162b/163b/164b/165b - Colon Stuff (Path, Clin features, IBD, Colon cancer) Flashcards
What imaging method is preferred to evaluate colorectal cancer?
Colonoscopy
- Allows for localization, biopsy, and removal of polyps
- Diagnostic of colon cancer
- Other modalities prompt need for colonoscopy if findings are suspicious
Which genetic mutation is asociated with flat or depressed adenomas?
What is the treatment?
Lynch syndrome (HNPCC)
Mutation in one of the mismatch repair genes
- Prophylactec sub-total colectomy
(can leave the rectum in place) - Screening for other cancers (esp endometrial, ovarian)
Which of the following is true?
- The incidence of colorectal cancer is generally lower in more developed countries
- In the US, colorectal cancer is the most common gastrointestinal cancer
- A diet high in fiber has been associated with a higher risk of colorectal cancer
- Obesity has been associated with a lower risk of colorectal cancer
b.
In the US, colorectal cancer is the most common gastrointestinal cancer
Which of the following is true regarding microscopic colitis?
- It is predominantly seen in young, male patients
- Abdominal pain is a common symptom
- Ranitidine has been implicated as a possible trigger
- Presence of > than 10 intraepithelial lymphocytes per high power field is diagnostic of lymphocytic colitis
c. Ranitidine has been implicated as a possible trigger
* PPIs, H2 blockers, and NSAIDs are implicated as triggers
Which two syndromes have multiple harmatomatous polyps?
How can you differentiate between them on presentation?
-
Peutz-Jeghers (STK11 mutation, autosomal dominant)
- Mucocutaneous hyperpigmentation
- May present with intussusception
- More “arborization” on histology due to smooth muscle predominance
-
Juvenile polyposis (SMAD4 mutation, autosomal dominant)
- Rectal bleeding + digital clubbing
What is the dignostic test of choice for diverticulitis?
What findings would confirm the diagnosis?
CT scan
- Presence of diverticula
- Thickened colonic wall >4mm
- Inflammation within pericolic fat +/- fluid collection
**Barium enema and colonoscopy are contraindicated if diverticulitis is suspected; risk of perforation**
Crohn’s or Ulcerative Colitis?
More likely to have anal lesons
Crohn’s
Crohn’s or Ulcerative Colitis?
Skip lesions
Crohn’s
What is the treatment of choice for colorectal cancer?
Surgery
- Completely remove lesion w/clear margin + vessels and nodes
- Even if surgery is not curative, operate to treat obstruction and bleeding
- In some patients, resect mets to liver and/or lung
Chemotherapy and radiation are usually adjuvants or for palliation
What are crypts supposed to look like?
“Tubes in a rack”
If they look like anything else, something is wrong
Crohn’s or Ulcerative Colitis?
Crypt abscesses filled with neutrophils
Ulcerative Colitis
Why are diverticula most prevalent in the sigmoid colon?
Smallest diameter = highest pressure during segmentation
Is a colonoscopy indicated after the first episode of diverticulitis?
Yes
But not immediately! Wait for episode to subside, then colonoscopy later to figure out what’s going on
What histologic findings are diagnostic of microscopic colitis?
- Lymphocytic colitis:
- Collagenous colitis:
- Lymphocytic colitis: >20 lymphocytes/hpf
- Collagenous colitis: collagen band >10 micrometers
Crohn’s or Ulcerative Colitis?
Inflammation limited to the mucosa
Ulcerative Colitis
What gene is associated with Crohn’s disease?
What does the gene do?
NOD2 (aka CARD 15) on Chromosome 16
- Encodes for a protein that binds bacterial peptidoglycan
- -> Activation of NFK-b
- -> Transcription of proinflammatory and protective molecules
- When this is disrupted -> Crohn’s
- Implicated in 20% of Crohn’s in Caucasian and Jewish populations
Diverticular bleeding is most likely coming from a diverticulum in which location?
Right colon (usually divirticula here are wider-mouthed?)
(Even though the most common location for diverticula formation is the sigmoid colon)
What diagnostic tests are useful in diagnosing ishcemic colitis?
- Imaging
- Look for thumb-printing (edema) and pneumomatosis
- Colonoscopy is diagnostic
- And helpful in determining whether parts need to be removed
- Single stripe sign is diagnostic
Describe the signs and symptoms of colon cancer (6)
How does presentation differe in right-side vs. left side?
- Abdominal or rectal pain
- Change in bowel movement pattern
- Hematochezia
- Anemia
- Weight loss/fatigue
- Obstruction
- Right
- More blood loss, fatigue, anemia
- Left
- Obstruction more likely
- More hematochezia
Crohn’s or Ulcerative Colitis?
Must involve the rectum
Ulcerative Colitis
(UC involves the rectum by definition; Crohn’s can affect any part of the GI tract, including the rectum)
Crohn’s or Ulcerative Colitis?
More likely to cause perforation, fistula, or stricture
Crohn’s
(inflammation is transmural, vs UC is limited to the mucosa)
If a patient with a family history of colon cancer diagnosed before age 50 has congenital hypertrophy of retinal pigment epithelium, what should you do?
What genetic mutation do they likely have?
Early screening for colon cancer!!
They likely have FAP (mutation in APC gene)
-> basically 100% lifetime risk of colon cancer
List 4 neoplastic polyps
Are they precursors to colon cancer?
- Tubular adenoma
- Villous adenoma
- Tubulovillous adenoma
- Sessile serrated adenoma
These ARE precursors to colon cancer