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Thursday, February 18, 2021

PARTIAL NEPHRECTOMY

PARTIAL NEPHRECTOMY

Although radical nephrectomy is the standard surgical treatment for large renal tumors, nephron-sparing surgery has become the new standard of care for small (<4.0 cm) renal masses (SRMs).

In a partial nephrectomy, the renal tumor and a small margin of normal tissue are removed. The remainder of the parenchyma is spared, so as to preserve renal function. Although partial nephrectomy offers benefits to all patients with SRMs, it is especially beneficial for patients with multiple or bilateral masses, tumors in a solitary kidney, or medical diseases that threaten future kidney function.

There is substantial evidence that for tumors 4.0 cm in diameter, partial nephrectomy provides oncologic outcomes that are comparable to those of radical nephrectomy. The potential for tumor recurrence or progression to metastatic disease is low, with 10-year cancer-specific survival rates between 87% and 90% in large patient series.

 

OPEN PARTIAL NEPHRECTOMY: RETROPERITONEAL (FLANK) APPROACH
Plate 10-22
OPEN PARTIAL NEPHRECTOMY: RETROPERITONEAL (FLANK) APPROACH

EVALUATION

The preoperative evaluation should include basic laboratory tests (complete blood count, serum chemistries, liver function tests), a chest radiograph, and comprehensive axial imaging of the abdomen (either CT or MRI) with renal protocols. Patients should receive counseling on all available management options, which include active surveillance, partial nephrectomy, percutaneous ablation (see Plate 10-24), and radical nephrectomy (see Plate 10-20). In elderly patients or patients with significant medical comorbidities, ablation or active surveillance are often more appropriate choices because of the high risk of perioperative complications. Patients must be informed of the potential for a planned partial nephrectomy to become a radical nephrectomy based on the operative course.

 

TECHNIQUE

Partial nephrectomy may be performed from either an open or laparoscopic approach. Both techniques are equally effective for the treatment of a renal mass, but laparoscopic partial nephrectomy is typically associated with less blood loss, less pain, a lower risk of postoperative ileus, and a shorter hospitalization and overall convalescence time. In addition, laparoscopic procedures require smaller skin incisions, which yield better cosmetic results.

Both open and laparoscopic partial nephrectomy procedures may be performed using transperitoneal or retroperitoneal (flank) approaches. The different incision sites, as well as the techniques for approaching the kidney, are the same as described in the section on simple and radical nephrectomy (see Plate 10-21).

Once visualized, the renal fascia should be mobilized free of its attachments and then opened and dissected. The renal hilum should be carefully identified and exposed. The tumor should be accurately localized using a combination of high-quality preoperative imaging, intraoperative visualization, and intraoperative ultrasonography (which establishes the location and depth of the lesion in three dimensions). Using intraoperative color Doppler ultrasound, it should be confirmed that occlusion of the renal vessels results in complete interruption of blood flow to the tumor and surrounding parenchyma.

Once the tumor has been characterized, intravenous mannitol should be infused to help minimize renal ischemic injury during tumor excision. Mannitol increases renal plasma flow, reduces intracellular edema, and promotes osmotic diuresis to flush out debris and casts from the renal tubules (see Plate 10-1).

Open Partial Nephrectomy (OPN). Approximately 5 to 15 minutes after the administration of mannitol, the renal artery and vein are clamped using atraumatic bulldog vascular clamps. An ice-slush mixture is placed around the kidney for approximately 10 minutes so that it is cooled to 20° to 25° C. This process reduces metabolic demands and slows the consumption of oxygen, permitting up to 3 hours of renal artery clamping without long-term ischemic damage.

Once cooling is complete, the tumor is excised using a scalpel or Metzenbaum scissors, allowing for a margin of normal parenchyma around the excised mass. The removal of endophytic tumors often leads to collecting system injury, which requires reconstruction using absorbable sutures. Bleeding is surgically controlled with absorbable sutures. The bed of the cortical defect is cauterized using standard electrocautery or an argon beam coagulator. Hemostatic agents are placed on the parenchyma, and the renal capsule is closed using interrupted absorbable sutures. The vascular clamps are then removed, hemostasis is confirmed, and the surgical field is closed.

Laparoscopic Partial Nephrectomy (LPN). Five to fifteen minutes after the administration of mannitol, the renal artery is clamped using an atraumatic bulldog vascular clamp. Renal parenchymal hypothermia remains a challenge during laparoscopic partial nephrectomy because of the logistical challenges of introducing ice into the field. Therefore, the renal vein is typically left patent, which may help minimize ischemic damage by allowing retrograde perfusion of the kidney. Excessive bleeding is usually not a concern because of the tamponade effect of the pneumoperitoneum.

The tumor is excised using laparoscopic scissors. Collecting system defects are repaired, and the bed of the defect is cauterized. Any further bleeding is con- trolled using absorbable sutures and hemostatic agents. The parenchymal defect is then closed. The vascular clamps are removed, and hemostasis is again confirmed. The pneumoperitoneum is reduced to ensure that bleeding does not occur without its tamponade effect. The tumor is then removed intact in an entrapment bag, and the trocar sites are closed.

 

LAPAROSCOPIC PARTIAL NEPHRECTOMY: TRANSPERITONEAL APPROACH
Plate 10-23
LAPAROSCOPIC PARTIAL NEPHRECTOMY: TRANSPERITONEAL APPROACH

COMPLICATIONS

At present there is no difference in complication rates between open and laparoscopic partial nephrectomy. The most common postoperative complications are bleeding and urine leak (urinoma).

In situations where postoperative bleeding is suspected, the patient should be managed with serial complete blood counts, bed rest, and blood transfusions as needed. Conservative measures are often adequate when the bleeding is modest, but interventions such as selective arterial embolization or surgical reexploration may sometimes be required.

Urine leakage can result from inadequate intraoperative closure of a collecting system defect or ureteral obstruction from a blood clot, which increases backflow pressure. A surgical drain should therefore be used when the renal collecting system has been violated to monitor for postoperative leak. In addition, the patient should retain a Foley catheter to ensure bladder decompression and low upper tract pressure. Urine leaks are usually transient and heal without intervention; however, a persistent leak may require the placement of a ureteral stent to facilitate drainage and healing.

In addition to bleeding and urine leak, other potential complications include wound infection, ileus, pneumonia, injury to adjacent organs, and transient renal insufficiency.


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