European radiology
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Renal vasoconstriction with resultant tissue hypoxia, especially in the renal medulla, has been suggested to play a role in contrast media (CM)-induced nephropathy. In this study we investigated the effects of injection of the non-ionic low-osmolar CM iopromide with and without pretreatment with the selective adenosine A1-receptor antagonist DPCPX. The effects were evaluated on regional renal blood flow, outer medullary oxygen tension (PO2) and urine output in normal anaesthetised rats. ⋯ Urine output increased 28-fold by CM while arterial blood pressure was reduced. The CM-mediated effect on haemodynamics, PO2, urine output and blood pressure was unaffected by the A1-receptor antagonist. Adenosine A1-receptors are not important mediators of the depression of outer medullary blood flow and PO2 caused by the CM iopromide in the normal rat; however, A1-receptors are tonically active to regulate renal haemodynamics, PO2 and urine production during normal physiological conditions.
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We describe a rare case of adult pilocytic astrocytoma in which exophytic growth from the brain stem presented as a right cerebellopontine angle mass. An initial MRI examination using T2- and T1-weighted images without and with contrast suggested the diagnosis of schwannoma. Subsequent use of 3D CISS (three-dimensional constructive interference in steady state) and T1-weighted contrast-enhanced 3D MP-RAGE (three-dimensional magnetization prepared rapid acquisition gradient echo) sequences led to the diagnosis of an exophytic brain stem tumor, documented the precise relationships of the tumor to cranial nerve VIII, revealed encasement of cranial nerves IX-XII (later confirmed intraoperatively), and provided the proper basis for planning surgical management.