000 Ileitis

Etymology

Derived from the Greek word “ileos,” meaning twisted or constricted, ileitis refers to inflammation of the ileum.

AKA

  • Terminal ileitis
  • Regional ileitis

What is it?

Ileitis is an inflammatory condition that affects the ileum, the distal portion of the small intestine. It may result from a variety of causes, including inflammatory bowel disease, infections, and other systemic conditions.

Caused by:

Most common:
  • Crohn’s disease (2)
Other causes:
  • Inflammation/Immune: Ulcerative colitis with backwash ileitis, eosinophilic gastroenteritis (4)
  • Infection: Tuberculosis, Yersinia enterocolitica, Salmonella, Campylobacter, Clostridium difficile (7, 19)
  • Neoplasm: Lymphoma, metastatic carcinoma (5)
  • Mechanical: Obstruction, intussusception
  • Trauma: Surgical resection, radiation-induced damage
  • Metabolic: Vasculitis-related ischemia
  • Inherited/Congenital: Meckel’s diverticulum
  • Iatrogenic: Post-surgical adhesions
  • Idiopathic: Nonspecific ileitis (17)

Resulting in:

  • Mucosal and submucosal inflammation
  • Edema and ulceration
  • Fistula or abscess formation in severe cases

Structural changes:

  • Parts: Involves terminal ileum, though proximal ileum and cecum may also be affected
  • Size: Can involve a segmental portion or diffuse ileum
  • Shape: Luminal narrowing, cobblestone pattern
  • Position: Predominantly right lower quadrant
  • Character: Inflammatory thickening, ulceration, or perforation
  • Time: Acute or chronic

Pathophysiology:

Inflammation leads to mucosal disruption, granuloma formation, and fibrosis, which can progress to strictures or fistulas in chronic cases (1).

Pathology:

Granulomas are characteristic in Crohn’s disease and can help differentiate from other causes (3).

Diagnosis:

  • Clinical: Abdominal pain, diarrhea, weight loss, fever
  • Radiology: Imaging plays a crucial role in identifying and characterizing ileitis
  • Labs: Elevated inflammatory markers, stool studies, and specific tests for infections

Radiology and Imaging:

X-Ray:
  • Findings: Luminal narrowing, thumbprinting, and cobblestone pattern with barium studies (8)
  • Associated Findings: Strictures and fistulas
CT:
  • Findings: Mural thickening, hyperenhancement, and “comb sign” mesenteric hypervascularity (10)
  • Associated Findings: Abscess, fistula, creeping fat (11)
MRI:
  • Findings: Mural edema, ulcerations, and stratified enhancement (12)
  • Associated Findings: Backwash ileitis, fistulas (14)
Ultrasound:
  • Findings: Thickened bowel loops, hypervascularity on Doppler (16)
  • Associated Findings: Peri-intestinal fluid collections

Other Diagnostic Procedures:

  • Capsule endoscopy: Identifies mucosal changes not visualized on other modalities
  • Colonoscopy: Confirms inflammation and allows biopsy

Differential Diagnosis:

Most common:
  • Crohn’s disease (6)
  • Tuberculosis (18)
Other categories:
  • Inflammation/Immune: Autoimmune enteritis
  • Infection: Yersinia, Salmonella (19)
  • Neoplasm: Adenocarcinoma, lymphoma
  • Mechanical: Obstruction, volvulus

Recommendations:

  • Comprehensive imaging using CT or MRI enterography
  • Consider endoscopy and biopsy for confirmation
  • Address underlying cause with targeted therapy (e.g., anti-inflammatory, antibiotics)

Key Points and Pearls:

  • Cobblestone pattern on barium studies is a hallmark finding in Crohn’s ileitis (8).
  • MRI and CT enterography provide superior visualization of transmural inflammation and complications (10).
  • Granulomas on histology support a diagnosis of Crohn’s disease over infectious causes (3).

Let me know if you need additional details or edits!

References

Basic Science

  1. Imaging Inflammation and Infection in the Gastrointestinal Tract
    First Author: Frickenstein AN Journal: International Journal of Molecular Sciences. 2019;21(1):E243.
  2. Evidence-Based Review of Current Cross-Sectional Imaging of Inflammatory Bowel Disease First Author: Kim J Journal: Radiologic Clinics of North America. 2024;62(6):1025-1034.
  3. Advances in Imaging of Inflammation, Fibrosis, and Cancer in the Gastrointestinal Tract First Author: Harold KM Journal: International Journal of Molecular Sciences. 2022;23(24):16109.

