Epitrochlear cat scratch disease: unique imaging features allowing differentiation from other soft tissue masses of...

Evaluate anatomic and imaging features of epitrochlear regional adenopathy secondary to cat scratch disease (CSD) to assist differentiation of CSD from other soft tissue masses at the elbow.

Retrospective review of 24 confirmed cases of CSD. Patient demographics, clinical presentation and radiographic (R; n = 10), CT (n = 3), ultrasound (US; n = 5), and MR (n = 21) images were reviewed. Lesion location, size, number of masses, and intrinsic characteristics on R/CT/US/MR and presence of soft tissue inflammatory changes or adjacent bone or joint involvement were established through the consensus interpretation by four musculoskeletal radiologists.

The average patient age was 18.6 years. Mass location was anterior and superficial to the medial intermuscular septum (100 %) with the masses posterior or posteromedial to the basilic vein (92 %). Three or fewer lymph nodes were involved in 92 %. Masses were noncalcified with adjacent inflammatory change (R = 90 %, CT = 100 %). US showed hypoechoic soft tissue echogenicity masses with defined to minimally irregular margins (80 %) and preserved central hilar hypervascularity on Doppler (100 % of cases). On MR, masses were T1 isointense (62 %), T2 isointense (54 %), intermediate signal on T2 images with fat suppression (55 %), and had perilesional inflammatory changes (95 %), perilesional fluid collections (38 %), adjacent muscle edema (81 %), hyperintense cental hilar vascular enhancement (65 %) and occasional preserved central hilar fat (14 %).

Cat scratch disease is suggested by the characteristic location of a medial epitrochlear mass superficial to the brachial fascia and posterior to the basilic vein with surrounding inflammatory changes and preservation of hilar vascular architecture, hilar enhancement and occasional hilar fat.