To help you prepare for clinical exams, this case study is designed to walk you through a Differential Diagnosis between Crohn Disease (CD) and Ulcerative Colitis (UC). We will use a “Step-by-Step” clinical reasoning format.
Part 1: The Clinical Presentation
Patient Profile: * Name: Maria, a 26-year-old female.
- Presenting Symptoms: 3-month history of intermittent abdominal pain and loose stools.
- Physical Findings: Maria appears thin and pale. She has a painful, red, raised lump on her right shin. Her abdomen is tender to the touch, specifically in the right lower quadrant.
Critical Thinking Checkpoint #1
- Based on the location of the pain (RLQ), which disease is more likely?
- What is the likely name of the skin lesion on her shin?
Answer: > 1. Crohn Disease. The terminal ileum is located in the Right Lower Quadrant and is the most common site for CD. UC typically presents with Left Lower Quadrant pain.
2. Erythema Nodosum. This is a common extraintestinal manifestation of IBD.
Part 2: The Endoscopic Clues
Maria undergoes a colonoscopy. The gastroenterologist observes the following:
- Rectum: Completely normal (Rectal sparing).
- Descending Colon: Healthy tissue.
- Terminal Ileum: Significant swelling with deep, linear, “knife-like” cracks. Between these cracks, the tissue looks like “cobblestones.”
Critical Thinking Checkpoint #2
- What is the term for the healthy tissue found between the diseased segments?
- How would this endoscopy look different if Maria had Ulcerative Colitis?
Answer:
- Skip Lesions. CD is patchy; UC is continuous.
- In UC, the inflammation would start at the rectum and move upward without stopping (continuous). You would see “red sandpaper” (granular) tissue rather than deep cracks.
Part 3: The Microscopic Evidence
Biopsies are taken from the “cobblestone” areas. The pathology report describes:
- Depth: Inflammation extending through the mucosa, into the muscle, and reaching the outer fat layer.
- Structures: Clusters of macrophages forming non-caseating granulomas.
Critical Thinking Checkpoint #3
- What is the term for inflammation that affects all layers of the bowel wall?
- True or False: If the pathologist saw “Crypt Abscesses,” the diagnosis must be Ulcerative Colitis.
Answer:
- Transmural Inflammation.
- False. While crypt abscesses are very common in UC, they can also appear in CD. However, granulomas are only found in CD.
Part 4: The Surgical Conclusion
Maria eventually develops a stricture (narrowing) in her ileum that causes a bowel obstruction. She undergoes surgery to remove the damaged segment.
Final Synthesis Question
Why is this surgery considered a “management of complications” rather than a “cure”?
Answer: > Because Crohn’s can occur anywhere from the mouth to the anus. Removing one segment does not prevent the immune system from attacking a different part of the GI tract later. In contrast, removing the colon (colectomy) is considered a cure for UC because the disease is limited to that organ.
Summary Table for Exam Review
| Feature | Maria’s Findings (CD) | If it were UC |
| Pain Location | Right Lower Quadrant | Left Lower Quadrant / Rectum |
| Blood in Stool | Often absent/occult | Visible/Gross blood |
| Endoscopy | Skip lesions & Cobblestones | Continuous & Granular |
| Depth | Transmural (Deep) | Mucosal (Shallow) |
| Complications | Fistulas & Strictures | Toxic Megacolon |