Background and purpose: Obtaining a negative surgical margin during laparoscopic partial nephrectomy (LPN) is paramount to optimizing the oncologic efficacy of the procedure. Limitations of laparoscopy hinder the ability to extrapolate the intraparenchymal tumor extension from the exophytic portion. We developed a technique wherein ultrasound-confirmed needle localization of the deep tumor margin prior to tumor extirpation ensured negative surgical margins.
Materials and methods: Our technique was developed and initially tested using an agar-based ultrasound phantom designed to mimic 2-cm exophytic renal tumors. Needle placement was imaged with ultrasonography and subsequently correlated with findings on sectioning of the tumor mimic. Laparoscopic extirpation of the tumor mimic following needle placement was carried out in a pelvic trainer. The technique has subsequently been incorporated into our LPN technique in four patients.
Results: Ultrasound-confirmed needle localization of intraparenchymal tumor extension was feasible and reproducible in an ultrasound phantom. Ultrasound findings correlated with gross findings. Needle placement prior to tumor resection helped to ensure negative surgical margins when applied in the pelvic trainer and when used in three patients. In the remaining patient, improper needle placement resulted in a grossly positive deep margin.
Conclusion: Ultrasound-confirmed needle placement effectively and reproducibly marks the deep margin of small renal tumors in a mimic as well as in vivo. Our needle technique eliminates the guesswork and unreliability associated with mental visualization and extrapolation of tumor extent during LPN.