The use of ultrasound in the clinical practice involves the use of frequencies between 1 and 30 MHz [15].

The transducer transmits ultrasonic waves and receives reflected echoes. Image resolution and penetration into the tissue depend on the frequency. If the frequency is lower, then also the resolution becomes lower, but the penetration of the waves is definitely increased.

The frequency normally used for laparoscopy with ultrasound guidance is between 7.5 and 10 MHz. A probe with a frequency of 7.5 MHz can surely provide excellent images by distances ranging from 1 to 4 cm. In this context ultrasound is able to detect tumours up to 3 mm in diameter, cysts of 2 mm and stones below 1 mm [16].

The probe may be linear, with multiple transducers positioned longitudinally or convex. The first is particularly effective for scanning organs with large flat surfaces such as the liver, while the second for tissue with curved surfaces such as the kidney. The saline irrigation is often able to eliminate the possible presence of air on the contact surface, to make the best image resolution [17].

In most surgical procedures performed in laparoscopic or robot-assisted technique, the assistant rather than the surgeon controls the laparoscopic ultrasound probe, which might limit surgeon autonomy and precision. Additionally, the laparoscopic probe might require adjustment of probe positioning with also a robotic instrument to reduce probe slippage from tumour surface [18, 19].

Recently there have been the introduction and use of ultrasound probes, which are directly related to the robotic arm and then directly controlled by the surgeon. The robotic ultrasound probe (e.g. Hitachi Aloka, Tokyo, Japan) has a grooved ridge on its ventral aspect that fits the robotic grasping instrument. The probe has a flexible cable that allows the passage through the assistant port and allows for full articulation of the robotic instruments. Ultrasound images were shown as a picture-on-picture image on the console screen using the TilePro feature of the da Vinci Surgical System (Intuitive Surgical, Sunnyvale, CA, USA) [18].

Finally, in different series of laparoscopic or robot-assisted partial nephrectomy (LPN or RPN) with laparoscopic ultrasonography, they have been described with more difficulties in finding the near and far tumour border, because when the laparoscopic probe is turned at a right angle, the transducer is not exactly perpendicular to the surface of the kidney. The robotic ultrasound probe can be manoeuvred independently by the surgeon, achieving difficult angles while maintaining perpendicular contact of the probe with the kidney surface [19].

The goal of surgery in renal cancers localized to the kidney is to obtain an adequate tumour-free margin to prevent recurrence with a complete resection of the lesions, while preserving nephrons and therefore renal function [20]. The technique described by the school of Cleveland has become the most widely used for the execution of the LPN [21]. According to the American and European Urological Association guidelines [22], PN should be offered to all patients who have T1 tumours (i.e. tumours <7 cm), and it has been found to have comparable, possibly better, survival than RN [23]. Although the RENAL or PADUA nephrometry scoring system [24, 25], which is based on cross-sectional imaging, could help the surgeon’s decision between PN and RN, IOUS provides more detailed real-time guidance in the operating room for selected T1 lesions. CT and MRI clearly showed the proximity of a lesion to the renal sinus fat or involvement of the renal vessels, but on the other hand, IOUS helps determine whether the distance between a main or segmental blood vessel and the tumour is greater than 3–5 mm [11, 12], thus making PN feasible. Kletscher et al. reported that 6 % of patients undergoing RN had unsuspected multifocal tumours that were not seen on cross-sectional imaging and suggested that this true unknown may correspond to the recurrence rate if a PN is performed [26].

Therefore, there is a perceived need for IOUS, especially if the tumour is intraparenchymal and complex according to the nephrometry score (Figs. 11.3 and 11.4).

The intraoperative ultrasound with laparoscopic probe has revolutionized our diagnostic possibilities for small indeterminate renal masses and for tumour identification to facilitate complete tumour removal [8, 10, 27]. It is able to assist the surgeon in locating the mass to be removed remarking with precision the margin of a tumour. Gilbert et al. reported the use of intraoperative ultrasonography to help identify renal cell carcinoma in patients with poorly visualized and non-palpable disease [28]. IOUS does not require the removal of perirenal fat tissue, and it is particularly useful in cases where there is a particularly dense perirenal adipose tissue with predominant fibrous component potentially reducing the surgical time. Such a technique allows the targeted removal and minimizes the removal of normal parenchyma, again minimizing the loss of nephrons. It could also get a good view of the organ to have further confirmation that there are no further injuries, possibly not identified preoperative imaging. Assimos et al. reported using intraoperative ultrasonography for tumour identification to achieve negative surgical margins during partial nephrectomy and recommended its use to facilitate precise identification of adequate resection margins [10].

Marshall et al. reported their experience with intraoperative ultrasonography in 41 kidney surgeries and found intraoperative ultrasonography to be most beneficial for the identification of extrarenal venous extension and multifocality and the identification of associated renal cysts [27]. In a subsequent analysis of 100 cases, Marshall et al. reported that the use of intraoperative ultrasonography influenced the choice of surgical approach in 13 % of cases [8].

Gill et al. described laparoscopic ultrasonography for laparoscopic kidney surgery [29] and the use of this technique as a routine step for deciding on the line of parenchymal incision during LPN [30].

In some cases, the use of colour Doppler is able to facilitate the surgeon in the search and isolation of the renal artery for the execution of the selective clamping, in anticipation of a resection with ischemia [31].

CEUS is a well-established technique for imaging the kidney study [32] and plays a key role in the characterization of malignant renal lesions [33].