Journal of the Medical Association of Thailand Vol 102, No 10:OCTOBER 2019 0125-2208 102 10 2019 Oct Ultrasound in Pediatric Patients with Clinically First Joint Pain 1046-52 EN Suphaneewan Jaovisidha Rattanaporn Chunharas Patarawan Woratanarat Soamarat Vilaiyuk Niyata Chitrapazt Original Article To evaluate association of physical examination and ultrasound findings in pediatric patients with clinically first joint pain and association of ultrasound findings and final diagnosis. Children (16 years old or younger) with clinically first joint pain but equivocal clinical diagnosis were eligible if they were sent for ultrasound of the joint. Images were reviewed by two investigators using consensus agreement. The ultrasound findings were assessed for joint effusion, synovial thickening, synovial hyperemia, peri-articular soft tissue swelling, and bone erosion. Clinical examination and final diagnosis were reviewed from medical record. Patients with incomplete clinical data and those with underlying disease of hemophilia were excluded. The retrospective study consisted of 50 patients (87 joints). Most common ultrasound abnormality was joint effusion in 19 of 87 (21.8%) joints. There was significant association between ultrasound findings and physical examination (p<0.001). Ultrasound detected abnormal findings in two of 30 joints, which were not detected on physical examination. Provisional diagnoses were septic arthritis (44%) and acute inflammatory arthritis (26%). Only eight patients (16%) were sent under clinical suspicion of JIA. Thirty-three patients had diagnoses changed after ultrasound. At the final diagnosis, only one patient (2%) was diagnosed as septic arthritis and 17 patients (34%) as JIA. Most common diagnosis associated with synovial thickening and synovial hyperemia was JIA [in 10 of 15 (66.7%) and six of eight (75%) of cases, respectively]. Negative ultrasound finding was found in cases clinically suspected of neoplasm. Ultrasound in pediatric patients with clinically first joint pain showed significant correlation with physical examination. In some cases, ultrasound can contribute positive findings even when physical sign is not present. Synovial thickening, synovial hyperemia, peri-articular soft tissue swelling, and negative finding by ultrasound showed significant correlation with final diagnoses. The findings of synovial thickening and synovial hyperemia frequently associated with JIA. Pediatric Joint pain Ultrasound Juvenile idiopathic arthritisReceived 25 Apr 2018 | Revised 2 Jan 2019 | Accepted 3 Jan 2019