The internal anal sphincter: new insights into faecal incontinence
Article Abstract:
Fecal incontinence is a condition in which the patient is unable to control the passage of feces through the anus. This frequently results from dysfunction of either the external anal sphincter (a skeletal muscle under voluntary control), the internal anal sphincter (a smooth muscle under control of the involuntary nervous system), or some combination of the two. In the past, attention has focused on the voluntarily controlled external sphincter. In cases where there is no identifiable organic damage causing the condition, it is known as idiopathic fecal incontinence. It is known that damage to the nerve supply of the external sphincter and puborectalis muscles, sometimes as a result of childbirth, leads to weakening of the external sphincter muscles and subsequent incontinence. Only in recent years, with advances in anal manometry (recording of intra-anal pressure changes), ultrasonic imaging of the anal region, morphological techniques for studying the subcellular organization of the sphincter muscles, and electrophysiological methods for recording electrical activity of the internal and external sphincters, has the importance of the internal sphincter in the origin of fecal incontinence come to the fore. In addition, organ bath studies with isolated segments of smooth muscle taken from dysfunctional internal anal sphincters show pronounced abnormalities in response to pharmacological manipulation. It is now coming to be recognized that dysfunction of the internal sphincter is at least as important as the external sphincter in the development of idiopathic fecal incontinence. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: Gut
Subject: Health
ISSN: 0017-5749
Year: 1991
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Evidence for motor neuropathy and reduced filling of the rectum in chronic intractable constipation
Article Abstract:
Chronic intractable constipation is a disease afflicting predominantly young women, in which spontaneous bowel movements occur only once or twice per month. In some women, there is a deformation of the pelvis that results in a mechanical impediment to the passage of feces through the large intestine. In others, there is no apparent cause for the disorder, and these women are generally resistant to conventional medical treatment. Surgical treatment, removal of part of the colon, is usually the only resort, and it is not always successful. In order to investigate the neuromuscular basis of this disorder, eight women with chronic intractable constipation and 12 normal controls were studied. Mechanical sensors were placed in the colon, rectum, and anus of each subject, and intestinal neuromuscular activity was automatically recorded with a portable encoder box and cassette recorder. A distinctive pattern of pressure changes (known as sampling responses) was seen in the normal controls and consistent with previously reported data. These sampling responses occurred at a greatly reduced frequency in the constipated subjects. In addition, rectal motor complexes (wavelike contractions of the rectum necessary for normal defecation) were greatly reduced in amplitude in the constipated subjects. These results suggest that reduced transit of feces from the colon to the rectum may be part of the underlying cause of the constipation, and that a motor neuropathy (defective nerve supply to the large intestine) may be responsible. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: Gut
Subject: Health
ISSN: 0017-5749
Year: 1990
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