**3. Equipment**

For CEUS technique, the ultrasound device must be capable of functioning in harmonic mode and benefit from the acoustic power adjustment. The transducers, similar to those currently used for B and Doppler mode examinations, differ in the ability to operate in contrast mode. The harmonic mode allows a real and effective discrimination of the echoes from the blood column to those from the tissues. The acoustic power regulation is set to a value of 0.09–0.11, which leads to the generation of harmonic echoes at the microbubble level, minimizing the harmonic echoes at the tissue level and the artifacts.

**5. Precautions**

examinations [12, 13].

**6. Contraindications**

been reported so far after using CEUS.

**7. CEUS in renal pseudo-tumors**

failure or patients with history of thyrotoxicosis.

The sulfur hexafluoride, the gaze part of the contrast agent is inert, nontoxic, with biocompatible membranes and easily eliminated by breathing. The metabolism of the membranes covering the microbubbles is done in the liver. These features make CEUS exploration independent of renal or thyroid functions, being an alternative to computer tomography in cases of renal

Harmonic Contrast-Enhanced Ultrasound (CEUS) of Kidney Tumors

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Very rare side effects are possible due to the interaction of ultrasound with microbubbles. These interactions may be mechanical or chemical. Mechanical features include bubble expansion and capillary rupture. Transient hyperthermia during bubbles recovering after expansion can generate free radicals. The precipitating factor for these reactions is the use of a mechanical index of about 0.4 [11]. Anaphylactic reactions were reported in 0.002% of

CEUS contraindications are: severe coronary artery disease and pulmonary hypertension, unstable ischemic heart disease, age <18 years, and pregnancy [14]. No renal side effects have

Renal pseudotumors refer to persistent fetal lobulation, dromedary hump, and hypertrophied column of Bertin. These mass-like lesions are frequently detected on conventional ultrasound. The characteristic features are: location between overlapping portions of two renal sinus systems, clear demarcation from the renal sinus, size <3 cm, similar echogenicity to renal parenchyma, and lesions being bordered by a junctional parenchyma line; the Doppler mode

There are, however, a number of situations in which their diagnosis is difficult—they may be miss-interpreted as kidney tumors through 2D gray scale techniques. This confounding is found in the following circumstances: modified echogenicity compared to the parenchymal environment, infiltrative tumor formations (metastases and lymphomas) [16], abnormal vas-

As CEUS is able to depict the microcirculation, this procedure could make the differential diagnosis between a pseudotumor and a solid mass. The vascular pattern of the "pseudotumors" is similar to adjacent parenchyma [18] (**Figures 4** and **5**). The accuracy of CEUS is similar to contrast-enhanced computer tomography (CE-CT) or magnetic resonance imaging

(MRI) for the depiction of a normal vascular pattern in a pseudotumor mass [18].

demonstrates the regular, branch-like blood flow in the lesion [15].

cular tracts [17], and obese or noncooperative patients (**Figure 3**).
