Nephron-Sparing Surgery for Small Renal Masses Minimizes Risk of Chronic Renal Insufficiency

As cross-sectional imaging technology improves and as more patients undergo abdominal CT scans, more small renal masses (≤7 cm) are incidentally found. Today, an estimated 70 percent are detected incidentally.

In the past, all renal masses were treated by radical nephrectomy. This radical procedure may predispose the patient to developing chronic renal insufficiency. For instance, many patients who develop renal masses are older than 60 years, diabetic, overweight, and hypertensive — the exact same risk criteria for chronic kidney disease (CKD). Recent studies have demonstrated that up to 25 percent of patients who present with renal masses may in fact have unrecognized CKD. Radical nephrectomy would serve to enhance progression of CKD and risk of cardiovascular comorbidity.

These serious risks are especially concerning when data show that 20 percent to 25 percent of all small renal masses are benign and as many as 66 percent are low grade or indolent tumors. Mayo Clinic is among the leading centers to develop a new approach to avoid over treating select patients with small renal masses.

Mini-flank incision

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Global and regional ischemia

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A New Approach

By 1990, Mayo researchers were testing partial nephrectomy — nephron-sparing surgery (NSS) — as an alternative means to treat small renal masses. The goal was to improve overall renal health and, in particular, to minimize the impact of kidney failure on other organ systems.

In nephron-sparing surgery, the tumor is removed through a 9- to 12-cm mini-flank incision under conditions of regional and global ischemia. Regional ischemia spares unaffected nephron tissues vital for kidney function. By the late 1990s, positive outcomes supported this new approach and a shift in the treatment of small renal masses was under way.

Advantages of Nephron-Sparing Surgery

NSS offers the advantages of:

• Comparable oncologic outcomes to the radical approach
• Preserving kidney function and thereby helping prevent complications of chronic renal failure. Mayo Clinic researchers published data in 2000 showing that radical nephrectomy patients were two times more likely than NSS patients to develop chronic renal insufficiency. Other institutions have validated the efficacy of NSS in select patients.
• The mini-flank incision is half the size of a radical nephrectomy incision and affords patients faster and easier recovery and reduced hospital costs.

Elements of Success

The key to successful NSS is mastery of technique to operate in a bloodless field. A bloodless field provides optimal visualization of transecting arteries and veins and reconstructed elements. In terms of surgical skill, NSS requires mastering multiple techniques for the surgical interruption of blood flow that include hypothermic global ischemia, warm ischemia, and regional ischemia.

Through varying the strategic placement of specialized instruments, the NSS surgeon maintains vascular control that permits accurate, swift performance of surgical maneuvers. Restoring blood flow to the kidney under conditions of warm ischemia within 12 minutes avoids damaging the organ. On the other hand, 50 percent of NSS at Mayo utilizes regional ischemia wherein non–tumor-bearing renal tissue is not subjected to the damaging effects of ischemia.

Modified clamp for vascular control

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Suitable Candidates

In general, all patients diagnosed with a small renal mass no larger than 7 cm should be evaluated for NSS. Tumors that are well circumscribed are most suitable. The ideal mass for regional ischemia is one that grows outside the kidney surface, is polar in location and is away from hilar structures. Global ischemia is considered for an internally growing mass and centrally located tumors.

NSS Underutilized

At Mayo Clinic, more than 80 percent of procedures to remove small renal masses are now nephron-sparing surgery. Underutilization of NSS may be attributable to lack of familiarity with the procedure and training to safely perform it. In the hands of experienced NSS practitioners, however, outcome data suggest nephron-sparing surgery is the new standard of care for properly selected patients with small renal masses.