transit time may be normal, but delayed in the rectum and sigmoid colon.

Definitions and terminology

Definition and classification of constipation

Constipation is usually divided into two groups: primary and secondary. Primary constipation is caused by disrupted regulation of neuromuscular function of in the colon and the rectum, and also disruption of brain–gut neuroenteric function. Secondary constipation is caused by many other different factors such as diet, drugs, behavioral, endocrine, metabolic, neurological, and other disorders. There are main subtypes of primary constipation which are recognized, although overlap exists : dyssynergic defecation, slow transit constipation and irritable bowel syndrome with constipation.

Definition and terminology of obstructed defecation syndrome

Obstructed defecation is one of the causes of chronic constipation. ODS is a loose term, consisting of a constellation of possible symptoms, caused by multiple, complex and poorly understood disorders which may include both functional and organic disorders. The topic of defecation disorders is very complicated, and there is a lot of confusion regarding terminology and classification in published literature. Occasionally some sources inappropriately treat ODS as a synonym of anismus. Although anismus is a major cause of ODS, there are other possible causes. Other authors use the term ODS to refer to defecatory dysfunction in the absence of any pathological findings. Furthermore, many different terms have been used for ODS, which appear to refer to the same clinical entity. The term ODS does not appear in the ICD-11 and Rome-IV classifications, which both instead refer to "functional defecation disorders". One publication criticized such classifications as being ambiguous and based on symptoms rather than distinct etiopathological entities. The authors suggested that "evacuation disorders" be used as a descriptive term, which would be subclassified to include all possible factors that may be contributory to the symptoms.
In 2001, the American Society of Colon and Rectal Surgeons, the Colorectal Surgical Society of Australia,
and the Association of Coloproctology of Great Britain and Ireland published a consensus statement which covered definitions relevant to this topic. A revised consensus statement was published by the ASCRS in 2018. Wherever possible, this article generally follows the definitions and terminology of the 2018 consensus statement, wherein ODS is defined as "a subset of functional constipation in which patients report symptoms of incomplete rectal emptying with or without an actual reduction in the number of bowel movements per week." Functional constipation is usually defined as infrequent bowel movements and hard stools. In contrast, ODS may occur with frequent bowel movements and even with soft stools, and the colonic transit time may be normal.

Co-existence of different constipation subtypes

The ODS may or may not co-exist with other functional bowel disorders, such as slow transit constipation or irritable bowel syndrome.
Of all cases of primary constipation, it is reported that 58% are dyssynergic defecation, 47% are slow transit constipation and 58% are irritable bowel syndrome. Significant overlap exists. For example, approximately 60% of patients with dyssynergic defecation also have STC. In a study of 1,411 patients with chronic constipation referred to a tertiary center, 68% had normal transit constipation, 28% had evacuation disorders and less than 1% had slow transit constipation without any evacuation disorder.

ICD-11

The term "obstructed defecation syndrome" does not appear in ICD-11. However, the following entries are present, as well as separate codes for most of the individual organic lesions listed in this article:
  • Functional anorectal disorders: "anorectal disorders which principally present anorectal and defecation complaints without apparent morphological changes of anorectal regions." A note is added: "However, the distinction between organic and functional anorectal disorders may be difficult to make in individual patients."
  • Functional defecation disorders: this is listed as a sub-entry of functional anorectal disorders. It includes dyssynergic defecation, and inadequate defecatory propulsion. A note is added: "The patients must satisfy diagnostic criteria for functional constipation."
  • Incomplete defecation: this entity exists as a sub-code of fecal incontinence, with no definition.

    Rome-IV

The term "obstructed defecation syndrome" does not appear in the Rome IV classification. However, diagnostic criteria for functional defecation disorders are listed. According to Rome-IV, this is defined as "features of impaired evacuation" during repeated attempts to defecate. To qualify for this diagnosis, patients must meet the Rome diagnostic criteria for functional constipation or irritable bowel syndrome with constipation. Furthermore, 2 of the following 3 tests must show abnormal results: balloon expulsion test, anorectal manometry or anal surface electromyography, or imaging. Two subcategories exist within the functional defecation disorders category: Inadequate defecatory propulsive and Dyssynergic defecation. These are defined as "Inadequate propulsive forces as measured with manometry with or without inappropriate contraction of the anal sphincter and/or pelvic floor muscles", and "Inappropriate contraction of the pelvic floor as measured with anal surface EMG or manometry with adequate propulsive forces during attempted defecation" respectively. The subcategories F3a and F3b are defined by age- and gender-appropriate normal values for the technique. For all of these Rome-IV diagnoses, diagnostic criteria must have been fulfilled for the last 3 months with symptom onset at least 6 months prior to diagnosis.

