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Tobias full > Rectum, Anus and Perineum > Flashcards

Rectum, Anus and Perineum Flashcards

1
Q

What is unique about the resting membrance potential in GI smooth muscle cells?

A

The resting membrane potential is not constant. It oscillates in slow waves over time, generated by pacemaker cells called the interstitial cells of Cajal

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2
Q

How many bacteria are there per gram of faeces?

A

10^9 bacteria per gram of faeces
- Up to 90% anaerobes

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3
Q

What periop ABx are suitable?

A
  • 2nd gen cephalosporins
  • Aminoglycoside + Beta-lactam or clindamycin
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4
Q

List the approaches to the rectum

A
  • Ventral +/- symphysiotomy or bilateral pubic and ischial osteotomy (cranial rectum and colorectal junction)
  • Dorsal (caudal to mid-rectum)
  • Lateral (small focal lesion, not commonly used)
  • Caudal (eversion, trancutaneous rectal pull through, transanal rectal pullthrough, Swensons pullthrough)
  • Combined abdominal transanal approach
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5
Q

List Tx options for an anal stricture

A
  • Faecal softeners
  • Balloon dilatation or bougienage
  • Resection and anastomosis
  • Z-plasty
  • Radial incisional anoplasty (+/- transverse closure)
  • Circumferantial anoplasty
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6
Q

What has been shown to increase the risk of faecal incontinence?

A
  • Resection of 6cm of rectum
  • Removal of distal 1.5cm of rectum
  • Removal of more than half the circumference of external anal sphincter
  • Damage to perineal nerves
  • Resection of the peritoneal reflection
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7
Q

List the 4 types of atresia ani

A
  • Type 1 - Stenosis of the anus
  • Type II - Persistance of anal membrane with rectum ending as blind sac immediately cranial to imperforate anus
  • Type III - Imperforate anus but the rectal sac is further cranial
  • Type IV - Anus and terminal rectum can develop normally but the cranial rectum ends as a blind pouch within pelvic canal
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8
Q

What are potential complications associated wth atresia ani?

A
  • Established megacolon, potentially requiring subtotal colectomy
  • Inability to provide normal faecal continence
  • Development of anal stricture
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9
Q

What is rectovaginal/urethrorectal fistula?
What are they often associated with?

A
  • Failure of the developing urorectal septum to seperate the cloaca
  • Commonly assoc with atresia ani, particularly type II
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10
Q

What are the Tx options for a rectovaginal fistula?

A
  • Transverse incision between anus and vulva to isolate the fistula to resect the fistula, close the assoc defects and correct the atresia ani
  • Transection of the rectum cranial to the fistula, fistulous section resected and rectum sutures to anus
  • Transection of fistulous tract near the vagina and then use the distal rectal portion for reconstruction of the anus

Prognosis is good :)

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11
Q

What is an anogenital cleft?

A

Rare condition in which urine and faeces enter a common cavity and body opening (cloaca)

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12
Q

What other diseases may be seen concurrently with perianal adenoma?

A
  • Perineal hernia (10%)
  • Testicular tumours
  • Hyperadrenocorticism (source of androgen for females)
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13
Q

What % of rectal tumours are incorrectly diagnosed based on endoscopic biopsy?
What it the most common colorectal tumour?

A
  • 1/3 incorrectly diagnosed
  • Adenocarcinoma most common in dogs, LSA in cats
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14
Q

What are the three forms of rectal adenocarcinoma?

A
  • Pedunculated
  • Cobblestone
  • Infiltrative (classic ‘napkin-ring’)

Pedunculated and cobblestone have a good prognosis with surgical resection. Infiltrative/annular poor prognosis

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15
Q

What cell type do GISTs arise from?

A

The interstitial cells of Cajal

Can be differentiated from leiomyosarcoma on IHC with CD117

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16
Q

List some paraneoplastic syndromes which can be seen with rectal neoplasia?

