What is anismus?
Anismus or obstructive defecation is translated as difficulty in defecating. It is caused by a misalignment between the anus and the rectum, which prevents stool from passing normally. This condition prevents proper relaxation of the anus during defecation, or a paradoxical contraction occurs, so that there is a lack of coordination of the process and the patient has the sensation of incomplete evacuation, in addition to constipation. Anismus is observed in about half of the patients with functional constipation.
Prognosis of the disease
In principle, if after diagnostic studies no anatomical alteration is observed, anismus should not be an extremely serious pathology, but it should be treated, otherwise constipation can become chronic and lead to problems in the body.
Symptoms of anismus
Anismus is characterized by paradoxical contraction or failure to relax the sphincter and pelvic floor muscles at the time of defecation. This results in obstructive defecation, incomplete evacuation and constipation as the main symptoms.
In many cases other associated symptoms, also as causes of this disorder, are stress and anxiety.
Medical tests for anismus
To confirm anismus, the symptoms of incomplete evacuation and the existence of propulsive forces during defecatory attempts will be considered. Thereafter, various studies will be performed (manometry, balloon expulsion test, proctography, electromyography and defecography, as no specific test has been shown to confirm the diagnosis.
However, the first thing to be done is a detailed anamnesis including a 15-30 day defecation diary (duration of constipation, use or not of laxatives, frequency and consistency of bowel movements, whether straining to go to the toilet, whether digital maneuvers are required to evacuate, associated symptoms that may alert of irritable bowel syndrome, etc). This will allow distinguishing between the different possible pathologies.
This is accompanied by a physical examination that includes a rectal examination and anal inspection. This will allow to rule out any possible organic lesion and to evaluate if there is fecal soiling and pathological perineal descent, how is the consistency of the stool, as well as the possible existence of rectal prolapse (with or without effort) or rectocele. Rectal examination will also allow us to analyze whether, when the patient makes a defecatory effort, the pressure in the anal canal decreases, something that can be effective in ruling out the possibility of anismus. Otherwise, if there is an increase in pressure in the canal, it does not ensure that it always exists, but will need to be confirmed by other diagnostic studies.
Anoscopy and rectosigmoidoscopy will also be performed which, in addition to ruling out neoplasms, allows us to detect the existence of occult mucosal prolapse, rectal ulcers or to see melanosis coli (which is caused by laxative abuse). If there is a perineal descent in the patient, clinical perineometry will be used, which is defined as such when the anus is below the biischiatic line, at rest or during defecatory effort. Although its use is not widespread, it is a procedure that allows the detection of a possible pathological perineal descent in patients with anismus.
On the other hand, endocrine and metabolic causes should also be ruled out by analyzing thyroid hormones, calcium and phosphorus. Barium enemas of the colon will also allow us to rule out possible neoplasms and/or the existence of other structural abnormalities (dolichocolon or dilatations of the colon and/or rectum).
In addition, a study of colic motility should be made by means of colic transit time, something that allows to rule out or confirm constipation, distinguishing two types of patients: those who have slowing of colon transit and those who suffer obstructive defecation or anismus.
The anorectal function tests are those mentioned at the beginning of this section, and are aimed at detecting etiological factors of constipation. In this way the diagnosis and treatment can be oriented:
- Balloon expulsion test. It is a test that consists in the expulsion, with defecatory maneuvers (performed, if possible, sitting on the toilet), of a balloon in a rectal ampoule, swollen with 50ml of water. In normal cases it should be expelled in less than 1 minute, but up to a maximum of 8 minutes is acceptable. Failure to expel the balloon may be synonymous with anismus.
- Proctography. This includes a series of diagnostic techniques to study the mechanisms of continence and defecation, both at rest and during defecatory effort. They include defecography, dynamic pelvic magnetic resonance imaging, evacuation scintigraphy.
- Anorectal manometry. Although it is a study that does not detect alterations in the pressional profile of the canal in patients suffering from constipation, the absence of relaxation or the existence of sphincteric contractions during defecation will indicate the possibility of anismus, which will be confirmed with other studies.
- Electromyography. This is a technique that uses an anal sponge with surface electrodes, which is completely painless. This technique can detect increased electrical activity in the anal sphincter during the effort of defecation in patients suffering from anismus.
What are the causes of anismus?
Anismus or obstructive defecation without anatomical alterations is due to a failure in anal relaxation, or a paradoxical contraction of the sphincter and pelvic floor musculature during defecation.
In addition, stress and anxiety can influence its development, and it is therefore important that, in order to establish a diagnosis, a complete evaluation is performed with the complementary tests mentioned above.
Can it be prevented?
In anismus there is an alteration of the synergy of the defecation mechanism, so that the pelvic floor musculature contracts instead of relaxing synchronously with the effort of abdominal pressure and anal relaxation that occurs in defecation. This means that it is difficult to prevent, but not difficult or impossible to correct, since there are several techniques that allow “re-educate” the sphincter muscles to achieve this relaxation.
Treatments for anismus
Many patients with anismus can be successfully treated with medical treatment and dietary and hygienic advice. Thus, defecatory straining can be reduced if the patient eats a diet rich in fiber and consumes plenty of fluids.
The results of surgical treatment have not been very satisfactory, so conservative treatment with biofeedback techniques or botulinum toxin injection is currently recommended. Biofeedback are techniques that are performed on an outpatient basis to help the patient learn to relax the pelvic floor musculature when defecatory effort is made, and are based on sensory training and defecatory maneuvers with a rectal balloon. It can be performed with surface electriomyographic electrodes or with manometry probes.
The use of botulinum toxin has so far had limited effects and more studies are still needed to know the true effects.
Which specialist treats it?
The specialist who treats anismus is the coloproctologist and the specialist in General and Digestive Surgery.