Rectum, anus and perineum Flashcards
Name 3 complications that occurred following perineal hernia repair with incorporation of the sacrotuberous ligament as per Cinti 2021 in Vet Surg. What factors were associated with an increased risk of complications?
Temporary tenesmus, wound swelling, wound dehiscence.
(These were all minor. No recurrence reported.)
Age and treatment of recurrent hernia were associated with an increased risk of complications.
Name the following structures in the diagram from Bitten 2020 in Vet Surg.
In a study by Ahlberg 2024 in JAVMA, what surgical technique for perineal hernia repair was found to be non-inferior to use of an internal obturator transposition flap?
A fascia lata graft
In a study by Carbonell Rossello 2023 in JSAP, what technique was used for perineal hernia repair?
Combined internal obturator and superficial gluteal transposition.
Recurrence in this cohort of 17 dogs was 0%. Partial superficial dehiscence of the T-shaped incision occurred in 5 dogs.
In a study by Salonen 2024 in VRU, did caudal rectal dimensions on CT return to normal after surgical repair of perineal hernia (either IOT or fascia lata graft) in dogs? Did prostate position change?
No - caudal rectal dimensions remained unchanged. Intrapelvic dimensions actually increased after surgery, although the rectum was straighter than prior.
The prostate position did not change, however the volume and number of prostates with cysts did reduce (dogs were castrated at the time of hernia repair).
In a study by Ahlberg 2022 in VRU, what changes to the prostate were identified in dogs with perineal hernia (6)?
Increased size, greater presence of cysts, larger cysts, paraprostatic cysts (17%), focal mineralization (33%), abnormal rotation and location.
In a study by Hubers 2022 in JSAP, what percentage of cats had a good outcome following perineal hernia repair with internal obturator transposition? Were neutered or intact patients more common?
74% (16% had a poor outcome, 3 of which had recurrence).
Tenesmus was a common short term complication which resolved in 75% of cases.
All patients were neutered (67% male, 33% female).
In a study by Griffin 2023 in JAVMA, what was the overall post-op complication rate following anal sacculectomy for massive AGASACA in dogs? What was the OST? What factor was associated with OST?
36% post-op complication rate (no permanent fecal incontinence, tensemus or anal stenosis). Local recurrence occurred in 37% of dogs.
OST was 671 days.
Nodal metastasis at the time of surgery was associated with decreased OST (also more likely to develop new metastasis [both LN and distant]).
In a study by Schlag 2020 in JSAP, what 3 factors were strong predictors of metastasis for AGASACA at presentation?
Primary tumour size, tumour stage (based on rectal or CT scan), and vascular invasion.
In a study by Sutton 2022 in JSAP, what was the prevalence of iliosacral lymphadenomegaly in dogs with AGASACA? What was the percentage of dogs with pulmonary metastasis?
71% of cases had local metastatic disease characterized by iliosacral lymphadenomegaly.
11% of dogs had pulmonary metastasis (no dogs had pulmonary metastasis without concurrent lymphadenomegaly).
In a study by Jimeno Sandoval 2022 in JSAP what was the most common post-operative complication in cats undergoing anal sacculectomy for non-neoplastic anal sac disease?
Short term defecatory complications. No permanent fecal incontinence or long term complications were recorded.
In a study by Swan 2021 in VRU, what was the MST for dogs undergoing stereotactic body radiation therapy for AGASACA?
991 days
All patients developed acute effects including mild colitis, alopecia, and erythema. Late effects included alopecia, variable dermal pigmentation and leuko- or melanotrichia, and rectal stricture in one patient
In a study by Cantatore 2022 in Vet Surg, what was the rate of recurrence following submucosal resection of epithelial rectal tumors? What 2 factors were associated with an increased risk of recurrence? What was the MST?
Rate of recurrence following submucosal resection was 21%.
Two factors associated with recurrence were incomplete margins and presence of complications.
MST was not reached (although survival was improved for benign tumours rather than carcinomas). Recurrence was associated with an increased risk of death.
