3. Crohn Disease
Crohn disease is a chronic transmural inflammatory disease that can affect any part of the
GI tract (mouth to anus) but most commonly involves the small bowel (terminal ileum).
Distribution: There are three major patterns of disease:
a. 40% have disease in the terminal ileum and cecum.
b. 30% have disease confined to the small intestine.
c. 20% have disease confined to the colon.
d. Rarely, other parts of GI tract may be involved (stomach, mouth, esophagus)
Sex: ♂ = ♀
Typical age of onset: bimodal distribution with one peak at 15–35 years and another one
at 55–70 years
Risk factors
• Familial aggregation
• Genetic predisposition (e.g., mutation of the NOD2 gene, HLA B27 association)
• Tobacco smoke
4. Pathology
a. Terminal ileum is the hallmark location, but other sites of GI tract may also be
involved.
b. Skip lesions—discontinuous involvement
c. Fistulae
d. Luminal strictures
e. Noncaseating granulomas
f. Transmural thickening and inflammation (full-thickness wall involvement)—
results in narrowing of the lumen.
g. Mesenteric “fat creeping” onto the antimesenteric border of small bowel.
h. Cobblestones appearnace
5. c/p:
Constitutional symptoms : Low-grade fever, Weight loss, Fatigue
Gastrointestinal symptoms : CD most commonly affects the terminal ileum
and colon, but involvement of any part of the GI tract (from mouth to anus) is
possible. In contrast to ulcerative colitis, rectal involvement is uncommon.
1. Chronic diarrhea
2. Lower gastrointestinal bleeding (uncommon)
3. Abdominal pain, typically in the RLQ
4. Palpable abdominal mass in the RLQ
5. Features of CD complications
• Malabsorption (e.g., weight loss, anemia, failure to thrive)
• Enterocutaneous or perianal fistulas, often associated with abscess
formation
7. Complications
1. Fistulae—between colon and other segments of intestine (enteroenteral), bladder
(enterovesical), vagina (enterovaginal), and skin (enterocutaneous)
2. Anorectal disease (in 30% of patients)—fissures, abscesses, perianal fistulas
3. SBO (in 20% to 30% of patients) is the most common indication for surgery.
4. Malignancy—increased risk of colonic and small bowel tumors (but less common
than risk of malignancy in UC).
5. Malabsorption of vitamin B12 and bile acids (both occur in terminal ileum).
6. Cholelithiasis may occur secondary to decreased bile acid absorption.
7. Nephrolithiasis—increased colonic absorption of dietary oxalate can lead to calcium
oxalate kidney stones.
8. Aphthous ulcers of lips, gingiva, and buccal mucosa (common)
9. Toxic megacolon—less common in Crohn disease than in UC
10. Growth retardation
8.
9. Ulcerative Colitis
• UC is a chronic inflammatory disease of the colon or rectal mucosa.
• It may occur at any age (usually begins in adolescence or young adulthood).
• Distribution: UC involves the rectum in all cases and can involve the colon either partially
or entirely, but is always continuous. There are no skip lesions as are seen in Crohn
disease.
1. Rectum alone (in 10% of cases)
2. Rectum and left colon (in 40% of cases)
3. Rectum, left colon, and right colon (in 30% of cases)
4. Pancolitis (in 30% of cases)
5. The small bowel is not usually involved in UC, but it may reach the distal ileum
in a small percentage of patients (“backwash ileitis” in 10% of cases)
• characterized by periodic exacerbations and periods of complete remission. Less than 5%
of patients have an initial attack without any recurrence.
10. Pathology
a. Uninterrupted involvement of rectum and/or colon
b. Inflammation is not transmural (as it is in Crohn disease). It is limited to the mucosa and
submucosa.
c. PMNs accumulate in the crypts of the colon causing crypt abscesses.
11. Clinical Features (wide ranges of presentation are seen)
1. Hematochezia (bloody diarrhea)
2. Abdominal pain
3. Bowel movements are frequent but small
4. Fever, anorexia, and weight loss (severe cases)
5. Tenesmus (rectal dry heaves)
6. Extraintestinal symptoms : mainly 1° sclerosing cholangitis. Associated with MPO
ANCA/p-ANCA.
Diagnosis: perform the following initial studies
1. Stool cultures for Clostridium difficile, ova, and parasites to rule out infectious
diarrhea.
2. Fecal leukocytes a. WBCs can appear in UC, ischemic colitis, or infectious diarrhea.
3. Colonoscopy to assess the extent of disease and the presence of any complications
12. Complications
1. Iron deficiency anemia
2. Hemorrhage
3. Electrolyte disturbances and dehydration secondary to diarrhea
4. Strictures, benign and malignant (usually malignant)
5. Colon cancer—The risk correlates with extent and duration of colitis. In distal
proctitis there is no increased risk of CRC.
6. Sclerosing cholangitis (SC)—Does not correlate with bowel disease and is not
prevented by colectomy.
7. Cholangiocarcinoma—Half of all bile duct cancers are associated with UC
8. Toxic megacolon is the leading cause of death in UC and affects <5% of patients.
It is associated with the risk of colonic perforation.
9. Growth retardation
10. Narcotic abuse
11. Psychosocial issues (e.g., depression) due to chronicity and often disabling nature
of the disease
