anal fistula

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fistula

 [fis´tu-lah] (pl. fistulas, fis´tulae) (L.)
any abnormal tubelike passage within body tissue, usually between two internal organs or leading from an internal organ to the body surface. Some fistulas are created surgically for diagnostic or therapeutic purposes; others occur as result of injury or as congenital abnormalities. Among the many kinds of fistulas, the anal type (fistula in ano) is one of the most common. It generally develops as a result of a break or fissure in the wall of the anal canal or rectum, or an abscess there. Treatment is by surgery.

In women, difficult labor in childbirth may result in formation of a vesicovaginal fistula between the bladder and the vagina with resulting leakage of urine into the vagina. In a vesicointestinal fistula, there is leakage of urine from the bladder into the intestine. In a rectovaginal fistula, feces escape through the wall of the anal canal or rectum into the vagina. This condition, formerly a serious hazard of childbirth, is now rare; like other kinds of fistula, it can be corrected by surgery.

With the types of fistulas described here, typical symptoms are pain in the affected region and an abnormal discharge through the skin near the anus or through the vagina. Fistulas at different places of the body may be caused by tuberculosis, actinomycosis (a fungus infection), the presence of diverticula, or certain other serious diseases, and the fistula itself may be a site of infection and discomfort.
abdominal fistula one between a hollow abdominal organ and the surface of the abdomen.
anal fistula (fistula in a´no) one opening on the cutaneous surface near the anus, which may or may not communicate with the rectum.
arteriovenous fistula one between an artery and a vein, either pathologic (such as a varicose aneurysm) or surgically created to ensure an access site for hemodialysis. The site must be allowed 6 to 8 weeks to mature before it can be cannulated. Such a fistula may be the anastomosis of a natural artery and vein, a bovine graft, or a synthetic polytetrafluoroethylene (PTFE) graft. The bovine graft is taken from the bovine carotid artery and anastomosed to the vein and artery of the patient. In a PTFE graft, fibers are woven into a mesh called Gore-Tex and made into a sleeve and flange; this is available in a variety of sizes.

Precautions necessary to insure patient safety when caring for an individual with an arteriovenous fistula include frequent assessments for adequate circulation in the fistula and the distal extremity. A bruit or thrill can be heard over the access site. Blood pressure measurements, withdrawal of blood, injections, and administration of intravenous fluids should not be done on the extremity with such a fistula.
Internal arteriovenous fistulas.
blind fistula one open at one end only, opening on the skin (external blind fistula) or on an internal surface (internal blind fistula).
branchial fistula a persistent pharyngeal groove (branchial cleft).
Brescia-Cimino fistula an arteriovenous fistula for hemodialysis access, connecting the cephalic vein and radial artery.
bronchopleural fistula one between a bronchus and the pleural cavity, causing an air leak into the pleural cavity; sometimes seen as a complication of empyema, fibrosis, or pneumonia.
cerebrospinal fluid fistula one between the subarachnoid space and a body cavity, such as from head trauma or bone erosion, with leakage of cerebrospinal fluid, usually in the form of rhinorrhea or otorrhea.
complete fistula one extending from the skin to an internal body cavity.
craniosinus fistula one between the cerebral space and a paranasal sinus, permitting escape of cerebrospinal fluid into the nose.
Eck's fistula an artificial communication made between the portal vein and the vena cava.
enterocutaneous fistula see enterocutaneous fistula.
enterovesical fistula one connecting some part of the intestine with the urinary bladder; called also vesicoenteric f.
fecal fistula one between the colon and the external surface of the body, discharging feces.
gastric fistula
1. one communicating between the stomach and some other body part.
2. a passage created artificially through the abdominal wall into the stomach.
horseshoe fistula one near the anus, having a semicircular tract with both openings on the skin.
incomplete fistula blind fistula.
perilymph fistula rupture of the round window with leakage of perilymph into the inner ear, so that changes in middle ear pressure directly affect the inner ear, causing sensorineural deafness as well as dizziness, vertigo, nausea, and vomiting. Head trauma and dramatic changes in atmospheric pressure are the most common causes. The usual treatment is restriction in activity (sometimes with complete bed rest), so that the fistula can heal. Surgical repair may be necessary, consisting of placement of a graft over the defect.
pilonidal fistula pilonidal sinus.
pulmonary arteriovenous fistula a congenital fistula between the pulmonary arterial and venous systems, allowing unoxygenated blood to enter the systemic circulation.
rectovaginal fistula one between the rectum and vagina.
rectovesical fistula one between the rectum and urinary bladder.
salivary fistula one between a salivary duct or gland and the cutaneous surface, or into the mouth through an abnormal pathway.
thoracic fistula one communicating with the thoracic cavity.
umbilical fistula one communicating with the intestine or urachus at the umbilicus.
urinary fistula any fistula communicating between the urinary tract and another organ or the surface of the body.
vesicoenteric fistula (vesicointestinal fistula) enterovesical fistula.
vesicovaginal fistula one from the bladder to the vagina.

