The “Clover Sign” of Internal Fistulas in Crohn Disease Volume 49- Issue 1

Aleksandar M Ivanovic*

• Department of Diagnostic Imaging, Center for Radiology and MRI, Clinical Center of Serbia, University of Belgrade, Faculty of Medicine Pasterova 2, Belgrade, Serbia

Received: February 10, 2023;   Published: March 06, 2023

*Corresponding author: Aleksandar M Ivanovic, Department of Diagnostic Imaging, Center for Radiology and MRI, Clinical Center of Serbia, University of Belgrade, Faculty of Medicine Pasterova 2, Belgrade, Serbia

DOI: 10.26717/BJSTR.2023.49.007749

Abstract PDF

The “Clover Sign” is radiological finding used to metaphorically describe imaging appearance of a complex fistula in Crohn disease. It refers to the presence of blossom-like arrangement of dilated bowel loops with internal fistula, resembling the clover leaves (Figure 1) [1,2]. CD is chronic, relapsing inflammatory disorder that may be seen in any segment of gastrointestinal tract but most frequently affects small and large intestine. Terminal ileum is involved in the majority of cases. CD can be divided in two types: perforating and nonperforating. Due to deep transmural inflammation and consequently formed ulcerations, main complications seen in perforating forms are fistulas, abscess formations, and free perforation [1]. Fistulas occur in up to 35% of patients with CD and can be further categorized as external and internal. External fistulas are defined as tracts that connect intestinal lumen and cutaneous surface. Most commonly seen localization of this type is in perianal region. Depending of origin and endpoint, internal fistulas can present as eneteroenteric, enterovaginal and enterovesical. Enteroenteric fistulas include gastrocolic, duodenocolic, ileoileal, ileocolic and colocolic fistulas [3]. Solitary and complex fistulas are different morphologic subcategories of internal fistulas. Both can be evaluated by MRI (enterography and enteroclysis) as well as their initial stages, presented by intestinal wall irregularities due to spiculated infiltrations into the surrounding mesenteric fat and also by blind-ending tubular structures, called sinus tracts.

Solitary fistula is hollow tract that arises from affected bowel segment and typically perforates into adjacent bowel or abscess cavity [1,4]. Complex fistula appears as a stellate configuration of two or more affected bowel loops interconnected with branched fistula converging toward centrally fixed point. This star-like or blossomlike arrangement of converging fistulous tracts and bowel loops to one central point resembling clover leaves is highly indicative for complex fistula [5] (Figure 1), and metaphoric photo, (Figure 2). MR (particularly enterography) is useful and accurate imaging technique for evaluation of luminal, transmural and extraluminal manifestations of CD as it provides high efficiency in assessment of the degree of disease activity and detection of possible complications [4]. Further treatment usually depends of these findings.

Figure 1

Figure 2

1. Herrmann KA, Michaely HJ, Zech CJ, MF Reiser, J Seiderer, et al. (2006) Internal fistulas in Crohn disease: magnetic resonance enteroclysis. Abdom Imaging 31: 675-687.
2. Iraha A, Koga E, Ohira T, Tetsu Kinjo, Jiro Fujita, et al. (2019) The clover sign of inter-nal fistulas in Crohn disease. Pol Arch Intern Med 129: 707-708.
3. Levy C, Tremaine WJ (2002) Management of internal fistulas in Crohn_s disease. Inflamm Bowel Dis 8: 106-111.
4. Bruining DH, Zimmermann EM, Loftus EV Jr, Scott A Strong, Cary G Sauer, et al. (2018) Consensus Recommendations for Evaluation, Interpretation, and Utilization of Computed Tomography and Magnetic Resonance Enterography in Patients with Small Bowel Crohn's Disease. Radiology 286: 776-799.
5. Herrmann KA, Zech CJ, Seiderer J, Maximilian F Reiser, Stefan O Schoenberg, et al. (2005) The ‘‘star-sign’’ in magnetic-resonance enteroclysis: a characteristic finding of internal fistulae in Crohn᾿s disease. Scand J Gastroenterol 41: 239-241.