==== Front Ann Saudi MedAnn Saudi MedAnnals of Saudi Medicine0256-49470975-4466King Faisal Specialist Hospital and Research Centre 1829965710.5144/0256-4947.2008.469aasm-6-469aWhat's Your Diagnosis?Diagnosis: Benign bowel distribution of lanthanum carbonate Wu Hsin-Chi Lin Shih-Hua From the Division of Nephrology, Department of Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan, ROCCorrepondence and reprints: Shih-Hua Lin, MD, Division of Nephrology, Department of Medicine, Tri-Service General Hospital, Number 325, Section 2, Cheng-Kung Road, Neihu 114, Taipei, Taiwan ROC, T: +886-2-87927213, F: +886-2-87927134, shihhualin@yahoo.comNov-Dec 2008 28 6 1 2 01 8 2008 Copyright © 2008, Annals of Saudi Medicine2008This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. ==== Body Hyperphosphatemia in uremic patients is associated with metastatic calcification such as tumoral calcinosis and vascular calcification, and an increased cardiovascular mortality and morbidity.1 To avoid hyperphosphatemia-related complications, the use of oral phosphate-binding agents is universal to reduce phosphate absorption in the gastrointestinal tract. “Old generation” phosphate binders with aluminum or calcium-based agents tend to cause neurological toxicity and exacerbation of calcium overloading and soft tissue or cardiovascular calcification, respectively.2 The “new generation” of aluminum or calcium-free phosphate binders has been shown to effectively control serum phosphate concentration with the attenuation of cardiovascular and soft tissue calcification. Lanthanum carbonate (La2(CO3)3), is a novel calcium-and aluminum-free phosphate binder for the treatment of hyperphosphatemia in ESRD patients. The element, lanthanum (La, atomic number 57, atomic weight 138.9) is a rare-earth natural metal belonging to group 3B of the periodic table and causes radiopacities in the roentgenogram, as does barium (atomic number 56) (Figure 1). The half-life of lanthanum elimination from plasma is 53 hours though the plasma level is extremely low and elimination half-life from bone is 2.0 to 3.6 years.3 The affinity of lanthanum compound for phosphate is >97% and is more potent than calcium or magnesium, and similar to aluminum.4 Lanthanum binds phosphate optimally at pH 3~5 and retains binding activity at pH 1~7.5 It is virtually non-absorbed (0.00005%) and chelates dietary phosphate into insoluble lanthanum phosphate by ionized form. Lanthanum phosphate and carbonate in the gut may form numerous radiopaque spots on the abdominal x-ray, which is not reported with other phosphate binders.6,7 These unexpected starry opacities disappear completely after the withdrawal of lanthanum carbonate. The patient continued lanthanum carbonate treatment because of no abdominal symptoms and improved pain. Due to this radiopaque feature, one can evaluate the compliance to this drug. Given the increasing usage of lanthanum carbonate in patients with ESRD, every physician must understand this typical benign radiopaque finding to avoid unnecessary examination and inappropriate management. Figure 1 Radiopaque lanthanum carbonate tablets milled in the gastrointestinal distribution. Starry opacities also seen. ==== Refs REFERENCES 1 Coladonato JA Control of hyperphosphatemia among patients with ESRD J Am Soc Nephrol 2005 16 Suppl 2 S107 114 16251245 2 Amann K Gross ML London GM Ritz E Hyperphosphataemia--a silent killer of patients with renal failure? Nephrol Dial Transplant 1999 14 2085 2087 10489212 3 Behets GJ Verberckmoes SC D’Haese PC De Broe ME Lanthanum carbonate: a new phosphate binder Curr Opin Nephrol Hypertens 2004 13 403 409 15199290 4 Fricker SP The therapeutic application of lanthanides Chem Soc Rev 2006 35 524 33 16729146 5 Albaaj F Hutchison AJ Lanthanum carbonate (Fosrenol): a novel agent for the treatment of hyperphosphataemia in renal failure and dialysis patients Int J clin Pract 2005 59 1091 1096 16115187 6 Savica V Calò LA Monardo P Santoro D Bellinghieri G Phosphate binders and management of hyperphosphataemia in end-stage renal disease Nephrol Dial Transplant 2006 21 1065 1068 7 de Freitas D Donne RL Hutchison AJ Lanthanum carbonate--a first line phosphate binder? Semin Dial 2007 20 325 328 17635822