94.Rectum_Anus_perineum Flashcards
what anatomical structure marks the caudal aspect of the rectum
external anal sphincter musclelevel of 2-3 caudal vertebra
T/Fthere is a small caudal portion of rectum that is retroperitoneal and lacks a serosal layer
TRUE
difference btwn dogs and cats terminal colon/rectal blood supply
dogs: rely on cranial rectal artery bc middle and caudal rectal artery contributions are minimalcats: middle and caudal rectal arteries are adequately supplying rectumMUST PRESERVE CRANIAL RECTAL ARTERY IN DOGS
zones of anal canal
1 cm anal canal 1. columnar zone2. intermediate zone (anocutaneous line)3. cutaneous zone (internal–anal sacs, external–perianal hepatoid glands)
anal canal vs external anal sphincter blood supply
anal canal—-internal pudendal arteryexternal anal sphincter–perineal arteries
innervation of the rectum and internal anal sphincter
PELVIC PLEXUS–pelvic n (PSNS)–hypogastric n (SYMP)PSNS stimulates rectum but inhibits internal anal sphincterSYMP inhibits rectum but excites internal anal sphincter
innervation of external anal sphincter
pudendal nerve—perineal branch SENSORY, caudal rectal branch–MOTOR
what is GOLYTELY
polyethylene glycol and electrolytes40 ml/kg x 2 doses
approaches to rectum
–ventral (bilateral ischial and pubic osteotomy, pubic symphsiotomy)–dorsal (mid rectal lesions, transect rectococcygeus m +/- levator ani m CAUTION pelvic nerve plexus laterally)–rectal pull through (mid to caudal lesions; anal sacculectomies performed; removing EAS will lead to incontinence–GOAL is to preserve 1.5 cm cuff)–transanal pull through (evert rectal wall, preserves distal rectal stump)–lateral (curvilinear perianal incision; preserve caudal rectal branch of pudendal nerve to EAS)
complications post rectal surgery
- dehiscence/leakage2. infection3. stricture4. incontinence5. recurrence massfrom poor apposition, narrowed lumen, too much tension, poor blood supply, disruption of nerves/EAS
sex and breed predisposed to congenital abnormalities of the rectum/anus
females 1.8 x more likelypoodlesboston terrierslook for other congenital abN
atresia ani classification
I. congenital stenosis of anus===multiple bougienage or removal of stenosisII. persistent anal membrane with rectum ending immediately cranial to membrane===perforate III. anus is closed and blind end of rectum is farther cranial==perforate and bring rectum caudallyIV. terminal rectum and anus develops normally but blind pouch is in the cranial rectum within pelvic canal===abdominal approachif diagnosis is delayed—>megacolon may be irreversible
rectovaginal fistulas
failure of separation of urorectal septum to separate cloacaoften associated atresia ahi type IIrectovaginal (female); urethrorectal (male)tx: fistulectomy, sterilization, +/- reconstruction
diagnostics for rectovaginal or urethrorectal fistula
–history, clinical signs, PE, rectal digital exam–positive contrast retrograde urethrography +/- fluoro***–voiding cystourethrography +/- fluoro–ab films RO megacolon, urinary stones–urine culture
complete vis partial rectal prolapse
partial —anal mucosa only protrudes, anal prolapsecomplete—rectal prolapse, all layers of rectum protrudeprobe will NOT pass easily (ddx intussusception)
most common anal and perianal tumor
perianal land adenoma—arises from circumanal or perianal hepatoid glandsrelated to androgen concentrations—seen in older male intact dogs (if diagnosed in female—check for cushings)cytology adenoma: hepatoid (large polyhedral)tx: castrate (submit histo) and mass removal adenocarcinoma–rare, not T dependent50% Adca had previous adenoma removed
treatment for rectal prolapse
—conservative if just anal or partial prolapse—complete prolapse: resection/amputation with rectal pull through technique (not recommended in cats because stricture likely), colopexy (preferred in cats) Left sided incisional or nonincisional 2.5 cm lateral to linea
perianal adenocarcinoma and prognostic indicators
> 5 cm incr tumor related death 11xpresence of mets incr tumor related death 45 x>5 cm and tumor invasion increased recurrence ratesconsider castration, LN excision if metastatic, adjuvant radiation
benign rectal tumors
–adenomatous polyps (single/multiple, raised, sessile, pedunculated usually distal)–can have malignant transformation 50% dogs; males Collies, WHWT–leiomyoma (intramural–good px with surgical excision); medium to large breed dogsbenign rectal tumors are NOT common in cats
what is carcinoma in situ in relation to rectal neoplasia
invade intestinal lamina propria, submucosa, but NOT the basement membrane
most common malignant rectal tumor