A
  • Adenomatous polyps - Leucocytosis
  • Eosinophilic masses - eosinophilia, neutrophilia, hypocholesterolaemia, hypoalbuminaemia
  • Leiomyosarcoma - hypoglycaemia
  • Secretory plasmacytomas - Hyperproteinaemia, monoclonal gammopathy
17
Q

List alternative therapies for anal and rectal tumours

A
  • NSAIDs
  • Immunosuppresive medications for inflammatory polyps
  • Pred and ivermectin (eosinophilic masses)
  • Chemotherapy (MST 2532d vs 70d for rectal lymphoma in dogs)
  • Orthovoltage irradiation
  • Colostomy
18
Q

What is the MST of rectal tumours according to morphology?

A
  • Pedunculated 32m
  • Nodular or cobblestone 12m
  • Annular 1.6m
19
Q

What it the most common location for rectal perforation?

A

Within the caudal 4cm leading to focal retroperitoneal infection

20
Q

What are surgical options for faecal incontinence?

A

Sphincter-enhancing procedures
- Semitendinosus muscle flap
- Rotation of rectum 225 degrees before anastomosis
- Implantation of polyester-impregnated silicone elastomer ring
- Sartorius muscle transposition
- Free neuromicrovascular transfer of t=latissimus dorsi

21
Q

What % of AGASACA express COX-2?
What molecule has been associated with a shorter survival?
What % of cases have paraneoplastic hypercalcaemia?

A
  • 100%
  • Decreased expression of e-cadherin assoc with shorter survival
  • 27% hypercalcaemia (20-90%)
22
Q

List the stages of AGASACA and their associated MST

A
  • Stage 1 - Tumour under 2.5cm, no mets. MST 40m
  • Stage 2 - Tumour over 2.5cm, no mets. MST 24m
  • Stage 3a - LN under 4.5cm. MST 15-16m
  • Stage 3b - LN over 4.5cm. MST 10-11m
  • Stage 4 - Distant mets. MST under 3m
23
Q

Where is the most common location for a perineal hernia in dogs?

A

Between external anal sphincter and levator ani

24
Q

What anatomical difference is there regarding the perineum in dogs and cats?

A

Cats do not have a sacrotuberous ligament

25
Q

What is the effect of castration on recurrence of perineal hernias?

A

Castration reduced recurrence from 43 to 23%
Risk of recurrence in intact male dogs is 2.7x greater

26
Q

How may benign prostatic hyperplasia be assoc with perineal hernias?

A
  • Prostate gland is the primary site of relaxin synthesis
  • Muscles of pelvic diaphragm with perineal hernia has higher expression of relaxin receptors

25-59% of dogs with perineal hernia have concurrent prostatic disease, 69.7% have testicular abnormalities

27
Q

List the surgical options for perineal hernias

A
  • Traditional herniorrhaphy
  • Internal obturator muscle transposition
  • Superficial gluteal muscle transposition
  • Semitendinosus muscle transposition
  • Prosthetic implants
  • Biomaterials (Porcine SIS, Porcine dermal collagen, autologous fascia)
  • Organopexy (colopexy, cystopexy, vas deferensopexy)
28
Q

List potential post-op complications after perineal hernia repair

A
  • SSI 6-43%
  • Faecal incontinence 0-33%, permanent 10-15%
  • Sciatic nerve injury - less than 5%. (If permanent - talocrural arthrodesis, long digital extensor muscle transfer to vastus lateralis, amputation)
  • Urinary tract complications - 0-15%
  • Tenesmus 4-43%
  • Rectal prolapse 0-17%
  • Recurrence 0-70% (10-48 traditional, 0-36 internal obturator, 36 superficial glut)
29
Q

List some unique features of perineal hernias in cats

A
  • Larger proportion are female
  • Bilateral disease more common
  • Perineal swelling less common (22.5%)

Tobias full (110 decks)

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