Inflammatory bowel disease

Inflammatory bowel disease, abbreviated IBD, is the bread 'n butter of gastroenterology.

It exists in two main flavours:

• Crohn's disease (CD).
• Ulcerative colitis (UC).

Both are associated with an increased risk of colorectal carcinoma.

Clinical

• It is important to differentiate UC and CD as the management is different.
• UC patients get pouches... CD patients do not.
  • It is said that: There 's nothing like a pouch to bring out Crohn's disease.
• People with long standing IBD have an increased risk for:
  • Carcinoma - usually colorectal carcinoma.
    • Small increased risk for small bowel adenocarcinoma in Crohn's disease.
  • Lymphoma - in association with thiopurine use.

Extra-intestinal manifestations of inflammatory bowel disease

Mnemonic (family-rated version) excellent cardiac surgery is pleasant and appreciated:

• Erythema nodosum.
• Clubbing.
• Sclerosing cholangitis.
• Iritis.
• Pyoderma gangrenosum.
• Aphthous ulcers.
• Arthritis.

Molecular

• NOD2 (AKA CARD15) variants are associated with stricturing CD, early need for surgery and recurrence.

General clinical differential diagnosis

• Crohn's disease.
• Ulcerative colitis.
• Infective colitis/enteritis.
• Ischemic colitis/enteritis.
• Radiation colitis.

Others:

• Irritable bowel syndrome.

Microscopic

Features helpful for the diagnosis of IBD - as based on a study:

1. Basal inflammation, i.e. crypt base, plasmacytosis with severe chronic inflammation.
   • Basal cell plasmacytosis makes an infectious etiology less likely.
   • "Basal plasmacytosis" = plasma cells in the lamina propria between the crypts and muscularis mucosae.
2. Crypt architectural abnormalities.
   • Atrophy = less glands ~ 3-4 glands/mm (normal = 7-8 glands/mm).
   • Branching = common (normal = very rare branching).
   • Distortion = bent glands, marked size variation (normal = "rack of test tubes").
3. Distal Paneth cell metaplasia.
   • Paneth cells should not be in the left colon - if you see 'em think of IBD and other long-standing injurious processes.
   • Some claim that (friendly right colonic) paneth cells and paneth cell metaplasia look quite different and can be distinguished.

Notes:

1. Microscopic features can be remembered by mnemonic CPP: Crypts (abnormal), Plasmacytosis, Paneth cells where they don't belong.
2. If you see architectural distortion (e.g. crypt branching) in the left colon, look for Paneth cells.
3. The hepatic flexure is considered the divider for normal paneth cells and abnormal paneth cells, i.e. paneth cells proximal to the hepatic flexure are normal; paneth cells distal to the hepatic flexure are abnormal.
4. Stretching of tissue may mimic atrophy; tip-off it is artefact: thinning of mucosa.

Images:

• Crohn's disease - beautiful granulomas in the colon - high mag. (WC).
• Crohn's disease - duodenum - intermed. mag. (WC).
• Cryptitis - high mag. (WC).
• Crypt branching (WC).

Grading

• Several systems exists.
• One that is often cited is by Gupta et al..

Grading schemes for IBD in a table

	Nil	Mild	Moderate	Severe
"A grading scheme"	-	cryptitis	PMN abscesses	erosions
Gupta	"0" (nil)	"1" (<50% of crypts have PMNs)	"2" (>50% of crypts have PMNs)	"3" (presence of ulcers or erosions)

Crohn's disease vs. ulcerative colitis

• Some cases cannot be classified by the experts (see "indeterminate colitis").

Robbins

UC features:

• Mucosal involvement -- sometimes submucosa.
• No skip lesions.
• Colon/rectum only.
  • UC may have 'ileal backwash' -- mild ileal inflammation due to backwash of inflammatory soup from colon.
• "No granulomas".
  • Superficial granulomas in the mucosa are non-specific, especially if they are beside an inflammed crypt, i.e. they may be present in UC.
    • Deep granulomas are specific for Crohn's disease.

Example of a superficial granuloma that is non-specific, i.e. this could be UC or CD:

• Colitis with a superficial granuloma (WC).

Kirsch

Features of UC - memory device DDDR:

• Diffuse inflammation.
• Diffuse arch. changes.
• Diffuse atrophy.
• Rectal involvement.

Words of caution

The following may be present in UC:

• Cecal patch (cecal involvement without pancolitis).
• Patchy involvement
  • Esp. in Tx'ed patients.
  • Esp. in children.
• Ileitis - esp. in the context of severe pancolitis; known as backwash ileitis.
• Deep inflammation (in a fissure).
• Upper GI tract involvement -- see below.

Upper gastrointestinal tract involvement

• The old dogma was upper GI tract = Crohn's disease.

Characteristics of upper GI tract UC:

• Most common:
  1. Focal gastritis.
  2. Mixed basal inflammation and superficial plasmacytosis in the stomach.
• Unique:
  • Diffuse chronic duodenitis.
  • ~ 10% of UC patients.
  • ~ 40% of UC + colectomy + pouchitis.

