**1. Introduction**

enhanced computed tomography as a potential predictor of treatment outcome in metastatic renal cell carcinoma patients receiving antiangiogenic therapy. *Cancer*,

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116(10), 2332-2342.

44 Renal Tumor

831-835.

16(1), 71-81.

*Urology*, 60(6), 1273-1279.

Over 64000 new renal-cell carcinomas (RCC) are annually detected in the United States, and 13000 people will die from the disease. Most RCC are discovered incidentally on medical imaging and a great percentage of them may be treated by surgery, but one third of patients will present either with locally advanced tumor or with metastases[1]. In addition, another third of patients may develop metastatic disease after initial treatment.

In cancer patients imaging techniques are essential in three aspects. First, at the time of diag‐ nosis and the extension study. Ultrasonography, computed tomography (CT) and magnetic resonance imaging (MRI) are currently available to evaluate renal masses.

Second, since most RCC are now early-stage disease suitable for surgery with curative intent, the patient is candidate to follow-up during years. Early detection of recurrence is vital, because single-organ disease may be trated by metastasectomy. Again, CT and MRI are essential in this setting. Also, these imaging modalities are useful to follow-up peo‐ ple with increased susceptibility for RCC, since we have tools to identify at least a sub‐ set of these patients.

And third, imaging techniques are fundamental to evaluate the response to treatment. RE‐ CIST criteria, published in 2000 and revised in 2009, has become the most widely accepted guideline for evaluate response [2]. Although RECIST criteria have been proved as a useful tool to asses response in solid tumors, some limitations have been noted. One of these limi‐ tations are observed in patients treated with specific targeted therapies [3].

Traditionally, RCC have been remarkably resistant to chemo- and radiotherapy. Over the last decade, there has been an increasing knowledge about pathophysiological processes in RCC

including oncology pathways due to a specific driver mutations: silencing von-Hippel Lindau gene, angiogenesis alterations, evasion of apoptosis or sustained angiogenesis.These features have enabled the emergence of a wide spectrum of novel oncology drugs that are designed to target and interfere with specific aberrant biological pathways. Therefore, morphological crite‐ ria may not provide meaningful data in this setting and the incorporation of new imaging tech‐ niques (MRI diffusion, perfusion CT, PET scan, etc....) in the diagnosis of extension and assessment of efficacy of this drugs may provide unique physiological data that can be correlat‐ ed with histopathological changes and may provide functional information.

Although it is an observer-dependent technique, it allows monitoring renal lesions growth and distinguish between cystic and solid lesions. Ultrasonographic features of cystic lesions

Imagen Thecniques in Renal-Cell Carcinoma http://dx.doi.org/10.5772/54190 47

**1.** Round morphology, smooth and well-defined walls, separating it from the surrounding

**2.** There is a strong posterior wall indicating good transmission through the cyst and en‐

**3.** Absence of internal echoes. The presence of thickened internal septa, calcifications, or

One of its limitations is the evaluation and characterization of small lesions. Jamis found that CT detected more renal lesions, especially if they were noncontour deforming. 5% of 2 cm lesions were not detected with CT, an 30% were missed in US. Of lesions under 1 cm, 24% were not detected in TC versus 80% with US [4]. Moreover, given the variability in the echogenicity of malignant kidney, it can be difficult, in the case of isoechoic images, the

In recent years it has become increasingly important the use of contrast-enhanced ultra‐ sound (CEUS). Current CEUS consist of intravenously injected microbubbles that increase the number of reflectors in the vascular space. It has different utilities. It is useful in the dif‐ ferential diagnosis of solid and cystic lesions so as to characterize cystic lesions in benign or malignant [5]. Solid lesions show early arterial enhancement, normally lower than sur‐ rounding parenchyma. The delayed enhancement varies and after an arterial phase lesions are isoechoic relative to parenchyma. Often because of intralesional necrosis, there are intra‐

It is of particular interest the characterization of complex cystic lesions. Some studies have reported a sensitivity and specificity similar to CT [6] [7]. It can be considered a valid alter‐ native to CT and MRI in monitoring these lesions that need prolonged follow [8]. It may also be useful in detecting small renal masses, improving the accuracy of simple ultrasound, since it allows to observe changes in the thickness of the cortical pyramidal space, not visible

Computed tomography (CT) is the modality of choice for the diagnosis and study of exten‐ sion of renal carcinoma, with a sensitivity greater than 95% (Figure 2) [9]. In addition, the development of multidetector CT has allowed an increase in the rate of detection and diag‐

For the evaluation of suspicious lesions, it is advisable to have a specific protocol. This should include a scan without contrast to determine the presence of calcification or fatty tis‐ sue within the tumor, and will serve as baseline study to study if these lesions enhance after

that allow distinction with malignant lesions or abscesses are:

hanced transmission beyond the cyst.

mural vascularity indicate malignancy.

identification and distinction of these lesions.

lesional areas without contrast enhancement.

in simple US.

**2.2. CT scan**

nosis in early stages [10].

contrast administration.

parenchyma.

In this chapter we will review the main techniques of radiological diagnosis and staging, the role of new imaging techniques and we will also discuss the validity of the classical criteria of interpretation of response.
