Radical (total) nephrectomy was for many years the accepted standard treatment for all organ-confined kidney tumors, but nephron-sparing surgery (partial nephrectomy) has now become the preferred treatment for small renal masses for which surgery is warranted. Nephron-sparing surgery, which may be performed by an open or a laparoscopic approach, involves targeted excision of the tumor along with an adequate rim of normal renal parenchyma, thereby preserving the uninvolved portion of that kidney.

 Chronic kidney disease is increasingly common (one study showed previously unrecognized chronic kidney disease in one quarter of the patients who had a small renal mass); therefore, renal functional preservation is an important consideration in management.

Open partial nephrectomy, the reference nephron-sparing procedure, is typically performed through a 6-in. or larger muscle-cutting incision in the flank, often with removal of a lower rib. Up to 50% of patients may have persistent incisional complications, such as flank bulge, discomfort, paresthesias, or hernia.

 Laparoscopic Partial Nephrectomy

Minimally invasive nephron-sparing procedures include laparoscopic or robotic partial nephrectomy and image-guided thermal ablation. In a large, retrospective, multi-institutional study comparing outcomes of laparoscopic partial nephrectomy with those of open partial nephrectomy for category T1 tumors that were 7 cm in diameter or smaller (78% of which were small renal masses), the treatment groups had similar rates of intraoperative complications (1.8%) and of positive surgical margins for cancer (1.6%), although the open-partial-nephrectomy group had more coexisting conditions and larger tumors. At the 3-year follow-up, oncologic outcomes and renal functional outcomes were similar. However, the laparoscopic-partial-nephrectomy group had a longer ischemia time than the open-partial-nephrectomy group (30 minutes vs. 20 minutes) and higher rates of postoperative hemorrhage (4.2% vs. 2%).Our recently described "early unclamping" technique during laparoscopic partial nephrectomy has resulted in lower ischemia times (mean, 14 minutes) and lower postoperative hemorrhage rates, approximating those reported with open partial nephrectomy. An observational study comparing laparoscopic and open partial nephrectomy showed similar 7-year overall mortality rates (16.9% and 16.5%, respectively) and cancer-specific mortality rates (3.1% and 2.3%, respectively).Laparoscopic partial nephrectomy is now used even for technically challenging small renal masses that are hilar, central, completely intrarenal, or located in a solitary kidney. Observational data indicate that laparoscopic partial nephrectomy is associated with shorter recovery times than is open partial nephrectomy. It should be noted that the laparoscopic procedure requires technical expertise, and studies showing good outcomes have been performed at selected tertiary centers. If laparoscopic expertise is lacking, open partial nephrectomy should be performed.

            Thermal Ablation

Thermal ablation is performed by inserting needle applicators within the renal mass to generate cytocidal temperatures. Cryoablation and radiofrequency ablation are the most common methods and are typically performed after needle biopsy for tissue diagnosis.

Data from a case series of 80 patients who underwent laparoscopic cryoablation, with a median follow-up of 8 years, indicate that cryoablated small renal masses gradually autoabsorb and shrink in size by an average of 57% at 1 year, 72% at 3 years, and 89% at 5 years, with 73% of cryoablated masses being undetectable on MRI at 5 years. At 10 years, overall mortality and cancer-specific mortality rates were 49% and 17%, respectively (31% of the patients had undergone previous surgery for metachronous renal-cell carcinoma). With refinements in probe size and design, a percutaneous image-guided approach may be preferable to a laparoscopic approach for thermal ablation, since procedure-associated morbidity would be lower.

Initial experiences with percutaneous radiofrequency ablation also indicate favorable short-term outcomes, although long-term data are not available. In three case series involving 286 patients who underwent radiofrequency ablation and were followed for an average of 1.2 to 2.3 years, tumor control was achieved in 90% of the patients. Tumor control was defined as an absence of contrast enhancement on CT or MRI.

Complications have been reported in approximately 10% of patients who have undergone cryoablation (hemorrhage in 1%, reoperation in 1%, pulmonary complications related to coexisting conditions in approximately 5%, and congestive heart failure related to coexisting conditions in 1%).Complications have been reported in approximately 10% of patients who have undergone radiofrequency ablation (hemorrhage in 1 to 5%, ureteral injury or stricture in 2%, and severe neuropathic pain in 1.6%). After thermal ablation, follow-up is empirically recommended at intervals of 6 to 12 months with dedicated MRI or CT, although data on appropriate follow-up intervals are lacking. Evidence of residual enhancement or growth in lesion size would suggest the need for additional therapy, including repeat ablation.