In a study by Meric 2023 in JVIM, what breed was at increased risk for colorectal polyp formation? What was the MST for patients undergoing colorectal polyp excision? What two factors were related to increased likelihood of recurrence?
West highland white terriers were 20 x more likely to have colorectal polyps.
Median survival time was not reached.
Increased polyp size and west highland white breed were associated with shorter time to recurrence.
What is the rough anatomic location of the rectoanal junction?
Ventral to the second or third caudal vertebra.
What are the layers of the rectum?
Mucosa, submucosa, muscularis, serosa. The retroperitoneal portion of the rectum lacks a serosa.
What is the main vascular supply to the terminal colon and rectum?
Cranial rectal artery. The middle and caudal rectal arteries (branches of the internal pudendal) supply variable and relatively insignificant amounts.
Due to the variable blood supply to the intrapelvic rectum the cranial rectal artery should be preserved during rectal resections unless the intrapelvic rectum is to be removed. In cats the intrapelvic blood supply appears more robust.
What are the zones of the anal canal and anus?
Anorectal line separates the stratified squamous epithelium of the rectum from the simple columnar epithelium of the anus.
The intermediate zone contains the anocutaneous line which separates the boundary between the mucous membrane and skin.
The cutaneous zone has internal (where the anal sacs open) and external zones (hairless zone surrounding the anus).
What is the vascular supply to the anus?
Caudal rectal arteries (branches of the internal pudendal). Venous drainage is via the caudal rectal and perineal veins (to the caudal vena cava), and cranial rectal vein (to the portal system).
To which lymph nodes do the lymphatics of the anal canal drain?
Sacral lymph nodes +/- medial iliac and internal iliacs.
Where are the anal sacs located?
Between the inner smooth and outer striated sphincter muscles of the anus.
What structures make up the pelvic diaphragm?
The pelvic fascia (convergence of fascia from the tail, pelvic region and thighs), paired coccygeus and levator ani muscles, external anal sphincter.
What are the glands of the anus and perineum?
Circumanal (regress in female dogs), paranal sinus (glands of the anal sac), anal glands proper (produce stable mucous coat for formed feces).
What is the muscular composition of the internal and external anal sphincter muscles?
Internal: smooth muscle, under involuntary control.
External: striated muscle, under voluntary control. Dorsal aspect is twice as thick as the ventral aspect.
What is the function of the rectococcygeus muscle?
Attaches to the fifth and sixth caudal vertebrae. Prevents the anal canal and rectum from being pulled cranially, and can also pull the rectum caudally during defecation.
What is the innervation to the rectum?
Pelvic nerve (S1-S3), parasympathetic: Inhibitory to the internal anal sphincter, excitatory to the rectum.
Hypogastric nerve (caudal mesenteric ganglion), sympathetic: Excitatory to the internal anal sphincter, and inhibitory to the rectum.
Pudendal nerve (caudal rectal branch), supplies voluntary motor innervation to the external anal sphincter. Perineal branch supplies sensory innervation.
How is bowel preparation performed prior to rectal surgery?
Feeding of a low-residue, high caloric diet for 2-7 days pre-operative, ideally enemas are not performed on the day of surgery (due to liquification of faeces, unless proctoscopy is to be performed). The terminal rectum should be digitally evacuated and the anal sacs expressed prior to surgery.
The use of preoperative mechanical bowel cleansing and antimicrobials is controversial, but antimicrobials may be of benefit.
What proportion of fecal bacteria are anaerobic?
90%. Remaining 10% a combination of aerobic gram positive and negative bacteria.
What prophylactic antimicrobial regimens have been recommended for use prior to rectal surgery in dogs?
Second generation cephalosporin (cefoxitin), or first generation cephalosporin (cefazolin)/beta lactam (ampicillin) and aminoglycoside (gentamicin) or clindamycin.
Enteral antimicrobials have also been used, such as neomycin and metronidazole.
