Idiopathic Pericardial Effusions in Children: Workup and Final Diagnoses.

Pediatric idiopathic pericardial effusions are common and often have a prolonged clinical course. We hypothesized that these effusions have no standardized diagnostic workup, and ultimately have a final etiology not initially appreciated. To test these hypotheses, a hospital system-wide retrospective (1/1/1990-10/1/2019) cohort study of pericardial effusions in children (< 18 years) was conducted. Effusions were grouped by etiology and patients receiving an initial idiopathic diagnosis were further analyzed. Effusion size, diagnostic workup, final diagnosis, and time to resolution were abstracted. In total, 42/366 effusions were initially diagnosed as idiopathic. Workup was not standardized and included up to six laboratory tests including pericardial fluid analysis and infectious, metabolic, rheumatologic and thyroid workups. Treatment course involved 1 readmission in 24%, and > 1 readmission in 12%. Resolution of effusion occurred in 83% of patients within a median of 1 admission (range 1-4). Of those effusions initially deemed idiopathic, 12/42 (29%) were later found to have an underlying etiologic diagnosis including: autoimmune (7, 58%), neoplastic (2, 16%), infectious (2, 16%), and renal (1, 8%). Children initially diagnosed with idiopathic pericardial effusions have an underlying etiologic diagnosis 29% of the time, and a standardized workup may prevent delays in definitive diagnosis and treatment.