Radiopacity of sodium zirconium cryosilicate on plain radiography

ABSTRACT

Introduction: Sodium zirconium cyclosilicate is a novel potassium binder developed by AstraZeneca and is sold under the brand name Lokelma (TM). It has been approved for use in England in 2020 for the treatment of non-lifethreatening hyperkalaemia, and stable hyperkalaemia in patients with chronic kidney disease.1 It is available as powder sachets (5 grams and 10 grams) and is designed to be mixed with water and administered enterally. The starting dose is recommended as 10 grams three times per day, and resolution of hyperkalaemia is usually seen within two days, after which a lower maintenence dose may be administered. The radiopaque properties of sodium zirconium cyclosilicate have previously been noted on computed tomography before in 2021,2 but, to our knowledge, this has not yet been described on plain radiography. Case presentation We present the case of a critically unwell lady in her 50s with COVID-19 pneumonitis. As a feature of her critical illness syndrome, she developed acute renal failure, and required renal replacement therapy. Persistent problems with hyperkalaemia were noted, and sodium zirconium cyclosilicate was administered enterally via a nasogastric tube as directed in the product literature. For unrelated reasons, she also required a chest radiograph within the following hour. On reviewing the radiograph, a radiopaque material was noted in the stomach, and was seen to very clearly outline the major anatomical features of the organ, including the greater and lesser curve, and gastric rugae. After discussion with our local radiology colleagues and finding the material is opaque on computed tomography, we concluded this material must be the recently administered sodium zirconium cyclosilicate. Investigation Image of radiograph showing radiopaque material in the stomach of a critically unwell patient. Discussion: To our knowledge, the radiopaque properties of sodium zirconium cyclosilicate have not been described before in the medical literature as relating to plain radiography. When interpreting plain radiographs, it is important to understand and exclude sources of artefact. As sodium zirconium cyclosilicate becomes widespread in critical care areas, we believe the above-described scenario will be commonly encountered. Moreover, we believe that sodium zirconium cyclosilicate may have additional utility as a well tolerated enteral contrast agent with the added benefit of lowering serum potassium concentration.