An endoscopic study of the lacuna magna and reappraisal of its clinical significance in contemporary urological practice.

OBJECTIVE

To endoscopically study the Lacuna Magna (LM) and attempt to explain some of the anatomical, clinical and embryological issues pertaining to it. The LM, stated to be present in 30 to 50 percent of males and linked to congenital distal urethral obstructions, post-void bloody-spotting and dysuria in young boys, has few studies on its endoscopic characterization. In this study, its incidence, normal spectrum of appearance and variations have been endoscopically recorded and documented.

METHODS

The fossa navicularis of 50 consecutive male patients undergoing endourological procedures for non-meatal pathologies was examined for the presence of the LM and its endoscopic characteristics, and variations were video-recorded. The variants of the LM were classified into 4 groups.

RESULTS

The LM could be demonstrated in 98% of subjects. Group-wise percentage was 2%, 52%, 26%, and 20% in Type O, Type I, Type II, and Type III categories, respectively. Variations included "bi-channeled" LM and deviations in positions of the orifices off the commonest position at 12 o'clock.

CONCLUSION

The LM is a constant structural component of the fossa navicularis. The "valve" of Guerin (1864), described as a leaflet between the LM and the urethra has no valvular properties. Type III variant of the LM could be mistaken for a urethral stricture during ureteroscopy as well as act as a mechanical obstruction to contrast during retrograde urethrography. The LM is indemonstrable on a micturating cystourethrogram. Further studies could determine whether the location and disposition of the LM favor the development of submeatal post-instrumentation strictures.