Dorsal diverticulum of the distal male urethra.

The lacuna magna is a congenital diverticulum embryologically arising from the dorsal aspect of the fossa navicularis. During a 1 year period, lacuna magna was diagnosed in five boys. Another 57 voiding cystourethrograms obtained in boys were reviewed retrospectively. Lacuna magna is demonstrable on properly performed voiding cystourethrography, but can be mimicked by pseudolesions created by improper radiographic technique. Clinical information, urographic evaluation, and methods of treatment are discussed.