36 - Colorectal Flashcards
Colon secretes _ and absorbs _
Secretes - K
Absorbs - water and Na
Layers of colon
Mucosa, submucosa, muscularis propria, serosa
Small interwoven inner muscle layer below mucosa but above basement membrane in colon
Muscularis mucosa
Portions of colon that are retroperitoneal
Ascending, descending and sigmoid
Peritoneum cover this portion of rectum
Anterior upper and middle 1/3
Transverse bands forming haustra
Plicae semilunaris
3 bands running longitudinally along the colon
Taenia coli
Distance of dentate line from anal verge
2cm
SMA supplies which portions of the colon (name branches)
Ascending - ileocolic, right colic
2/3 Transverse - middle colic
IMA supplies which portions of the colon/rectum (name branches)
1/3 Transverse - left colic
Descending - left colic
Sigmoid - sigmoidal branches
Upper rectum - superior rectal
Collateral flow connecting SMA and IMA
Marginal artery
Short direct connection between SMA and IMA
Arc of Riolan
Superior, middle and inferior rectal artery branches from
Superior - IMA
Middle - Internal iliac
Inferior Internal pudendal (branch of internal iliac)
Watershed areas of colon and there junctions
Splenic flexure (Griffith's point) - SMA and IMA junction Rectum (Sudaks point) - superior and middle rectal junction
Anal sphincter with voluntary control
External sphincter
Anal sphincter with involuntary control
Internal sphincter
External anal sphincter innervation and muscle (type)
Inferior rectal nerve (internal pudendal nerve branch) Levator ani (skeletal)
Internal anal sphincter innervation and muscle (type)
Pelvic splanchnic nerves Muscularis propria (smooth)
The inner and outer nerve plexus of the colon, respectively
Inner - Meissner’s plexus
Outer - Auerbach’s plexus
What forms the anal verge
0-5cm anal canal, 5-15cm rectum, 15-18cm rectosigmoid junction
Mucin secreting goblet cells of colon
Crypts of Lieberkuhn
Slow transit time of the colon
colonic inertia
Main nutrient of colonocytes
Short chain fatty acids
Tx for stump/diversion pouchitis of colon
Short chain fatty acid enema
Tx for infectious pouchitis
Metronidazole
Anterior colorectal fascia (rectovesicular/rectoprostatic - men; rectovaginal - women)
Denonvilliers fascia
Posterior colorectal fascia (rectosacral)
Waldeyer’s fascia
Most common colon polyp
Hyperplastic polyp
Most common neoplastic intestinal polyp
Tubular adenoma
Most likely to produce sxs, more often cancerous (50%0
Villous adenoma
Indications for increased cancer risk of intestinal polyps (3)
> 2cm, sessile, villous
Screening age for colon cancer, normal risk and family hx
Normal risk - 50yo Intermediate risk (fam hx) - 40yo or 10 yrs before youngest fam member
Screening options for colon cancer
- Colonoscopy q10 yrs
- Fecal occult blood testing (FOBT) q3yrs AND flex sigmoidoscopy q 5yrs
- FOBT annually
Definition of invasive cancer (T1) lesion in colorectal
Invasion INTO submucosa (past basement membrane)
Indications for adequate resection with polypectomy of T1 lesion (3)
Negative margins (2mm)
Well differentiated
No lymphovascular invasion
Low rectal villous adenoma with atypia tx with T1 vs T2 rectal lesion
T1 - transanal excision (2mm margins, no lymph/vasc invasion, well diff)
T2 - APR/LAR
2nd leading cause of Ca death
Colorectal cancer
Gene mutations for colon cancer (4)
APC
p53
DCC
k-ras
Most common site of colon cancer primary
Sigmoid
Most important prognostic factor colon cancer
Nodal status
Most common sites of colon cancer metastasis (1 & 2)
1 - Liver
2 - Lung
Colon cancer metastasizes to liver via _, and lung via _
Liver via portal vein
