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Inflammatory Bowel Disease (IBD): Crohn's vs. Ulcerative Colitis

With Dr. Yusra Sharif — Gastroenterologist, Hadassah Hospital


Inflammatory Bowel Disease (IBD) is a chronic inflammatory disorder of the gastrointestinal tract and one of the most important high-yield topics for IMLE and USMLE preparation. Understanding IBD requires connecting pathophysiology, clinical presentation, colonoscopy findings, and treatment decisions — not just memorizing tables.


Cross-section image of intestines, comparing Ulcerative Colitis with Crohn's Disease. Red inflamed tissue, purple labels, medical context.

In this session, Dr. Yusra Sharif — Gastroenterologist at Hadassah Hospital — guides you through the essentials of IBD in a structured, exam-focused way.


Inside Brocali, this video is accompanied by summary pages, clinical reasoning breakdowns, and integrated exam-style questions to maximize retention and prepare you for rotations or licensing exams.


🎬 Watch the full video lesson here



What Is Inflammatory Bowel Disease (IBD)?


IBD refers to chronic inflammatory disorders of the GI tract, including:

  • Crohn’s disease

  • Ulcerative colitis

Both involve recurrent intestinal inflammation, leading to:

  • Diarrhea

  • Abdominal pain

  • Weight loss

  • Fatigue

IBD is complex because it combines immune dysregulation, genetics, and environmental triggers to create chronic inflammation.

Epidemiology, Etiology & Risk Factors

Feature

Ulcerative Colitis

Crohn’s Disease

Age

2nd–4th decades, 7th–9th decades

2nd–4th decades, 7th–9th decades

Race

Jewish > Non-Jewish white > Black > Latino > Asian

Jewish > Non-Jewish white > Black > Latino > Asian

Gender ratio (F:M)

0.51–1.58

0.34–1.65

Key point for exams: Crohn’s disease is slightly more common in males, UC slightly more in females, and both peak in young adults.


The exact cause of IBD is unknown. It results from genetic predisposition + environmental triggers + immune dysregulation + microbiota interactions.

Factor

Ulcerative Colitis

Crohn’s Disease

Smoking

May prevent disease

May increase risk

Oral contraceptives

No risk

Increased risk (HR 2.82)

Appendectomy

Protective

Not protective

Venn diagram on IBD etiology shows genetics, immune dysregulation, and environment. Includes age onset graph and smoking risk for colitis/Crohn’s.

Pathophysiology


IBD occurs when the immune system mistakenly attacks the gut lining.

  • Crohn’s disease: Transmural inflammation → can affect any part of GI tract → thick bowel wall, skip lesions, fistulas, strictures.

  • Ulcerative colitis: Mucosal inflammation → continuous from rectum → thin bowel wall, pseudopolyps.

High-yield exam insight: Granulomas suggest Crohn’s; crypt abscesses suggest UC.

Clinical Features

Feature

Ulcerative Colitis

Crohn’s Disease

Abdominal pain

Yes

Yes

Diarrhea

Bloody with mucus

Chronic diarrhea

Fever

Yes

Yes, high spiking if abscess

Hematochezia

Common

Rare

Tenesmus

Yes

No

Perianal involvement

No

Common

Strictures & fistulas

No

Yes

Extraintestinal

Erythema nodosum, arthritis

Pyoderma gangrenosum, arthritis

Note: B12 deficiency occurs with Crohn’s if terminal ileum is involved.


Infographic of clinical signs: shared symptoms are abdominal pain, fever, weight loss; UC differentiates with bloody diarrhea, tenesmus; Crohn's with RLQ pain, B12 malabsorption.
Chart illustrating extra-intestinal manifestations linked to disease activity in a human body outline. Includes conditions like episcleritis, erythema nodosum, and more.

Diagnosis


Diagnosis relies on clinical features, colonoscopy, imaging, and histopathology.

Colonoscopy findings:

  • Crohn’s: Skip lesions, cobblestone mucosa, aphthous ulcers, strictures, fistulas

  • UC: Continuous mucosal inflammation, pseudopolyps, loss of haustra

Histopathology:

  • Crohn’s: Granulomas, transmural inflammation, deep ulcers

  • UC: Superficial mucosal inflammation, crypt abscesses, no granulomas

Imaging: CT/MRI enterography for bowel wall thickening, strictures, fistulas, abscesses

⚠️ Exam alert: Stool culture is essential to rule out infection before starting immunosuppressive therapy.
"Lab workup chart shows high CRP, ESR, low ferritin, high fecal calprotectin; p-ANCA and ASCA positive with antibody visuals."

Management of IBD


Treatment goals: Reduce inflammation, induce remission, maintain remission, prevent complications

Therapy

Indications

Examples

Amino-salicylates

Mild–moderate UC

Mesalamine, Sulfasalazine

Corticosteroids

Moderate–severe flares

Prednisone, Budesonide

Immunomodulators

Maintenance, steroid-resistant

Cyclosporine, 6-mercaptopurine

Biologics

Moderate–severe, refractory

Infliximab, Adalimumab

Surgery

Refractory disease, complications

Colectomy in UC, resection for Crohn’s strictures

High-yield pearl: Crohn’s with fistula → first-line = Infliximab

Non-pharmacological: Nutritional support, smoking cessation (especially in Crohn’s)


Pyramid diagram of pharmacological treatments shows levels: 5-ASA, Corticosteroids, Immunomodulators, Surgery. Strategy: Induce/Maintain remission.

Complications

Complication

Presentation

Management

Toxic megacolon

Severe colonic distension, sepsis

Emergency surgery (colectomy)

Strictures (Crohn’s)

Intestinal obstruction

Balloon dilation, surgery

Fistulas

Perianal, enterocutaneous

Biologics, antibiotics, surgery if refractory

Intra-abdominal abscess

Fever, leukocytosis

Drainage

Colorectal cancer

Chronic inflammation

Screening colonoscopy every 2 years after 8 years

Diagram of disease complications. Crohn's shows fistulas, strictures, fibrosis. UC illustrates megacolon, malignancy. Labels highlight issues.

How Brocali Teaches IBD Differently


With Brocali, you don’t just learn facts. You train your exam-thinking process:

  • Step-by-step video explanation

  • Summary pages for quick review

  • High-yield exam-style questions

  • Weak-point reinforcement

  • Integrated clinical reasoning



If you’re interested in seeing how Brocali works or have any questions about our learning platform, you can easily schedule a demo call at your convenience.




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