SA 16 - Detection and management of small renal masses
1. To understand the imaging features of small benign and malignant renal masses.
2. To learn about the treatment options using imaging-guided minimally invasive treatment.
3. To appreciate typical normal and abnormal imaging findings during treatment monitoring.
Small renal masses are often incidentally detected on cross-sectional imaging. Management of these focal renal lesions depends on the underlying histology, age and comorbidities of the patient. However, characterisation of these small renal masses is often a big challenge. Cystic real lesions are classified according to Bosniak. In recent years, differentiation of solid renal lesions has improved substantially mainly thanks to a multiparametric approach using MRI. In the past years, solid renal lesions were surgically resected in most centres; however, in recent years, active surveillance and imaging-guided minimally invasive treatment are increasingly used alternatives to partial nephrectomy depending on histology of the tumour and various patient factors. As a consequence treatment monitoring is not only based on change in size or macroscopic tumour recurrence, but needs more detailed knowledge of the performed treatment including normal and pathological findings and knowledge of functional imaging techniques to early evaluate treatment success or recurrence.
1. To understand the definition of small renal masses.
2. To understand the typical imaging findings of small renal masses on CT.
3. To become familiar with multiparametric MRI to characterise small renal masses.
Imaging is the main source of detection of small renal masses. Primary detection is based on US and CT. MRI may help in indeterminate cases, DWI playing a major role. Characterisation of solid component of a small renal mass is based on CT-contrast enhancement, but, when doubtful, DCE-MRI and CEUS are more sensitive. Considering cystic masses, Bosniak classification is required. Considering solid masses, characterisation of fat-rich angiomyolipomas is based on plain CT, but fat-poor AMLs can be distinguished from carcinomas by multiparametric MRI only. Multiparametric MRI includes chemical shift gradient echo (GRE) sequences, signal intensity on T2-weighted images, DCE sequences, diffusion-weighted sequences and late contrast-enhanced images. Using different combinations of two or several parameters, now makes it possible to clearly distinguish some renal tumours such as fat-poor AMLs, papillary carcinomas and clear cell carcinomas, the latter being difficult to separate from oncocytoma when a central scar is absent. A larger validation of all these combinations is still necessary to define those having a clinical significance for routine practice. Percutaneous biopsy remains mandatory before such a validation, as soon as pathological result is supposed to have an impact on tumour management.
1. To become familiar with the clinical management of small renal lesions.
2. To understand the minimally invasive treatment options of small renal lesions.
3. To learn about the current evidence on the minimal invasive treatment of small renal tumours.
The clinical management of small renal masses generates significant controversy. The gold standard still remains surgical excision; nevertheless, nephron sparing minimal invasive percutaneous ablation appears to offer similar oncologic outcomes and less complication than surgery. Active surveillance is only reserved for patients that are not suitable for any kind of treatment. Percutaneous ablation (radiofrequency, cryo or microwave) may be performed under local or general anaesthesia with minimal hospital stay; guidance may be performed under CT, MRI or US guidance and with the use of fusion and navigation systems. Long-term results and comparative data are now available. Psutka et al. [Eur Urol. 2013] report the results of 185 patients with Stage I renal tumour (median size 3 cm) treated with RFA and followed up for a median of 6.43 years (range: 5.3-7.7). Local recurrence occurred in 6.5% of the patients after a median time of 2.5 years; however, the 5-year recurrence-free survival was 96.1%. Olweny et al. [Eur Urol. 2012] identified no significant difference between RFA and open partial nephrectomy for the treatment of T1a RCC in terms of 5-year disease-free survival, metastasis-free survival and local recurrence-free survival. Furthermore, Thompson et al. [Eur Urol. 2015] recently published a retrospective single-centre comparison of ablation with partial nephrectomy for Stage I RCC of 1424 patients with no difference on recurrence-free survival and comparative oncologic results. Ablation is offering excellent long-term results for the management of small renal tumours and should be considered as a first-line therapy for T1a tumours.
1. To become familiar with imaging techniques for patients under active surveillance.
2. To understand typical imaging findings after minimally invasive treatment.
3. To appreciate functional imaging techniques to assess early treatment response.
Most frequent treatments for small renal masses (SRM) are partial nephrectomy, radiofrequency ablation, cryoablation and active surveillance. CT and MR are commonly used in the imaging follow-up of patients treated for SRM. Parenchymal changes after partial nephrectomy are the presence of postoperative granulomas, fat, scars or parenchymal defects at the excision site. Imaging patterns of recurrence are the presence of a mass with enhancement, increasing in size during the follow-up, at the excision site or perinephric space. Radiofrequency ablation and cryoablation are minimally invasive approach for the treatment of SRM. Both ablative treatments, performed with percutaneous approach under US or CT guidance, provide tissue necrosis. Since it is not possible to document histopathologically the complete tissue necrosis after renal ablation, an adequate radiological follow-up is mandatory. Recurrence patterns after ablative treatments are the presence of an enhancing nodule in the treated area, increasing in size during the follow-up. Active surveillance has emerged as an alternative to extirpative or ablative treatments for SRM, in elderly and comorbid patients. Serial abdominal imaging (CT/MR) is performed to monitorize tumour size, with delayed intervention reserved for those tumours that show clinical progression during follow-up. In treated kidneys imaging follow-up, the most effective imaging techniques were multiphasic acquisition (CT) and morphologic TSE T2w and dynamic ce-FS-GRE T1w sequences before and after digital subtraction technique (MR). MR diffusion-weighted imaging may also be helpful to identify foci of residual tumour when contrast enhancement is difficult to evaluate, or when contrast cannot be administered due to renal insufficiency.