Excision of what proportion of the rectum tends to produce excessive tension on the suture line?
Greater than 1/3 of the length of the rectum due to the short mesocolon limiting caudal mobilization in dogs. The rectum in cats is more mobile and this may be less of an issue.
What surgical approach to the rectum can be used to access to tumours in the cranial rectum or colorectal junction?
Ventral approach with 2cm margins.
Can be combined with pelvic symphysiotomy, pubic osteotomy, or bilateral pubic and ischial osteotomies for greater exposure to the intrapelvic rectum.
If there is tension on closure of a rectal anastomosis what closure is recommended?
Two layer appositional closure; first layer incorporating the mucosa and submucosa with the knots intraluminal, the second layer incorporating the serosa, muscularis and submucosa. Alternatively an EEA stapling device can be used.
What muscles require elevation when performing a pubic osteotomy?
Adductor muscles.
What surgical approach to the rectum can be used to access to tumours in the caudal to mid rectum?
Dorsal approach
Care must be taken not to damage the pelvic nerve plexus which fans along the lateral aspect of the rectum in the peritoneal reflection.
What surgical approach to the rectum might be reasonable to small, focal lesions of the caudal rectum (rectal diverticulum, rectocutaneous fistula, laceration, etc)?
Lateral approach.
Care must be taken not to damage the caudal rectal nerve during dissection.
What are the different caudal surgical approaches to the rectum?
- Anal approach via rectal eversion: small, superficial, benign tumours in the caudal to mid rectum.
- Transcutaneous rectal pull through procedure: lesions in the caudal to mid rectum. Dissection continued until a 1-2 cm margin if grossly normal tissue is achieved. Rectum is sutured to the skin in either 1 or 2 layers.
- Transanal rectal pull-through procedure: lesions in the caudal (incision started 1-2 cm cranial to the anocutaneous junction) to cranial (rectum everted and incision started more cranially) rectum.
- Combined abdominal transanal approach: tumours of the mid to cranial rectum that extend to the distal colon.
When might a linear stapling device be used for resection of rectal masses via rectal eversion?
Can be used for superficial tumours in the caudal third of the rectum with an attachment less than 3cm.
During a ventral approach to the rectum with a pelvic symphysiotomy, what percentage retraction of the pelvis is tolerated prior to SI luxation?
25%. Retraction of 50-70% results in unilateral SI luxation.
What are some complications of colorectal resection?
Hematochezia, dyschezia (few days to 2 weeks), tenesmus (1-2 months, may be prolonged in cases of stricture), dehiscence (increased risk with resections >6cm), fecal incontinence (typically resolves within 5-10 days).
Lameness and neurologic dysfunction may occur with symphyseal retraction. Non-union of osteotomy sites also reported.
What are some potential causes of stricture following colorectal resection?
Excessive tension or inflammation, inadequate blood supply, partial dehiscence, improper anastomosis, poor choice of suture, localized infection.
What are some treatment options for stricture following colorectal resection?
Balloon dilation, bougienage, surgical incision of the constricting band, resection and anastomosis.
If stricture involves the anus only, treatment may involve radial incisional anoplasty, Z-plasties, circumferential anoplasty +/- excision of the entire rectocutaneous junction.
What factors might contribute to fecal incontinence following colorectal resection?
Iatrogenic damage to the caudal rectal nerve, external anal sphincter, or cranial rectal peritoneal reflection, or resection of a large portion of the rectum (reduced reservoir capacity).
What are the four types of atresia ani?
Type 1: congenital stenosis.
Type 2: persistence of the anal membrane with the rectum ending immediately cranial to the imperforate anus.
Type 3: blind end of the rectum is situated further cranially.
Type 4: rectum ends as a blind pouch within the pelvic canal.
What are the clinical signs associated with atresia ani?
Type 1: normal until weaning.
Types 2-4: normal for the first 2-4 weeks of life, before becoming unthrifty and developing abdominal enlargement.
What are the surgical treatment options for atresia ani?
