Surgical approach to the colon, rectum and anus in small animals

Question 1

colorectal surgery - surgical approaches

Answer 1

Ventral Midline Laparotomy
Dorsal Perineal Approach
pelvic split
transanal

Question 2

colotomy

Answer 2

Full thickness biopsy of the colon
Same basic principles as enterotomy
risk of infection + wound breakdown

Question 3

Large intestinal resection & anastomosis

Answer 3

Same basic principles as for small intestine, but must

respect delayed healing of large intestine

Question 4

How much colon can you remove?

Answer 4

Removal of majority of colon - Loss of reservoir & absorptive capacities, ↑fecal frequency, watery faeces
Preservation of ileocaecolic junction - preserves ileal function, Prevents retrograde flow of colonic bacteria into SI -↓risk of bacterial overgrowth

Question 5

how much rectum can be removed

Answer 5

Rectal resections of 6cm or more are consistently

associated with faecal incontinence

Question 6

Large intestinal anastomosis - sutures - aims

Answer 6

Optimise wound healing
Faster gain in tensile strength
Minimise decrease in lumen diameter
Decreased incidence of complications

Question 7

Large intestinal anastomosis - staples

Answer 7

Rapid and reliable
Inserted via an incision in the caecum or via the anus
inverted anastomosis
Post-op bleeding
Higher anastomotic bursting pressures on day 7 compared to sutured anastomoses

Question 8

complications of colorectal

Answer 8

Dehiscence & septic peritonitis
Wound infection
Abscess
Faecal incontinence
Stricture & tenesmus
Rectal prolapse
haematochezia

Question 9

megacolon - define

Answer 9

Flaccid enlargement of the colon, distension of the colon

with feces and loss of function of the colonic muscle

Question 10

when would you find Primary/idiopathic megacolon

Answer 10

in cats

Question 11

secondary megacolon - causes

Answer 11

pelvic fractures
intrapelvic space-occupying lesions
Colorectal neoplasia
Colorectal abscess
Perineal hernia
Inappropriate diet

Question 12

megacolon - clinical signs

Answer 12

Chronic constipation, tenesmus, vomiting, anorexia, weight loss
Large colon containing fecal material, dehydration, poor body condition
Rule out underlying cause for constipation

Question 13

megacolon - treatment

Answer 13

Treat underlying disease
Medical - Manual evacuation of colon, Laxatives, Prokinetics, Frequent walks, High fibre, low residue diet
Surgery - subtotal colectomy
Post-op complications - Recurrent constipation, Increased defaecatory frequency, Soft to watery faeces, Tenesmus, Rectal prolapse
Prognosis - Good

Question 14

colorectal neoplasia

Answer 14

50/50 benign vs malignant
benign - Adenomatous polyps, leiomyomas - can transform to be malignant
malignant - Adenocarcinoma, leiomyosarcoma, lymphoma,
haemangiosarcoma, plasmacytoma

Question 15

Colorectal neoplasia - signalment

Answer 15

Older dogs: 6-9 yrs

Adenocarcinomas

Question 16

Colorectal neoplasia - history

Answer 16

Tenesmus
Haematochezia
Increased defecatory frequency
Ribbon-like faeces
Rectal prolapse
Weight loss

Question 17

Colorectal neoplasia: diagnosis

Answer 17

Rectal exam - polypoid mass, irregular mucosal surface, annular stricture
Radiography: abdomen & thorax
Ultrasound, fine needle aspirates
Colonoscopy, grab biopsy

Question 18

Colorectal neoplasia: treatment

Answer 18

Submucosal resection
Wide surgical excision with intestinal resection &
anastomosis

Question 19

colorectal neoplasia - prognosis

Answer 19

Adenomatous polyps - Surgical resection can result in a cure, 17% dogs: recurrence at 9-12 months, 25% dogs: malignant transformation at 9-17 months, Median survival > 2 years
Adenocarcinomas - Cure is possible with complete surgical excision due to low
rate of distant metastasis, but complete excision o
ften difficult due to tumour location, Median survival: 22 months
Conservative management with fecal softeners - Mean survival time: 15 months

Question 20

Rectal prolapse - causes

Answer 20

Gastrointestinal parasites
Rectal neoplasia
Perineal hernias

Question 21

Rectal prolapse - treatment

Answer 21

Anthelmintics
Faecal softeners
Low residue diet
Sedatives

Question 22

Anal sac impaction, inflammation & infection

Answer 22

History - Perineal irritation: scooting, licking or biting,
discomfort on defecation
Physical Exam - Enlarged non-painful/painful anal sac
Abnormal secretions - Normal-liquid brown, abnormal- thick white/yellow/green
Reddened inflamed skin or draining tract overlying
region of anal sac suggestive of infection or ruptured
abscess

Question 23

Anal sac impaction, inflammation & infection - treatment - medical

Answer 23

Impaction - Manual expression
Anal sacculitis/abscess - Sedation or anaesthesia, Catheterise duct opening: lacrimal cannulae, sample for culture and cytology, Lavage anal sac with 0.9% saline, dexamethasone and antibiotics
Systemic antibiotics, if evidence of abscess or systemic disease
Topical treatment of yeast overgrowth if indicated on cytology

Question 24

Anal sac impaction, inflammation & infection - treatment - surgical

Answer 24

anal sacculectomy

Question 25

anal sacculectomy - Complications

Answer 25

uncommon
Fecal incontinence if dissection was traumatic or aggressive - usually temporary unless both caudal rectal nerves were cut
Persistent infection with draining tracts - fail to remove all anal sac tissue

Question 26

Anal sac apocrine gland adenocarcinoma

Answer 26

Highly malignant: 50% metastases at diagnosis

Question 27

Anal sac apocrine gland adenocarcinoma - Perianal adenoma

Answer 27

benign, Common, Intact male, spayed females, Castration plus surgery

Question 28

Anal sac apocrine gland adenocarcinoma - Perianal adenocarcionma

Answer 28

Malignant, Rare, Treat as anal sac adenocarcinoma

Question 29

Anal sac apocrine gland adenocarcinoma - Paraneoplastic syndrome

Answer 29

Hypercalcaemia

polyuria and polydipsia

Question 30

Anal sac apocrine gland adenocarcinoma - diagnosis

Answer 30

Physical exam
Haematology, biochemistry, urinalysis
Fine needle aspirate/ incisional biopsy
Radiography /ultrasound of thorax and abdomen

Question 31

Anal sac apocrine gland adenocarcinoma - treatment

Answer 31

Surgery
Radiation therapy
Chemotherapy - mitoxantrone

Question 32

Anal sac apocrine gland adenocarcinoma - prognosis

Answer 32

Treatment incl. Surgery – 548 days

All 3 of the above – 956 days