Predictors of hematoma as a complication in pediatric kidney biopsies

Background Kidney biopsies are crucial in the diagnosis of kidney diseases but they carry the risk of various complications, most commonly hematoma. Here we tried to identify the predictors of hematomas as a complication of kidney biopsies and we constructed an algorithm to stratify the risk. Methods The present report retrospectively reviewed 118 pediatric percutaneous kidney biopsies of native kidneys in 102 children (59 females) with the median age of 9 years (range: 1-19 years) at Kumamoto University Hospital between August 2008 and October 2019. We defined hematoma size using the hematoma index: the short axis of the hematoma/major axis of the kidney on ultrasonography. The inclusion criteria for a hematoma as a complication of a kidney biopsy were hematoma index >= 0.1 and the presence of concomitant, post-kidney biopsy fever or flank pain. Results Eight patients presented with a hematoma as a complication. All had hematoma index >= 0.1 and age >= 6 years. On univariate logistic analysis, these patients had a larger hemoglobin (Hgb) decrease on post-biopsy day 1, which was unrelated to a Hgb decrease 2 h after the biopsy, than the patients with no hematoma. All eight patients with a hematoma presented with a fever or flank pain on post-biopsy days 5 to 7, underscoring the need to observe patients with decreased Hgb carefully for about 1 week after a biopsy. Conclusion Predictors of hematoma as a complication in children after a kidney biopsy were hematoma index >= 0.1, age >6 years, and Hgb decrease >= 15% on post-biopsy day 1.