Incidence characteristics of testicular microlithiasis and its association with risk of primary testicular tumors in children: a systematic review and meta-analysis

Background To systematically evaluate the incidence characteristics of testicular microlithiasis (TM) in children and its association with primary testicular tumors (PTT). Methods A systematic review and meta-analysis were conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) statement. A priori protocol was registered in the PROSPERO database (CRD42018111119), and a literature search of all relevant studies published until February 2019 was performed. Prospective, retrospective cohort, or cross-sectional studies containing ultrasonography (US) data on the incidence of TM or the association between TM and PTT were eligible for inclusion. Results Of the 102 identified articles, 18 studies involving 58,195 children were included in the final analysis. The overall incidence of TM in children with additional risk factors for PTT was 2.7%. In children, the proportion of left TM in unilateral cases was 55.7%, the frequency of bilateral TM was 69.0%, and proportion of classic TM was 71.8% [95% confidence interval (CI) 62.4–81.1%, P = 0.0, I 2 = 0.0%]. About 93.5% of TM remained unchanged, and newly detected PTT rate was very low (4/296) during follow-up. The overall risk ratio of TM in children with a concurrent diagnosis of PTT was 15.46 (95% CI 6.93–34.47, P < 0.00001). Conclusions The incidence of TM in children is highly variable. Nonetheless, TM is usually bilateral, of the classic type, and remains stable or unchanged at follow-up. Pediatric patients with TM and contributing factors for PTT have an increased risk for PTT; however, there is no evidence to support mandatory US surveillance of children with TM.