Summary
Highlights
Ulcerative colitis (UC) is twice as common as Crohn's disease. Both typically diagnosed between 15-30 years. UC is confined to the colon and rectum, while Crohn's can affect anywhere in the GI tract.
Both UC and Crohn's feature diarrhea, abdominal pain, urgency, and tenesmus. UC more likely involves bloody diarrhea and toxic megacolon. Crohn's can cause ulcers, strictures, and fistulas, commonly affecting the terminal ileum and proximal colon, leading to malabsorption.
Crohn's disease frequently exhibits extra-gastrointestinal effects, including arthritis, osteoporosis, skin issues (erythema nodosum, pyoderma gangrenosum), eye problems (uveitis, episcleritis), and liver involvement. Anemia is also included here which can come as a result of iron deficiency due to poor absorption or chronic bleeding as well as vitamin b12 and folate deficiencies.
Both diseases result from a combination of genetic susceptibility, environmental factors, and gut microbiome impact, leading to immune activation. Smoking is protective in UC. Certain medications, procedures such as tonsillectomy and appendectomy (for Crohn's), and diet are also risk factors.
Fecal calprotectin indicates GI inflammation, but colonoscopy and biopsy confirm the diagnosis. UC shows continuous lesions in the mucosal layers. Crohn's features discontinuous, transmural inflammation with a cobblestone pattern.
Histologically, UC has fewer goblet cells. The architecture of glands is better preserved in Crohn's. Inflammation is mucosal in UC and transmural in Crohn's. Granulomas are present in Crohn's but not UC.
Treatment includes corticosteroids (except in stricturing Crohn's), aminosalicylates (mesalazine for UC), thiopurines, immunomodulators, and biologics (anti-TNF alpha agents). Antibiotics and proton pump inhibitors may be used. Surgery, including bowel resection, is done in severe cases; total proctocolectomy is curative for UC.