Diagnostic ultrasound ( PDFDrive )

CHAPTER 9 The Kidney and Urinary Tract 343
From 5% to 7% of all RCCs are cystic tumors. 162 Four histologic
growth patterns within cystic RCCs have been described:
multilocular, unilocular, necrotic (cystic necrosis), and tumors
originating in a simple cyst 163 (Figs. 9.48 and 9.49). Recognition
of subtypes have clinical signiicance because the multilocular
FIG. 9.48 Cystic Growth Patterns of Renal Cell Carcinoma. Upper
pole, Multilocular; upper lateral, unilocular; lower lateral, cystic necrosis;
lower pole, origin in the wall of a simple cyst. (With permission from
Yamashita Y, Watanabe O, Miyazaki H, et al. Cystic renal cell carcinoma.
Acta Radiol. 1994;35:19-24. 162 )
and unilocular subtypes are less aggressive. 162 At sonography,
multilocular cystic RCC appears as a cystic mass with internal
septations. hese septations may be thick (>2 mm), nodular,
and may contain calciication (see Fig. 9.47). he characteristic
ultrasound appearance of a unilocular cystic RCC is a debris-illed
mass with thick, irregular walls that may be calciied. he appearance
of necrotic RCCs depends on the degree of tumor necrosis.
Tumors originating in a simple cyst are rare (excluding VHL
patients). At ultrasound, a mural tumor nodule will be found at
the base of a simple cyst. A combined approach with helical CT
and ultrasound allows accurate characterization of the internal
nature of most cystic renal lesions. 164
he use of Doppler ultrasound 165 for detection of tumor
vascularity has been reported. Most malignant renal tumors
(70%-83%) have Doppler shit frequency of 2.5 kHz. 165-169 Similar
changes may be noted with inlammatory masses; however,
patients with renal infection should be clinically apparent.
Unfortunately, the absence of high-frequency Doppler shit does
not exclude malignancy. 168 Conirmation of blood low within
malignant solid and cystic renal tumors has also been performed
with microbubble contrast agents and low–mechanical index
pulse inversion sonography. Criteria for neovascularity used with
CT or MRI for mass characterization—septal and nodular
enhancement—can also be used with stable, second-generation
ultrasound contrast agents 170,171 (Fig. 9.50). However, lack of US
Food and Drug Administration approval, reimbursement issues,
and logistics associated with technologist/radiologist-intensive,
contrast-enhanced sonography protocols have hindered widespread
adoption of this technique.
Biopsy and Prognosis
Recent pathologic and biopsy series of small (<3 cm), solid
enhancing renal masses have shown that a surprising number
of these lesions are benign (i.e., AML, oncocytoma, metanephric
adenoma). Moreover, image-directed needle biopsy (aspiration
or core) has been shown to be a relatively safe and usually
conclusive procedure. 172-176 Further advances in immunohistology
and greater acceptance of percutaneous ablation techniques
2
1
A
B
FIG. 9.49 Renal Cell Carcinoma Within Cyst. (A) Complex cyst with mural nodule. (B) Color Doppler shows low within septation. (Courtesy
of Vikram Dogra, MD.)