The dimensions and symmetry of the seminal vesicles

The traditional anatomical description of the seminal vesicles is based on autopsy and imaging studies. Trans-peritoneal robotic-assisted laproscopic surgery, with its three-dimensional magnified view and miniature articulated working instruments, provides an opportunity to perform accurate dissections of the seminal vesicles even when extremely long and tortuous. We used specimens obtained by robotic-assisted laparoscopic radical prostatectomy (RLRP) for accurate anatomic assessment of the dimensions of the seminal vesicles. Digital photos of 78 specimens from men (mean age 59 ± 6.1 years) who underwent RLRP were analyzed using the Image Pro Plus software. Seminal vesicle dimensions were correlated with patients' age, weight, height, prostate weight, sexual function profile (SHIM) and symptom severity score of the lower urinary tract symptoms (IPSS). We found that the length of the seminal vesicles is highly variable (range of 8.5-94.6 mm). The average seminal vesicle length was 31 ± 10.3 mm and its average volume 7.1 ± 5.2 ml. The right seminal vesicle was significantly larger than the left in length, width and volume (P < 0.003). The seminal vesicles were found to be highly asymmetric with a mean difference of 17.8% in length and 24.9% in width between the sides. No correlation between seminal vesicle dimensions and any of the parameters tested was found. We concluded that the normal human seminal vesicles are characterized by marked (11-fold) variation in length and are asymmetric in most patients. The right seminal vesicle is significantly larger than the left. Seminal vesicle dimensions cannot be predicted from other morphometric or physiologic parameters.