Anal Pathology Flashcards
Anal canal - histology
- rectum until the pectinate (dentate) line at junctional zone of epithelium –> cuboidal epithelium
- after pectinate line (anal canal) –> non-keratinised stratified squamous epithelium
- after external anal sphincter (anal skin) –> keratinised stratified squamous epithelium
Anus - Innervation
Internal Anal Sphincter
- involuntary (smooth muscle)
- contraction = sympathetic fibers from superior rectal and hypogastric plexuses
- inhibition of contraction = parasympathetic (pelvic splanchnic S2-S4)
External Anal Sphincter
- voluntary (skeletal muscle)
- contraction = Branch from S4 and from the inferior hemorrhoidal branch of the pudendal nerve (S2,3,4)
Defecation Reflexes
- faeces in rectum –> distension of rectal wall
- activation of stretch receptors
- afferent sensory fibres to spinal cord (S2-S4)
- Activation of myenteric plexus (Auerbach) –> smooth muscle –> peristalsis (intrinsic reflex)
- efferent pelvic splanchnic (parasympathetic reflex)
- relaxation of internal anal sphincter
- stool moves down the rectum
- voluntary inhibition of external anal sphincter
Haemorrhoids - definition
- Haemorrhoids are normal vascular-rich cushions made of sinusoids, connective tissue, and smooth muscle located within the anal canal, usually occupying the left lateral and right anterior and posterior positions.
- They become pathological as they enlarge and cause symptoms, termed haemorrhoidal disease.
Haemorrhoids - aetiology
- excessive straining due to either chronic constipation or diarrhoea
- increase in intra-abdominal pressure can be caused by pregnancy or ascites or obesity
therefore risk factors are:
- age between 45 and 65
- constipation
- pregnancy
- pelvic space occupying lesion eg large ovarian cyst
Internal haemorrhoids
- originate proximal to the dentate line and covered by insensate transitional epithelium
- not as painful due to autonomic innervation
- grade 1 = limited to anal canal
- grade 2 = beyond anal canal but reduces spontaneously on cessation of straining
- grade 3 = outside anal canal and manually reducible
- grade 4 = outside anal canal and irreducible
External haemorrhoids
- located in the distal anal canal, distal to the dentate line, and covered by sensate anoderm or skin
- more painful due to somatic innervation
Haemorrhoids - clinical features
- rectal bleeding = bright red bleeding in association with defecation or straining
commonly painless bleeding - Importantly, blood is seen on the surface of the stool, not mixed in.
- perianal discomfort: can have itching or feeling of incomplete evacuation
- moist, pink bumps in anus (or purple or blue)
- constant pain = thrombosed external haemorrhoids
Haemorrhoids - investigations
- Dx is clinical (rectal examination) or
- anoscopic examination (hollow tube device with a light attached at one end)
- FBC (may have microcytic anaemia)
consider colonoscopy/flexible sigmoidoscopy if you suspect serious pathology like IBD or cancer
Haemorrhoids - management
1st line - dietary and lifestyle modification = increased fibre intake and adequate fluids, consider fibre supplements and analgesia
- topical hydrocortisone rectal, topical local anaesthetic (lignocaine gel
- 2nd line = rubber band ligation (elastic bands around it and falls off) or sclerotherapy (injection of sclerosing agent - makes it shrink)
- 3rd line = surgical haemorrhoidectomy
(if large symptomatic, unresponsive to other tx or thrombosed)
Anal fissure - definition
Anal fissure is a split in the skin of the distal anal canal characterised by pain on defecation and rectal bleeding. It is a common condition in young to middle-aged adults.
Anal fissure - aetiology
- passage of a hard stool bolus may precipitate (tears the anal skin from the pectin - at the dentate line)
- IBD
- may begin during an episode of loose stool, or often spontaneously with no obvious precipitating factor
- opiate analgesia is a/w constipation and a subsequent increased incidence of anal fissure
- STIs e.g. HIV, syphilis, herpes
- may be an ischaemic ulcer with spasm of the IAS
therefore risk factors are:
- hard stools
- pregnancy
- opiate analgesia
- IBD
- STIs
Anal fissure - clinical features
- pain on defecation = severe pain, ‘like passing broken glass’, can also be burning. Occurs immediately after bowel movements and improves with time
- tearing sensation on passing stool
- fresh blood on stool or on paper
- anal spasm and tenderness of examination
- symptoms tend to come and go (intermittent)
- clinical Dx
Anal fissure - management
- conservative: high-fibre diet, adequate fluid intake, sitz baths, topical analgesia, lubricant before defecation (petroleum jelly)
- laxatives: bulk forming laxatives 1st line, lactulose 2nd line, stool softener
- topical glyceryl trinitrate (GTN) or topical diltiazem
- resistant fissures = botulinum toxin injection or surgical sphincterotomy
- The main complication is faecal incontinence
Anorectal abscess - definition
infection of the soft tissues around the anus. Severe perianal pain and swelling are the most common presenting complaints. Rarely, patients may present with life-threatening sepsis from an associated necrotising soft-tissue infection.
