The incidence of RCC is rising in large part due to increased utilization of imaging. Asymptomatic, localized T1a RCC (≤ 4.0 cm) constitutes the majority of new diagnoses. Nephron-sparing approaches are the standard treatment for these patients. Regarding T1a RCC, endophytic tumours are centrally located and nearer to the collecting system. Small, totally endophytic renal masses pose some difficulties in terms of laparoscopic nephron-sparing excision, especially in tumour identification and complete resection.
A small, totally endophytic renal mass cannot be accurately detected by conventional intraoperative observation or palpation. Intraoperative ultrasound probe is the conventional option for those tumours. This is also the case for the up-to-date robot-assisted procedure, so as to score the resection area on mass. However, its application depends on echoic difference from surrounding tissue and subjective operator’s experience[13, 14]. Although near-infrared fluorescence imaging has been considered transiently helpful in identifying the vascular anatomy, it is not accomplishable at all for endophytic tumours. The preoperative superselective transarterial delivery of a lipidol-indocyanine green (ICG) mixture to trace endophytic tumours has been described[3, 15], but related transarterial liquid diffusion and allergy must be taken into account. Additionally, intraoperative real-time localization has greater prospects for development; however, this method is not currently widely applied due to the high cost and prolonged operation time. There have also been case reports on the application of hook-wire localization prior to laparoscopic partial nephrectomy for an intrarenal mass[5, 16, 17]; nevertheless, persistent pain is problematic.
We have previously described a modified microcoil method for the precise preoperative localization of pulmonary nodules before video-assisted thoracoscopic surgery, with satisfactory results. We adopted a similar method in renal surgery to localize the renal mass. To our knowledge, this application of microcoil implantation prior to laparoscopic partial nephrectomy towards an intrarenal mass could be an early reported attempt for the localized method applied in renal surgery.
Our application provided the opportunity to avoid the use of intraoperative US or an alternative to US if it was not available. This method provides direct guidance in particularly tricky cases of endophytic tumours in which the surgeon requires confirmation of which strategy is best to achieve a safe operation for the patient.
There have been few published reports on the usefulness, efficacy and safety of the microcoil localization of tumours in nephron-sparing surgery. Evidence from video-assisted thoracic surgery suggests that microcoil localization is an effective and useful technique[19–22]. The patient in our report received an acceptable radiation dosage and experienced no discomfort. Microcoil localization could be a feasible and safe method that can be used preoperatively to provide enhanced insight into renal masses for urologists. Importantly, our method enables the tail of the microcoil to be easily placed outside the kidney surface. Consequently, the mass can be easily found during laparoscopy, reducing the time required for mass excision. The microcoil, which is usually used for blood vessel embolization, is preloaded and covered by synthetic fibres. These synthetic fibres are intended to activate coagulation and thus may also prevent puncture-related bleeding.
Notably, implantation of the microcoil does not need to be performed on the day of surgery, which is different from approaches using dyes or contrast agents. Concerning hook-wire localization, the introduction of the wire was carried out just before the surgery to minimize the potential risk of wire migration. Therefore, our preoperative localization method is more convenient than others and does not need special equipment or additional time on the day of surgery. After the microcoil was successfully implanted into the renal parenchyma towards the mass, urologists were able to observe the relationship between the microcoil and the endophytic mass on the subsequent CT scans, facilitating the following exploration during laparoscopy.
Although accurately identifying renal masses on CT without contrast perhaps is uneasy sometimes, we could recognize the target mass using CT plane information, for example, nearby blood vessels, bone markers, organs and tissues.As totally endophytic masses are not common among all resectable renal tumours, over the long term, this method could be applied in more cases with similar characteristics to gain more valuable and conclusive results. It is also expected that this microcoil localization with nowaday robot-assisted partial nephrectomy would further improve their application for endophytic masses.