Colon (Makary Ch 22) Flashcards
What disease/syndrome associated with a mutation in the APC gene?
Familial Adenomatous Polyposis
When should patients with FAP begin screening?
Flex sig starting at age 10-15
Should you palliate a low rectal obstructing tumor with an endoluminal stent?
No - cause pain and incontinence at this site. A sigmoid colostomy is a better option.
Do loop colostomies or loop ileostomies have more complications?
Loop colostomies - higher incidence of parastomal and incisional hernias, stomal prolapse, and fecal fistulas
The colon secretes ___ and reabsorbs ___ and water (electrolytes)
Secretes K, reabsorbs Na
Four layers of the colon
mucosa, submucosa, muscularis propria, serosa
Name of the transverse bands that form haustra
Plicae semilunares
Ascending and 2/3 of transverse colon supplies by the
SMA (ileocolic, right, middle colic)
1/3 transverse, descending colon, sigmoid colon, and upper portion of rectum supplied by the
IMA (left colic, sigmoid branches, superior rectal artery)
What artery runs along the colon margin, connecting the SMA and IMA
Marginal artery - provides collateral flow
What two layers of the colon receive 80% of the blood flow?
the mucosa and submucosa
The middle rectal artery is a branch of the
internal iliac artery
The inferior rectal artery is a branch of the
internal pudendal artery, which is a branch of the internal iliac
What are the two watershed areas?
splenic flexure - SMA and IMA junction
Rectum - superior rectal and middle rectal junction
Colon vs Small bowel - which is more sensitive to ischemia?
Colon - less collateral blood flow
What is the main nutrient of colonocytes?
Short chain fatty acids
What is the most common polyp? Cancer risk?
Hyperplastic polyps - no cancer risk
What is the most common intestinal neoplastic polyp?
Tubular adenoma
Does high grade dysplasia violate the basement membrane?
No. The basement membrane is in tact (carcinoma in situ)
To be considered invasive, the cancer must violate which layer?
The submucosa
Screening option:
- Colonoscopy q___ years
- FOBT Q___ years + Flex sigmoidoscopy Q ___ years
- FOBT only q ___ years
- Colonoscopy q10 years
- FOBT Q3 years + Flex sigmoidoscopy Q 5 years
- FOBT only q 1 year
Four things that can cause a false positive guaiac test
Beef, vitamin C, iron, cimetidine
for a polypectomy to be adequate, need ___ mm margin
2mm
Also should be well differentiated, have no vascular/lymphatic invasion
What is the treatment for extensive low rectal villous adenomas with atypia
Transanal excision. No APR unless cancer is present
Pathology shows T1 lesion after transanal excision of villous rectal polyp with 2mm margins. Adequate?
yes - if also well differentiated and no vascular/lymphatic invasion
Pathology shows T2 lesion after transanal excision of villous rectal polyp. Adequate?
No. Patient needs APR or LAR