A tabular comparison

Gross pathology:

Feature	Crohn's disease	Ulcerative colitis
Lesion distribution	patchy	diffuse
Strictures	maybe	no
Perianal disease	yes/no	no
Rectal involvement	no	yes
Ileal involvement	yes, classic	usu. no; seen in pancolitis
Upper GI tract involvement	yes	yes (gaining acceptance)
Associated with PSC	?	yes

Ulcerative colitis

• Often abbreviated as UC.

General

• May be associated with toxic megacolon.

Epidemiology:

• Associated with primary sclerosing cholangitis.
• Appendicitis is considered protective against UC.
• Smoking is protective; the opposite is true for Crohn's disease.

Gross

• Conventionally considered to be contiguous, i.e. no "skip lesions", with rectal involvement being most severe.
• Dependent on the study one reads... rectal sparing may be seen in 15% of UC patients.

Microscopic

Features:

• Lack of granulomas.
• No full wall-thickness inflammation.

Crohn's disease

• Often abbreviated as CD.

General

• Autoimmune disease.
• Increased risk for cancer - usu. rectal cancer; classically mucinous adenocarcinoma.

Associations:

• High socioeconomic status.
• Family history of IBD.
• City dwellers.
• Not breastfed.

Treatment:

• Immune suppression.
• Surgery considered treatment of last resort.

Gross

• Aphthous ulcer - first gross finding of IBD.
• Transmural inflammation, i.e. full thickness of bowel wall.
• Creeping fat (also "fat wrapping" and "fat hypertrophy") - abundant fat, fat on anti-mesenteric side of the bowel.
  • Can be seen radiologically; may be seen in vasculitis.
• Cobblestone appearance -- may be described as such on endoscopy; due to edema.
• Serpiginous ulcers.
  • Image: Serpiginous ulcer (endoscopy) - wikipedia.org.

Microscopic

Features:

• Segmental crypt architectural abnormalities.
• Mucin depletion -- less goblet cells. (???)
• Mucin preservation at the active sites.
• Focal chronic inflammation without crypt atrophy.

DDx:

• Infectious colitis:
  • Amebiasis.
• Ulcerative colitis.

Sign-out

A. TERMINAL ILEUM, BIOPSY
	- MODERATE GRANULOMATOUS ILEITIS.

B. CECUM, BIOPSY:
	- MILD PATCHY ACTIVE CECITIS.

C. SIGMOID COLON, BIOPSY: 
	- CHRONIC INFLAMMATORY CHANGES. NO ACTIVE COLITIS. 

COMMENT:
The histomorphological findings (patchy inflammation, granulomas, ileitis, paneth cell 
metaplasia, crypt loss and crypt elongation) are suggestive of Crohn's disease. An infective 
etiology should be considered, as it cannot be definitely excluded on pathologic grounds. 

"Indeterminate colitis"

• "Indeterminate colitis" is a confusing term and should be avoided.

Terminology

1. IBDU = IBD unclassified.
2. CUTE = Colitis of uncertain type or etiology.
   • Should be reserved for resection specimens only.

Dysplasia-associated lesion or mass

• Abbreviated DALM.

General

• Proving invasive malignancy (on histopathologic grounds alone) in the setting of chronic inflammation is difficult.
• This diagnosis depends on correlation of endoscopy and histopathology - important.
  • Biopsies are usually taken of the lesion and around the base.

Microscopic

Features:

• Flat or polypoid.
• Cytologic dysplasia - as in adenomatous polyps.

DDx:

• Sporadic adenomatous polyp -- favouring sporadic:
  • Sharp transition between lesion and the surrounding tissue.
  • Polyps not at site of active disease.

Image:

• DALM (nlm.nih.gov).

Pouchitis

General

• Inflammation of an ileal pouch - a treatment for ulcerative colitis.
• Chronic pouchitis seen in approximately 15% of patients.
• May be assessed by fecal calprotectin.
• Considered a clinico-pathologic diagnosis.

Microscopic

Features:

• Neutrophils.
• +/-Crypt abscess - indicator of moderate or severe.
• Ulceration.

Scoring system

Pouchitis disease activity index (PDAI) - based on clinical and pathologic factors:

• Active pouchitis >= 7.
• Remission < 7.

The histologic component of the PDAI:

• Neutrophils.
  • Mild.
  • Moderate - crypt abscesses.
  • Severe - crypt abscesses.
• Ulceration per LPF (mean).
  • <25%.
  • 25-50%.
  • >50.

See also

• Colon.
• Colorectal tumours.
• Common variable immunodeficiency.
• Gastrointestinal pathology.
• Intestinal polyps.

External links

• Crohn's disease vs. ulcerative colitis vs. pseudomembranous colitis puzzle (unibas.ch) in a collection of games by Katharina Glatz-Krieger.