IBD Pathology

Question 1

Name 4 important pathologic components of normal small bowel

Answer 1

Villi
Intraepithelial lymphocytes (~20/100)
Paneth cells
Brunners glands in duodenum

Question 2

Where are lymphoid aggregates?

Answer 2

Terminal ileum

Question 3

Contrast paneth cells from neuroendocrine cells

Answer 3

Neuroendocrine cells are on basement membrane of crypts have thinner/smaller nuclei

Paneth cells are closer to lumen and have chunkier pinker nuclei

Question 4

What are the two diseases in IBD?

Answer 4

Crohn’s disease and ulcerative colitis

Question 5

Describe basic epidemiology of IBD

Answer 5

Presents in teens and younger 20s
Most common among caucasians– Norther America, Norther Europe, Australia
3-5 more common in Ashkenazi jews

Question 6

What are four large factors in pathogenesis in IBD?

Answer 6

Genetics, microbial factors, environmental factors, immune dysfunction

Question 7

What gene is strongly associated with Crohn’s disease? What is its function?

Answer 7

NOD2 on chromosome 16. Detects MDP and binds to bacterial peptidoglycans and initiates NF-kB and MAPK-dependent gene transcritipn

Question 8

IBD associated genes are involved in responses to what type of bacteria?

Answer 8

Mycobacteria including M. Tuberculosis and M. Leprae

Question 9

What are the features of chronicity in IBD? (4)

Answer 9

Architectural distortion
Basal lymphoplasmacytosis
Paneth cell metaplasia (left side only)
Pyloric metaplasia (terminal ileum/cecum)

Question 10

What are other causes of chronic mucosal injury? (3)

Answer 10

Ischemia
XRT/chemo
Chronic infection

Chronic mucosal injury does not mean it is IBD. Need clinical/endoscopic findings or full thickness section

Question 11

What does “activity” in IBD mean?

Answer 11

Activity refers to the presence of neutrophils– They are never normal in lamina propria or crypt epithelium

Question 12

Describe the different lesion patterns of crohn disease vs. ulcerative colitis

Answer 12

Crohn’s disease: skip lesions with transmural inflammation, ulcerations and fissures

UC: continuous colonic involvement that goes rectum up with pseudopolyps and ulcers

Question 13

What is presentation of Crohn’s disease?

Answer 13

Intermittent attacks of diarrhea, fever and abdominal pain that are interrupted by asymptomatic periods that last for weeks-months

Smoking is a strong exogenous risk factor for development of Crohn’s

Question 14

What are most common sites of chohn’s disease?

Answer 14

It can occur anywhere in GI tract….but most common sites are terminal ileum, ileocecal valve and cecum.

Small intestine alone=40%
SI+colon=30%

Question 15

What are major perianal complications of Crohn’s? How common is it?

Answer 15

35-45% of patients are affected

Major complications include fissures, fistulas, abscesses and stenosis

Question 16

What are the macroscopic features of Crohn’s disease? (6)

Answer 16

Skip lesions
Cobblestoning
Strictures (due to hypertrophy of muscular propria)
Creeping fat
Fissures
Fistulas (due to transmural inflammation)

Question 17

What are the microscopic features of Crohn’s disease? (5)

Answer 17

Transmural inflammation: from mucosa to serosa
Features of chronic mucosal injury
Active disease: cryptitis or crypt abscesses
Knife-like ulcerations
Non-Caveating epithelioid granulomas (35%)

Question 18

Where is ulcerative colitis usually present?

Answer 18

Limited to colon and rectum (though can get backwash ileitis)
If entire colon is diseased– pancolitis
If just rectum: ulcerative proctitis

Question 19

What are macroscopic features of UC? (3)

Answer 19

Abrupt transition between diseased/uninvolved colon
Ulcers and inflammatory pseudopolyps
Mucosal bridges: fusion of tips of polyps

No fissures, fistulas, mural thickening, serositis or non-neoplastic strictures

Question 20

What are the microscopic features of UC?

Answer 20

Chronic mucosal damage
If active, cryptitits, crypt abscesses
Diffuse inflammatory process limited to mucosa and superficial subucosa

Question 21

How do you tell Crohn’s and UC apart microscopically?

Answer 21

Crohn’s: Transmural inflammation from mucosa to serosa

UC: Diffuse inflammatory process limited to mucosa and superficial submucosa. Mucularis propria is spared

Question 22

What is a mucin-granuloma or crypt-rupture granuloma?

Answer 22

Describes crypts that are destroyed by neutrophilic infiltrate. It can occur in either UC or Crohn’s.

DO NOT CONFUSE WITH EPITHELIOID GRANULOMA OF CROHN’S

Question 23

What is backwash ileitis?

When do you see it?

Answer 23

Incompetence of ileocecal valve due to severe colonic disease results in retrograde flow of colonic contents into distal ileum, leading to inflammation.

Backwash ileitis is observed in UC patients with pancolitis

Question 24

What is the relationship between IBD and colorectal carcinoma?

Answer 24

Duration of IBD is associated with risk of developing colorectal carcinoma

Question 25

What is best marker for risk of carcinogenesis?

Answer 25

Dysplasia

Question 26

What are the types of dysplasia? Which one can be seen on endoscopy?

Answer 26

Can be flat or raised.

Flat– Not endoscopically visible

Question 27

What is DALM?

Answer 27

DALM is endoscopically visible dysplasia associated lesion or mass

Question 28

What is strategy for flat dysplasia?

Answer 28

If low grade, repeat in 6 months. If still see dysplasia then colectomy.
If high grade dysplasia, do a colectomy