Mechanical problems in continuous ambulatory peritoneal dialysis (CAPD) can result in ultrafiltration failure and disruption of CAPD therapy. The recently described tool of CT peritoneography with water-soluble contrast medium has the disadvantage of radiation and instillation of nephrotoxic substances. We report a child with a peritoneal leak diagnosed by MRI after instillation of a gadodiamide-dialysate mixture. This method provided good anatomical detail without radiation or nephrotoxic agents.