Few studies have attempted to apply elastography in the imaging of renal masses. Fahey and colleagues investigated the use of acoustic radiation force impulse (ARFI) imaging for real-time visualization of abdominal malignancies, including renal masses [8]. Clevert and colleagues reported shear wave velocity values in a small series of 12 solid renal cell carcinomas, using ARFI [9]. Tan and colleagues demonstrated the feasibility of real-time elastography in differentiating angiomyolipomas from renal cell carcinomas, by the use of both elasticity patterns and strain ratios [10]. In our opinion more experience is necessary to evaluate the potential role of elastography in separating benign and malignant tumors.

Sonoelastography has been also proposed as noninvasive method to detect fibrosis in chronic kidney diseases. Several studies have been performed on renal transplants because the superficial location allow a more accurate measurements. Most of them were performed with high-frequency probes (Fig. 50.2). The results reported in the literature are quite controversial, and the number of enrolled patients for biopsy is quite limited [11].

In pediatric patients with VU reflux, ARFI values decrease in the kidneys with secondary reflux compared to the normal kidney [12].

It is well known that B-mode US has a limited sensitivity and specificity (40–50 %) for prostate cancer detection. The use of US-based elasticity imaging for the detection of prostate cancer relies on the fact that these tumors can be detected because they are firmer than the surrounding normal parenchyma. Usually, the normal gland has a green-coded strain with blue parts near the capsule (Fig. 50.3). In the prostate having a benign prostate hyperplasia, the map is less homogeneous and the blue areas are more present. Normally periurethral zone appears firmer due to its sphinterial component. Prostate carcinoma (Pca) appears as a firmer area with respect to the surrounding parenchyma (Fig. 50.4). For Pca detection, strain elastography and shear wave imaging are used. In the case of strain elastography, the tissue to be examined is compressed by the examiner using the ultrasound probe. The comparison of ultrasound images before and after compression makes it possible to make conclusions about the stiffness of the tissue based on the degree of deformation. Adequate application of compression and the interpretation of the color-coded images in real time are difficult to standardize and yield heterogeneous, examiner-dependent results. In shear wave elastography, the forces are applied directly by the ultrasound probe, and the stiffness of the tissue is calculated based on the propagation speed of the shear waves in the tissue. The main advantage of this method is the high intraindividual and interindividual reproducibility [13]. In general, the firmer areas are suspicious of cancer, but prostatitis, fibrosis, atrophy, or nodule of benign prostate hyperplasia can also be associated with increased stiffness. False-negative findings can be also present in Pca with a Gleason score ≤7 in which normal tissue and prostate cancer cells can relay next to one another [14].

Several recent studies demonstrated that this technique is promising. These studies are of two types. The first type of studies evaluated the technique as a diagnostic tool for Pca detection [15]. Most of these studies showed that elastography improved the detection rate of Pca and the detection increased with higher Gleason scores [16]. The second type of studies is based on elastography-targeted biopsy results and evaluated the method as a tool to support TRUS-guided systematic random biopsy [15].

Elastosonography can be used also to discriminate malignant from benign testicular lesions. At elastosonography the normal testicles show mainly a medium level of elasticity (displayed in green); some linear “red” structures within the testes are related to fluid component, such as vessels and cysts (not ever). After some anecdotal reports, in 2012 Goddi et al. have published an interesting paper about 88 patients having 144 focal lesions [17]. They proposed a 5-point scale based on Itoh classification for breast lesions [5], finding a strong correlation with the biological characteristics of the tissues. In their research, the results of the elastograms gave 28 TP, 110 TN, 2 FP, and 4 FN cases, accounting for 87.5 % sensitivity, 98.2 % specificity, 93.3 % PPV, 96.4 % NPV, and 95.8 % accuracy in differentiating malignant from benign lesions in the 144 nodules/pseudo-nodules. Similar results were found by Aigner et al. [18] in 50 patients, reaching a sensitivity of 100 %, a specificity of 81 %, a negative predictive value of 100 %, a positive predictive value of 92 %, and an accuracy of 94 % in the diagnosis of testicular tumors. In our experience, elastosonography is useful in the differentiation of malignant lesions from most of benign lesions (Fig. 50.5) [19].