adenocarcinoma–dogsslower to met and less invasive compared to adenocarcinoma in small intestine1. pedunculated (distal)–32 mo2. cobblestone (middle)–12 mo3. infiltrative (annular lesion)–classic napkin ring, WORSE PX–1.6 moLSA–most common in cats
% of rectal masses felt on digital examination
63% of dogs with colorectal adenocarcinoma had palpable masses on digital rectal examcircumferential lesion is very suggestive of rectal adenocarcinoma
histological type of endoscopically biopsied colonic masses
incorrect in 30% with surgical biopsies revealing a more malignant diagnosis
most common complication following EEA stapling transrectally for colonic R& A based on Banz et al 2008
40% complicationsstricture and transient colitis most common
px for rectal tumors
polyps, leiomyoma, carcinoma in situ good with resectionpolyp recur 17%carcinoma in situ 55%
surgical options for fecal incontinence
–nerve from biceps femurs created onto EAS–neuromicrovascular free transfer from latissimuss–semitendinous muscle flap–clockwise rotation following rectal resection 225 degrees
why is there speculated to be lower incidence of anal sac disease in cats vs dogs
cats have more sebaceous glands in their anal sacs (have a more sufficient amount of lipid–to help avert occlusion of duct and secretions are not to viscous)
incidence of apocrine gland adenocarcinoma of the anal sac
diagnosed incidentally on PE in 40% dogsbilateral tumors < 10%incidence of paraneoplastic hypercalcemia 27%>50% (36-96%) have mets at time of presentation (check sub lumbar LN)not common in cats but poor px
4 systemic signs and 2 bloodworm abN associated with apocrine gland adenocarcinoma of anal sac
PU/PDweaknessvomitingconstipationhyperCa, hypoP
negative prognostic indicators for survival in dogs with apocrine gland adenocarcinoma
–lack of therapy–presence of LN or distant mets–primary tumor size > 10 cm 2 worse–hyperCa (controversial)
MST for apocrine gland adenocarcinoma
OVERALL 544 dayssx alone (sign shorter than with multimodal tx) 402 daysmultimodal tx 548 days
anal sacculectomy
avoid trauma to EAS and caudal branch of pudendal nerve to maintain continenceclosed, modified open, or standard open approachesmore complications noted with open approachoverall complications: scoot, inflm, drainage, seroma, incontinence (permanent if longer than 3-4 mo, bilateral damage), fistulation/infection (incomplete removal–open tech), stricture
4 medical options for perianal fistulas (sinuses)
- cyclosporin 8.8 weeks 70-100% success (many patients have recurrence with discontinuation rx); + ketoconazole (inhibits p450 cytochrome enzymes resulting in incr cyclosporin concentration decr dose 75%, incr saving 60%)2. GCC (prednisone)3. Tacrolimus (topical, $$$)4. azathioprine–metronidazole (may not cause complete resolution but more economical)
types of perineal hernia
- caudal (btwn levator ani, internal obturator, EAS)–MOST COMMON2. dorsal (btwn levator ani and coccygeus)3. ventral (btwn ischiocavernosus, ischiourethralis, bulbocarvernosus)4. laterally (btwn coccygeus and ST ligament) aka sciatic perineal hernialevator ani is the most commonly atrophied muscle
castration at the time of perineal hernia repair recommendations
NEUTERrisk of recurrence was 2.7x greater for intact dogsneutering reduced recurrence rate from 43% to 23%
concurrent prostatic disease incidence in dogs with perineal hernia
25-60% concurrent prostatic disease
unilateral vs bilateral perineal hernia
unilateral 60% (RIGHT IS MORE COMMON–70%)bilateral 40%other side may still be “weak” in pararectal fossa
bladder retroflexion in cases is perineal hernia
20-30%
surgical treatment for perineal hernia
T-I-S-S-PT—– traditional primary herniorraphyI —– internal obturator flapS —-semitendinous muscle transposition (ventral hernia)S —-superficial gluteal muscle transpositionI —– implants (Prolene mesh, SIS, fascia lata)+/- pexy procedures (cystopexy, colopexy, vas deferens vasopexy)
blood vessels crossing caudomedially over internal obturator muscle
internal pudendal vessel and pudendal nervegive rise to casual rectal vessels and nerve
length of elevation of the internal obturator muscle for perineal hernia repair
DO NOT proceed farther cranially than the caudal edge of the obturator foramento avoid damage to the obturator nerve
complications following perineal hernia repair
- seroma2. wound infection/drainage/abscess3. incontinence4. straining/tenesmus ~50% (esp with colopexy)5. sciatic nerve injury < 5%6. fistulation < 15%7. urinary dysfunction (bladder atony)8. recurrence
recurrence rate of perineal hernia with experienced surgeon vs inexperiences surgeon
70% inexperienced10% experienced
recurrence rate of traditional herniorraphy vs internal obturator transposition
traditional 10-50%internal obturator 0-40%
