Overview Anal fissure is one of the most common lesions to consider in differential diagnosis of anal pain. Think about them as vertical ulcers usually occurring in the posterior midline of the skin just outside the entry to the rectum. Its persistence is due to spasm of the internal sphincter muscle. It can be associated with Crohn's disease. It typically causes episodic pain that occurs during defecation and for one to two hours afterwards. Anal fissures usually occur in the anterior or posterior parts of the anus and underlies the internal anal sphincter.
| Definition Anal Fissure: A superficial linear tear in the anoderm distal to the pectinate line (dentate line) commonly caused by passage of hard stool Fistula in ano: abnormal communication between the anorectal lining and perineal or vaginal epithelium. Nearly always associated with anal abscess Perianal abscess: Abscess within the soft tissues surrounding the anal canal Anal haemorrhoids: Dilation of haemorrhoids plexus either internal or external. |
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. |
Clinical Presentation
| Side note Acute fissures typically heal with medical management after 4 to 6 weeks, chronic fissures persist beyond 6 weeks. |
Examination - Location of fissure
Secondary anal fissures (pathological causes)
| Side note Fissure that do not occur midline are possibly due to an underlying pathology. Often there fissure are multiple |
Not usually indicated, unless diagnosis uncertain or secondary fissure suspected.
Anal fissures usually occur in the anterior or posterior parts of the anus and underlies the internal anal sphincter. Muscles spasm are due to contraction of the internal anal sphincter causing ischaemia → pain
| Pharmacology GTN (common medication for angina). Mechanism of action is by activting guanylyl cyclase increasing cGMP causing smooth muscle relaxation reducing muscle spasms in the perianal area. Side effects of topical GTN: headaches |
