Kapitel 94 - Rectum, anus och Peritoneum

Question 1

What is the main blood supply of the rectum in dogs and in cats?

Answer 1

Dogs: Cranial rectal artery provides the most in dogs (should be preserved unless intrapelvic rectum is resected)

Cats: middle & caudal rectal artery

Question 2

What are the proposed landmarks for the colorectal junction?

Answer 2

proposed landmarks include the pubic brim, the pelvic inlet, the seventh lumbar vertebra, or the point at which the cranial rectal artery penetrates the seromuscular layer of the intestinal tract.

Question 3

Where is the rectoanal junction?

Answer 3

roughly ventral to the second or third caudal vertebra

Question 4

What is rectum bounded by?

Answer 4

dorsally by the right and left ventral sacrocaudal muscles, laterally by the levator ani muscle, and ventrally by the vagina and cervix in the female and the urethra in the male

Question 5

What makes up the pelvic diaphragm?

Answer 5

pelvic fascia, combined with the paired coccygeus and levator ani muscles

Question 6

what is the function of the pudendal nerve?

Answer 6

It provides voluntary, motor innervation to the external anal sphincter.

Question 7

Give examples of bowel clensing

Answer 7

• Oral administration of polyethylene glycol and electrolyte preparation: 20-40 ml/kg the night before and a few h before colonscopy
• Laxatives such as magnesium sulfate, bisacodyl (Dulcolax) or lactulose 24-48 h before procedure

+/- enemas before the procedure.

Obs!! Enemas are contraindicated if perforation is suspected!

Question 8

List the approaches to rectum

Answer 8

• Ventral approach (to reach the colorectal junction via an ventral midline incision and the following):
  o Pelvic symphosiotomy
  o Pubic and ischial osteotomies
• Dorsal approach (for middle third of the rectum)
• Lateral approach (for isolated small lesions)
• Caudal approach (for the caudal third of the rectum)
  o Anal Approach via Rectal Eversion
  o Transcutaneous Rectal Pull-Through Procedure
  o Transanal Rectal Pull-Through Procedure
  o Combined Abdominal-Transanal Approach (Also called Swenson’s pull through procedure)

Question 9

What are the recommended margins of a malignant lesion in the rectum?

Answer 9

At least 2 cm of grossly normal tissue on each side of the lesion.

Question 10

What is the preferred suture material and technique preferred for rectal anastomoses?

Answer 10

a. synthetic absorbable materials such as polydioxanone (PDS) or polyglyconate (Maxon), 3-0 or 4-0 monofilament suture is recommended.

b. Sutures should be placed 3 mm apart and 2 to 4 mm from the incised rectal edge in an simple interrupted pattern.

Question 11

What can you do if tension across the anastomosis is anticipated, what would be an alternative closure method?

Answer 11

a. a two-layer appositional closure can be used. The first layer incorporates the mucosa and the submucosa, with the knots placed intraluminally; the second layer incorporates the serosa, muscularis, and submucosa.

b. Alternatively, an end-to-end anastomosis (EEA) stapler can be used.

Question 12

What is a possible complication of pelvic symphysiotomy and retraction?

Answer 12

Retraction after pelvic symphysiotomy might lead to sacroiliac luxation. Especially with abaxial retraction of 50-75 % of the sacral with.

Question 13

What muscles are transected during a dorsal approach to the rectum? What criticall structure do you have to aware of and avoid damaging?

Answer 13

a. Rectococcygeus muscles and levator ani muscles

b. Pelvic nerve plexus that fans along the lateral surface of the rectum in the peritoneal reflection. Damage or resection of this plexus can result in fecal incontinence.

Question 14

1What can be the cause of post-op rectal strictures?

Answer 14

a. excessive tension from extensive colorectal resection
b. excessive inflammation
c. inadequate blood supply
d. partial dehiscence
e. improper anastomosis with luminal narrowing
f. poor choice of suture material
g. localized infection

Question 15

How can post-operative rectal strictures be treated?

Answer 15

a. Bougienage
b. Balloon dilation
c. Surgical incision of the constricting band
d. Surgical resection and anastomosis of the affected segment

Question 16

What’s the treatment for anal strictures?

Answer 16

a. radial incisional anoplasty, with a few craniocaudal incisions made at various points on the circumference to divide the band of scar tissue, to be followed by transverse closure of these longitudinal wounds.

b. Z-plasties of the anus.

c. Circumferential anoplasty. This involves making a circumferential incision in the skin overlying the ring of scar tissue, trimming away the scar tissue until the anal constriction is relieved, and closing the skin. If the scar tissue is extensive, excision of the entire rectocutaneous junction with apposition of the rectum to the skin may be required.

Question 17

When is the risk for dehiscence greatest after rectal surgery?

Answer 17

a. 3-5 days post-op
b. With resections > 6 cm

Question 18

What are two important factors contributing to fecal incontinence?

