Answer to the question from page 235.

Correct answer: C.

The analysis of fig. 1 proves that the bulge in the outer outline of the kidney is caused by the shape of the cortical layer (the same echogenicity of this fragment of the kidney) and the pyramid located in the vicinity (left side of fig. 2). The correct angioarchitecture in this part of the kidney, as visualized by color Doppler, confirms such a diagnosis (right side of fig. 2). A similar example, which meets the same ultrasound criteria, is presented in fig. 3. Only the pyramid in fig. 3 shows lower echogenicity and may be erroneously interpreted as a subcortical cyst. In differential diagnosis, the most important pathology that needs to be taken into account is renal carcinoma which sometimes manifests itself as an isoechoic lesion. An example is presented at the left side of fig. 4. The neoplasm reached the size of 15 mm and practically, it is not different from the surrounding parenchyma. The only alarming sign is the chaotic central arrangement of the vessels in the nodule (right side of the figure). Doubts may be resolved by scanning the same lesion with the patient assuming a standing position (fig. 5). In this figure, the lesion presented in fig. 4 is better circumscribed, slightly hyperechoic and with its appearance, it may imitate angiomyolipoma. However, when carefully observed, microcysts may be noticed, which is a sign that does not normally accompany angiomyolipomas. It must be emphasized that the sonograms in figs. 4 and 5 were obtained by the method of harmonic imaging with pulse inversion. At this point, it is worth considering whether kidney examination should be performed with the patient in a standing position. According to my own experience, it is an important methodical element for two reasons. Firstly, in the majority of patients, the thorough examination of the kidneys is hindered by the ribs. The change to the standing position causes the caudal movement of the kidney to the degree depending on an individual patient. Thereby, the fragments of the kidney, which would otherwise be concealed, are visible. This refers to the detection of small lesions – up to 30 mm. Secondly, a standing position causes the tension of the spinal muscles and abdominal integuments. The so-called corset muscles of the abdominal cavity are activated, which increases adherence of the organs and this, in turn, improves imaging. A similar effect may be obtained by compressing the integuments with the transducer. The application of the standing position and probe compression may considerably improve the visualization of not only the kidneys. By changing the patient's position while performing US examination in the case of renal carcinoma, it was demonstrated that the same lesion, despite identical ultrasound conditions, presents different echogenicity: in a lying position it is isoechoic and in a standing one – hyperechoic. In the pioneer period of ultrasound diagnosis, the vast majority of renal carcinomas were isoechoic (86%), 10% manifested themselves as hypoechoic lesions and merely 4% – as hyperechoic ones(. In the 1990s, several studies revealed that especially small carcinomas (not greater than 3 cm) are characterized by higher echogenicity than the surrounding parenchyma – from 29 to 77%(. The material of Forman et al.( showed that carcinomas with the size smaller than 3 cm and hyperechoic pattern are encountered twice as frequently as similar lesions of greater mass (77% vs. 32%). A number of papers proved the diagnostic value of morphological signs observed in a B-mode presentation in differentiating between hyperechoic renal cell carcinomas and angiomyolipomas. Only in the case of the former lesions, a hypoechoic rim is encountered – a pseudocapsule (from 8 to 84%) and microcysts (from 12 to 34%). The latter lesions, however, are characterized by acoustic shadow (from 21 to 34%). The more adipose tissue is present in the mass, the more frequently the acoustic shadow is encountered(. Another feature that must be considered in the differential diagnosis is the presence and type of vascularization on Doppler examination. However, the greatest number of certain data may be obtained after the administration of contrast agents(.

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