Colorectal Flashcards
Colon secretes______ and absorbs____
Potassium and reabsorbs sodium and water
Layers of colon
Mucosa
submucosa
muscularis propria
serosa
Which parts of colon are retroperitoneal
Ascending, descending and sigmoid
Anterior upper and middle 1/3rd of rectum
vascular supply Ascending: Transverse Descending Sigmoid Rectum
Ascending: SMA(Ileocolic and Right colic)
Transverse (proximal 2/3 by SMA. Distal 1/3 by IMA. Middle colic)
Descending: IMA Left colic
Sigmoid IMA: Sigmoid
Rectum Upper: IMA Superior rectal
Lower: internal Iliac: Middle rectal; internal Iliac to internal pudendal to inferior rectal.
Marignal artery of drummond: Connects SMA to IMA
Venous supply of colon
Follows arterial. SMV joins IMV to form portal vein behind pancreas
Rectum: Inferior rectal vein to internal iliac veins.
Superior and middle drain to IMV to portal.
Lymph nodes are similar
Watershed areas
Griffiths point: Splenic flexure at SMA and IMA junction and
Sudaks Point at rectum at superior and middle rectal junction
External sphincter: Which muscle. Controlled by?
Puborectalis, extension of levator Ani, controlled by CNS: Inferior rectal branch of internal pudendal nerve
Internal Sphincter: which muscles and Control
Extension of muscularis propria
Involuntary bypelvic splanchnic nerves
Meissner and auerbach
INNER plexus
Auerbach: Outer
distance from anal verge:
Anal canal
Rectum
Rectosigmoid junction
5cm
5-15
15-18
main nutrient of colonocytes
Short chain fatty acids
tx of stump pouchitis
Short chain fatty acid enema
Tx of infectious pouchitis
Flagyl
Denonvilliers fascia and waldeyers fascia
Rectovesicular and rectoprostatic (denon)
waldeyers: Retrosacral fascia
most common polyp
Hyperplastic
Most common neoplastic
Tubular adenoma most are pedunculated
Most likely polyp to cause symptoms
Villous adenoma. Likely sessile
Polyp characteristics likely to cause ca:
> 2cm, sessile, villous
polypectomy vs segmental resection. When is polypectomy sufficient
If margin >2mm, not poorly differentiated and no evidence of lymphovascular involvement.
high grade dysplasia vs intramucosal vs invasive ca
in first two, basement membrane remains intact, in invasive ca, submucosa involved
false positive guaic fobt causes
beef, vitamin c, iron, cimetidine
contraindications to colonoscopy
recent MI, splenomegaly, pregnancy(if fluoro)
tx of extensive low rectal villous adenomas with atypia
trans anal excision ( NO APR unless cancer
transanal exsion shows T1 cancer. Further tx needed?
No. If margins are adequate(2mm), no lymphovascular invasion and well differentiated.
Transanal excision shows T2: further Tx needed?
APR or LAR needed.
symptoms of colorectal ca;
anemia, bleeding constipation
colon ca a/w which infxn?
clostridium septicum.
main mutations in colon ca
p53, DCC, KRAS, APC
Most common site
Sigmoid
Mets to
liver(via portal vein) and lung(via iliac vein)
5 year survival in liver mets?
35% if resectable with adequate liver fxn
5 YS in lung mets
25% after resection
rectal ca mets to spine via?
Batsons plexus(venous)
prognosis with lymphocytic penetration? Mucoepidermoid ca?
LC: improved prognosis
ME: Worse
TRUS
BEST test of assesing T and N status
Goals of resection
EN bloc resection with adequate margins, mesocolon, regional adenectomy
2cm margins
best way to pick intrahepatic mets
intraop u/s. 3-5mm resolution vs conventionu/s 10mm vs ct/mri (5-10)
APR Indications
Malignant lesions only, not amenable to LAR.
Lesions with <2cm margin from levator ani
Criteria for transanal excision of low rectal T1 lesions
<4cm. Negative margins, well differentiated, no lymhovascular involvement.
T2 or higher: APR/LAR
Chemo.
colon: Stage III and IV
rectal stage II and III
rectal IV
colon: Stage III and IV: postop
rectal stage II and III neoadjuvant
rectal IV chemo +radio possibly surgery
chemo regimen: 5FU leucovorin, oxaliplatin
XRT. damage, advantage
Can cause vasculitis, thrombosis, ulcers, strictures, bleeding
can allow downstaging, helping avoid morbid operations
FAP gene? when do polyps form age of prophylactic colectomy other common cancer surgery
AD
APC gene, chromosome 5
20y. prophylactic colectomy, rectal mucosectomy, ileoanal pouch
periampullary duodenal tumors.
Other APC gene associated tumors:
Gardners: FAP and desmoid tumors/osteomas
turcot: Colon ca and brain ca
Lynch syndrome Gene Lynch 1 vs 2 Amsterdam criteria when to start screening.
AD DNA mismatch repair genes.
1: just colon ca. 2: increase risk of ovarian, endometrial, bladder and stomach.
Amsterdam: 3-2-1. 3 first degree relatives, 2 generations, 1 cancer before 50.
screen at 25 or 10 years before
total proctocolectomy
cecal vs sigmoid volvulu
age. cecal in young, 20-30s, sig in old, psych patients, neuro dysfxn, laxative abuse,
