Anatomic Layers of the Penis on MRI
MRI clearly delineates distinct penile layers from superficial to deep: skin, dartos fascia, Buck's fascia, tunica albuginea, and the erectile tissues (corpora cavernosa and corpus spongiosum), along with the glans structures including its lamina propria and urothelium 1, 2.
Superficial to Deep Layer Organization
Covering Tissues (Superficial Layers)
- Skin: The outermost layer, readily visible on MRI sequences
- Dartos fascia: Contains axial pattern vessels with dorsomedial and dorsolateral branches, showing relative avascularity at the dorsal midline in most cases 1
- Hypodermis/subcutaneous connective tissue: Separates dartos from deeper structures 2
Buck's Fascia and Deep Structures
- Buck's fascia: A critical fascial plane that envelops the erectile bodies and contains the neurovascular bundle. This layer has a subglanular extension that fuses with the basal lamina propria of the glans, forming a barrier between the corpora tips and intraglanular vascular arcade 1
- Tunica albuginea: The dense fibrous covering of the erectile bodies, clearly resolved on MRI. A superficial glans tunica albuginea has been identified as a distinct structure 3
Erectile Tissues
- Corpora cavernosa (paired dorsal structures): Demonstrate characteristic vascular tissue on T2-weighted sequences with visible deep arteries 2, 4
- Corpus spongiosum: Surrounds the urethra ventrally, with distinct signal characteristics from the corpora cavernosa 2
Glans Anatomy
- Glans urothelium: The epithelial surface
- Lamina propria of glans: Underlying connective tissue layer
- Intraglanular vascular arcade: Formed by branches of the dorsal penile artery 1
Vascular Landmarks Visible on MRI
MRI, particularly with contrast enhancement, demonstrates:
- Dorsal penile vessels (superficial dorsal vein and arteries)
- Deep penile arteries within the corpora cavernosa
- Collateral vessels at the coronal sulcus connecting external and internal pudendal circulation 1
- Perforators along the corpus spongiosum 1
Clinical Relevance
This detailed anatomic resolution makes MRI particularly valuable for assessing corporal invasion (distinguishing T2 from T3 penile cancer), evaluating trauma to the tunica albuginea, and planning organ-sparing surgical approaches 5, 6. The ability to visualize these distinct tissue planes without ionizing radiation provides superior soft tissue characterization compared to other imaging modalities 2, 7.
Technical Considerations
Optimal visualization requires appropriate surface coil selection and multiplanar imaging (sagittal, coronal, and transverse planes) using both T1- and T2-weighted sequences 2, 7. Post-contrast imaging enhances vascular structure delineation 1.