Chapter 36 - Colorectal Flashcards
Muscular anatomy of colon?
Muscularis mucosa, muscularis propria, plica semilunaris (haustra), taenia coli
Vascular supply of ascending colon?
SMA - ileocolic, right colic arteries
Vascular supply of transverse colon?
2/3: SMA - right and middle colic, 1/3: IMA - L. colic
Vascular supply of descending colon?
IMA - L. colic
Vascular supply of the rectum?
IMA and internal iliac
Vascular supply of sigmoid colon?
IMA - sigmoid a.
% of blood flow to mucosa/submucosa?
80%
What are the watershed areas?
Splenic flexure (Griffith’s point), rectum (Sudak’s point)
What muscle makes up the external sphincter?
Puborectalis, continuation of the levator ani
Neuro control of external sphincter?
CNS (voluntary); inferior rectal branch of internal pudendal n, perineal branch (S4)
What muscle makes up the internal sphincter?
Continuation of circular bands of the colon muscle
Measurement from anal verge to anal canal?
0-5cm
Measurement from anal verge to rectum?
5-15cm
Measurement from anal verge to rectosigmoid junction?
15-18cm
Transition point between anal canal and rectum?
Levator ani
Main nutrients of colonocytes?
Short chain fatty acids (butyrate)
Treatment for stump pouchitis?
Short chain fatty acid enemas
Treatment for infectious pouchitis?
Flagyl
Treatment for lymphocytic colitis?
Sulfasalazine
What is the name of the anterior, rectovesicular/rectovaginal fascia?
Denonvillier’s
What is the name of the posterior, rectosacral fascia?
Waldeyer’s
What are the characteristics of polyps associated with increased cancer risk?
> 2cm, sessile, villous
What are the screening guidelines for patients with FAP?
Starting at 10-12y, annual sigmoidoscopy
What are the screening guidelines for patients with attenuated adenomatous polyposis coli?
Starting in late teens, annual colonoscopy
What are the screening guidelines for patients with HNPCC?
Starting at 20-25y, biennial colonoscopy
What is the treatment when polypectomy shows T1 lesion?
Polypectomy only if 2mm margins, well-differentiated, no vascular involvement; otherwise segmental resection
What is the treatment for extensive low rectal villous adenomas with atypia?
Transanal excision (with or without mucosectomy); APR only if cancer is present
What is the treatment for T2 lesion after transanal excision of polyp?
APR or LAR
What will cause a false-positive guaiac?
Beef, Vit C, iron, antacids, cimetidine
Colonoscopy contraindications?
Recent MI, splenomegaly, pregnancy if fluoroscopy planned
What is the 2nd leading cause of cancer death?
Colorectal cancer
Main gene mutations in colon ca?
APC, DCC, p53, k-ras
Most common site of primary colorectal cancer?
Sigmoid
Poor prognostic factors for primary colorectal cancer?
Age <40, symptomatic patients, obstruction & perforation, rectosigmoid/rectal location, ulcerative tumors, blood vessel/lymphatic/perineural invasion, aneuploidy, elevated CEA prior to resection
5 year survival rate with liver mets?
25% if resectable and leaves adequate liver function
5 year survival with lung mets?
20%
Route of metastasis of colon cancer?
To liver via portal vein, to lung via iliac vein
Rout of metastasis of rectal cancer?
Can go directly to spine via Batson’s plexus
Positive prognostic factor for primary colorectal cancer?
Lymphocytic penetration
Goals of resection for colon ca?
En bloc resection, adequate (2cm) margins, regional adenectomy
Treatment for rectal cancer with rectal pain?
APR
What is the best method of picking up hepatic mets?
Intraoperative ultrasound
Margin needed for LAR?
2cm from levator ani
Side effects of APR?
Impotence and bladder dysfunction
Local recurrence higher with rectal or colon ca?
Rectal ca
Advantages of preoperative chemo/XRT?
Produces complete response in some patients with rectal ca; preserves sphincter function in some
Treatment for low rectal T1 lesion?
Transanal excision if <4cm, negative margins (1cm), well differentiated, no neurologic or vascular invasion; otherwise LAR or APR
Treatment for low rectal T2 or higher?
APR or LAR
Chemo for stage III and VI colon CA (node positive or distant mets)?
Post op chemo, no XRT (III - 5FU, leucovorin, oxaliplatin; IV - 5FU and leucovorin)
Chemotherapy for stage II and III rectal ca?
Pre op or post op chemo and XRT (5FU, leucovorin, oxaliplatin)
Chemotherapy for stage IV rectal ca?
Chemo and XRT +/- surgery (5FU, leucovorin)
When is postop XRT needed for rectal ca?
T3 tumors or positive nodes
Most common site of XRT damage?
Rectum; vasculitis, thrombosis, ulcers, strictures
% of patients that will have recurrence?
20% (50% within 6mo, 100% within 3 years)
% that will have another primary?
5% (main reason for surveillance colonoscopy)
Gene mutation related to FAP?
APC gene, chromosome 5
% of FAP syndromes are spontaneous?
20%
When do polyps present in FAP?
Puberty
Surveillance for FAP?
Flex sig to check for polyps; EGD every 2 years
Treatment for FAP?
Total colectomy at age 20; proctocolectomy, rectal mucosectomy and ileoanal pouch
Tumors associated with Gardner’s syndrome?
Colon ca, desmoid tumors, osteomas
Gene mutation associated with Gardner’s syndrome?
APC gene
Tumors associated with Turcot’s syndrome?
Colon ca, brain tumors
Gene mutation associated with Turcot’s syndrome?
APC gene
Lynch syndrome inheritance?
Autosomal dominant
Gene mutation assocaited with Lynch syndrome?
DNA mismatch repair gene
Lynch I has increased risk of what?
Colon cancer
Lynch II has increased risk of what?
Colon cancer, ovarian, endometrial, bladder, stomach cancer