Effectiveness of preoperative ultrasonography in predicting metachronous contralateral inguinal hernia in children: a single-arm prospective study using a historical control for comparison

Purpose To analyze the value of ultrasonography in predicting metachronous contralateral inguinal hernia (MCIH) and diagnosing contralateral persistent processus vaginalis (CPPV) in children with unilateral inguinal hernia, a prospective study was conducted. Methods All participants underwent a preoperative ultrasound on the contralateral groin. Patients in group A1 received operating procedure according to ultrasound results (patients with negative contralateral US results received hernia repair on the affected side), and patients in group A2 received operation according to laparoscopic results (patients received hernia repair and CPPV ligation). All patients were followed up 2 years and compared to a historical control (group B) who underwent open hernia repair only on the affected side regardless of contralateral US results. Results In groups A1 and A2, laparoscopic exploration revealed the presence of a CPPV in 490 cases. Ultrasound was found to be accurate in 104 out of the 490 cases with four false-positive and 386 false-negative results. This yielded an accuracy of 59.3%, a sensitivity of 21.2%, and a specificity of 99.2%. 10 patients in group A1, and 74 patients in group B developed MCIH. The accuracy, sensitivity, and specificity of the value of ultrasonography in predicting MCIH were 89.3%, 52.4%, and 92.5%, respectively. Conclusions Preoperative ultrasonography of the contralateral groin is currently unable to accurately detect CPPV, but it appears to be a promising method in predicting MCIH by using rigorous diagnosing criteria.