Lung via iliac vein
5yr survival rate of colon cancer with liver metastasis and lung metastasis, respectively
35% - liver
25% - lung
Rectal cancer can metastasize to spine via
Batson’s plexus
Worst prognosis colorectal cancer
Mucoepidermoid
Best test for T and N status; assessing depth of invasion
Transrectal ultrasound
Margins for colorectal cancer resection
2cm
Best method for picking up intrahepatic metastasis
Intraoperative ultrasound
Indication for APR vs LAR
Need 2cm margin from levator ani muscles for LAR, otherwise need APR
T staging for colorectal cancer
1 - into submucosa
2 - into muscularis propria
3 - into subserosa or through muscularis propria
4 - through serosa, into adjacent organs/peritoneal space
N staging for colorectal cancer
0 - nodes negative
1 - 1-3 regional nodes
2 - >/= 4 regional nodes
3 - central nodes
Chemo regimen for colorectal cancer
FOLFOX (5FU, Leucovorin (folic acid), Oxaliplatin
Colon cancer stage getting postop chemo
Stage 3-4 (no XRT in colon)
Rectal cancer stage getting neoadjuvant chemo-XRT
Stage 2-3
Rectal cancer stage getting chemo-XRT, +/- surgery
Stage 4 (avoid APR with pts with mets)
Most common site of damage from XRT
Rectum
Rate of recurrence of rectal cancer within first yr
20%
FAP inheritance and gene mutation (+ chromosome)
Autosomal dominant; APC gene (chromosome 5)
Age for total colectomy (prophylactically)
20yo
Surgical procedure for FAP
Proctocolectomy, rectal mucosectomy, ileoanal pouch
Alternate is total proctocolectomy with end ileostomy
MCC death in FAP after colectomy
Duodenal tumors (periampullary)
Gardner’s syndrome
Colon ca + intra-abd desmoid tumors
Turcot’s syndrome
Colon ca + brain tumors
Inheritance and gene with Lynch syndrome (HNPCC)
Autosomal dominant; DNA mismatch repair gene
Lynch 1 vs lynch 2 risks
1 - just colon cancer risk
2 - also at risk for ovarian, endometrial, bladder, stomach
Amsterdam criteria for Lynch syndrome
3, 2, 1
- 3 first degree relatives
- over 2 generations
- 1 person w/ cancer before 50yo
Surveillance colonoscopy time-frame for lynch syndrome
25yo or 10 yrs before primary relative
Tx for sigmoid volvulus
Colonoscopic decompression -> bowel prep/rectal tube -> sigmoidectomy same admission
Tx for cecal volvulus
Right hemicolectomy
Tx for maintenance vs acute UC
acute - steroids
maintenance - 5-ASA (mesalazine)/sulfasalazinea and loperamide
Most common site of perforation for UC
Transverse colon
Most common site of perforation for Crohn’s
Distal ileum
Cancer risk for UC pts with pancolitis
1% per yr starting 10yrs after initial dx with pancolotis
Most common extraintestinal manifestation of UC requiring total colectomy
Failure to thrive in children
Which conditions (2) do NOT improve with colectomy in UC
Primary sclerosing cholangitis, ankylosing spondilitis
Which conditions (3-4) improve with colectomy in UC
Ocular problems, arthritis and anemia/(50% pyoderma gangranosum)
HLA B27 associated with
UC, ankylosing spondylitis, sacroiliitis
Tx for pyoderma gangrenosum
Steroids
Most common location of colon perf 2/2 obstruction
cecum
MCC of colonic obstruction 1 & 2
1 - cancer
2 - diverticulitis
Tx for amoebic colitis
Flagyl
Yellow-white sulfur granule pathology of colonic mass/abscess; tx
Actinomyces; tx - penicillin
Most common presentation of right sided and left sided diverticula, respectively
Right - Bleeding
Left - Diverticulitis
Bleeding amount for arteriography to pick up in GI bleed
> /= 0.5cc/min
Bleeding amount for tagged RBC scan to pick up in GI bleed
> /= 0.1cc/min
Best dx test for colovesicular fistula
cystoscopy