Type 1: gentle bougienage or balloon dilatation.
Types 2, 3: Incision over the anal dimple with mobilization of the rectum and suturing to the skin.
Type 4: may require an abdominal approach for adequate rectal mobilization.
What are some complications associated with correction of atresia ani?
Continued stricture (type 1 may need repeat balloon dilation or bougienage), irreversible megacolon necessitating subtotal colectomy, permanent fecal incontinence due to damage to the external anal sphincter or nerve innervation.
Rectovaginal or urethrorectal fistulas are commonly associated with which type of atresia ani?
Type 2. More common in dogs than cats
What imaging technique is useful for diagnosis of rectovaginal or urethrorectal fistulas?
Rectovaginal: positive contrast vaginal or rectal radiography.
Urethrorectal: retrograde contrast urethrography (+/- fluoroscopy).
Urinalysis and culture with abdominal radiography or ultrasonography should also be performed for detection of UTI or bladder calculi.
What are surgical treatment options for rectovaginal or urethrorectal fistulas?
Rectovaginal: primary transection, rectal pull through cranial to fistulous location, use of the fistula to reconstruct the anal canal and anus.
Urethrorectal: transection via a pubic symphysiotomy, pubic osteotomy, or perineal approach.
Concurrent neutering is recommended due to suspected heritable component.
What are some potential complications associated with rectovaginal or urethrorectal fistulas?
UTI, dehiscence, fecal incontinence, tenesmus, obstipation, rectal prolapse, anal stenosis, perianal edema.
What condition is depicted?
Anogenital cleft. Mucosa of the anus or rectum and vestibule are continuous along the perineal raphe. Commonly results in fecal incontinence, soiling of the perineum, perineal irritation, ascending UTIs and pyelonephritis.
What condition is common in male patients with anogenital cleft?
Hypospadias.
What are the two types of anal/rectal prolapse?
Partial: only the anal mucosa protrudes.
Complete: all layers protrude.
What are some predisposing factors for anal/rectal prolapse?
Weakness of the perirectal and perianal supporting tissues, uncoordinated peristaltic contractions, excessive straining, and inflammation and edema of the rectal mucosa.
What diagnostics should be performed for the work-up of anal/rectal prolapse?
Fecal analysis, CBC/biochem, urinalysis culture, abdominal and thoracic radiography, and abdominal ultrasonography. In some cases, particularly when neoplasia is suspected, proctoscopy or colonoscopy with biopsy may be indicated.
What are treatment options for rectal prolapse?
- Topical treatment with 50% dextrose +/- furosemide and manual reduction. Placement of purse-string for 3-5 days. Use of low-residue diet and lactulose (+/- retention enemas with hydrocortisone).
- Colopexy in recurrent cases.
- Resection and anastomosis if unable to be reduced.
What are some potential complications associated with rectal resection and anastomosis for rectal prolapse?
Incontinence, dehiscence, leakage, recurrence of the prolapse, and anorectal strictures (particularly in cats).
What is the most common perianal tumor?
Perianal adenoma (affecting the circumanal glands). Cocker spaniels are predisposed. Usually older male entire dogs.
Concurrent testicular interstitial cell tumours are common. Perineal hernia present in 10% of cases.
In what percentage of male dogs is excision of perianal adenoma curative?
90%.
Castration may result in complete resolution of small lesions.
What is the most common malignant tumour of the perianal region?
Perianal adenocarcinoma. Typically affects male intact dogs weighing more than 35 kg.
German shepherds and arctic dog breeds might be predisposed.
Are perianal adenocarcinomas hormonally dependent?
No, do not tend to display hormone dependent growth.
What percentage of perianal adenocarcinomas have metastatic disease at the time of diagnosis?
15% to the sublumbar lymph nodes.
Metastasis to the lungs, liver, spleen, kidney and bone also reported. Hypercalcemia is seen in some cases.
How much is the risk for tumour related death for perianal adenocarcinoma increased with tumours >5cm?
