Coats' disease and persistent hyperplastic primary vitreous. Role of MR imaging and CT.

Coats' disease is an idiopathic disorder in which telangiectatic and aneurysmal retinal vessels leak a lipoproteinaceous exudate, with consequent bullous retinal detachment. It is a diagnostic challenge, and CT and MR imaging provide valuable information to differentiate it from other pathologies, particularly from retinoblastoma. Typical, advanced Coats' disease shows on CT a denser substance posterior to the vitreous, which on MR is hyperintense on all pulse sequences. Contrast administration on both CT and MR might give slight linear enhancement at the boundary between vitreous and exudation. Persistent hyperplastic primary vitreous (PHPV) is a unilateral disorder in a microphthalmic eye, seen in full-term infants. PHPV rarely is bilateral in patients with Norrie's disease, Warburg syndrome, or patients with retinal dysplasia. Persistent fetal vasculature leads to fibrosis, resulting in elongation of the ciliary processes, retinal detachment, and spontaneous cataracts. The CT appearance in the disorder is quite variable; however, MR imaging may be superior in demonstrating the enhancing retrolental mass and the elongated ciliary processes.