Signs and symptoms

There is a constellation of possible symptoms.
  • Straining, and attempting to defecate for a long period of time.
  • Inability to voluntarily empty the rectum.
  • Use of, or dependence on, enemas and/or laxatives.
  • Self-digitation.
  • Posturing.
  • Frequent urge to defecate, and frequent bowel movements/toilet visits, where only fecal pellets may be passed.
  • Conversely, there may reduced number of bowel movements per week.
  • Abnormal stool texture, which may be anything from watery/loose, to fragmented, very hard or pellet-shaped.
  • Actual or subjective sensation of incomplete evacuation. even with soft stools.
  • Unsuccessful attempts at bowel movements.
  • Painful bowel movements.
  • Tenesmus.
  • Bowel urgency.
  • Feeling of occupation or "mass" in the vagina.
  • Pelvic heaviness.
  • Pelvic pain and cramping.
  • Bloating, and abdominal discomfort.
  • Fecal incontinence, which may occur after defecation.
  • Urinary incontinence.
  • Poor appetite and early satiety when eating.
Fecal incontinence to gas, liquid, solid stool, or mucus in the presence of obstructed defecation symptoms may indicate internal rectal prolapse, internal/external anal sphincter dysfunction, or descending perineum syndrome. ODS often occurs together with fecal incontinence, especially in geriatric people. Where ODS occurs with fecal incontinence, it may represent fecal impaction combined with overflow diarrhea.
Self-digitation is the use of the digits to apply pressure in order to achieve defecation. Most people recognize the need for digitation as a symptom, and not a treatment. Medical professionals generally do not recommend it, since it may lead to complications and is not very effective, only removing feces in the lower part of the rectum. There are 3 methods: vaginal, perineal and rectal. Gloves are used for hygiene. Vaginal digitation is when the patient presses the posterior wall of the vagina to support it, or to push the rectocele pouch from inside the vagina, which makes the anorectum straight and facilitates defecation. "Milking" pressure can also be applied on the posterior vaginal wall. Perineal digitation, is pushing on the perineum, which acts to stimulate the transverse muscles of the perineum causing a reflex contraction of the rectum which helps to evacuate the feces. Rectal digitation is when patients insert a finger into the anus to "hook" out fecal pellets, or to apply pressure to the walls of the anus and/or the rectum, or to support an obstructing anatomic defect such as a sigmoidocele. Possible complications of rectal digitation are injury of the lining of the rectum, such as ulcerations with bleeding and discomfort, and anal fibrosis leading to a rectal stricture.

Pathophysiology

Relevant anatomy and physiology

In order to understand ODS, it is necessary to understand the normal anatomy and defecation process.
The pelvic floor can be divided into 4 compartments: Anterior or urinary, Middle or genital, Posterior, and Peritoneal.
Defecation is a complex physiologic process, involving interaction between neural processes, reflexes, colorectal contractility and the biomechanics of straining.
In the normal state, the muscular tonus of the puborectalis muscle maintains an angle between anal canal and the rectum. This angle is called the anorectal angle. When feces reach the rectum, the rectal walls become naturally distended, stimulating nerve receptors. Brain centres for defecation respond to this sensation and stimulate mass colonic movement in the colon and the rectum. These mass contractions move feces along the colon and into the rectum. Occasionally some straining helps, which normally transmits forces to the upper part of the rectum, and aids defecation. Reflexive relaxation of the external anal sphincter is also triggered. For defecation to occur, rectal pressure must be greater than pressure in the anal canal, which depends on the relaxation of the external anal sphincter, the puborectalis and the intra-abdominal force applied. In normal defecation, the pressure in the rectum increases at the same time as the pressure in the anal canal falls, leading to a propulsive rectoanal pressure gradient. Relaxation of puborectalis muscle allows the anorectal angle to straighten out.
According to some experts in ODS, defecation should normally occur once per day. However many sources assert that it is medically "normal" for bowel movements to occur anywhere between three times per week up to three times per day.