11-fold.
45-fold increase for tumours with metastasis. MST with confirmed metastasis is 7-months.
How does stage affect prognosis for dogs with perianal adenocarcinoma?
Increasing stage worsens prognosis (T1, tumour less than 2cm = 2 year survival of 75%, compared to T4, invasive tumour = MST 6-12 months).
What surgical procedures are described for excision of perianal adenocarcinoma?
En bloc excision with or without anoplasty and excision of lymph nodes affected by metastasis. Ideally 1-3 cm of normal tissue is included around the tumour. Concurrent castration is recommended.
Are perianal adenocarcinomas radiation responsive?
No, although adjuvant chemotherapy has been described.
What are some complications associated with perianal adenocarcinoma excision?
Hemotochezia, tenesmus, dehiscence, fecal incontinence.
Are malignant melanomas and SCC of the perianal region typically more or less aggressive than other locations?
More aggressive, associated with a poor prognosis.
What percentage of colorectal tumours are malignant? What are the most common types?
50% are malignant.
Adenocarcinoma, followed by leiomyoma and leiomyosarcoma are the most common types.
Male large breed dogs are overrepresented.
In what percentage of cases do carcinoma in situ rectal polyps progress to malignancy?
17-50%.
Carcinoma in situ is when the polyp invades the lamina propria and submucosa but not the basement membrane.
Polyps that measure greater than 1cm have a greater potential for malignancy. Colonoscopy useful in determining extent +/- obtaining biopsies.
What is the reported survival of patients with carcinoma in situ?
5-24 months following excision. 55% recurrence reported (compared to 17% for adenomatous polyp).
Are rectal tumours more common in males or female dogs?
Male large breed dogs. German shepherds and poodles predisposed.
Is rectal adenocarcinoma more or less aggressive than small intestinal adenocarcinoma?
Less aggressive. Metastatic rates vary from 0-80%.
The infiltrative annular (rather than pedunculated) form has a poor prognosis. Good survival times are reported with resection of pedunculated tumours.
What is the MST for rectal lymphosarcoma in cats?
1697 days
How far are most rectal tumours located from the anus?
3-8 cm, making digital rectal examination very useful.
What tests should be included in the diagnostic work-up of colorectal tumours?
CBC, biochemistry, urinalysis (hypoglycemia sometimes observed with leiomyosarcoma, leukocytosis with adenomatous polyps), abdominal and thoracic radiography +/- contrast, ultrasonography (+/- intrarectal to assess tumour and lymph node involvement), endoscopy, CT.
What percentage of endoscopic biopsies collected from colorectal tumours give an incorrect histologic diagnosis?
Up to 30%.
What is the survival time after local excision of adenomatous polyps?
> 2 years, 17% recurrence. 2cm margins are recommended to prevent recurrence. Can be full-thickness or submucosal.
Use of cryosurgery on the base of the lesion may help to prevent recurrence.
What percentage of rectal tumours express COX?
38% COX-1 positive, 38% had occasional COX-2 expression, 20% negative.
NSAIDs have been used both palliatively and therapeutically.
What was the MST for dogs with rectal lymphoma receiving chemotherapy (CHOP)?
2532 days (compared to 70 days without).
What are the reported MST for rectal adenocarcinoma?
32 months for pedunculated mass, 12 months for nodular or cobblestone masses, 1.6 months for annular lesions. 5 cm resection margins are recommended but not always achievable.
What is the MST for smooth muscle tumours of the rectum?
MST 21 months (75% 1-year survival)
What diagnostics might be useful in the work-up of anal stricture?
Rectal examination, proctoscopy, contrast radiography, CT. Biopsy is prudent to rule out neoplastic disease with annular lesions.
What factors can cause fecal incontinence after rectal surgery?
Resection of >4cm of the rectum, resection of the terminal 1.5cm of the rectum, damage to the perineal nerves, or if >50% of the anal sphincter is damaged or removed.
What are some medical management options for managing fecal incontinence?
