Overview Ano in fistula is an abnormal tunnel between the anal canal (hollow viscus) and the surface of the body. It is very common, especially in otherwise fit young adults. The great majority result from an initial abscess forming in one of the anal glands that pass from the submucosa of the anal canal to open within its lumen. May occur in the presence of Crohn's Disease, and has an association with obesity and diabetes. Treatment is mainly surgical, medical treatment such as antibiotics can treat associated sepsis (usually secondary to abscess).
Definition Fistula: An abnormal connection of two epithelial surfaces Fistula in Ano: abnormal connection of the anorectal epithelial surface to the perineal or vaginal skin. Sinus: Granulating track leading from a source of infection to a surface |
Remember Crohn Disease is associated with ano-rectal disease |
Overview The hindgut makes up the last 1/3 of the transverse colon, the descending colon, sigmoid colon, rectum and part of the anus. The anal canal commences at the level where th rectum passes through the pelvic diaphragm and ends at the anal verge
Layers of the rectum mucosa (from inner to outer)
Anal Sphincters
Intersphincteric Plane
Anal glands
Pectinate line (dentate line)
PECTINATE LINE (DENTATE LINE) | ||
Distinction | Above Pectinate line | Below Pectinate line |
Embryological origin | Endoderm | Ectoderm |
Epithelium | Colomnar epithelium | Stratified squamous epithelium |
Lymph drainage | Internal iliac lymph node | Superficial inguinal lymph nodes |
Artery | Superior rectal artery | Middle and inferior rectal arteries |
Veins | Superior rectal veins | Middle and inferior rectal veins |
Innervation | Inferior hypogastric plexus | Inferior rectal nerve |
Haemorrhoids | Internal haemorrhoids | External haemorrhoids |
Hilton's Line also called while line/anocutaneous line indicates lower end of the internal sphincter. Ischiorectal abscess when communicates with anal canal usually opens at or below Hilton's line. |
A fistula is an abnormal connection of two epithelial surfaces and the two surfaces joined in fistula-in-ano are anorectal lining and the perineal or vaginal skin. Anal fistulae are classified according to their position and relation to the internal and external anal sphincters.
Clinical Presentation Patient usually complains of a non-healing abscess. Acute perianal abscess presents as rapid onset of severe perianal pain, swelling and erythema (+/- fever and tachycardia).
Examination
Goodsall's rule (law): Relates the external opening of an anal fistula to its internal opening. Fistulas can be described as anterior or posterior relating to a line drawn in the coronal plane across the anus. Anterior fistulas will have a direct track into the anal canal. Posterior fistulas will have a curved track with their internal opening lying in the posterior midline of the anal canal. An exception to the rule are anterior fistulas lying more than 3cm from the anus, which may open in the anterior midline of the anal canal. |
Diagnosis Clinical Diagnosis with history and physical examination findings (3Ps):
Remember 3Ps for anal fistula diagnosis: Pain, Purulent drainage, perirectal skin lesion |
The majority of anorectal fistulas originate from an infected anal crypt gland
Optimal treatment depends upon correctly classifying the fistula. Surgery is gold standard.
Surgical
Non-surgical
VIDEO: Fistula in Ano |