[Radiographic disappearance of lanthanum]

In 2006, Cerny and Kunzendorf in the New England Journal of Medicine Images in clinical medicine, showed the radiographic appearance of lanthanum for the first time. After many years we noticed the inverse phenomenon. In a peritoneal dialysis patient treated with lanthanum carbonate, we had two radiography of the abdomen for monitoring the peritoneal catheter. In the first radiography contrast material was seen in colon. In the most recent radiography contrast material disappeared. The patient was always taking the same dose of lanthanum carbonate (1000 mg bid), although at the time of the first radiography he took the chewable tablets, for the last radiography he took the new powder formulation. We found a report in literature highlighting this phenomenon meanwhile indicating a greater chelating effect for the powder. Our hypothesis is that despite the same lanthanum dose, powder provides a greater surface area of binding and a more dispersed bowel distribution to explain a masked radio-opacity. Considering the wide availability of the powder, this must be taken into account especially in evaluating therapeutic compliance.