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Defecation follows digestion, and is a necessary process by which organisms eliminate a solid, semisolid, or liquid waste material known as feces from the digestive tract via the anus. The act has a variety of names ranging from the common, like pooping or crapping, to the technical, e.g. bowel movement, to the obscene (shitting), to the euphemistic, to the juvenile. The topic, usually avoided in polite company, can become the basis for some potty humor.
Fecal incontinence (FI), or in some forms encopresis, is a lack of control over defecation, leading to involuntary loss of bowel contents, both liquid stool elements and mucus, or solid feces. When this loss includes flatus (gas), it is referred to as anal incontinence. FI is a sign or a symptom, not a diagnosis. Incontinence can result from different causes and might occur with either constipation or diarrhea. Continence is maintained by several interrelated factors, including the anal sampling mechanism, and incontinence usually results from a deficiency of multiple mechanisms. The most common causes are thought to be immediate or delayed damage from childbirth, complications from prior anorectal surgery, altered bowel habits. An estimated 2.2% of community-dwelling adults are affected. However, reported prevalence figures vary. A prevalence of 8.39% among non-institutionalized U.S adults between 2005 and 2010 has been reported, and among institutionalized elders figures come close to 50%.
An anal fissure is a break or tear in the skin of the anal canal. Anal fissures may be noticed by bright red anal bleeding on toilet paper and undergarments, or sometimes in the toilet. If acute they are painful after defecation, but with chronic fissures, pain intensity often reduces.
A rectal prolapse occurs when walls of the rectum have prolapsed to such a degree that they protrude out of the anus and are visible outside the body. However, most researchers agree that there are 3 to 5 different types of rectal prolapse, depending on whether the prolapsed section is visible externally, and whether the full or only partial thickness of the rectal wall is involved.
A fecal impaction or an impacted bowel is a solid, immobile bulk of feces that can develop in the rectum as a result of chronic constipation. Fecal impaction is a common result of neurogenic bowel dysfunction and causes immense discomfort and pain. Its treatment includes laxatives, enemas, and pulsed irrigation evacuation (PIE) as well as digital removal. It is not a condition that resolves without direct treatment.
The internal anal sphincter, IAS, is a ring of smooth muscle that surrounds about 2.5–4.0 cm of the anal canal. It is about 5 mm thick, and is formed by an aggregation of the smooth (involuntary) circular muscle fibers of the rectum. it terminates distally about 6 mm from the anal orifice.
Anal fistula is a chronic abnormal communication between the anal canal and the perianal skin. An anal fistula can be described as a narrow tunnel with its internal opening in the anal canal and its external opening in the skin near the anus. Anal fistulae commonly occur in people with a history of anal abscesses. They can form when anal abscesses do not heal properly.
An anal plug is a medical device that is often used to treat fecal incontinence, the accidental passing of bowel moments, by physically blocking involuntary loss of fecal material. Fecal material such as feces are solid remains of food that does not get digested in the small intestines; rather, it is broken down by bacteria in the large intestine. Anal plugs vary in design and composition, but they are typically single-use, intra-anal, disposable devices made out of soft materials to contain fecal material and prevent it from leaking out of the rectum. The idea of an anal insert for fecal incontinence was first evaluated in a study of 10 participants with three different designs of anal inserts.
Lateral internal sphincterotomy is an operation performed on the internal anal sphincter muscle for the treatment of chronic anal fissure. The internal anal sphincter is one of two muscles that comprise the anal sphincter which controls the passage of feces. The procedure helps by lowering the resting pressure of the internal anal sphincter, which improves blood supply to the fissure and allows faster healing. The procedure has been shown to be very effective, with 96% of fissures healing at a median of 3 weeks in one trial.
Sacral nerve stimulation, also termed sacral neuromodulation, is a type of medical electrical stimulation therapy.
Defecography is a type of medical radiological imaging in which the mechanics of a patient's defecation are visualized in real time using a fluoroscope. The anatomy and function of the anorectum and pelvic floor can be dynamically studied at various stages during defecation.
The rectum is the final straight portion of the large intestine in humans and some other mammals, and the gut in others. The adult human rectum is about 12 centimetres (4.7 in) long, and begins at the rectosigmoid junction at the level of the third sacral vertebra or the sacral promontory depending upon what definition is used. Its diameter is similar to that of the sigmoid colon at its commencement, but it is dilated near its termination, forming the rectal ampulla. It terminates at the level of the anorectal ring or the dentate line, again depending upon which definition is used. In humans, the rectum is followed by the anal canal which is about 4 centimetres (1.6 in) long, before the gastrointestinal tract terminates at the anal verge. The word rectum comes from the Latin rectumintestinum, meaning straight intestine.