Low-residue diet, use of opioids to slow fecal transit time, induced defecation by administration of enemas and rectal stimulation.
What are some surgical management options for managing fecal incontinence?
Few clinical reports, but include sphincter enhancing procedures (fascial sling, silicone elastomer, dynamic myoplasty).
What are the three most common non-neoplastic diseases of the anal sac?
Impaction, sacculitis (with or without concurrent obstruction), abscessation.
Uncommon in cats, suspected due to less viscid secretions.
What are the indications for surgical excision of the anal sacs for non-neoplastic disease?
Recurrent episodes of impaction; chronic sacculitis and abscessation; failure of an anal sac abscess to resolve following incision, drainage, culture and lavage; development of anal sac sinuses; failure of medical therapy.
Is the risk for AGASACA higher in male or female dogs?
Male dogs, neutered animals at increased risk (1.4:1). Spaniel breeds appear predisposed.
What proportion of AGASACA express KIT and COX?
3% express KIT, 20% express PDGF-B. This provides a biologic basis for use of receptor tyrosine kinase inhibitors.
100% express COX.
A lower expression of E-cadherin was associated with deceased MST.
In what percentage of dogs is AGASACA an incidental finding on routine rectal examination?
7-39%.
What is the mechanism behind hypercalcemia seen with AGASACA? In what percentage of dogs is this seen?
Secretion of a substance with biologic activity similar to parathyroid hormone.
Seen in 20-90% of affected dogs.
What was the reported metastatic rate of AGASACA at the time of presentation?
36-96%. Most commonly to the sublumbar lymph nodes. Size on ultrasonography is associated with the risk of metastasis.
Pulmonary metastasis in 16-53% of cases.
What are treatment options for hypercalcemia in patients with AGASACA?
Diuresis with 0.9% saline +/- furosemide to prevent calcium reabsorption.
What is the MST following excision of AGASACA?
16-18 months
Adjunctive chemotherapy, radiation and toceranib may improve survival.
MST of radiation alone reported to be 657 days. Chemotherapy alone 212 days. Combination of surgery, radiotherapy and mitoxantrone MST 956 days.
What was the response rate of AGASACA to toceranib?
88% (partial response in 25%, stable disease in 63%). Thought to be due to inhibition of PDGFR-B.
What is the rate of recurrence of AGASACA post-operatively?
29-45%
What are some post-operative complications reported following removal of AGASACA?
Recurrence (29-45%), infection (7%), fecal incontinence (19-33%), persistent or recurrent hypercalcemia (35-50%).
What are negative prognostic indicators associated with AGASACA removal?
Larger tumor size (tumours >2.5cm having poorer prognosis), presence of lymph node metastasis, presence of distant metastasis, advanced clinical stage, E-cadherin expression, not performing surgery, treatment with chemotherapy alone, and no therapy.
86% of tumours larger than 5cm will have lymph node metastasis at the time of diagnosis.
What is the simplified staging system that has been described for AGASACA?
Is anal sac neoplasia common in cats?
No.
61% are female.
Hypercalcemia is uncommon.
What is the MST for cats with AGASACA?
MST 3 months (metastasis in only 15% indicating that aggressive local disease is more important).
What sacculectomy technique is depicted?
Closed
What sacculectomy technique is depicted?
Open
What are some disadvantages of the open sacculectomy technique?
Trauma to the external anal sphincter, risk of infection from contamination by anal sac contents, risk of dissemination of tumour.
What are some complications associated with anal sacculectomy?
Intraoperative: hemorrhage, rectal perforation, nerve trauma.
Short term: scooting, inflammation, bruising, drainage, infection, dehiscence, seroma, tenesmus, dyschezia, constipation.
Long term (1-15%): licking of the surgery site, fecal incontinence, sinus/fistula development, stricture formation.
What is the percentage of dogs that suffer from problems with defecation (particularly incontinence) following bilateral anal sacculectomy?
3 - 15%. Typically resolve within 10 days.
