THE HISTOPATHOLOGY OF X-RAY CONTRAST-MEDIUM INDUCED RENAL DROPLETS (VACUOLES)

A small but significant proportion of patients given X-ra contrast age nts subsequently experience a decline in renal function. Experimental studies in rats aimed at identifying the mechanism of renal effects sh ow vacuolation of proximal convoluted tubules. This report documents t hat such vacuoles normally have a proteinaceous content and that C-14- radiolabelled contrast agent (iodixanol) is specifically localised wit hin the vacuolated tubules 24 h after administration. On the basis of the persistence of some large droplets in proximal tubules, a small pe rcentage of the administered dose of X-ray contrast agent appears to b e trapped intracellularly within large proteinaceous droplets (the vac uoles) and slowly released over several weeks. Enzyme histochemistry i dentifies contrast-medium-induced droplets as an abnormal population o f lysosomes. We propose that in the absence of pre-existing renal impa irment, this slowly reversing lysosomal abnormality of proximal tubule s is within the kidney's functional reserve capacity.