Colorectal Surgery Flashcards
In what 3 ways does the large intestine differ from the small intestine is regards to surgery?
- higher bacterial population
- slower wound healing due to collagenolysis
- more segmental blood supply
(+ collection of stool increases tension)
What are the 3 major blood supplies to the large intestine?
- ileocolic
- cranial mesenteric
- caudal mesenteric
What are the 3 indications for colotomies? How are they closed?
- foreign body removal (not common, if it made it to the rectum, it will likely pass)
- impacted feces
- biopsy**
longitudinal closure in a single layer of simple interrupted appositional pattern
What is a colopexy? What should be avoided?
creation of a permanent seromuscular adhesion between the colon and abdominal wall
creating an adhesion close to the ventral midline - easy to nick in future abdominal surgeries
What are the 3 most common complications associated with colopexies?
- infection
- dehiscence
- recurrence
What are the 2 major indications for colopexies?
- recurrent rectal prolapse
- perineal hernia
How are incisional colopexies performed?
- apply cranial traction to the descending colon
- create a longitudinal incision to the colon
- create another longitudinal incision through the seromuscular layers of the transversus abdominus of the body wall
- suture (fish mouth) them together
(can perform in more than one spot on the colon)
What is the purpose of colopexies?
prevent the caudal displacement of the colon and rectum
(especially with recurrent rectal prolapse)
What are the 4 indications for colonic R/A?
- megacolon
- perforation
- neoplasia
- irreducible/necrotic intussusception
What is the preferred technique for performing colonic R/A?
subtotal with colocolic anastamosis
- preserving the ileocecal valve is ideal and doable because megacolon most commonly occurs in the transverse and descending colon
- colon is 2x the diameter of the ileum and anastomosis is difficult
In what animals is megacolon most common? What are 3 causes?
older Manx cats
- mechanical or functional colonic obstruction
- neurologic
- idiopathic
What is the pathophysiology behind the development of megacolon?
- feces concretions form, which are painful and too large to pass, causing the colon to stretch
- prolonged distension leads to smooth muscle and nerve damage
What is the cause of congenital megacolon?
aganglionic distal colonic segment causes the absence of inhibitory neurons, essentially a functional obstruction
(rare, cats)
What are 5 causes of neurologic conditions that lead to megacolon?
- lumbosacral disease
- dysautonomia
- Key-Gaskell disease - feline progressive dysautonomia
- autonomic ganglioneuritis
- sacral spinal cord deformity
How does pelvic trauma cause megacolon? How is it treated?
callus formation from a healing pelvic fracture or SI luxation causes pelvic nerve injury
pelvic osteotomy (hemipelvectomy) to take out offending piece of bones
What is the most common cause of obstruction/entrapment of the colon that leads to megacolon? How is it treated?
adhesion formation from ovariohysterectomy - a delayed complication weeks to years post-op or an incidental finding on exploratories
surgical dissection and removal with potential for R/A
What is feline idiopathic megacolon? What is thought to cause a similar disorder in dogs?
acquired disorder characterized by colonic dilation and ineffective transport of feces, resulting in chronic constipation
perianal fistulas
What is postulated to be the etiology in feline idiopathic megacolon? What signalment is most common?
neural or smooth muscle defects (aganglionosis rare)
middle-aged males
What are the most common signs of feline idiopathic megacolon?
- constipation
- tenesmus
- inappetence
- depression
- weight loss (commonly not seen due to pot-bellied appearance)
- poor hair coat
How is feline idiopathic megacolon diagnosed?
- palpation of feces-filled colon
- survey radiology to r/o narrowing of bony pelvic canal
- US, barium enema, proctoscopy to r/o stricture or pelvic mass
How does diagnosis of feline idiopathic megacolon compare in barium enemas and proctoscopy?
BARIUM ENEMA - colon must be empty, uses mushroom-tip or Pezzer catheter
PROCTOSCOPY - evacuate distal colon, easier and faster
How can feline idiopathic megacolon be medically managed?
- warm water enemas
- lubrication and/or digital breakdown of feces
- general anesthesia and manual evacuation
(provides only short-term relief!!)
What are the 2 main surgical managements of feline idiopathic megacolon? What is not recommended?
- TOTAL COLECTOMY - removal of colon, ileocolic valve, and cecum with ileorectal end-to-end anastromosis (electrolyte imbalance, diarrhea)
- SUBTOTAL COLECTOMY - partial removal of colon with preservation of the ileocolic valve and colorectal anastomosis
colotomy —> bowel is compromised and unlikely to decrease in size
What presurgical considerations are used for colectomies?
- prophylactic antibiotics: high aerobe and anaerobe contents
- extent of proximal resection is determined by the extent of dilation
(preoperative enemas are unnecessary and ineffective)
How are colectomies performed?
