Ultrasound settings reshape testicular stiffness readings in varicocele study

Testicular stiffness measured with shear wave elastography falls in men with varicocele, and the drop becomes more pronounced as the disease grade rises, according to a prospective comparative study published in Basic and Clinical Andrology. The same study found that the stiffness values themselves depend heavily on how the measurement is taken: two different ultrasound probes and four different region-of-interest sizes produced significantly different readings in healthy testes, a methodological finding the authors say should make clinicians cautious when comparing elastography results across studies and machines.

Varicocele, an abnormal dilation of the veins in the pampiniform plexus that drains the testicle, affects an estimated 15 to 20 percent of men in the general population and up to 80 percent of men with secondary infertility. Prolonged venous reflux is thought to raise testicular temperature, increase oxidative stress, and allow toxic metabolites to reflux into the gonad, processes that can lead to testicular atrophy, impaired sperm production, and reduced fertility. Surgical ligation and embolization are considered effective treatments, particularly for men with abnormal semen parameters or a shrunken testicle, but their impact on fertility remains controversial, because not every patient benefits from surgery.

Current follow-up tools have blind spots. Color doppler ultrasound, the preferred imaging modality for diagnosing varicocele and monitoring it after treatment, reveals only venous reflux and blood-flow changes inside the testicle; it says nothing about structural or pathological alterations in the tissue itself. Testicular biopsy is the diagnostic gold standard but is invasive and unsuitable for routine use. Semen analysis, the other mainstay of monitoring, is subject to considerable variability, and testicular atrophy is believed to develop gradually, which limits early detection of parenchymal damage. Shear wave elastography offers a noninvasive alternative: the technique tracks how fast shear waves propagate through tissue, and because stiffer tissue conducts these waves faster, it can reconstruct real-time maps of tissue stiffness. It is already used in liver, thyroid, and breast disease, and higher testicular stiffness values have been linked to orchitis, malignancy, and torsion.

Yet the literature on testicular elastography in varicocele is contradictory. Some studies report that affected testicles are stiffer and smaller than healthy ones; others find decreased stiffness without significant volume changes; still others detect no difference in either measure. The authors of the new study attribute this confusion partly to the absence of a consensus measurement protocol, which has produced widely varying stiffness values for both normal and diseased testes. To address the problem, the team, led by researchers including Lisu Zhang and Jun Huang, first asked a basic methodological question: how much do probe frequency and the size of the sampling region change the numbers?

The study was conducted between October 2024 and January 2025 and enrolled 175 men, including 76 patients with left-sided varicocele and 99 healthy men, all examined by a urologist and scanned by an experienced ultrasonographer on the same day. Men with right-sided or bilateral varicocele, testicular conditions such as microlithiasis, cysts, orchitis, tumors, torsion, or hydrocele, and cardiovascular or cerebrovascular disease that prevented cooperation with the exam were excluded. Varicocele was diagnosed with the Chiou ultrasound scoring system, which evaluates maximum vein diameter, pampiniform plexus characteristics, and venous-flow changes during the Valsalva maneuver, with a cumulative score of 4 or more considered diagnostic. Clinical severity was graded by physical examination using the Dubin and Amelar scheme: grade I veins are palpable only during Valsalva, grade II veins are palpable during normal breathing, and grade III veins are visible at rest.

For the methodological arm, shear wave elastography was performed on 62 testes from 31 healthy men using an Aixplorer system equipped with two linear probes of different frequencies, the SL10-2 and the SL15-4, and four circular region-of-interest diameters of 4, 6, 8, and 10 millimeters. The region of interest was standardized at 1 centimeter within the central testicular parenchyma on the maximal longitudinal section, deliberately avoiding the mediastinum testis and the fibrous tunica albuginea. Three consecutive measurements were taken at each setting and averaged, and the coefficient of variation was calculated for every combination. The results were unambiguous: measurements with the lower-frequency SL10-2 probe were significantly higher than those with the SL15-4 probe, and stiffness values increased with region-of-interest size for both probes, although the difference between the 4 and 6 millimeter settings was not statistically significant. The high-frequency SL15-4 probe showed lower overall variability, with the lowest coefficient of variation at the 4 millimeter region, and coefficients of variation across settings ranged from roughly 4 to 6 percent.

