Perianal

Question 1

Anal canal: anatomical position

Answer 1

Anal triangle of perineum

4cm in length

Question 2

Anal sphincters

Answer 2

Internal: surrounds upper 2/3 of canal

External: voluntary muscle lower 2/3 of anal, blends superiorly with puborectalis muscle of pelvic floor

Question 3

Pectinate line

Answer 3

Or Dentate line

Irregular circle formed by anal valves

Question 4

Histology of anal canal

Answer 4

Superior: columnar epithelium
Transitional or cloacogenic zone: columnar, transitional, or stratified squamous epithelium
Inferior to pectinate: non-keratinised stratified squamous

Question 5

Embryology of anal canal

Answer 5

Above pectinate: embryonic hindgut

Below: ectoderm of proctoderm

Question 6

Arterial supply to anal canal

Answer 6

Above pectinate: superior rectal artery (branch of IMA)
Below: inferior rectal artery (branch of internal pudendal artery)

Anastomose to form middle rectal

Question 7

Venous drainage of anal canal

Answer 7

Above pectinate: superior rectal vein (drains into inferior mesenteric vein, portal system)
Below: Inferior rectal vein (emptied into internal pudendal vein, systemic system)

Anastomosis form haemorrhoids

Question 8

Nerve supply: anal canal

Answer 8

Above pectinate: visceral innervation via inferior hypogastric plexus
Below: somatic innervation via inferior rectal nerves (branches of pudendal nerve)

Question 9

Lymphatic drainage of anal canal

Answer 9

Above pectinate: internal iliac lymph nodes

Below: superficial inguinal lymph nodes

Question 10

Spaces around anal canal

Answer 10

Perianal space: 
Intersphincteric space
Ischiorectal space
Supralevator space
Deep postanal space

Question 11

Anorectal abscess

Answer 11

Collection of pus in anal/rectal region
Plugging of anal ducts result in fluid stasis and infection
Common organisms: E coli, bactericides spp
Categories by area: Perianal, Ischiorectal, Intersphincteric, Supralevator
Rx: EUA, I&D, Abx
Assess for fistula-in-ano

Question 12

Fistula-in-ano (Perianal fistula): classification

Answer 12

Abnormal collection between anal canal and perianal skin
Majority associated with anorectal abscess
Park’s classification system:
Inter-sphincteric
Trans-sphincteric
Supra-sphincteric
Extra-sphincteric

Question 13

Fistula-in-ano, cause and clinical

Answer 13

IBD
Systemic disease: DM
History of trauma
Previous radiation

Sx: recurrent perianal abscess, discharge, opening may be seen on exam.

Question 14

Fistula-in-ano management

Answer 14

Surgical:
Fistulotomy
Seton placement

Question 15

Pilonidal sinus

Answer 15

Formation of sinus in cleft of buttocks
Caused by inflamed hair follicle in intergluteal cleft
RF: sweating, buttock friction, obesity, poor hygiene
Sx: discharging/painful sinus
Can form abscess
Rx: I&D

Question 16

Anal cancer

Answer 16

4% of colorectal cancer
Majority (90%) are SCC below dentate line. Rest (10%) are adenocarcinoma from upper anal canal. Rare: melanoma/skin cancer
RFs: HPV, HIV, age, smoking, Crohn's
Ix: US-FNA. CTTAP, MRI pelvis
Rx: Chemorads. APR.

Question 17

Haemorrhoids, classification

Answer 17

Abnormal swelling or enlargement of anal vascular cushions
1st degree: remain in rectum
2nd: prolapse through anus on defecation but spontaneously reduce
3rd: prolapse through anus on defecation but require digital reduction
4th: remain persistently prolapsed

Question 18

Haemorrhoids, RF, clinical

Answer 18

RF: excessive straining, constipation, age, increased IAP (pregnancy, ascites, coughing)
Rx: 1st & 2nd: rubber-band ligation
2nd & 3rd: haemorrhoids ligation
3rd & 4th: haemorrhoidectomy

Question 19

Anal fissure

Answer 19

Tear in mucosal lining
Acute <6 weeks, chronic >6 weeks
Rx: laxatives, GTN cream, diltiazem cream
Surgical: botox, lateral sphincterotomy