## 1 Introduction  
Statistics from the American Cancer Society have shown that kidney and renal pelvis cancers are among the top 10 most frequently diagnosed cancers [1]. Approximately one-third of renal cell carcinoma (RCC) patients have metastases at diagnosis. The most frequent histological type is clear-cell RCC (ccRCC), accounting for about 80% of all renal tumors, with poor prognosis in the metastatic stage [2]. Over the past two decades there have been remarkable advances in the understanding of RCC's oncogenesis, leading to the emergence of new targeted therapeutic options such as biologic antineoplastic drugs. Consequently, a marked improvement in clinical outcomes has been found with the advent of immune checkpoint inhibitors (ICIs), both in monotherapy and in association with other drugs [3]. The International Metastatic Renal Cell Carcinoma Database Consortium (IMDC) has subclassified RCC into favorable, intermediate, and poor prognosis [4]. First-line treatment with dual immunotherapy (ICI/ICI) is recommended by the guidelines of the European Association of Urology in the IMDC intermediate and poor risk subgroups, while for all IMDC risk groups they recommend first-line treatments with combined ICI/VEGFtherapies. However, despite the therapeutic advances in recent years, distant-stage mRCC has only a 13% of 5-year relative survival rate [5].  
Numerous tissue-based tumoral biomarkers--including histological features, PD-L1 protein expression, infiltrating T-cell exhaustion markers, somatic mutations, and transcriptomic signatures--have been studied for the evaluation of systemic therapies [6; 7; 8; 9; 10]. However, these biomarkers have several limitations due to their low predictive capacity, lack of standardization, invasiveness of the biopsy, or sampling errors related to lesion heterogeneity [11]. Imaging is of fundamental importance for diagnosis, non-invasive qualitative and quantitative analysis of tissues, tumor staging treatment planning, response to therapy, and follow-up [12; 13; 14]. The most widely used imaging technique in RCC is contrast-enhanced computed tomography (CT) [15]. CT protocols for the detection and staging of RCC involve arterial and nephrographic post-contrast phases, as the histological subtypes of RCC can have variable post-contrastographic appearance [16]. Metastatic lesions generally exhibit contrast enhancement similar to that of the primary lesion [16]. Some metastases, such those from cRCC, can have arterial contrast enhancement. RCC can metastasize to any organ; the lung is the first organ most affected by RCC metastases, followed by the lymph nodes and bone [17]. The morphology of lymph node metastases is fundamental for diagnosis; in particular, a short axis of the lymph node greater than 10 mm indicates potential disease involvement.  
ICIs, unlike other systemic therapies, may exhibit atypical response patterns. A systematic review of 38 studies demonstrated an atypical response rate of 6% [18]. Two atypical patterns of response called pseudoprogression and hyperprogression were reported. Pseudoprogression is a transient increase followed by a decrease in total tumor burden, while a rapid increase of at least twice the expected tumor growth rate defines hyperprogression [19; 20].  
Furthermore, tumor heterogeneity, through texture analysis, provides information that is not visible with the naked eye, which can be detected through CT approaches, possibly helping to predict tumor behavior and outcomes [21]. By generating quantitative parameters, texture analysis provides important information on the features of the tissue, offering valuable prognostic information.  
The present literature review is focused on the role of CT in evaluating ICIs' effects on mRCC, providing an overview of both the CT manifestation of ICIs and the potential predictive value to estimate tumor response to these therapies.