ABSITE Colorectal Verified Exam Questions and Answers Latest
update 2026/2027
Question:
infectious agent assc with colon cancer
Answer:
clostridium septicum
Question:
Describe differences between APR and LAR
Answer:
APR: abdominal perineal resection: removal of distal colon, rectum, and anal sphincter complex
through perineum and ant abd wall
*requires permanent colostomy
- LAR: low anterior resection: removal of rectum, then attach colon to remaining rectum
Question:
Treatment for low rectal villous adenomas with atypia or T1
Answer:
<4cm & can completely resect with 2mm margins: transanal excision (using tools through the anus to
resect mucosa + primary repair)
Question:
Treatment for colonic polyps
Answer:
endoscopic removal (T1, into submucosa)
- if can't remove completely (like sessile polyps) or margins not clear -> segmental resection
Question:
Features of potentially malignant colon polyps
Answer:
>2cm (large), sessile (flat) or villous (looks like shaggy villi)
Question:
Stump Pouchitis
Answer:
the main nutrient of colonocytes are short chain fatty acids, so in stumps that are not used or have
diversion, they can undergo inflammatory changes. TXT: SCFA enema
,Question:
Colonic inertia
Answer:
slow transit time; patients may need subtotal colectomy
Question:
Crypts of Lieberkuhn
Answer:
mucin-secreting goblet cells
Question:
Auerbach's Plexus
Answer:
myenteric plexus
- located between longitudinal and circular muscular layers
Question:
Meissner's Plexus
Answer:
submucosal plexus
- controls glands and mucosal folds
Question:
internal anal sphincter
Answer:
involuntary control
- pelvic splanchnic nerves (parasympathetic)
- continuation of muscularis propria
Question:
external anal sphincter
Answer:
voluntary control
- internal pudendal nerve
- continuation of levator ani muscle
, Question:
watershed zones of colon
Answer:
splenic flexure (Griffith's point) - SMA and IMA junction
- rectum (Sudak's point) - superior rectal and middle rectal junction
**colon more sensitive to ischemia than small bowel due to decreased collaterals
Question:
what makes the inferior rectal vein special?
Answer:
the superior and middle rectal veins drain into the IMV and eventually the portal venous system, while
the inferior rectal vein drains into the internal iliac veins and the systemic venous system, acting as the
alternative method of circulation return for patients with cirrhosis.
Question:
inferior rectal artery is a branch of the
Answer:
internal pudendal artery (branch of internal iliac)
Question:
middle rectal artery is a branch of the
Answer:
branch of internal iliac
Question:
Colorectal Muscularis Mucosa vs Propria
Answer:
Muscularis mucosa:
small interwoven inner muscle layer just below mucosa but above basement membrane
-Muscularis propria: circular + longitudinal layer of muscle, contains myenteric plexus
(Auerbach's plexus)
Question:
most common site of primary tumor in colorectal cancer
Answer:
sigmoid colon
update 2026/2027
Question:
infectious agent assc with colon cancer
Answer:
clostridium septicum
Question:
Describe differences between APR and LAR
Answer:
APR: abdominal perineal resection: removal of distal colon, rectum, and anal sphincter complex
through perineum and ant abd wall
*requires permanent colostomy
- LAR: low anterior resection: removal of rectum, then attach colon to remaining rectum
Question:
Treatment for low rectal villous adenomas with atypia or T1
Answer:
<4cm & can completely resect with 2mm margins: transanal excision (using tools through the anus to
resect mucosa + primary repair)
Question:
Treatment for colonic polyps
Answer:
endoscopic removal (T1, into submucosa)
- if can't remove completely (like sessile polyps) or margins not clear -> segmental resection
Question:
Features of potentially malignant colon polyps
Answer:
>2cm (large), sessile (flat) or villous (looks like shaggy villi)
Question:
Stump Pouchitis
Answer:
the main nutrient of colonocytes are short chain fatty acids, so in stumps that are not used or have
diversion, they can undergo inflammatory changes. TXT: SCFA enema
,Question:
Colonic inertia
Answer:
slow transit time; patients may need subtotal colectomy
Question:
Crypts of Lieberkuhn
Answer:
mucin-secreting goblet cells
Question:
Auerbach's Plexus
Answer:
myenteric plexus
- located between longitudinal and circular muscular layers
Question:
Meissner's Plexus
Answer:
submucosal plexus
- controls glands and mucosal folds
Question:
internal anal sphincter
Answer:
involuntary control
- pelvic splanchnic nerves (parasympathetic)
- continuation of muscularis propria
Question:
external anal sphincter
Answer:
voluntary control
- internal pudendal nerve
- continuation of levator ani muscle
, Question:
watershed zones of colon
Answer:
splenic flexure (Griffith's point) - SMA and IMA junction
- rectum (Sudak's point) - superior rectal and middle rectal junction
**colon more sensitive to ischemia than small bowel due to decreased collaterals
Question:
what makes the inferior rectal vein special?
Answer:
the superior and middle rectal veins drain into the IMV and eventually the portal venous system, while
the inferior rectal vein drains into the internal iliac veins and the systemic venous system, acting as the
alternative method of circulation return for patients with cirrhosis.
Question:
inferior rectal artery is a branch of the
Answer:
internal pudendal artery (branch of internal iliac)
Question:
middle rectal artery is a branch of the
Answer:
branch of internal iliac
Question:
Colorectal Muscularis Mucosa vs Propria
Answer:
Muscularis mucosa:
small interwoven inner muscle layer just below mucosa but above basement membrane
-Muscularis propria: circular + longitudinal layer of muscle, contains myenteric plexus
(Auerbach's plexus)
Question:
most common site of primary tumor in colorectal cancer
Answer:
sigmoid colon
