Crohn’s Disease Clinical Overview
I. The "On-Call" Snapshot
Clinical Significance in Malaysia: While historically less common than in the West, the incidence of Crohn's Disease is rising in Malaysia. It's a key differential in young patients presenting with chronic diarrhea, abdominal pain, and weight loss. Misdiagnosis, especially with intestinal tuberculosis, can lead to significant morbidity.
High-Yield Definition: Crohn's Disease is a chronic inflammatory bowel disease (IBD) characterized by transmural, granulomatous inflammation that can affect any part of the gastrointestinal tract, from the mouth to the anus, often in a discontinuous pattern (skip lesions). (Source: Malaysian CPG on Management of Inflammatory Bowel Disease, 2nd Ed., 2019).
Clinical One-Liner: Basically, it's a chronic, full-thickness gut inflammation that can pop up anywhere, causing ulcers, strictures, and fistulas.
II. Etiology & Risk Factors
Etiology: The exact cause is unknown. It's understood to be an inappropriate immune response to intestinal microbes in a genetically susceptible individual, triggered by environmental factors.
Risk Factors:
Genetic: Positive family history is the strongest risk factor.
Age: Bimodal distribution, with peaks at 15-30 years and 60-80 years.
Smoking: Strongly associated with both development and worsening of Crohn's Disease. This is a key differentiator from Ulcerative Colitis, where smoking can be protective.
Diet: High intake of processed foods and animal fats has been implicated.
III. Quick Pathophysiology
Three key features explain everything you see clinically. Remember them:
Transmural Inflammation: The inflammation goes through the entire bowel wall. This is why patients develop strictures (from scarring and fibrosis) and fistulas (abnormal tracts connecting the bowel to other structures like the skin, bladder, or other loops of bowel).
Skip Lesions: The inflammation is patchy. You can have a segment of diseased bowel, followed by a segment of completely normal bowel, then more disease. This is unlike Ulcerative Colitis, which is continuous.
Non-caseating Granulomas: This is the classic histological finding, but it's only present in about 50-60% of biopsies. Its absence does not rule out Crohn's.
IV. Clinical Assessment
Red Flags & Immediate Actions:
High-grade fever, tachycardia, severe abdominal pain: Suspect intra-abdominal abscess or perforation. Keep NBM, alert senior, get urgent surgical review.
Vomiting and inability to pass flatus/stool: Suspect bowel obstruction from a stricture. Keep NBM, insert a Ryle's tube for decompression, get an urgent AXR/CXR, and call your senior.
Perianal pain with fluctuant swelling: Suspect a perianal abscess. Requires urgent surgical drainage.
History:
Common (>50%): Chronic, colicky abdominal pain (often right lower quadrant, mimicking appendicitis), non-bloody diarrhea, significant weight loss, fatigue.
Less Common (10-50%): Low-grade fever, nausea, vomiting (if stricture present), perianal disease (fissures, fistulas, skin tags).
Extra-intestinal Manifestations (EIMs): Actively ask about these. They can be the presenting complaint.
MSK: Arthritis (peripheral or axial).
Ocular: Uveitis, episcleritis (ask about red, painful eyes).
Dermatological: Erythema nodosum, pyoderma gangrenosum.
Hepatobiliary: Primary sclerosing cholangitis (more common in UC, but can occur).
Physical Examination:
General: Look for cachexia, pallor (anemia). Check for oral aphthous ulcers.
Abdomen: May reveal a tender mass, especially in the right iliac fossa (RIF), representing inflamed bowel loops.
Perianal Examination: This is mandatory. Look for skin tags, fissures, fistulas, or abscesses. This is a huge clue for Crohn's.
Clinical Pearl: The combination of chronic diarrhea, weight loss, and perianal disease in a young person is Crohn's disease until proven otherwise.
V. Diagnostic Workflow
Differential Diagnosis:
Intestinal Tuberculosis (ITB):
Points For: Can perfectly mimic Crohn's clinically, radiologically, and endoscopically (affects terminal ileum, causes strictures). Both can have granulomas.
Points Against: History of TB contact, concomitant pulmonary TB on CXR, positive TB serology/IGRA.
How to Differentiate: This is a critical distinction. Biopsies must be sent for TB PCR and AFB culture. A trial of anti-tuberculous therapy is sometimes required if diagnosis is uncertain. Never start immunosuppressants if ITB is suspected.
Ulcerative Colitis (UC):
Points For: Both cause diarrhea and abdominal pain.
Points Against: UC almost always has bloody diarrhea, is confined to the colon, and inflammation is continuous (not patchy). Perianal disease and strictures are rare in UC.
How to Differentiate: Colonoscopy with biopsy.
Appendicitis:
Points For: RIF pain, fever.
Points Against: The history in Crohn's is usually chronic and relapsing, not acute over 24-48 hours.
How to Differentiate: CT scan of the abdomen.
Investigations Plan:
First-Line Labs (During a flare):
FBC: Look for anemia (chronic disease, iron/B12 deficiency), thrombocytosis (acute phase reactant).
Inflammatory Markers: CRP and ESR will be elevated.
Albumin: Hypoalbuminemia indicates malnutrition and severe disease.
