Perianal Surgery

Question 1

Rectum

Answer 1

12cm
Sacral promontory to levator ani muscle
The 3 tenia coli fuse around the rectum to form a continuous muscle layer

Question 2

Anal Canal

Answer 2

4cm
levator ani muscle to anal verge

Upper 2/3 of canal

• lined by columnar epithelium
• insensate
• sup rectal artery + vein
• internal iliac nodes

Lower 1/3 of canal

• lined by squamous epithelium
• Middle and inf rectal arteries + vein
• superficial inguinal nodes

Dentate line - squamomucosal junction
White line - where anal canal becomes true skin

Question 3

Anal Sphincters

Answer 3

Internal

• thickening of rectal smooth muscle
• involuntary control

External 
- 3 rings of skeletal muscle
 Deep
 Superficial
 Subcutaneous 
- voluntary control

Anorectal Ring
 Deep segment of external sphincter which is continuous
w puboretalis muscle (part of levator ani)
 Palpable on PR ~5cm from the anus
 Demarcates junction between anal canal and rectum.
 Must be preserved to maintain continence

Question 4

Perianal Haematoma

Answer 4

Subcut bleeding from burst venule < straining or passage of hard stool
(also called external pile - misnomer)

Presents - tender blue lump at anal margin
- pain worsened by defecation or movement

Rx - analgesia + spontaneous resolution -
- evacuation under local

Question 5

Proctalgia Fugax

Answer 5

Young, anxious men
Crampy anorectal pain, worse @ night
Unrelated to defecation
Assw trigeminal neuralgia

Rx - reassurance
- GTN cream

Question 6

Perianal warts

Answer 6

Commonly seen in MSM

Condylomata accuminata
 HPV
 Rx: podophyllin paint, cryo, surgical excision

Condylomata lata
 Syphilis
 Rx: penicillin

Question 7

Pruritis Ani

Answer 7

 50% idiopathic
 Poor hygiene
 Haemorrhoids
 Anal fissure
 Anal fistula
 Fungi, worms
 Crohn’s
 Neoplasia