Imaging: General Topics

4. Inflammatory Bowel Disease Imaging: Current Practice and Future Directions First Author: Kilcoyne A Journal: World Journal of Gastroenterology. 2016;22(3):917-932.

5.Radiological Imaging of the Small Bowel First Author: Schreyer AG Journal: Digestive Diseases. 2011;29 Suppl 1:22-26.

X-Ray/Fluoroscopy/Barium

  1. Small Bowel Tuberculosis: A Comparative Study of MR Enterography and Small-Bowel Follow-Through
    Huang L Journal: American Journal of Roentgenology. 2012;252(1):573-580.
  2. Radiological Features of Crohn’s Disease: Importance of Barium Studies First Author: Kelvin FM Journal: American Journal of Roentgenology. 1975;124(3):573-580.
  3. Double-Contrast Barium Enema in Ileitis: Radiographic Characteristics of Non-Crohn’s Causes First Author: Patel VA Journal: Radiology. 2009;252(3):633-641.

CT

9. CT Findings in Infectious Ileitis: Mimics of Inflammatory Bowel Disease
First Author: Paulsen SR Journal: Radiographics. 2006;26(3):641-657.

10. Small Bowel Crohn Disease at CT Enterography: Imaging Glossary and Key Findings
First Author: Guglielmo FF
Journal: Radiographics. 2020;40(2):354-375.

11. CT Enterography in Crohn’s Disease: Mimics and Complications
First Author: Fletcher JG Journal: Radiographics. 2010;30(2):367-384.

Magnetic Resonance Imaging (MRI)

12. A Practical Index to Distinguish Backwash Ileitis From Crohn’s Terminal Ileitis in MR Enterography.  Khosravi B, Salehnia A, Pak N, et al.  Inflammatory Bowel Diseases. 2023;29(1):42-50.

13, Clinical Relevance of Transabdominal Ultrasonography and Magnetic Resonance Imaging in Patients With Inflammatory Bowel Disease of the Terminal Ileum and Large Bowel Zhang J Gastroenterology. 2021;161(1):200-214.

14. Small Bowel Crohn Disease at CT and MR Enterography: Imaging Atlas and Glossary of Terms Guglielmo FF Radiographics. 2020;40(2):354-375.

15. MR Imaging of the Small Bowel. Fidler JL, Guimaraes L, Einstein DM. Radiographics : A Review Publication of the Radiological Society of North America, Inc. 2009;29(6):1811-25. doi:10.1148/rg.296095507.

15. Evidence-Based Review of Current Cross-Sectional Imaging of Inflammatory Bowel Disease Liu J Abdominal Radiology. 2019;44(4):1102-1115.

16. CT and MRI Evaluations in Crohn’s Complications: A Guide for the Radiologist Deepak P AJR. American Journal of Roentgenology. 2020;215(4):984-998.

17, Interdisciplinary Updates in Crohn’s Disease Reporting Nomenclature, and Cross-Sectional Disease Monitoring
Greer MC Gut. 2020;69(8):1537-1547.

18, Imaging of the Colon in Inflammatory Bowel Disease: Ready for Prime Time? Carter D Inflammatory Bowel Diseases. 2021;27(7):1053-1062.

Ultrasound (US)

19. Clinical Relevance of Transabdominal Ultrasonography and Magnetic Resonance Imaging in Patients With Inflammatory Bowel Disease of the Terminal Ileum and Large Bowel Zhang J Gastroenterology. 2021;161(1):200-214.

20. Systematic Review: The Use of Ultrasonography, Computed Tomography and Magnetic Resonance Imaging for the Diagnosis, Assessment of Activity and Abdominal Complications of Crohn’s Disease Liu J Abdominal Radiology. 2019;44(4):1102-1115.

21. Imaging of the Colon in Inflammatory Bowel Disease: Ready for Prime Time? Carter D Inflammatory Bowel Diseases. 2021;27(7):1053-1062.

Clinical

  1. Revised Algorithmic Approach to Differentiate Between Nonspecific and Specific Etiologies of Chronic Terminal Ileitis
    First Author: Sharma K Journal: American Journal of Roentgenology. 2015;130(3):573-582.
  2. Differentiating Crohn’s Disease From Intestinal Tuberculosis
    First Author: Singh S Journal: The New England Journal of Medicine. 2010;383(25):2520-2534.
  3. Clinical, Endoscopic, and Histological Differentiations Between Crohn’s Disease and Intestinal Tuberculosis First Author: Makharia GK Journal: The American Journal of Gastroenterology. 2010;105(3):642-651.
  4. Crohn’s Disease Diagnosis and Management: Current Clinical Perspectives
    First Author: Wilkins T Journal: American Family Physician. 2018;98(11):661-669.