Lacuna magna
The male urethra laid open on its anterior (upper) surface, lacuna magna labeled near the glans penis (bottom).
Latinlacuna magna
Anatomical terminology

In male anatomy, the lacuna magna (also called Guérin's sinus) is the largest of several recesses in the roof of the navicular fossa of the male urethra.


The lacuna magna is a large recess in the roof of the navicular fossa of the male urethra.[1]


The embryological origin of the lacuna magna is contested.[2] However, recent evidence suggests it and the navicular fossa of the male urethra derive from infiltrating endodermal cells of the urethral plate.[2]

Clinical significance

In young males, the presence of the lacuna magna is associated with painful urination (dysuria), bloody urine (hematuria), and bloody spotting of underwear.[3][4]


  1. ^ Shenoy, Sunil P.; Marla, Prashanth K.; Venugopal, P.; Adappa, Karunakara K.; Tantry, Trivikrama Padur; Shankar, Murali; Rai, Guruprasad D. (2011-11-01). "An Endoscopic Study of the Lacuna Magna and Reappraisal of Its Clinical Significance in Contemporary Urological Practice". Urology. 78 (5): 1009–1015. doi:10.1016/j.urology.2011.05.013. ISSN 0090-4295. PMID 21777960.
  2. ^ a b Kurzrock E, Baskin L, Cunha G (1999). "Ontogeny of the male urethra: theory of endodermal differentiation". Differentiation. 64 (2): 115–22. doi:10.1046/j.1432-0436.1999.6420115.x. PMID 10234808.
  3. ^ Bellinger M, Purohit G, Duckett J, Cromie W (1983). "Lacuna magna: a hidden cause of dysuria and bloody spotting in boys". J. Pediatr. Surg. 18 (2): 163–6. doi:10.1016/S0022-3468(83)80542-9. PMID 6854496.
  4. ^ Sommer J, Stephens F (1980). "Dorsal urethral diverticulum of the fossa navicularis: symptoms, diagnosis and treatment". J. Urol. 124 (1): 94–7. doi:10.1016/s0022-5347(17)55312-4. PMID 7411733.