First diagnostic criteria for isolated perianal Crohn's disease

Researchers at Imperial College London lead international collaboration to better identify and treat isolated perianal Crohn’s disease.

Researchers from Imperial’s Department of Metabolism, Digestion and Reproduction have led a international study proposing the first formal diagnostic criteria and management advice for a poorly defined form of Crohn’s disease that only affects the area around the anus, known as isolated perianal Crohn’s disease (ipCD).

Published in The Lancet Gastroenterology & Hepatology, the study addresses long-standing clinical challenges in distinguishing ipCD from other types of anal fistulas, which are abnormal channels that form between the anal canal and the skin. While some fistulas result from infection alone (idiopathic), others are a manifestation of Crohn’s disease, a chronic inflammatory bowel condition. The distinction is critical, as the treatment paths differ significantly.

“Patients with ipCD often present with perianal fistulas but no detectable inflammation in their digestive tract,” explained Dr Luke Hanna, Clinical Research Fellow and joint first author. “Until now, there has been no standardised way to diagnose or treat this condition, which has hampered both clinical care and research.”

A new diagnostic framework

The newly proposed criteria offer clinicians a structured scoring system to identify ipCD in patients who lack gastrointestinal inflammation but present other signs suggestive of Crohn’s disease. This marks the first step towards bringing consistency to diagnosis and patient management in this area.

In addition to diagnostic guidelines, the study presents management recommendations derived from a systematic review of the literature and a consensus process involving global experts in inflammatory bowel disease (IBD).

The research could have several key implications:

• Improved diagnosis: The criteria enable earlier and more accurate identification of patients who may benefit from IBD medications, rather than surgery alone.
• Standardised research: With clearer definitions, researchers can more reliably study this patient population and develop targeted therapies.
• Better patient outcomes: Earlier, more tailored treatment could help prevent complications and improve quality of life for patients with ipCD.
• Greater awareness: By highlighting that some cases labelled “idiopathic” may in fact be undiagnosed Crohn’s, the study may shift clinical perspectives and practices.

Future Directions

The authors acknowledge that the criteria require validation through larger, multi-centre studies. Plans are already in place to test the criteria in an international cohort through the TOpClass consortium. The team also aims to explore biological markers in fistula tissue, which may offer further diagnostic tools in the future.

“This is an important first step towards standardising the approach to a condition that has remained poorly understood. We hope that our work will help clinicians recognise ipCD earlier and manage it more effectively, improving outcomes for patients worldwide,” siad Dr Luke Hanna.

Isolated perianal Crohn's disease: a systematic review and expert consensus proposing novel diagnostic criteria and management advice
Luke Nathan Hanna, Liesbeth Jozefien Munster, Shivani Joshi, Jarmila Dagmara Wendelien van der Bilt, Christianne Johanna Buskens, Ailsa Hart, Phil Tozer, on behalf of the TOpClass Collaborators. The Lancet Gastroenterology & Hepatology. Published April 29, 2025. DOI: 10.1016/S2468-1253(25)00007-X