Fecal incontinence persisting for longer than how many months is unlikely to resolve?
3-4 months.
Are formation of persistent draining tracts more common after open or closed anal sacculectomy?
Open
What breed of dog is most commonly affected by perianal fistula?
Middle aged, German shepherds
What are the proposed etiologies of perianal fistula?
Anatomic: low tail carriage, deeply situated anal sacs.
Infectious: abscessed anal glands, impaction of anal sinuses/crypts, microabscess formaton, inflammation of aprocrine glands (German shepherds have a higher concentration), infection of hair follicles.
Immune: inflammation characterized by infiltration of large numbers of lymphocytes, macrophages and plasma cells. Disease also responsive to immunosuppresive therapy.
Endocrine.
What are the medical management options for perianal fistula?
Topical application of antibiotics, corticosteroids or chlorhexidine rinses; systemic antimicrobials; clipping of the hair; tail braces.
Additional immunosuppressant therapy recommended:
- Cyclosporine (5mg/kg q12 tapering dose): resolution in 70-100% of cases. Can be combined with anal sacculectomy and tract resection if lesions do not completely resolve.
- Ketaconazole and cyclosporine: ketaconazole affects cyclosporine metabolism lowering dose requirements (75% lower).
- Glucocortioids (tapering dose): improvement in 1/3 of dogs, no change in 1/3.
- Tacrolimus: 10-100 times as potent as cyclosporine. Usually administered topically twice daily in conjunction with other immunosuppressants.
- Azathioprine-metronidazole: more economical than cyclosporine and few side effects. Rarely results in resolution but may make lesions more amenable to surgery.
What are the surgical treatment options for perianal fistula?
Excision of fistulous tracts with bilateral anal sacculectomy +/- partial or complete anoplasty (may result in fecal incontinence).
Can be combined with pre-operative immunotherapy to improve outcomes.
What are the complications associated with surgical treatment of perianal fistulas?
Wound dehiscence (14-50%), stenosis/stricture (14%), flatulence, fecal incontinence (20-33%), recurrence (17-56%).
Describe the perineal anatomy of the dog.
What is the most common location for perineal herniation?
Between the levator ani, internal obturator, and external anal sphincter (caudal perineal hernia).
Lateral, ventral and dorsolateral herniation are also described.
What is the origin and attachment of the sacrotuberous ligament?
Ischiatic tuberosity to the sacrum and first caudal vertebra.
It is not present in cats.
What are some proposed causes of perineal herniation?
- Rectal abnormalities: 100% of dogs with PH have rectal deviation, and 40% have dilatation. Thought to be a sequelae of PH, but increased straining could predispose to herniation.
- Androgens: risk of recurrence in intact males is 2.7 x greater than castrated males. Androgen receptors of the pelvic diaphragm muscles of lower quantity and sensitivity in dogs with PH.
- Gender related anatomic differences: females have larger, broader and stronger levator ani muscles, larger sacrotuberous ligaments, more cranial boundary to the peritoneal cavity.
- Relaxin: greater expression of relaxin receptors in the pelvic diaphragm of dogs with PH. Prostatic cysts contain high concentrations of relaxin and cystic hyperplasia is common in conjunction with PH.
- Prostatic disease: 25-60% of dogs with PH have concurrent prostatic disease. Testicular abnormalities (primarily seminomas and interstitial cell tumours) found in 70% of dogs with PH.
- Neurogenic atrophy of the levator ani and coccygeus muscles. Tenesmus is thought to provide traction on the sacral nerves.
What are the most common clinical signs associated with perineal hernia?
Unilateral or bilateral swelling, straining to defecate and constipation.
Which side is most commonly affected with perineal herniation?
Right side (59-84%).
50/50 unilateral and bilateral presentation.
What percentage of patients operated on unilaterally for perineal hernia develop a contralateral hernia within 1-3 years?
10%
What percentage of dogs with perineal herniation have bladder retroflexion?