The authors offer a physical explanation for these effects. The elasticity image is not uniform: a softer blue region typically appears at the center of the sampling box, while stiffer green or yellow-green values cluster near the edges, because the push pulse is strongest at the center and weaker at the sides, causing less tissue movement there and leading the system to display falsely stiff values at the periphery. A larger region of interest may therefore incorporate these edge artifacts, inflating the measured stiffness. The fibrous capsule surrounding the testis can also contaminate the measurement. Differences in probe vibration frequency, bandwidth, and spatial resolution, as well as in how arrival time and shear wave velocity are calculated, may further explain why the two probes disagree. The consistency with prior phantom and liver studies, including work by Dillman and by pediatric liver elastography researchers, suggests the effect is not unique to the testis.

Armed with the least-variable configuration, the SL15-4 probe with a 4 millimeter region of interest, the team compared the left testes of 76 varicocele patients with 68 healthy controls. The median stiffness was 2.03 kilopascals in the control group, 2.01 in grade I varicocele, 1.77 in grade II, and 1.51 in grade III, with the values progressively and significantly lower as grade increased and negatively correlated with severity. Compared with controls, varicocele patients overall had significantly lower stiffness values. The one exception was grade I disease, where stiffness was only slightly below controls and the difference was not statistically significant, which the authors interpret to mean that mild varicocele may not yet induce parenchymal changes detectable by elastography. Notably, median testicular volumes did not differ significantly between groups, at 13.08 milliliters in controls versus 12.26, 13.06, and 11.84 milliliters in grades I, II, and III respectively, and no significant correlation emerged between stiffness and volume in any group. The authors suggest that in early disease, venous reflux may induce testicular swelling and reduced tissue density, lowering stiffness, whereas late-stage cell injury and interstitial fibrosis could eventually stiffen the gland.

The clinical implications cut both ways. Because stiffness changed while volume did not, the authors argue that elastography can detect subtle parenchymal alterations before overt morphological changes appear, potentially complementing semen analysis and volume measurement in follow-up. They also cite prior surgical series suggesting that stiffness may carry prognostic weight: in one study of 69 patients who underwent microscopic varicocelectomy, those with larger preoperative testicular volume and lower stiffness showed greater improvement in semen quality after surgery, and in another cohort of 82 surgical patients, postoperative stiffness values fell alongside improvements in testicular histopathology. The authors propose that combining volume and stiffness measurements may serve as an auxiliary indicator for evaluating testicular parenchymal alterations and may help clinicians weigh surgery against conservative management in young patients with normal volume and semen parameters who are concerned about future fertility.

The study has clear limits, which the authors acknowledge. All measurements were obtained by a single operator at a single center using a single ultrasound system, so reproducibility across operators and devices was not tested, and the equipment could not automatically calculate reliability metrics. Only the central portion of the testis was sampled, potentially missing regional stiffness variation, no testicular biopsies were performed to histologically confirm the parenchymal changes, and semen parameters were not collected, preventing any correlation between stiffness and sperm-producing function. The varicocele group was relatively small, and patients with right-sided or bilateral disease were excluded. The authors call for large multicenter studies on different machines, ideally paired with semen analysis, to validate and generalize the findings. Until then, the practical message stands: probe frequency and region-of-interest size significantly influence testicular elastography values, and anyone interpreting or comparing stiffness numbers should know exactly how they were measured.

Subject of Research: Shear wave elastography measurement of testicular stiffness in varicocele

Article Title: Testicular shear wave elastography in varicocele: measurement strategy and clinical application

Article References: Zhang, L., Li, Y., Zhang, L., Liang, Y., Zhuo, Y., & Huang, J. (2026). Testicular shear wave elastography in varicocele: measurement strategy and clinical application. Basic and Clinical Andrology, 36(1), Article 11. https://doi.org/10.1186/s12610-026-00310-8

Image Credits: AI Generated

DOI: 10.1186/s12610-026-00310-8

Keywords: varicocele, shear wave elastography, testicular stiffness, ultrasound, probe frequency, region of interest, male infertility, testicular volume, coefficient of variation, parenchymal changes, Testicular, shear