Surgical Approach to Colon, Rectum and Anus

Question 1

What technique do you use to open caudal abdomen to visualize colon/rectum for colorectal surgery?

Answer 1

Pelvic split - involves sawing through symphysis of pelvis in order to get to distal portion of colon
Burr holes in pelvis prior to splitting to aid with alignment once sx is over
Feed wire through holes to keep pelvis opposed

Question 2

What is Coloctomy?

Answer 2

Full thickness biopsy of the colon

Question 3

What part of the GIT is the limiting factor in digestion?

Answer 3

Small intestine

Question 4

How does healing of LI compare to healing of SI?

Answer 4

LI = delayed healing

Question 5

What suture pattern/type should you use in large intestine surgery and why?

Answer 5

Single layer simple interrupted APPOSITIONAL sutures
Best not to use inverted in order to promote healing
- Faster gain in tensile strength
- Minimize decrease in lumen diameter
- Decrease incidence of complications

Question 6

What are the results if you remove majority of colon?

Answer 6

Loss of reservoir and absorptive capacities
Increase in fecal frequency, watery feces

Question 7

Why is it super important to preserve the ileocecocolic junction?

Answer 7

Preserves function of ileum (site of vitamin B absorption - important!)
Also functions as sphincter which prevents retrograde flow of colon bacteria back into small intestine (bacterial overgrowth risk)

Question 8

Resections of >4cm of rectum are associated with WHAT?

Answer 8

Fecal incontinence

Question 9

What is the only nerve that supplies the rectum? What is this nerve a branch from?

Answer 9

Caudal rectal nerve - branch of sciatic –> pudendal nerve
Resection results in incontinence

Question 10

What are some complications associated with rectal surgery?

Answer 10

• Fecal incontinence, Rectal prolapse, Stricture and tenesmus
• Dehiscence and septic peritonitis, Wound infection and abscess
• Hematochezia - passage of fresh blood through anus (in feces)

Question 11

What is megacolon? How do you diagnose megacolon?

Answer 11

Flaccid enlargement of the colon, distension of the colon with feces and loss of function of the colonic muscle
Diagnosis:
Diagnose by equating diameter of 2nd lumbar vertebrae L2 to diameter of colon
Normal diameter of colon = L2
In megacolon diameter of colon should be >1.5x diameter of L7
Must rule out underlying cause for constipation

Question 12

Describe primary vs secondary megacolon

Answer 12

Primary - idiopathic megacolon
- common in cats, possibly due to issues with
innervation of colonic wall (?)
Secondary - Intrapelvic space-occupying lesion (Ex. neoplasia, lymphadenopathy, abscess)
- Colorectal neoplasia, colorectal abscess
- perineal hernia, pelvic fractures
- inappropriate diet (not enough fiber/fluid
content = obstipation - severe constipation)

Question 13

How do you treat megacolon?

Answer 13

Medical management:
- Manual evacuation of colon
- Laxatives (Ex. lactulose)
- Prokinetics (Ex. ranitidine)
- Frequent walks
- Change in diet (low residue diet/increase insoluble fiber Ex. psillium husk)
Surgery:
- subtotal colectomy - post-op complications
- recurrent constipation, increase in fecal frequency, soft to watery feces, tenesmus, rectal prolapse

Question 14

What is a subtotal colectomy?
Which arteries must be preserved and why?

Answer 14

Partial removal of the colon
Must preserve caudal mesenteric artery and cranial rectal ileocolic artery (only blood supply to rectum)

Question 15

What is the incidence of malignant vs benign colorectal neoplasia?

Answer 15

50% malignant/50% benign

Question 16

Give some examples of benign colorectal neoplasias?
Which of these can transform into a malignant growth?

Answer 16

Adenomatous polyp - up to 50% transform into malignant growth
Leiomyomas

Question 17

Give some examples of malignant colorectal neoplasias?

Answer 17

adenocarcinoma
Leiomyosarcoma
Lymphoma
Hemangiosarcoma
Plasmacytoma

Question 18

What is the typical signalment of a dog with colorectal neoplasia?

Answer 18

Older dogs
Adenocarcinoma - a malignant tumor formed from glandular structures in epithelial tissue
GSD, Great Dane, Doberman, Boxer

Question 19

What is the typical presenting history of a patient with colorectal neoplasia?

Answer 19

Tenesmus, Hematochezia, Increased defecatory frequency, ribbon-like feces, rectal prolapse, weight loss

Question 20

Where are most colorectal adenocarcinomas located in the rectum?
How can they present?

Answer 20

60-80% located in the mid-caudal rectum
Adenocarcinoma can present as polyp/mass, irregular mucosal surface, or annular stricture

Question 21

How do you diagnose colorectal neoplasia?