Stool Examination (FEMEC/C&S): Crucial to rule out infective colitis before starting immunosuppression.
Imaging:
CT Enterography / MR Enterography: These are the key imaging modalities to assess the extent of small bowel involvement, detect complications like strictures, fistulas, and abscesses.
Confirmatory / Gold Standard:
Ileocolonoscopy with biopsy: The definitive test. Allows direct visualization of mucosal inflammation (cobblestoning, deep linear ulcers) and collection of tissue samples from multiple sites (including normal-looking areas) to look for skip lesions and granulomas.
VI. Staging & Severity Assessment
We use clinical parameters to classify a flare.
Mild-to-Moderate: Ambulatory, tolerating oral intake, no signs of dehydration, toxicity, or abdominal tenderness. CRP is usually <50.
Moderate-to-Severe: Failed treatment for mild disease OR presents with fever, significant weight loss, abdominal pain/tenderness, or significant anemia.
Severe/Fulminant: Persistent symptoms despite steroids OR evidence of systemic toxicity (high fever, tachycardia), obstruction, abscess, or cachexia. Requires admission.
VII. Management Plan
(Gastroenterology team will guide long-term therapy, but you need to know how to start.)
Immediate Stabilisation (For a severe flare):
ABCDE: Secure IV access, give fluid resuscitation if dehydrated.
NBM & IV Fluids: Rest the bowel.
IV Hydrocortisone 100mg QID or IV Methylprednisolone 40-60mg OD. This is the cornerstone of managing an acute flare.
VTE Prophylaxis: IBD patients are at high risk for clots. Start prophylactic heparin (e.g., T. Clexane 40mg SC OD).
Consult GI and Surgery urgently if there are signs of obstruction, perforation or abscess.
Definitive Treatment (The Ward Round Plan):
Inducing Remission (Flare Management):
First-Line: Oral Prednisolone (e.g., 40mg OD), tapered down over 8 weeks once symptoms improve.
Nutritional Therapy: Exclusive enteral nutrition (EEN) can be used as a first-line therapy to induce remission, especially in the paediatric population.
Maintaining Remission (Long-term, started by GI team):
First-Line (Mild disease): Budesonide may be used for ileocecal disease. 5-ASA agents (Mesalazine) have a limited role in Crohn's, unlike in UC.
Immunomodulators: Azathioprine (Imuran) or 6-Mercaptopurine are the workhorses for maintenance.
Biologic Therapy: Anti-TNF agents (Infliximab, Adalimumab) or other biologics (Vedolizumab, Ustekinumab) are used for moderate-to-severe disease refractory to other treatments. These are initiated at the tertiary level.
Long-Term & Discharge Plan:
Smoking cessation is non-negotiable.
Ensure follow-up with the Gastroenterology clinic.
Educate on recognizing symptoms of a flare.
Vaccinations (e.g., Pneumococcal, Influenza) are important, especially before starting immunosuppressants.
VIII. Complications
Gastrointestinal:
Strictures & Obstruction: Management: Can be managed with endoscopic balloon dilatation or surgical stricturoplasty/resection.
Fistulas & Abscesses: Management: Requires antibiotics and often surgical drainage/intervention.
Perianal Disease: Management: A complex issue often requiring a combination of medical and surgical management.
Systemic:
Malnutrition & Vitamin Deficiencies (Iron, B12, Vit D).
Anemia of chronic disease.
Colorectal Cancer: Increased risk, requires surveillance colonoscopy.
IX. Prognosis
Crohn's is a chronic, lifelong condition with a relapsing and remitting course.
It does not typically shorten life expectancy, but can significantly impact quality of life.
Up to 50% of patients will require surgery at some point in their lives.
X. How to Present to Your Senior
"Dr, for your review. This is [Patient Name], a 25-year-old gentleman, who presents with a 3-month history of colicky RIF pain, non-bloody diarrhea, and a 5kg weight loss.
On examination, he is afebrile and hemodynamically stable. There is a tender, ill-defined mass in the RIF. Perianal exam shows a few skin tags.
My main differential is Crohn's Disease, with intestinal TB as a key differential to exclude.
Bloods show a high CRP of 80 and mild anemia. I have sent stool for FEMEC to rule out infection. I would like to consult the gastroenterology team for an urgent scope and suggest a CT enterography to assess for small bowel involvement and complications. I will also do a CXR and send a TB Quantiferon test to start the workup for TB."
XI. Summary & Further Reading
Top 3 Takeaways:
Think Crohn's in a young patient with chronic abdominal pain, diarrhea, and weight loss. Always examine the perianal area.
Intestinal TB is the great mimicker in Malaysia. A thorough workup to exclude TB is mandatory before starting any immunosuppressive therapy.
Management involves inducing remission (usually with steroids) and maintaining it (with immunomodulators/biologics). It requires a multidisciplinary approach with the GI team.
Key Resources:
Primary Guideline: Malaysian Society of Gastroenterology & Hepatology CPG on Inflammatory Bowel Disease (2019)
UpToDate: Search for "Crohn disease in adults: Clinical manifestations and diagnosis".
Amboss: Search for "Crohn disease".
