Disease of the Caecum & reperfusion injury

Question 1

what side of the abdominal cavity does the caecum lie on

Answer 1

RIght abdominal wall - between ileum & ventral colon

Question 2

what is the volume of the caecum

Answer 2

30L

Question 3

what is the Haustrae

Answer 3

The caecum has 4 bands of smooth muscle (taenia) which form pouches know has the haustrae
it is responsible for mixing contents and delays transport

Question 4

What is responsible for caecal motility

Answer 4

Pacemaker in ventral caecal wall, 10-15cm from apex - generates the neural impulses that cause caecal motility

Question 5

what are the two types of contractions of the caecum

Answer 5

1. segmental contraction: mixes ingesta; mainly towards the apex
2. Progressive contractions - large caecal segements contract at 3-5 minute intervals, produces mass movements which force the caecal content into the colon

Question 6

What factors inhibit the contraction of the caecum

Answer 6

Alpha agonist (xylazine, detomidine) & opioids

Question 7

what factors stimulate the contraction of the caecum

Answer 7

Parasympathominetics (neostigmine, bethanechol, erythromycin)

Question 8

What are the functions of the caecum

Answer 8

1. water reabsorption
2. Electrolyte resorption (na, Cl)
3. initiates microbial digestion of complex carbohydrates (fibre)

Question 9

what is the most common caecal disease

Answer 9

Caecal impaction (40-50%)
Dehydrated faecal material accumulating at caecal BASE

Question 10

What are the risk factors for caecal impaction

Answer 10

Hospitalization/surgery - esp MUSCULOKELETAL  & OPTHALMOLOGY CASES 
poor dentition 
poor quality hay/access water 
Parasites - thromboembolism 
Anoplocephal perfoliata

Question 11

what are the Cs of caecal impaction

Answer 11

often very mild & intermittent colic - Hr normal to slight increase
May rupture caecum with no significant signs of abdominal pain
Decreased faecal production
Decreased borborygmi

Question 12

How do you diagnose caecal impaction

Answer 12

RECTAL PALPATION
- tight ventral caecal band palbale on RIGHT side of the abdomen
ABDOMINOCENTESIS - Normal

Question 13

What medical txm can be used for caecal impaction

Answer 13

provide analgesia
NGT if relfux due to concurrent SI distension
Softens digesta (laxatives)
Prevent further caecal filling - withhold feed
Motility stimulants not used as may potentiate rupture
Address any risk factors

Question 14

what is the surgical options for a caecal impaction

Answer 14

Typhlectomyn

Caecocolostomy, Jejunocolostomy

Question 15

what is Caecal tympany

Answer 15

Gaseous distension of the colon

Question 16

what is primary caecal tympany

Answer 16

Rapid gass production (lush pasture, high grain diets) or reduced caecal motility

Question 17

what us secondary caecal tympany

Answer 17

More common

Outflow obstrcution aboral to caecum (i.e colon displacement)

Question 18

what are the Cs of caecal tympany

Answer 18

Abdominal distension (1 R flank) 
intermittent ==> severe pain 
tachycardia 
tachypnoea
decrease borborygmi 
Abdominal percussion: PING R DORSAL FLANK

Question 19

what is a clinical path finding that can reflect primary caecal tympany

Answer 19

Corticosteroid (stress) leukogram

Question 20

what is the txm for caecal tympany

Answer 20

Visceral analgesia -Xyalazine 
Gastric decompression 
fluid therapy: IV +/- NGT 
laxatives 
withold food 
surgica; decompression 
trocarisation if severe but beware as risk of leakage, peritonitis, cellulitis

Question 21

what is the difference between primary and secondary caecal perforation

Answer 21

primary = broodmares after parturition without evidence of caecal outflow obstruction
secondary (more common) - caecal outflow obstruction

Rupture of caecal base most common with relatively empty ventral colon and ingested filled caecum

Question 22

what is the main risk factors for caecal intussusception

Answer 22

tapeworm infestation

Question 23

How do you diagnose caecal intussusception

Answer 23

adbominocentesis; normal if acute ==> serosanguineous as disease progressed
clin path; normal ==> dehydration & metabolic acidosis

ULTRASOUND: THICKENED CAECAL WALL (‘DOUBLE DONUT’)

Question 24

what is a reperfusion injury

Answer 24

Damage to tissue caused when blood supply returns to tissue after a period of ischaemia

Question 25

what are the consequences of ishcaemia

Answer 25

Membrane ion pump function altered - entry of ca, na, water into cell
mitochondrial dysfunction - cell membrane failure - cell necrosis
Reactive oxygen species (ROS) production
Proinflammatory cytokines produces - increases tissue vulnerability to further injury on reperfusion

Question 26

ishcaemia can cause the release of leucocytes chemotaxis & activation what is the consequence of this

Answer 26

Activated leukocytes release ROS - damage cell membranes - increased vascular permeability, oedema, thrombosis, cell death

Question 27

what is the consequence of calcium overload

Answer 27

Cell dysfunction & smooth muscle contraction

Question 28

Impacts of Reperfusion injury on small intestestine

Answer 28

Fluid sequeters in subepithelial space
Epithelium begins to loosen from its underlying attachments to the basement membrane- SLOUGHING OF SHEETS OF CELLS
The vili are completely denuded of epithelium by 3 hours & contract to the level of the crypts
Complete necrosis of mucosal epithelium extending to the base of the crypt occur by 4-5 hours

Question 29

What are the consequences of reperfusion injury in the large colon

Answer 29

Necrosis of culmps of surface epithelial cells
Cells then loosen from attachment at their base & neighbouring cells - SLOUGHING OF SMALL CLUSTER OF SURFACE EPITHELIAL CELLS rather than sheets of cells, as observed in SI

Question 30

how does reperfusion injury lead to endotoxaemia

Answer 30

Mucosal epithelial injury ==> disruption of mucosal barrier ==> migration of luminal bacteria and endotoxins into systemic circulation

Question 31

What is the recovery time for a horse suferring fomr reperfusion injury

Answer 31

If horse survives initial period of mucosal necrosis & sloughing + viable enterocytes presents
- mucosa can regenerate by migration o these cells
defect can be covered by epithelium within 12-14h

Question 32

what is the txm for reperfusion injury

Answer 32

Prevent formation of reactive oxygen metabolites
Stop cytokine production
Prevent endothelial cell damage
Stop neutrophil chemotaxis or activation
Treat tissue inflammation

Flunixin - nsaid
Lignocaine - membrane stabilisation, analgesia, anti-inflammatory