Answer 21

Rectal exam - feel for mid-caudal rectum
Radiography

Question 22

What is the treatment for colorectal neoplasia?
Give appropriate margins

Answer 22

Submucosal resection (mass removal and anastomosis)
2cm margins ideal, 1cm margins ok
Simple interrupted sutures
Start on dorsal wall first

Question 23

What surgical technique should you use for lesions in caudal 1/3 - 1/2 of rectum?

Answer 23

Rectal pull-through

Question 24

What is the prognosis for a patient with adenomatous polyps?
What about for adenocarcinomas?
What about conservative management?

Answer 24

Polyps - >2 years
- complete surgical resection can result in cure
- 17% dogs recurrence at 9-12months
- 25% dogs malignant transformation 9-17months
Adenocarcinomas - Median survival 22 months
- Cure possible with complete excision, but can be difficult due to location
Conservative management - 15 month survival

Question 25

What should you do if you are worried the margins you are taking might be too large in the colorectal region?

Answer 25

Take smaller margins - prognosis can still be ok
Better to take smaller margins than risk incontinence/digestive issues
Send out resected sample for pathology diagnosis and reassess with results in hand

Question 26

What are the causes of rectal prolapse?

Answer 26

GI parasites
Rectal neoplasia
Perineal hernias (due ot weakness of the muscles of the pelvic floor)

Question 27

What are the treatment options for rectal prolapse?

Answer 27

1. Purse string suture
2. Anthelmintics, Fecal softeners, low residue diet, sedatives
3. Colopexy - fix colon internally

Question 28

Give the typical presentation/history of a patient with anal sac impaction/inflammation?

Answer 28

Perineal irritation - scooting, licking/biting, discomfort on defecation
Enlarged non-painful or painful anal sac
Redenned inflamed skin/potential draining tract overlying anal sac suggestive of infection or ruptured abscess
Abnormal secretions - thick white/yellow/green discharge (normal = liquid brown)

Question 29

What are the treatment options for anal sac impaction?

Answer 29

Manual expression (if mild)
Sedated expression/repair of sacs
Surgical removal of anal sacs (if recurrent episodes)

Question 30

Give the steps for proper medical management (under sedation) of anal sacculitis

Answer 30

• Sedation or anesthesia → collect sample for culture/cytology
• Catheterize duct opening: lacrimal cannula
• Lavage anal sac with 0.9% saline
• Instill dexamethasone/antibiotics → systemic abx if evidence of
  abscess or systemic disease
• Topical treatment of yeast overgrowth if indicated on cytology

Question 31

Open vs closed sacculectomy - which is better and why?

Answer 31

Closed - better, less traumatic
Open - not recommended

Question 32

Give some anal sacculectomy complications - how common are they?

Answer 32

Uncommon
Fecal incontinence if dissection was traumatic/aggressive (particularly open technique)
Persistent infection with draining tracts due to failure to remove all anal sac tissue

Question 33

What is the name for a highly malignant anal sac tumor?

Answer 33

Anal Sac Apocrine Gland Adenocarcinoma
50% metastases at diagnosis
HIGHLY malignant

Question 34

What are other DDx for Anal Sac Apocrine Gland Adenocarcinoma?

Answer 34

Perianal adenoma - benign, common in intact males or spayed females, castration during surgery recommended
Perianal adenocarcinoma - malignant, rare, treat same as anal sac adenocarcinoma

Question 35

What is paraneoplastic syndrome? How does this relate to Anal Sac Apocrine Gland Adenocarcinoma? What symptoms does this cause in a patient?

Answer 35

Paraneoplastic syndromes (PNS) result in changes to bodily structure or function that are not directly related to the primary tumor or metastasis. These are most commonly caused by tumor production of small molecules such as hormones or cytokines.
Important to recognize as these changes can be the first sign of neoplasia.
PU/PD, Hypercalcemia

Question 36

Give treatment options for Anal Sac Apocrine Gland Adenocarcinoma

Answer 36

Surgery
Radiation Therapy
Chemotherapy

Question 37

What is the prognosis for a patient with Anal Sac Apocrine Gland Adenocarcinoma?

Answer 37

Surgery alone - 1-1.5 years
All 3 treatment modalities combined (surgery, radiation, chemo) - 2-3 years

Question 38

What is this condition called? What is the cause?

Answer 38

Anal furunculosis - Perianal fistulation or sinus formation (cause unknown)
- Potentially related to immune deficiency?

Question 39

How should you approach diagnosis of anal furunculosis?

Answer 39

Perform exploration under heavy sedation/anesthesia
Explore the area - anal tone, area of skin affected, depth of lesions, involvement of anal sacs, rectal disease/stricture
+/- biopsy for histopath and bacterial culture

Question 40

What is the recommended treatment for anal furunculosis?

Answer 40

Atopica - Immunosuppressive (cyclosporine)
- Give antibiotics only if culture positive Ketoconazole - Antifungal (give concurrently)
- Slows down metabolism of cyclosporin → which ensures that levels in the blood stay higher for a longer period of time
*Surgery only indicated when anal sacs involved (drainage)