- carefully pack off the colon
- place a clamp at the distal resection at the junction of the colon and rectum approximately 2-3 cm cranial to the pubis
- place a clamp at the proximal resection site
- ligate colonic, mesenteric, and jejunal vessels
- correct any lumen disparity and perform an end-to-end anastomosis with 3-0 or 4-0 monofilament suture (single or double layer) or EEA staples (double layer inversion)
What is the goal of subtotal colectomies?
remove as much colon as possible
How do colocolostomies and ileocolostomies compare?
COLOCOLOSTOMY - tension-free apposition more difficult due to the immovable nature of the colon
ILEOCOLOSTOMY - increased incidence of severe diarrhea
What medical treatment can help in cats with idiopathic megacolon?
- Cisapride - gastroprokinetic agent
- stool softeners
What is associated with removal of the ileocolic valve during colectomies?
reflux of colonic contents results in small intestine bacterial overgrowth (SIBO) and loose stool
What commonly occurs in patients following colectomies?
- tarry feces: normal bleeding into the GIT for 2-3 days
- tenesmus for 5-7 days, but may never become completely normal
- anorexia: nasogastric or PEG tube placement
What is not commonly affected by colectomies? What diets are used post-op?
clinical changes in fluid, electrolyte, or vitamin absorption —> remaining bowel increases absorption
low residue - improve fecal consistency and decreases fecal volume
What is the most common post-op complication following colectomies?
surigcal site infections (SSI) - most common following intra-abdominal surgery due to handling of the colon
- flushing of the abdomen and changing of gloves, equipment, and gown is recommended before closing the abdomen
What are some common complications following intestinal surgery?
- ileus
- adhesions
- obstruction from intussusception, entrapment, or stenosis
- dehiscence
- peritonitis
- short bowel syndrome
What are 4 major risk factors for dehiscence after intestinal surgery?
- foreign bodies and trauma
- pre-op albumin <2.5 g/dL results in delayed healing
- post-op rise in band neutrophils indicates and active infection
- pre-operative peritonitis
What increases mortality in patients undergoing intestinal surgery?
leakage or dehiscence
What is cecal inversion? In what animals is it most common? What are some clinical signs?
cecal intussusception causes an obstruction of the ileocolic junction
young dogs < 4 years
NONSPECIFIC - diarrhea, hematochezia, tenesmus, weight loss
How is cecal inversion diagnosed? Treated?
- plain radiographs: small fluid-dense intraluminal mass in proximal colon
- contrast radiographs: inverted cecum surrounded by contrast material in proximal colon
- endoscopy
typhlectomy, manual reduction, colotomy
What are 4 indications for typhlectomies?
- cecal impaction
- cecal inversion
- perforation
- neoplasia
How are typhlectomies performed?
- ligate arterial supply
- dissect ileocolic fold
- milk out contents
- transect and suture/staple
What are the 3 most common cecal neoplasias? How are they treated? What is MST like?
- leiomyoma
- leiomyosarcoma
- gastrointestinal stromal tumor (GIST), a subclassification of leiomyosarcoma
surgical excision with wide borders in malignancies
7-12 months
What are the 3 most common congenital diseases of the anus? Rectum?
- atresia ani
- rectovaginal fistula
- anogenital clefts
- prolapse
- neoplasia
- strictures
What is atresia ani?
stenosis or persistent membrane of the anus
What are rectovaginal fistulas associated with? How are they diagnosed?
UTIs
contrast
What are anogenital clefts? What do they lead to?
common opening for anus and genital tract
UTI
What are anal prolapses? How are the treated?
anal mucosa protruding from orifice
- determine underlying cause and treat
- manually reduce and place a purse string before it becomes necrotic
What is a complete rectal prolapse? What are 4 predisposing factors? What is the most common signalment?
all layers of the rectum protrude through the anal orifice
- parasites
- colitis
- urogenital disease
- tumors - vaginal leiomyoma causes constant straining
younger patients
What is the primary differential of rectal prolapse?
prolapsed intussusception —> blunt probe/finger cannot be inserted
How is a rectal prolapse with viable tissue treated?
- manually reduce with cool saline, lubricants, or mannitol
- place a purse string to keep reduced, but allow soft feces through
- leave for several days
How is a rectal prolapse with non-viable tissue treated?
- surgically prep the area
- place 4 full-thickness stay sutures
- insert a lubricated test tube to minimize contamination and resect 1-2 cm from the anus around 180 degrees around
- place simple interrupted sutures
- repeat for the other 180 degrees
- reduce prolapse
What are the 4 most common complications following rectal prolapse amputation?
- infection
- dehiscence
- stricture
- recurrence, if underlying cause is not corrected
How is a recurrent rectal prolapse treated/prevented?
incisional colopexy
- > 3 cm incision through serosa and transversus layers
- fish-mouth colon and muscle wall
(can perform in more than one area)
What are the most common rectal tumors? In what animals are they most common?
adenomatous polyps —> benign, malignant transformation
Collies
What is the most common malignant rectal tumor? In what animals are they most common?
adenocarcinoma —> not as aggressive as in the small intestine
older GSDs
What clinical signs are associated with rectal tumors?
