The cardiovascular calcifications (CVC) represent a central complication of chronic kidney disease (CKD) responsible of high cardiovascular mortality particularly in patients on peritoneal dialysis. Unfortunately, electron beam and multislice computed tomography, planar X-ray, ultrasonography or cardiac echocardiography methods are not accurate to detect calcium phosphate microcrystals since of its small size. We investigated the ectopic calcifications by Von Kossa staining and infrared microspectroscopy using synchrotron radiation (SR μFTIR) and infrared microspectroscopy in formalin-fixed peritoneal tissues from 3 cases. Von Kossa staining allowed us to detect vascular calcifications only in one of 3 studied peritoneal biopsies. Vascular calcifications contained mainly carbapatite accordingly to the presence of the IR absorption bands positioned at 1030 cm-1 (ν3), 960 cm-1 (ν1). In all studied biopsy, we found several tissue microcrystals also composed by carbapatite. To our knowledge, we report for the first time the usefulness of infrared microscopy and SR μFTIR for the assessment of calcium phosphate microcrystals and identification of biochemical composition of VC associated with CKD in peritoneal membrane from patients on peritoneal dialysis. SR μFTIR technique and infrared microspectroscopy are new, remarkable, and rapid tools for detection of early stage of ectopic calcifications associated with peritoneal dialysis. Investigation of calcium phosphate microcrystals by both methods might improve our understanding of early stage of CVC pathophysiology. Citation: Pozdzik AA, Demetter P, Tooulou M, Hamade A, Nortier J, et al. (2015) Infrared Microspectroscopy using Synchrotron Radiation (Sr Μftir) and Infrared Microspectroscopy as New Tools for Rapid Detection of Ectopic Calcifications Associated with Peritoneal Dialysis.