48 - Large Bowel

Question 1

Define anatomical / radiographic differences of the canine and feline caecum

Answer 1

Canine:

• Semicircular / compartmentalized
• Often contains gas
• R abdomen
• Seperate junctions: Caecocolic, and ileocolic

Feline:

• Cone shaped diverticulum of ascending colon
• Usually not radiographically visible
• Does not tend to contain gas / faeces
• No distinct caecocolic junction, no compartmentalisation

Question 2

Where are the right and left colic flexures located?

Answer 2

Left: Between ascending and transverse

Right: Between transverse and descending

Question 3

What are the boundaries of the rectum?

Answer 3

Pelvic inlet -> anal canal

Question 4

Associations of colon with other organs

Answer 4

Question 5

List 4 non-pathological causes of increased colonic gas / fluid on radiographs

Answer 5

• Abdo palp
• Aerophagia
• Rectal
• Enema

Question 6

Name 4 broad categories for causes of pneumatosis coli

Answer 6

1) Bacterial theory
2) Mucosal damage theory
3) Mechanical theory
4) Pulmonary disease theory

NB: When seen, endevaour to find cause. May be clinically insignificant, but in some cases may indicate significant disease. => Can lead to pneumoperitoneum

Question 7

List 7 possible findings in barium enema

Answer 7

1) Mucosal irregularity
2) Spasm of lumen
3) Occlusion
4) Outpouching (hernia / divert)
5) Twisting
6) Displacement
7) Perforation

Question 8

List 4 indcations for barium enema

Answer 8

1) Cannot pass endoscope
2) Limitations of endoscope do not allow examination of colon / caecum
3) Torsion
4) Mural or extramural lesions suspected but not visualised endoscopically

Question 9

Approximate dose of barium for enema

Answer 9

7-15ml per kg/BW

Question 10

List 4 possible pitfalls / normal variants seen with barium enema

Answer 10

1) Adherence to mucus
2) Clumping / Flocculation of media
3) Filling defects of faeces
4) Lymphoid follicles (colon - dog; caeceum / colon - cat)

=> Spicules or pinpoint radiopacities en face. DIfferentiate from ulcers!

Question 11

LIst 4 possible causes of rupture during barium enema

Answer 11

1) After cleansing enema
2) Inappropriate use of catheter
3) Overdistension
4) After biopsy

=> IF SUSPECTED use aqueous nonionic contrast, however poorer mucosal coating

Question 12

Radiographic measures of colonic diameter

Answer 12

Dogs:

• < length of L7

Cats (without GI dz):

• < 2.2 x SI diameter
• < 2.8 x cranial endplate L2
• < 1.3 x length of L5

Cats - constipation / obstipation vs megacolon:

• Colon - L5 length ratio >1.5

=>supports megacolon

Question 13

Definitions of constipation, obstipation and megacolon

Answer 13

Constipation:

• Infrequent and reversable faecal retention

Obstipation:

• permanent but reversible loss of colonic function

Megacolon:

• permanent and irreversible colonic distension

Question 14

List 7 categories of aetiology for megacolon

Answer 14

1) Idiopathic
2) Chronic constipation / obstipation
3) Spinal (caudosacral agenesis in manx cats, LS dz)
4) Neuromuscular
5) Metabolic (hypokalaemia, hypoT)
6) Ureterocolic diversion (surgical procedure)
7) Congenital anorectal anomalies

Question 15

List 7 congenital anomalies of the large bowel

Answer 15

1) Imperforate anus
2) Atresia ani
3) Atresia coli
4) Fistulation
5) Diverticula
6) Duplication of large bowel / rectum
7) Short straight colon (caecum in left hemiabdomen)

Question 16

Patterns of displacement of descending colon and rectum

Answer 16

Question 17

List 5 causes of colonic stricture

Answer 17

1) Neoplasia (most common. E.g. carcinoma, LSA)
2) Adenoma
3) Eosinophilic colitis
4) Scar tissue
5) Ulcerative colitis

Question 18

US Features of feline short colon syndrome

Answer 18

1) Short colon!
2) Left displacement of junction
3) Irretular wall thickening (associated with large bowel d+)

Question 19

Normal colonic thickness (both spp)?

Answer 19

1-2.5mm

Question 20

US characteristics of large intestinal lympoid tissue.

And other US layer nuances!

Answer 20

1) Colonic submucosal micronodules (dogs and cats)
2) Caecal hypoechoic coalescing mucosal / submucosal nodules “follicular layer” (cats)

=> Non-specific normal vs inflamm/neoplasia

ALSO: Hyperechoic line in canine muscularis = fibrosis between inner circular and outer longitudinal muscular layers. NORMAL

Question 21

DDx for large bowel wall thickening / layering alterations (x 3 large groups and specifics within)

Answer 21

1) Neoplasia
2) Inflammation
- Remember Eosiniophilic sclerosing fibroplasia (cats)!
3) Infection
- Remember Mycobacteriosis, fungal disease (pythiosis)

Question 22

List names and locations of colic LNs

Answer 22

1) Right colic LN (Ileocolic junction)
2) Middle colic LN (Transverse colon)
3) Left colic LN (Descending colon)