Colorectal

Question 1

what does the SMA supply?

Answer 1

Entire small bowel, ascending colon and part of transverse colon.

Question 2

What are the branches of the IMA and what parts of the colon does it supply?

Answer 2

Branches: Left colic, sigmoid branches and superior rectal artery.
Supply: Distal transverse, descending colon, sigmoid.

Question 3

What 2 branches provide collateral flow between the SMA and IMA?

Answer 3

Marginal artery

Arc of Riolan (typically connects the middle colic branch of SMA with left colic branch of IMA)

Question 4

What are the water shed ares of the colon?

Answer 4

Griffiths point (splenic flexure) 
Sudeck’s point (superior and middle rectal artery meet)

Question 5

What is the blood supply to the rectum?

Answer 5

Superior - superior rectal branch of IMA
Middle - middle rectal branch of hypogastric (internal iliac artery)
Inferior - inferior rectal artery (branch of pudendal of internal iliac)

Question 6

What is the venous drainage of the rectum?

Answer 6

Superior and middle drain into the IMV (portal circulation)
Inferior drain into internal iliac vein (systemic circulation)
(Clinically relevant as to location of metastasis based on site within rectum)

Question 7

How do you determine the transition from colon to rectum?

Answer 7

From where the tenia splay

Length of 15cm from anus on rigid rectal proctoscopy

Question 8

What defines the anal canal?

Answer 8

Anal canal starts from puborectalis sling and ends at squamous mucosa that blends with perianal skin.

Question 9

What defines the anal margin?

Answer 9

5cm radially from squamoumucocutanous junction and splay out laterally, that’s the anal margin.

Question 10

Where are anal fissures located?

Answer 10

Posterior midline (90%) 
(Females can have anal fissures in 25% of cases)

Question 11

What is the medical treatment for anal fissure?

Answer 11

Bulking agents (movicol)
Sitz baths
topical anaesthetic or nitrates (headaches)
Topical Ca2+ channel blocker (fewer side effects)
Botox injection

Question 12

What are the surgical options for treatment of anal fissure?

Answer 12

Lateral internal sphincterotomy (high efficacy rates though risk is faecal incontinence) - evaluate incontinence before procedure.
Anal cutaneous flap (flap and cover the fissure) - incidence of faecal incontinence rates is low

Question 13

What are the 5 different locations for an anal abscesses?

Answer 13

1) Perianal space
2) Ischiorectal space
3) Intersphincteric space
4) Superlevator space
5) Submucosal space

Question 14

What may you need to consider if requiring drainage of a deep perianal abscess?

Answer 14

Internal transanal drainage.

Question 15

Whats the risk of a fistula in patients post incision and drainage?

Answer 15

1/3 of patients represent with fistula in ano.

Question 16

What are the various fistula in ano we come across?

Answer 16

Intersphinteric
Transphinteric
Suprasphinteric
Extrasphincter

Question 17

What would be your approach to a simple fistula in ano?

Answer 17

Open the tract up

Question 18

What would be in approach for patients who have a perianal abscess and fistula with 25% of the sphincter involved?

Answer 18

Drain the abscess and place a seton

This allows further drainage, fibrosis of tract to occur, and converts a high tract to a low tract