The role of ultrasound in assessment of male fertility.

Ultrasonography (US) is a widely used and well tolerated imaging modality for evaluation of pathologic conditions of the testes. Recent technical advances of US applications and post processing developments have enabled new aspects in the structural and functional analysis of testicular tissue and therefore male fertility. This review covers the most relevant approaches due to recent technical advances. Testicular volume measured by B-mode US correlated significantly with testicular function. Increased resistive index (RI) and pulsatility index (PI) of capsular branches of testicular arteries on unenhanced color Doppler US examination may be an indicator of impaired testicular microcirculation in patients with clinical varicocele. FSH was inversely correlated with testicular volume and directly correlated with testicular vascularization, suggesting that ultrasonographic and color Doppler scanning of the testes may be used, if a sperm count is not available, to indirectly assess the gonadal function. Perfusion mapping, performed with the use of color Doppler ultrasound, has shown for the first time that in patients suffering from azoospermia, sperm quality and quantity depend on tissue perfusion within the testicle. Testicular arterial blood flow was found to be significantly decreased in men with varicocele. This may be a reflection of the impaired microcirculation. Following decreased testicular arterial blood flow, impaired spermatogenesis may result from defective energy metabolism in the microcirculatory bed. Contrast-enhanced ultrasound (CEUS) imaging is potentially applicable to the investigation of vascular disorders of the testis. Pulse inversion (PI) US data can correctly determine relative testicular perfusion based on nonlinear curve fitting of the US backscatter intensity as a function of time and spectral analysis of the intensity time trace. PI imaging, compared with conventional Doppler US methods, provides superior assessment of perfusion in the setting of acute testicular ischemia. New contrast-enhanced US techniques like microvessel imaging (proposed by Philips) and CPS (proposed by Siemens-Acuson) allow for a better determination of tissue perfusion based on time intensity curves and an illustration of vessel distribution inside the testis. First results show a lower vessel density in atrophic testes and a difference in contrast dynamics in testes with impaired function. Real-time elastography, a method for illustration of tissue stiffness under real-time conditions, demonstrates different elasticity values dependent on testicular volume and function. Further studies will prove if these techniques can evolve into clinical practice.