Intestinal Tuberculosis Vs Cronhn's disease

### **Intestinal Tuberculosis (ITB) vs Crohn's Disease (CD)**

Intestinal Tuberculosis (ITB) and Crohn’s Disease (CD) are two distinct diseases that can present with similar clinical, endoscopic, and imaging findings, making differentiation challenging. Below is a **detailed comparison** to help distinguish between the two conditions.

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### **1. Etiology**

• **ITB**: Caused by **Mycobacterium tuberculosis**, a bacterial infection.
• **CD**: A chronic, **idiopathic immune-mediated inflammatory disease** of the gastrointestinal (GI) tract.

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### **2. Geographic Distribution**

• **ITB**: Common in **tuberculosis-endemic regions** (e.g., India, Africa, Southeast Asia).
• **CD**: More common in **developed countries** (e.g., North America, Europe).

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### **3. Age of Onset**

• **ITB**: Typically affects **young adults** (20–40 years).
• **CD**: Can occur at any age, but peak incidence is in the **teens and 20s**.

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### **4. Systemic Symptoms**

• **ITB**: Often associated with **constitutional symptoms** such as fever, night sweats, weight loss, and anorexia.
• **CD**: Less commonly associated with systemic symptoms; weight loss and fatigue may occur.

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### **5. Site of Involvement**

• **ITB**: Predominantly affects the **ileocecal region** (ileum + cecum).
• **CD**: Can involve **any part of the GI tract** (mouth to anus), with the **terminal ileum** being the most common site.

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### **6. Endoscopic Features**

• **ITB**:
• **Transverse ulcers** (oriented circumferentially).
• Granular or nodular mucosa.
• **Caseating granulomas** on biopsy.
• Localized disease.
• **CD**:
• **Longitudinal ulcers** (along the bowel axis).
• Cobblestone appearance.
• **Non-caseating granulomas** on biopsy.
• Skip lesions (patchy involvement).

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### **7. Histopathology**

• **ITB**:
• **Caseating granulomas** (necrosis present).
• Coalescing granulomas.
• Acid-fast bacilli detectable on Ziehl-Neelsen staining.
• Positive for **TB PCR**.
• **CD**:
• **Non-caseating granulomas** (no necrosis).
• Poorly organized granulomas.
• Negative for acid-fast bacilli.
• Negative for TB PCR.

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### **8. Imaging Features**

• **ITB**:
• **Stierlin sign**: Narrowing of the terminal ileum with a contracted cecum.
• Enlarged, necrotic mesenteric lymph nodes.
• Ascites may be present.
• Calcified lymph nodes.
• **CD**:
• Long segment strictures.
• **Creeping fat**: Fatty proliferation of mesentery.
• Skip lesions.
• No necrotic or calcified lymph nodes.

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### **9. Granuloma Characteristics**

• **ITB**: Large granulomas (>400 µm), coalescing, and caseating.
• **CD**: Small granulomas (<200 µm), poorly organized, and non-caseating.

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### **10. Perianal Disease**

• **ITB**: Rare.
• **CD**: Common (fistulas, abscesses, skin tags).

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### **11. Chest X-ray Findings**

• **ITB**: Often shows evidence of **pulmonary tuberculosis** in ~50% of cases.
• **CD**: Normal (unless extraintestinal manifestations occur).

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### **12. Diagnostic Tools**

• **ITB**:
• Positive **Ziehl-Neelsen stain** for acid-fast bacilli.
• Positive **Xpert MTB/RIF PCR** for TB DNA.
• Positive **Mantoux test** or **IGRA**.
• **CD**:
• Negative for TB tests.
• Colonoscopy with biopsy showing **non-caseating granulomas**.
• Serology: ASCA (anti-Saccharomyces cerevisiae antibodies) and pANCA.

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### **13. Response to Therapy**

• **ITB**: Responds well to **anti-tubercular therapy (ATT)** for 6–9 months.
• **CD**: Requires **immunosuppressive therapy** (e.g., corticosteroids, biologics like anti-TNF agents).

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### **14. Complications**

• **ITB**:
• Strictures.
• Fistulas (less common than in CD).
• Perforation.
• Obstruction due to mass effect.
• **CD**:
• Strictures.
• Fistulas (common).
• Abscess formation.
• Perianal disease.

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### **Key Differentiating Features**

| **Feature** | **Intestinal Tuberculosis** | **Crohn’s Disease** |

|--------------------------|----------------------------------|----------------------------------|

| **Granulomas** | Caseating | Non-caseating |

| **Ulcer Orientation** | Transverse | Longitudinal |

| **Imaging** | Necrotic lymph nodes, ascites | Skip lesions, creeping fat |

| **Response to Therapy** | Anti-tubercular drugs | Immunosuppressives |

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### **Clinical Pearls**

1. In **tuberculosis-endemic areas**, always consider ITB as a differential diagnosis for Crohn’s disease.

2. If **caseating granulomas** or **necrotic lymph nodes** are present, ITB is more likely.

3. A **trial of anti-tubercular therapy** can be diagnostic if histological differentiation is inconclusive.

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### **Summary**

Differentiating ITB from CD is crucial for initiating the correct treatment. Misdiagnosis can lead to inappropriate use of immunosuppressive therapy in ITB, which can worsen the condition. Conversely, untreated CD can lead to progressive complications.