- tenesmus
- dyschezia
- rectal prolapse
- protrusion of polyp
How are rectal tumors diagnosed?
- direct observation/rectal palpation
- colonoscopy: determine extent
- biopsy: determines stage and surgery, submission
- thoracic radiographs
- abdominal ultrasound
What pre-operative measures should be done before rectal surgery?
- withhold food 24-48 hours prior
- multiple warm water enemas up to 12 hours prior
- prophylactic antibiotics
When are enemas contraindicated before rectal surgery?
with obstructive lesions
What surgical approach to the rectum is rarely used?
lateral —> limited exposure
When is the transanal approach to rectal surgery most commonly performed?
excision of small, non-invasive, pedunculated polyps in the caudal 4-6 cm of the rectum
How is the dorsal approach to rectal surgery began? When is it used?
inverted U incision above the anus
excision of tumors of the caudal to mid rectum
How are rectal pull-throughs performed? When are they most common?
- evert rectal wall
- place stay sutures
- dissect the rectum from the external anal sphincter
- mobilize rectum caudally and resect
excision of distal colonic or caudal to mid rectal tumors
When is the ventral approach to rectal surgery performed?
lesions at the colorectal junction or more extensive lesions
What approaches are recommended for rectal polyp and annular/more cranial tumors?
transanal submucosal resection per anus, since most are within 2 cm of the anus
dorsal, rectal-pull through, ventral
What is the prognosis of colorectal tumors?
large/sessile tumors are more likely to recur due to a limited approach causing an inability to get proper margins (+ tension at the colon)
- euthanasia is most commonly recommended due to failure to control dyschezia or hematochezia
What are the most common benign and malignant colorectal tumors?
BENIGN - adenomatous polyps, leiomyoma, fibroma
MALIGNANT - adenocarcinoma, leiomyosarcoma, lymphosarcoma
What are the most common clinical signs of rectal adenomas? How do they present?
- hematochezia
- tenesmus/dyschezia
- visible (intermittent) mass
most occur in the distal rectum and are polypoid, sessile, or multiple
How are colorectal tumors treated?
surgical excision - transanal, dorsal, mucosal resection
Why is cryosurgery not commonly recommended for colorectal tumor treatment?
- can’t evaluate margins
- can’t confirm diagnosis
Where are colorectal adenocarcinomas most commonly found? What lesion is a poor prognostic indicator? How do they act?
50% are abdominal
annular “napkin ring”
metastasis to regional lymph nodes and liver common
What are the 3 most common surgical approaches colorectal tumor resection?
- anal - caudal rectum or anal canal
- dorsal - caudal or middle rectum, NOT anal canal
- rectal pull-through - distal colonal or midrectal lesions not approachable through the abdomen
What is a Swenson’s pull-through?
combines anal and ventral approach to reach lesions that extend beyond peritoneal reflection into the abdominal cavity
What are the 4 most common complications following rectal surgery?
- dehiscence
- infection
- stricture
- sphincteric/sensory incontinence
What are the most common anal sac diseases? In what animals is this most common?
anal sac impaction, leading to anal sacculitis or abscesses
small dogs —> Poodle, Chihuahua
How are anal sacculectomies pre-treated? Where are the anal sacs found?
manage infection or abscesses medically until inflammation involves and the anal sacs can be removed
within external anal sphincter
How is an open anal sacculectomy performed?
- insert one blade of scissors into the sac
- apply upward pressure to tips to minimize tissue cut or insert the groove director or probe through duct into anal sac
- incise over instrument with caudal tension to minimize damage to sphincter
- dissect anal sac away from sphincter
SPHINCTER TO SAC
How is a closed anal sacculectomy performed?
excise over anal sac and dissect away from sphincter
SAC TO SPHINCTER
What are the 3 most common complications associated with anal sacculectomies?
- infection
- draining tracts due to incomplete removal of anal sac
- fecal incontinence
What are the most common perianal gland tumors? In what animals are they most common?
adenomas/adenocarcinomas
intact males (benign) —> castration and resection with good prognosis
What anal sac tumors are most common? What are 3 common signs?
apocrine gland adenocarcinomas
- paraneoplastic hypercalcemia
- PU/PD
- renal failure
In what animals are perianal fistulas most common? What is thought to be its etiology? What is the most common clinical sign?
GSDs
immune-mediated
painful, perianal draining with fistulous tracts
What are 3 common options for medical management of perianal fistulas? When is surgical intervention recommended?
- specialized diet - IBD may predispose/potentiate signs
- Cyclosporine*, Azithioprine, Tacrolimus - commonly recurs when discontinued, $$$
- Ketoconazole, glucocorticoids, Metronidazole
nonresponsiveness to medical management
