Paying the price for standing tall: Fluid mechanics of prostate pathology

Abstract

Background Age‐dependent increase in the incidence of benign prostatic hyperplasia (BPH) and prostate cancer (PCa) are both related to cell proliferation and survival controlled by intraprostatic free testosterone (FT) concentration. Paradoxically, BPH and PCa occur as circulating testosterone levels decrease, so any possible relationship between testosterone levels and development of BPH and PCa remains obscure. Results In BPH the enlarging prostate is exposed to high testosterone levels arriving directly from the testes at concentrations about hundredfold higher than systemic FT. This occurs because venous blood from the testes is diverted into the prostate due to the elevated hydrostatic pressure of blood in the internal spermatic veins (ISVs). Elevated pressure is caused by the destruction of one‐way valves (clinically detected as varicocele), a unique phenomenon related to human erect posture. While standing, human males are ISVs vertically oriented, resulting in high intraluminal hydrostatic pressures—a phenomenon not found in quadrupeds. In this communication, we demonstrate the fluid mechanics' phenomena at the basis of varicocele leading to prostate pathology. Conclusions So far, varicocele has been studied mostly for its etiologic role in male infertility and, thus, for its effects on the testes. It is becoming clear that varicocele is a major etiologic factor in BPH and likely also in PCa. Restoring normal testicular venous pressure by treatment of the abnormal ISV's in varicocele has been shown to avert the flow from the prostate with the effect of reducing prostate volume, alleviating symptoms of BPH, and increasing concentrations of circulating FT.

The Evolving Landscape of Male Varicocele Pathophysiology in the Era of Multi-Omics: A Narrative Review of the Current Literature

“…Varicoceles are generally left-sided due to the elevated position of the left kidney causing increased hydrostatic pressure. Some clinicians have instead attributed this laterality bias to the 90-degree angle between the insertion of the gonadal vein to the left renal vein, but this is in direct contradiction to the fundamental hydrostatics principle of Pascal's law and the accompanying visual experiment of Pascal's vases [15,16]. Alternatively, others have proposed that skeletal growth leads to the compression of the left renal vein from the superior mesenteric artery and the aorta, thereby contributing to the increased hydrostatic pressure on the left side.…”