Large Intestine

Question 1

Difference between volvulus and torsion (applies elsewhere in GIT)

Answer 1

Volvulus - twist along the long axis of the mesentery (eg RVA in cows, the abomasum itself isn’t twisted, it is twisted along the axis of the lesser omentum)

Torsion - twist along the long axis of the viscus itself

Question 2

Incidence of repeat large colon volvulus after first presentation and correction by ex lap

Answer 2

15% will have repeat episodes required second laparotomy

Colopexy is recommended at the first recurrence

Question 3

Liklihood of recurrence of LCV after 2 episodes

Answer 3

80% that LCV will happen for a third time

Question 4

According to Hall and Rodgerson (EVE probably 2020); what is the approach for colopexy dehiscence

Answer 4

NB if operating on a horse with previous colopexy, need to make a more caudal approach as the colopexy is incorporated into the cranial aspect of the midline incision (if that technique is chosen).

Repeat the colopexy at the same site/scar or previous colopexy.

Suture the lateral taenia of the left ventral colon approx 40cm from the caecocolic ligament into the cranial portion of the midline incisional closure (for 10-15cm)

Good outcome in the 3 reported cases

Question 5

Methods of colopexy for LCV

Answer 5

*Performed at second surgery (first recurrence - 15% recurrence rate)

*May choose to perform at first surgery for younger broodmares (age 5-12) as high risk of recurrence (more potential subsequent pregnancies?)

1. Incorporation of the lateral free taenial band of the left ventral colon into the cranial 15cm of the ventral midline laparotomy (need to make a more cranial lap incision; 25cm beginning 5-10cm caudal to the xyphoid - this is what is done a t Hagyards)
2. Suturing left and right colonic taenial bands together
3. Suturing left and right colon together and left colon to left ventral body wall
4. Suturing 35cm of the lateral free band of the left ventral colon to the left ventral abdominal wall
5. Suturing right and left ventral colons to the respective sides of the body wall
6. Laparoscopic approach also described with lateral band of LVC

Question 6

Label the blood supply to the large intestine

Answer 6

1 - cranial mesenteric aa

2 - jejunal arteries

3 - medial caecal aa

4 - lateral caecal aa

5 - ileal artery

6 - colic branch of ileocolic aa

7 - right colic aa (goes to dorsal colon)

8 - middle colic aa

Medial vs lateral caecal aas are labelled wrong on diagram? Or CC band is in wrong place?

Question 7

Blood supply to the caecum

Answer 7

Cranial mesenteric aa -> ileocolic branch -> common origin of medial and lateral caecal bands running in respective taenia

No collateral supply, susceptible to thromboelbolic disease

Question 8

Blood supply to the asscending colon

Answer 8

Vental colon: colic branch of the ileocolic aa (a branch of cranial mesenteric)

Dorsal colon: right colic branch of the cranial mesenteric aa

The mesocolon connects dorsal and ventral colons and carries the blood supply to each. Contains the medial and lateral mesocolic bands of the ventral colon (left and right)

Question 9

Taenia of the ascending colon

Answer 9

Caecum - 4 (dorsal attaches to ileum, lateral to colon)

RVC - 4

LVC - 4

LDC - 1 (mesocolic)

RDC - 3 (1 mesocolic, 2 free)

Small colon -2 (1 mesenteric 1 free)

The ventral colon has lateral and medial mesocolic and lateral and medial free taenia

Question 10

Which bands of the caecum connect to colon and ileum

Answer 10

Caecocolic band = Lateral caecal band to lateral free taenia of the RVC

Ileocaecal = dorsal band of the caecum to the antimesenteric border of the ileum

Question 11

Phenylephrine MOA?

Answer 11

α1-adrenergic receptor agonist/sympathomimetic

Used in the tx of NSE although reports are conflicting WRT efficacy over exercise/feed restriction alone

Care re fatal bleeding described in older horses

Question 12

Main findings of Gillen 2019 (JAVMA) WRT outcomes following medical management of NSE

Answer 12

1. Phenylephrine administration in combination with exercise, +/- trocarisation, was successfully used to treat 72 of 134 (53.7%) SUSPECTED and 72/100 (72%) CONFIRMED NSE cases
2. Confirmed NSE cases that did not respond to medical management that had sx where NSE was the only finding (n= 25) all survived to DC. 3 that didn’t respond to medical management were euthanised without surgery
3. Of those undergoing sx with other dx (34), 24 (71%) STS - inaccurate pre-op dx can delay required sx tx and worsen px for survival so non-responders should be treated quickly w sx
4. Trocharisation did not seem to improve the outcome over phenylephrine/exercise alone, although there no complications observed
5. Medical management was performed from 1-10 times; resolution medically was signifcantly more likely to be successful with those receiving 1-2tx than those receiving >2