INVESTIGATIVE UROLOGY

The Complex Structure of the Smooth Muscle Layer of Spermatic Veins and Its Potential Role in the Development of Varicocele Testis
Tilki D, Kilic E, Tauber R, Pfeiffer D, Stief CG, Tauber R, Ergün S
Department of Urology, University Hospital Grosshadern-Munich, Munich, Germany
Eur Urol. 2007; 51: 1402-9; discussion 1410

• Objectives: Varicocele, a dilatation of the pampiniform venous plexus, is considered to cause male infertility. The exact mechanism of varicocele development is not clarified yet. This study focused on the structure of varicocele veins, compared with normal spermatic veins, and its potential role in varicocele development.
• Methods: Morphologic and immunohistochemical studies using antibodies against vWF and neurofilament-200 (NF-200) were performed on spermatic vein fragments of 20 varicocele patients and 40 normal spermatic cords. Casting preparation of veins was performed on five normal spermatic cords.
• Results: Casting preparation frequently revealed circular constrictions of normal spermatic vein lumina. Histologic evaluation showed a strong longitudinal smooth muscle layer in the adventitia of large veins in addition to the circularly organised tunica media. Serial sections showed smooth muscle fibres branching from the outer longitudinal into the inner circular layer. Immunostaining for vWF revealed high vascularisation of this outer layer. Interestingly, the number of nerve fibres marked by NF-200 immunostaining was considerably higher in large veins compared to the testicular artery. The longitudinal smooth muscle layer was significantly degraded in the presence of varicocele grades I and II, and did not even exist in varicocele grade III. Correspondingly, the number of vasa vasorum and nerve fibres was reduced in varicocele veins.
• Conclusions: Our data show a complex smooth muscle organisation of spermatic veins, which serves the basis for a contractile mechanism, providing an effective blood transport through pampiniform plexus. This mechanism is obviously damaged in the varicocele. Molecular processes behind this impairment remain to be clarified.
  
  
• Editorial Comment
  The authors of this interesting and original study aimed to assess whether there are anatomic and structural differences between normal spermatic veins and varicocele veins, and whether these differences might serve as a basis for an explanation of the development of varicocele.
  They demonstrated by the first time that the anatomic structure of the large spermatic veins of the pampiniform plexus is composed of a strong longitudinal smooth muscle layer in the tunica adventitia with oblique muscle fibers that reach the inner circular smooth muscle layer of the tunica media. The authors proposed that this assemblage of muscle layers could lead to a mechanism of peristaltic venous transportation. This contractile function apparently is disturbed in varicocele by morphological changes of the venous wall that may lead to impairment of blood venous return, promoting the development of varicocele.
  The take home message of this paper is that the morphologic changes of the venous wall of spermatic cord veins, including a degeneration of the outer smooth muscle layer, lead to an impairment of the contractile function and blood return of the veins, promoting the development of varicocele testis.

Dr. Francisco J.B. Sampaio
Full-Professor and Chair, Urogenital Research Unit
State University of Rio de Janeiro
Rio de Janeiro, RJ, Brazil
sampaio@urogenitalresearch.org