[Lacuna magna: diverticulum of the anterior urethra in childhood].

Three successfully treated cases of lacuna magna are presented. These small diverticula in the dorsal wall of the anterior urethra are often difficult to diagnose, despite the typical clinical signs (intermittent dysuria, hematuria and/or bloody spotting on underwear). Transmeatal excision of the valve-like leaflet (Guérin's valve) is a simple and effective form of treatment.