a·nal fis·tu·la

a fistula opening at or near the anus, usually, but not always, opening into the rectum above the internal sphincter.

anal fistula

an abnormal opening on the cutaneous surface near the anus, usually resulting from a local abscess of the crypt and common in Crohn's disease. A perianal fistula may or may not communicate with the rectum. Also called fistula-in-ano.

a·nal fis·tu·la

(ā'năl fis'tyū-lă)
A fistula opening at or near the anus; usually, but not always, opening into the rectum above the internal sphincter.

anal fistula

A persistent discharging track between the anus and the exterior, opening on the skin near the anus. Fistula is usually associated with an abscess in the tissues surrounding the anal canal.

anal

relating to the anus.

anal abscess
acute, purulent infections in the area of the anus, usually caused by gram-negative organisms. In dogs, these most often arise from the anal sacs.
anal atresia, atresia ani
congenital absence or stenosis of the anus manifested by an absence of feces and a gradual development of abdominal distention. Fistulae may develop between the rectum and urogenital tract. The anomalous development can occur in several forms and may be accompanied by similar atresia at higher levels of the intestine. There is usually normal development of sphincters. A dimple is usually evident at the point at which surgical intervention is required.
anal canal
the short, terminal, retroperitoneal segment of the intestinal tract between the rectum and anus.
anal constriction
a congenital constriction combined with vulvar constriction occurs in Jersey cattle.
anal fibroma
occurs in cattle and excision effected for esthetic reasons.
anal fistula
see perianal fistula.
anal fold
see anal fold.
anal furunculosis
see perianal fistula.
anal membrane
the dorsal part of the cloacal membrane in the embryo; when it eventually breaks down the dorsal passage becomes the rectoanal passage.
anal-perineal laceration
see rectovaginal fistula.
anal prolapse
the protrusion of a small amount of mucosa through the anus.
anal reflex
the pursing of the anal orifice when the perineum is stimulated; indicative of an animal with intact sacral segments of the spinal cord.
anal sac
see anal sacs.
Enlarge picture
Anal sacs in the dog. By permission from McCurnin D, Poffenbarger EM, Small Animal Physical Diagnosis and Clinical Procedures, Saunders, 1991
anal sacculitis
inflammation of the anal sacs.
anal sphincter
the internal anal sphincter is formed from smooth muscle of the anal canal while the external anal sphincter, which is larger and of greater importance in fecal continence, consists of striated muscle.
anal sphincter hypertrophy
occurs in aged dogs and may give rise to difficult and painful defecation.
anal stenosis
scar formation after perianal fistulae, trauma, severe anal sac disease, or treatment for neoplasia may result in a reduced lumen and particularly a loss of the capacity to dilate with passage of feces. Straining, passage of ribbon-like feces and constipation result.
anal ulceration
inflammation and ulceration of the perianal skin which may be associated with anal sac disease. Seen most commonly in German shepherd dogs.