Causes of Varicocele
Primary Anatomical and Hemodynamic Mechanisms
Varicocele results from abnormal dilation of the internal testicular vein and pampiniform venous plexus within the spermatic cord, caused by incompetent or absent valves in the internal spermatic vein leading to retrograde blood flow. 1, 2
The underlying pathophysiology involves several anatomical and hemodynamic factors:
Left-Sided Predominance Mechanisms
- The left internal spermatic vein drains into the left renal vein at a 90-degree angle, creating higher hydrostatic pressure compared to the right side which drains directly into the inferior vena cava at an acute angle 2
- This anatomical difference explains why left varicoceles are far more common than right-sided varicoceles 1
- The longer course of the left testicular vein increases the column of blood and hydrostatic pressure 2
Venous Obstruction Patterns
Preoperative venography studies have identified three distinct etiological types of varicocele 3:
- Primary varicocele arising from incompetent valves within the internal spermatic vein itself 3
- Secondary varicocele caused by obstruction of the common iliac vein 3
- Combined patterns involving both internal spermatic vein incompetence and iliac vein obstruction 3
Complex Venous Anatomy
Detailed intraoperative anatomical studies reveal the complexity of varicocele formation 4:
- Enlarged external spermatic veins are present in 74% of varicoceles, contributing to the overall venous dilation 4
- Enlarged gubernacular veins exiting the testis are found in 48% of cases 4
- Small internal spermatic veins typically drain into larger veins more proximally in the spermatic cord, creating multiple potential sites for venous reflux 4
Important Clinical Caveats
Red Flag Causes Requiring Investigation
- New-onset, large, or non-reducible varicoceles require abdominal imaging to exclude secondary causes such as renal masses or retroperitoneal venous obstruction 1
- Right-sided or bilateral varicoceles, especially if the right side is large, warrant imaging to exclude retroperitoneal pathology 1
- These atypical presentations may indicate compression or obstruction of the testicular vein by abdominal or retroperitoneal masses 1
Pathophysiological Consequences
Once established, varicocele causes testicular dysfunction through multiple mechanisms 5:
- Higher scrotal temperature from venous pooling 5
- Testicular hypoxia from impaired venous drainage 5
- Reflux of toxic metabolites from renal and adrenal veins 5
- Increased oxidative stress and DNA damage 5
Epidemiological Context
- Varicoceles affect approximately 15% of the general male population but increase to 35-40% among men presenting with infertility 5, 1, 6
- The prevalence markedly increases with pubertal development, being rare in prepubertal boys 7
- Only 20% of men with documented varicocele will ultimately suffer from fertility problems, indicating that anatomical presence does not always translate to clinical significance 2