In humans, the anus is the external opening of the rectum, located inside the intergluteal cleft and separated from the genitals by the perineum. Two sphincters control the exit of feces from the body during an act of defecation, which is the primary function of the anus. These are the internal anal sphincter and the external anal sphincter, which are circular muscles that normally maintain constriction of the orifice and which relaxes as required by normal physiological functioning. The inner sphincter is involuntary and the outer is voluntary. It is located behind the perineum which is located behind the vulva or scrotum.
Anorectal manometry (ARM) is a medical test used to measure pressures in the anus and rectum and to assess their function. The test is performed by inserting a catheter, that contains a probe embedded with pressure sensors, through the anus and into the rectum. Patients may be asked to perform certain maneuvers, such as coughing or attempting to defecate, to assess for pressure changes. Anorectal manometry is a safe and low risk procedure.
Rectal discharge is intermittent or continuous expression of liquid from the anus. Normal rectal mucus is needed for proper excretion of waste. Otherwise, this is closely related to types of fecal incontinence but the term rectal discharge does not necessarily imply degrees of incontinence. Types of fecal incontinence that produce a liquid leakage could be thought of as a type of rectal discharge.
Anismus or dyssynergic defecation is the failure of normal relaxation of pelvic floor muscles during attempted defecation. It can occur in both children and adults, and in both men and women. It can be caused by physical defects or it can occur for other reasons or unknown reasons. Anismus that has a behavioral cause could be viewed as having similarities with parcopresis, or psychogenic fecal retention.
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.
Dyssynergia is any disturbance of muscular coordination, resulting in uncoordinated and abrupt movements. This is also an aspect of ataxia. It is typical for dyssynergic patients to split a movement into several smaller movements. Types of dyssynergia include Ramsay Hunt syndrome type 1, bladder sphincter dyssynergia, and anal sphincter dyssynergia.
In fecal incontinence (FI), surgery may be carried out if conservative measures alone are not sufficient to control symptoms. There are many surgical options described for FI, and they can be considered in 4 general groups.
Neurogenic bowel dysfunction (NBD) is the inability to control defecation due to a deterioration of or injury to the nervous system, resulting in faecal incontinence or constipation. It is common in people with spinal cord injury (SCI), multiple sclerosis (MS) or spina bifida.
References
- 1 2 Zbar AP, Aslam M, Gold DM, Gatzen C, Gosling A, Kmiot WA (February 1998). "Parameters of the rectoanal inhibitory reflex in patients with idiopathic fecal incontinence and chronic constipation". Diseases of the Colon and Rectum. 41 (2): 200–8. doi:10.1007/bf02238249. PMID 9556245. S2CID 9535999.
- ↑ Barrett KE (2014). "Intestinal Motility". Gastrointestinal Physiology (2nd ed.). New York: Lange Medical Books/McGraw-Hill. p. 180. ISBN 978-0071774017.
- ↑ Rao SS (January 2004). "Pathophysiology of adult fecal incontinence". Gastroenterology. 126 (1 Suppl 1): S14–22. doi: 10.1053/j.gastro.2003.10.013 . PMID 14978634.
- ↑ de Lorijn F, de Jonge WJ, Wedel T, Vanderwinden JM, Benninga MA, Boeckxstaens GE (August 2005). "Interstitial cells of Cajal are involved in the afferent limb of the rectoanal inhibitory reflex". Gut. 54 (8): 1107–13. doi:10.1136/gut.2004.051045. PMC 1774907 . PMID 16009682.
- ↑ Roberts PL (2005). "Rectoanal Inhibition" (PDF). In Wexner SD, Zbar AP, Pescatori M (eds.). Complex Anorectal Disorders: Investigation and Management. London: Springer Science+Business Media. p. 39. ISBN 978-1-85233-690-5.
- ↑ Deen KI, Premaratna R, Fonseka MM, De Silva HJ (November 1998). "The recto-anal inhibitory reflex: abnormal response in diabetics suggests an intrinsic neuroenteropathy". Journal of Gastroenterology and Hepatology. 13 (11): 1107–10. doi: 10.1111/j.1440-1746.1998.tb00584.x . PMID 9870796. S2CID 23202851.
- ↑ Remes-Troche JM, Rao SS (June 2008). "Neurophysiological testing in anorectal disorders". Expert Review of Gastroenterology & Hepatology. 2 (3): 323–35. doi:10.1586/17474124.2.3.323. PMC 3764614 . PMID 19072383.
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