The prevalence of small renal masses (SRM) has risen, paralleling the increased usage of cross-sectional imaging. A large proportion of these SRMs are not malignant, and do not require invasive treatment such as nephrectomy. Therefore, differentation between early renal cell carcinoma (RCC) and benign SRM is critical to achieve proper management. This article reviews the radiological features of benign SRMs, with focus on two of the most common benign entities, angiomyolipoma and oncocytoma, in terms of their common imaging findings and differential features from RCC. Furthermore, the role of percutaneous biopsy is discussed as imaging is yet imperfect, therefore necessitating biopsy in certain circumstances to confirm the benignity of SRMs.
Abdominal Fat/pathology ; Adenoma, Oxyphilic/diagnosis/radiography/ultrasonography ; Angiomyolipoma/diagnosis/radiography/ultrasonography ; Carcinoma, Renal Cell/*diagnosis/radiography/ultrasonography ; Diagnosis, Differential ; Humans ; Kidney Neoplasms/*diagnosis/*radiography/ultrasonography ; Leiomyoma/diagnosis/radiography/ultrasonography

OBJECTIVE: To evaluate the value of enhancement features and quantitative parameters of contrast-enhanced ultrasonography (CEUS) in differentiating solid hypoechoic renal angiomyolipomas (AMLs) from clear cell renal cell carcinomas (ccRCCs). MATERIALS AND METHODS: We analyzed the enhancement features and quantitative parameters of CEUS in 174 hypoechoic renal masses (32 AMLs and 142 ccRCCs) included in the study. RESULTS: Centripetal enhancement pattern was more common in AMLs than in ccRCCs on CEUS (71.9% vs. 23.2%, p < 0.001). At peak enhancement, all AMLs showed homogeneous enhancement (100% in AML, 27.5% in ccRCCs; p < 0.001). Quantitative analysis showed no significant difference between rise time and time to peak. Tumor-to-cortex (TOC) enhancement ratio in AMLs was significantly lower than that in ccRCCs (p < 0.001). The criteria of centripetal enhancement and homogeneous peak enhancement together with TOC ratio < 91.0% used to differentiate hypoechoic AMLs from ccRCCs resulted in a sensitivity and specificity of 68.9% and 95.8%, respectively. CONCLUSION: Both qualitative and quantitative analysis with CEUS are valuable in the differential diagnosis of hypoechoic renal AMLs from ccRCCs.
Adult ; Aged ; Angiomyolipoma/*diagnosis/pathology/*ultrasonography ; Carcinoma, Renal Cell/*diagnosis/pathology/*ultrasonography ; Contrast Media ; Diagnosis, Differential ; Female ; Humans ; Kidney Neoplasms/diagnosis/pathology/*ultrasonography ; Language ; Lipoma/ultrasonography ; Male ; Middle Aged ; Sensitivity and Specificity

OBJECTIVETo study the diagnosis and management of renal angiomyolipoma (RAML), and to identify risk factors affecting spontaneous angiomyolipoma rupture.

METHODSThe data of 68 patients with RAML from 1989 to 2002 were retrospectively reviewed. These patients were divided in two groups on the basis of tumor size, 35 patients in group A ( 4 cm).

RESULTSSeven patients were identified by image-guided percutaneous biopsy, and no major complications was noted. Sixteen patients with RAML were examined with angiography and 9 of 16 patients had got spontaneous rupture. 41.2% of patients were symptomatic, 4 cases (11.4%) in group A and 24 (72.7%) cases in group B (P < 0.01). There were significant differences in mean tumor size (11.6 cm +/- 5.1 cm vs 5.3 cm +/- 2.9 cm, P < 0.01) and mean aneurysm size (13.6 mm +/- 5.8 mm vs 2.6 mm +/- 3.0 mm, P < 0.01) between 9 cases of the ruptured tumor and 59 cases of unruptured tumor, 9 cases of the ruptured and 7 cases of unruptured tumor with angiography, respectively. Treatment consisted of conservative observation in 10 patients (no radiographic changes during the follow-up of 2 - 7 years); partial nephrectomy in 14 patients, tumor enucleation in 30 patients, total nephrectomy in 14 and posterior laparoscopic nephrectomy in 3 (no recurrence and complication correlation to operation during the follow-up of 2 - 144 months).

CONCLUSIONSIt is an important role that percutaneous biopsy guided by ultrasonography or computerized tomography performs in managing suspicious and/or indeterminate RAML. A higher probability of rupture is related to tumor and/or aneurysms size. Nephron-sparing surgery is the first choice for surgical treatment of RAML.

Adolescent ; Aged ; Angiomyolipoma ; diagnosis ; pathology ; therapy ; Biopsy, Needle ; Female ; Follow-Up Studies ; Humans ; Kidney Neoplasms ; diagnosis ; pathology ; therapy ; Male ; Middle Aged ; Nephrectomy ; methods ; Rupture, Spontaneous ; Tomography, X-Ray Computed ; Ultrasonography, Interventional