Answer 18

a. The external anal sphincter function (provided by the muscular component of the sphincter and the caudal rectal branch of the pudendal nerve) and reservoir continence (ability of the descending colon and rectum to distend and store feces before voluntary defecation).

b. Iatrogenic damage to the caudal rectal nerve, external anal sphincter, or cranial rectal peritoneal reflection and resection of a large proportion of the rectum may therefore all result in incontinence

Question 19

What are the 4 different types of atresia ani?

Answer 19

a. Type I atresia ani - congenital stenosis of the anus.

b. Animals with types II, III, and IV have varying degrees of rectal agenesis along with anal abnormalities.
- type II anomalies have persistence of the anal membrane, and the rectum ends immediately cranial to the imperforate anus as a blind pouch.
- In type III the anus is also closed, but the blind end of the rectum is situated farther cranially.
- In type IV the anus and terminal rectum can develop normally, but the cranial rectum ends as a blind pouch within the pelvic canal.

Question 20

What is possible treatment for atresia ani?

Answer 20

Type 1 are treated with gentle bougienage or balloon dilation of the stricture or excision of the stenosed portion of the rectum.

Type 2 and 3: Surgical correction via a vertical incision in the skin over the anal dimple. distal rectal pouch is brought caudally through the sphincter muscle. After it has been exposed through the skin incision, the rectum is incised, opened, and sutured to the surrounding subcutaneous tissues.

Type 4: Surgical correction via an abdominal approach to mobilize the distal colon and rectum.

Question 21

What other congenital condition can be associated with atresia ani? And in what type is it most commonly reported in?

Answer 21

a. Rectovaginal and urethrorectal fistula
b. Type 2 atresia ani

Question 22

List possible complications after surgery of urethrorectal fistulas

Answer 22

a. fecal incontinence (possibly from lack of a functional anal sphincter or direct damage to innervation during surgical dissection)
b. urinary tract signs from undetected uroliths
c. wound dehiscence secondary to tension and/or fecal contamination of the surgery site
d. tenesmus, obstipation
e. rectal prolapse
f. anal stenosis
g. perianal edema

Question 23

What is the difference between partial and complete rectal prolapse?

Answer 23

a. Partial (also called anal prolapse): only anal mucosa, at any point around the circumference, protrudes through the anal orifice

b. Complete: all layers of the rectum around the entire circumference protrude through the anal orifice as an elongated, cylindrical mass.

Question 24

What is the best method for diagnosing urethrorectal fistulas?

Answer 24

Positive contrast retrograde urethrography

Question 25

List possible causes of rectal prolapse

Answer 25

a. gastrointestinal parasitism b. typhlitis, colitis, proctitis c. colonic duplication d. congenital defects e. tumors of the colon, rectum, or anus f. rectal foreign bodies g. perineal hernia h. anal laxity i. cystitis or cystocele j. prostatic disease k. urolithiasis l. dystocia

Question 26

Describe the diagnostic workup for animals with rectal prolapse

Answer 26

a. thorough history, physical examination, and digital rectal examination are essential. b. Additional diagnostic tests include - fecal analysis for parasites and infection - a complete blood count and chemistry panel - urinalysis and urine culture - abdominal and thoracic radiography, and abdominal ultrasonography. - In some cases, particularly when neoplasia is suspected, proctoscopy or colonoscopy with biopsy may be indicated.

Question 27

What are the treatment options for rectal prolapses?

Answer 27

If the rectal tissue remains vital: - Gentle pressure is placed on the lubricated, protruding mass until the prolapse is reduced, and a nonabsorbable monofilament purse-string suture is inserted at the mucocutaneous junction and tied loosely (e.g., over a syringe case or finger), The suture is kept in place for 3 to 5 days to prevent recurrence and to allow time to treat the underlying condition. - If that is not successful, colopexy can be an additional treatment If the rectal tissue devitalized or cannot be reduced: - Rectal resection and anastomosis. The prolapsed tissue is transected 1 to 2 cm from the anus, caudal to the stay sutures (Figure 94.13). The two ends are anastomosed with a single layer of simple interrupted, synthetic, absorbable monofilament sutures. Sutures are placed full thickness to ensure that the submucosa is included in each bite.

Question 28

What is the three most common tumors of the perianal region?

Answer 28

a. perianal (circumanal) gland adenoma (most common) and adenocarcinoma b. apocrine gland anal sac adenocarcinoma

Question 29

what concurrent condition can be associated with perianal adenomas in female dogs?

Answer 29

Hyperadrenocorticism (with the adrenal gland the source of androgenic stimulation)

Question 30

What are the three most common types of colorectal tumors?

Answer 30

a. adenocarcinoma (most common) b. leiomyoma c. leiomyosarcoma (More than 50% of colorectal tumors are malignant)

Question 31

what is the most common rectal tumor in cats?

Answer 31

Lymphosarcoma

Question 32

What is the two main processes of fecal incontinence?

