INTRACRANIAL RING ENHANCING LESIONS IN DOGS - A CORRELATIVE CT SCANNING AND NEUROPATHOLOGIC STUDY

This retrospective analysis of 15 dogs with postcontrast ring enhancin g brain lesions, each detected by a single Computed Tomography [CT] ex amination, searched for any association between their CT appearance an d the pathologic diagnosis. In a subgroup of these dogs [n = 7] necrop sied within 2 days of the last CT scan, we evaluated whether there was any anatomic correlation between the ring zone and the histopathologi c features of the lesions. Our study consisted of eight dogs with prim ary brain tumors [3 meningiomas, 3 astrocytomas, 1 mixed glioma, 1 oli godendroglioma], 4 with metastatic brain tumors [2 fibrosarcomas, 1 ma mmary carcinoma, 1 melanoma] and 3 with non-neoplastic brain lesions [ 2 intraparenchymal hemorrhages, 1 pyogranulomatous meninogoencephaliti s]. The overall size and shape of the contrast enhancing CT lesions, a s well as the thickness, surface texture and degree of enhancement of the ring were subjectively evaluated. No association was found between the CT lesion characteristics and the pathologic diagnosis. In the su b-group of dogs euthanatized within 2 days of the CT examination, dist inct histologic features which anatomically correlated with the zone o f ring enhancement were found in 3 of 7 lesions. The findings of this study are consistent with those of ring-enhancing lesions in people, a nd indicates that CT ring enhancement is a non-specific phenomenon whi ch can occur in a variety of neoplastic and non-neoplastic lesions in the dog.