48 - Large Bowel Flashcards
Define anatomical / radiographic differences of the canine and feline caecum
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
Where are the right and left colic flexures located?
Left: Between ascending and transverse
Right: Between transverse and descending
What are the boundaries of the rectum?
Pelvic inlet -> anal canal
Associations of colon with other organs
List 4 non-pathological causes of increased colonic gas / fluid on radiographs
- Abdo palp
- Aerophagia
- Rectal
- Enema
Name 4 broad categories for causes of pneumatosis coli
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
List 7 possible findings in barium enema
1) Mucosal irregularity
2) Spasm of lumen
3) Occlusion
4) Outpouching (hernia / divert)
5) Twisting
6) Displacement
7) Perforation
List 4 indcations for barium enema
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
Approximate dose of barium for enema
7-15ml per kg/BW
List 4 possible pitfalls / normal variants seen with barium enema
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!
LIst 4 possible causes of rupture during barium enema
1) After cleansing enema
2) Inappropriate use of catheter
3) Overdistension
4) After biopsy
=> IF SUSPECTED use aqueous nonionic contrast, however poorer mucosal coating
Radiographic measures of colonic diameter
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
Definitions of constipation, obstipation and megacolon
Constipation:
- Infrequent and reversable faecal retention
Obstipation:
- permanent but reversible loss of colonic function
Megacolon:
- permanent and irreversible colonic distension
List 7 categories of aetiology for megacolon
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
List 7 congenital anomalies of the large bowel
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)
Patterns of displacement of descending colon and rectum
List 5 causes of colonic stricture
1) Neoplasia (most common. E.g. carcinoma, LSA)
2) Adenoma
3) Eosinophilic colitis
4) Scar tissue
5) Ulcerative colitis
US Features of feline short colon syndrome
1) Short colon!
2) Left displacement of junction
3) Irretular wall thickening (associated with large bowel d+)
Normal colonic thickness (both spp)?
1-2.5mm
US characteristics of large intestinal lympoid tissue.
And other US layer nuances!
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
DDx for large bowel wall thickening / layering alterations (x 3 large groups and specifics within)
1) Neoplasia
2) Inflammation
- Remember Eosiniophilic sclerosing fibroplasia (cats)!
3) Infection
- Remember Mycobacteriosis, fungal disease (pythiosis)
List names and locations of colic LNs
1) Right colic LN (Ileocolic junction)
2) Middle colic LN (Transverse colon)
3) Left colic LN (Descending colon)
