Blood supply and innervation of the prostate: improving clinical outcomes after radical prostatectomy
Alanazi, Ghazi Mobarak
BACKGROUND: Radical prostatectomy remains the main choice of treatment for prostate cancer. However, despite improvements in surgical techniques and neurovascular sparing procedures, rates of erectile dysfunction and urinary incontinence remain high. This is due, at least in part, to an incomplete understanding of the neurovascular supply surrounding and inside the prostate. OBJECTIVES: To provide a comprehensive, detailed external and internal description of the distribution of nerves and blood vessels associated with the prostate, as well as correlate the internal distribution of prostatic neurovascular structures with patients’ clinical outcomes after radical prostatectomy. METHODS: For the gross dissection element of the research, cadaveric bodies were obtained from the University of Edinburgh’s Anatomy unit, regulated by the Human Tissue [Scotland] Act 2006. Detailed dissection of 24 embalmed hemipelvises was performed employing a novel approach designed to preserve the entire prostate in situ, facilitating reliable and consistent identification and tracing of neurovascular structures supplying and surrounding the prostate. For the histological element of the research, internal neurovascular structures of the prostate were investigated in a total of 309 slides obtained from the apex, body and base of prostates from 15 patients who underwent non-nerve-sparing radical prostatectomy. Immunohistochemical staining was performed to identify and distinguish between parasympathetic and sympathetic nerves, whereas H&E staining was used to identify blood vessels. The total number, density and relative position of nerves and blood vessels was established using quantitative morphometry. One-way ANOVA tests and unpaired t tests were applied to establish statistically significant differences across the measured variables. Finally, patient-specific outcome data were used to establish whether the internal distribution of nerves and blood vessels within the prostate influenced the nature and extent of complications (urinary incontinence and erectile dysfunction) after surgery. RESULTS: A total of 48 prostatic arteries were identified by gross dissection, arising either directly from the internal iliac artery or one of its branches, including the inferior vesical artery, the superior vesical artery and the middle rectal artery. The nerves of the prostate were observed to be derived from the pelvic plexus in all preparations investigated. However, the location of their penetration into the gland was variable. Nerves, as well as blood vessels, were present across all prostatic levels and regions examined at the histological level. However, their number and density varied considerably within regions. Assessment of the precise positioning of neurovascular structures revealed that the majority of nerve fibres were located within dorsal and peripheral aspects of the gland. In contrast, the highest density of blood vessels was found predominantly within ventral and dorsal midline regions. All patients included in the study experienced erectile dysfunction and urinary incontinence after radical prostatectomy. None of the patients recovered their erectile function after two years of follow-up, whereas the recovery period of the urinary continence occurred over a variable time course. The number of intraprostatic nerves was found to be significantly lower in patients who recovered their continence within less than 12 months after surgery, compared to those whose recovery took 12 months or longer. No significant correlation was identified between the distribution of neurovascular structures inside the gland and the aggression level of the prostatic tumour. CONCLUSION: A novel dissection approach has been developed and successfully applied, facilitating a clear lateral view of the prostate in situ and reliable tracing of associated external neurovascular structures, including the location of penetration into the gland. We identified widespread regional differences in the localization of nerves and blood vessels inside the prostate. We report a surprising disconnect between the localization of nerves and blood vessels, showing that they are predominantly localised to different regions of the prostate. Sparing of neurovascular structures at any anatomical position of the gland, with less traumatic manipulation, during surgery will be required to protect the majority of neuronal structures and decrease complications following radical prostatectomy.