Objective. To identify whether pop-off mechanisms act as protective factors against chronic or end-stage renal disease in patients with posterior urethral valves. Materials and methods.A retrospective cohort study of patients with posterior urethral valves treated at a tertiary care children's hospital was carried out. Demographic, clinical, analytical, and radiological variables were collected. Considered as pop-off mechanisms were: unilateral high-grade vesicoureteral reflux with ipsilateral renal dysplasia and without involvement of the contralateral kidney, urinoma, prenatal urinary ascites, large bladder diverticulum, and persistent urachus. Multiple logistic regression and multivariate Cox regression were used for statistical analysis.Results. 70 patients undergoing posterior urethral valve surgery in our institution from 2010 to August 2020 were included. 14 (20%) had pop-off mechanisms and 56 (80%) did not. Pop-off mechanisms protected against developing chronic renal disease (0% vs. 27%; p = 0.03) and could protect against the need for renal replacement therapy (0% vs. 9%; p = 0.58). Nadir creatinine values (mg/dl) were predictors for the development of chronic renal disease (0.37 vs. 0.53; p < 0.0001) and the need for renal replacement therapy (0.38 vs. 1.21; p < 0.001).Conclusions. Pop-off mechanisms act as a protective factor against chronic renal disease in patients with posterior urethral valves. Nadir creatinine is a predictor of chronic renal disease and the need for renal replacement therapy. A larger sample size is needed to determine whether pop-off mechanisms protect against the need for renal replacement therapy.

Congenital midline cervical cleft is a rare malformation. Typical case shows an area of hypotrophic skin, a cranial nipple-like structure, and a caudal blind sinus. Cervical extension is limited. Relapse of the retraction is common following cutaneous z-plasty. The aim of this study is to describe the radiological, surgical, and histological findings of the 4 cases treated in our center in the last 8 years and communicate the finding of a contractile structure, anterior to the platysma, composed by striated muscle, figure not previously described. This distinct muscular band is responsible for neck retraction. Removal of this releases cervical tension and is essential to avoid the relapse.