Answer 32

a. Reservior incontinence – failure of the colon and rectum to adapt to and contain their contents. Affected animals sense the urge to defecate but lose voluntary inhibition of the act, with subsequent passage of soft, unformed, or liquefied feces b. Sphincter incontinence – failure of the anal sphincter mechanism to resist the propulsive forces in the rectum, and feces are passed involuntarily, with a lack of awareness by the animal. (both this has to function for fecal continence)

Question 33

List the possible causes of reservoir incontinence

Answer 33

a. colorectal disease, such as colitis, proctitis b. neoplasia c. surgical excision of parts of the rectum

Question 34

list the possible causes of sphincter incontinence

Answer 34

Nonneurogenic causes: - severe perianal disease - rectal prolapse - accidental and iatrogenic anorectal and perineal trauma - perianal fistulas - perineal hernia. Neurogenic causes: - damage to the S1-S3 spinal cord segment, pudendal nerves, caudal rectal nerves, or pelvic plexus or pelvic nerves - central nervous system disease - peripheral neuropathies.

Question 35

What surgical circumstances may result in fecal incontinence post-op?

Answer 35

a. if more than 4 cm of the rectum is excised b. if the terminal 1.5 cm of the rectum is excised c. if the perineal nerves are damaged d. if more than half of the anal sphincter is damaged or removed.

Question 36

Give examples of sphincter enhancing procedures

Answer 36

a. use of a fascial sling b. silicone elastomer c. dynamic myoplasty (transposition of semitendinosus. Sartorius muscle has also been used)

Question 37

what is the cause of possible hypercalcemia and hypophosphatemia in animals with apocrine gland adenocarcinomas?

Answer 37

a paraneoplastic pseudohyperparathyroidism from secretion of a substance with biologic activity similar to parathyroid hormone (Seen in 27 % of cases in the largest study reported.)

Question 38

list the negative prognostic factors for apocrine gland adenocarcinomas

Answer 38

a. larger tumor size with tumors larger than 2.5 cm having a poorer prognosis b. presence of lymph node metastasis and/or presence of distant metastasis c. advanced clinical stage i. renal failure secondary to hypercalcemia d. E-cadherin expression (canser biomarker) e. not performing surgery f. treatment with chemotherapy alone g. no therapy.

Question 39

What is the medical management of perianal fistulas?

Answer 39

a. topical application of antibiotics, corticosteroids, or chlorhexidine rinses; b. systemic antibiotics if necessary c. clipping hair from the perianal region d. tail braces. e. As well as immunosuppressive medicines: i. Cyclosporine ii. Ketoconazole and Cyclosporine iii. Glucocorticoids iv. Tacrolimus v. Azathioprine-Metronidazole

Question 40

What are the surgical options for perianal fistulas?

Answer 40

a. direct surgical excision of sinuses and fistulous tracts (recommended treatment) b. anal sacculectomy c. cryosurgery d. surgical debridement with chemical cauterization e. high tail amputation f. deroofing and fulguration of diseased tissue g. laser excision

Question 41

List the different perineal hernias. Which is the most common one?

Answer 41

a. Caudal – between the levator ani, internal obturator and external sphincter muscle (most common) b. Dorsolaterally – between the coccygeus and levator ani muscles c. Ventral – between the ischiourethralis, bulbocavernosus, and ischiocavernosus muscles d. laterally – between the coccygeus muscle and the sacrotuberous ligament (also known as sciatic perineal hernia)

Question 42

what is the boarders of peritoneum and what makes up the perineal diaphragm?

Answer 42

a. Boarders: 3rd caudal vertebra dorsally, sacrotuberous ligament laterally and ishial arch ventrally. b. The perineal diaphragm is the principal structure of the perineum and consists of the supporting structures of the pelvic outlet, including the levator ani and coccygeus muscles and perineal fascia, and the external anal sphincter

Question 43

List the surgical techniques for perineal hernia repair

Answer 43

a. Traditional herniorrhaphy b. transposition of the internal obturator muscle c. Transposition of the superficial gluteal d. Transposition of the semitendinosusmuscle e. Prosthetic implants - Polypropylene and polypropylene-poliglecaprone mesh. (Orientation of the mesh is important, because polypropylene mesh will accommodate a significantly higher load and energy to yield when its longitudinal cords are oriented parallel to the tension axis.) f. biomaterials - Porcine small intestine submucosa - Porcine dermal collagen - Autogenous fascia (facia lata and vaginal tunic) This procedures can be combined with organopexies: colopexy, cystopexy and/or Vas deferensopexy

Question 44

What vital structures has to be avoided during perineal surgery?

Answer 44

a. Internal pudenal nerve b. Caudal rectal vessels c. Caudal rectal nerve

Question 45

List preexisting or concurrent condition that can lead to perineal hernia in cats

Answer 45

a. recent perineal urethrostomy (25% of cats) b. megacolon c. perineal masses d. chronic fibrosing colitis e. trauma f. recent postpartum state g. cutaneous asthenia