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The incidence of small renal masses is increasing, as a result of the wide adoption of imaging exams. Their management, however, is complicated, especially in patients with decreased life expectancy or comorbidities. Approximately 20% of small renal masses are benign and, even if malignant, just 10% show aggressive pathological features. Furthermore, competing cause mortality seems to exceed the cancer-specific mortality in patients aged over 70 years. The role of percutaneous tumor biopsy is still not well defined. All these observations raise the concern as to whether surgery might represent an overtreatment for some cases of small renal masses, calling into question the role of active surveillance. The aim of this review was to evaluate the current evidence pertaining to several hot questions that need to be addressed when contemplating active surveillance for small renal masses. The most relevant publications on this subject available in the literature were selected. Five representative series of active surveillance along with the main related variables were identified. Some relevant items surrounding the field of active surveillance were identified and submitted to an evidence-based discussion. According to the recent evidence, small renal masses under active surveillance tend to show an indolent course with a low probability of disease progression, the latter being triggered most of the time by a tendency to grow faster. Unfortunately, we are currently unable to predict those few cases with aggressive behavior. According to the current evidence, active surveillance is feasible and safe in elderly and comorbid patients. [ABSTRACT FROM AUTHOR]

What's known on the subject? and What does the study add? Optical Coherence Tomography (OCT) was developed in the early 1990s for ophthalmological application and is currently widely accepted in ophthalmology for retinal imaging purposes. In kidneys, the first experiments were performed on transplant kidneys to investigate the ability of OCT to assess ischaemic damage of kidneys. An ex vivo pilot study on the ability of OCT to differentiate normal renal tissue from malignant renal tissue, showed positive results and here we present the results of the first in vivo experiment. The study shows for the first time that in vivo OCT is feasible and safe to perform in humans and that a significant different attenuation coefficient (as a quantitative measurement of the OCT images) is found between normal renal tissue and malignant renal tumours with a clear trend towards significance in the difference between benign and malignant renal tumours in a small pilot study. This suggests potential use of OCT in different clinical settings for diagnostic purposes in the course of renal tumours, and justifies further research. OBJECTIVE To determine the ability of optical coherence tomography (OCT) in differentiating human renal tumours in an in-vivo setting by assessing differences in attenuation coefficient (µOCT; mm-1) as a quantitative measurement., METHODS Consecutive patients undergoing nephrectomy (partial/radical) or cryoablation for an enhancing solid renal tumour were included in our centre between October 2010 and May 2011., In vivo OCT images were obtained from renal tumour and normal parenchyma during surgery. Ex vivo OCT images of internal (subcapsular) tissue were obtained after longitudinal dissection of the extirpated specimen., Attenuation coefficients of the OCT images were determined off-line and compared between normal renal parenchyma and renal tumours (grouped per tissue type and per individual patient); and between OCT images recorded from tissue surface vs internal (subcapsular) tissue., RESULTS In vivo OCT was performed in 16 cases (11 renal cell carcinoma, three benign tumours, one non-diagnostic biopsy and one not-accessible tumour)., Median attenuation coefficient of normal renal parenchyma was 5.0 mm−1 vs 8.2 mm−1 for tumour tissue ( P < 0.001) with normal parenchyma differing significantly from malignant tumour (9.2 mm−1, P < 0.001) and non-significantly from benign tumour (7.0 mm−1, P= 0.050). The attenuation coefficient of benign tumours did not differ significantly from that of malignant tumours (7.0 vs 9.2 mm−1, P= 0.139)., Using patients as their own control, attenuation coefficients of normal renal parenchyma differed significantly from malignant tumour ( P < 0.001) and non-significantly from benign tumour ( P= 0.109)., Assessed in 10 patients, there was no significant difference between attenuation coefficients of tumour surface and internal tumour (8.5 vs 9.7 mm−1 respectively, P= 0.260)., CONCLUSIONS In this first in vivo study on OCT for differentiation of renal tumours in humans the attenuation coefficients (as a quantitative assessment) differed significantly between normal renal parenchyma and malignant tumour., Tumour surface and internal tumour did not differ significantly, suggesting that a superficial OCT attenuation coefficient reliably assesses tissue composition inside the tumour., These results justify further research on OCT for various clinical applications in the diagnosis of renal tumours. [ABSTRACT FROM AUTHOR]