20-30%. Can be diagnosed with retrograde constrast urethrocystography or ultrasound.
What diagnostic techniques are useful for evaluation of perineal hernation?
Rectal examination, abdominal radiography +/- urinary contrast studies, ultrasonography.
What are medical management options for treatment of perineal hernia?
Not recommended unless surgery is not an option. Involves high fiber diets, lactulose, periodic evacuation of feces, and application of counterpressure to the skin during defecation.
What are the goals of surgical treatment for perineal hernia?
Removal of fecal material from the rectum, return of herniated viscera to their normal position, closure of the hernia defect.
Castration via a scrotal or prescrotal incision should be performed concurrently.
What are the surgical options for repair of a perineal hernia?
Traditional herniorrhaphy, internal obturator muscle transposition, superficial gluteal muscle transposition, semitendinosus muscle transposition, prosthetic implants, biomaterials +/- organopexy and castration.
What surgical technique for repair of perineal hernia is depicted?
Traditional herniorrhaphy. Involves closure of the external anal sphincter to the levator ani/coccygeus and internal obturator (without elevation).
What is the cranial extent of elevation of the internal obturator during transposition?
Caudal edge of the obturator foramen to prevent damage to the obturator nerve.
Should the tendon of the internal obturator be transected medial or lateral to the point where it passes over the body of the ischium?
Medial to prevent damage to the sciatic nerve.
Which blood vessel needs to be preserved during semitendinosus muscle transposition for perineal hernia repair?
Caudal gluteal artery and vein (which are the major blood supply to the proximal half of the muscle).
What was the most common complication reported with the use of polypropylene or polypropylene-poliglecaprone mesh for perineal hernia repair?
Suture sinuses (resolved after removal of the offending suture).
Recurrence rates of around 10% reported when used alone or to augment internal obturator transposition.
What are some biomaterials that have been used for the repair of perineal herniation? What are their reported success rates?
Porcine SIS (10% recurrence), porcine dermal collagen (59% success), autologous fascia (100% success).
Which of the following materials was the strongest for perineal hernia repair?
1. Prosthetic mesh
2. Autologous fascia
3. Single layer porcine SIS
4. Double layer porcine SIS
Autologous fascia, then mesh, double layer SIS, single layer SIS.
What autologous fascia tissues have been used for perineal hernia repair?
Lateral thigh (resulting in occasional lameness), vaginal tunic.
What are some organopexy procedures that can be performed in conjunction with perineal hernia repair?
Colopexy, vas deferens pexy, cystopexy.
How is cystopexy performed?
Scarification and attachment of the bladder neck to the right body wall, attachment of the bladder apex to the body wall without scarification, temporary cystostomy tube.
Does a vas deferensopexy prevent bladder retroflexion?
No
What is the most common complication associated with organopexy procedures?
Tenesmus.
What constitutes a complicated perineal hernia?
Significant rectal dilatation, concurrent surgical prostatic disease, retroflexed bladder, recurrent.
May benefit from staging of surgical repair.
What are the major complications observed after perineal hernia repair?
Overall complication rates range from 5-68%.
The main reported complications
1. Infection (6-43%) and dehiscence (0-29%)
2. Fecal incontinence (0-33%, permanent in 10-15% of cases).
3. Sciatic nerve injury (<5%).
4. Urinary tract complications (10-15%) including bladder atony (10-29%) and urinary incontinence (4-37%).
5. Tenesmus (3-43%, resulting in rectal prolapse in 0-17% of patients).
6. Recurrence (0-70%, although most techniques report ~30% recurrence rates).
What factors might influence the rate of recurrence following perineal hernia repair?
Surgeon experience, surgical technique, previous surgical repair (83% v. 43% in one study), type of suture material used, local tissue strength, amount of tension, ongoing predisposing factors, neuter status.
What are the major differences between perineal hernias in dogs and cats?
25% of affected cats are female and perineal swelling is less common.
Surgical management is similar, although superficial gluteal transposition is not described.
Complications are less frequent.
