The incidence of renal tumors and particularly small renal masses (SRMs) has increased significantly, mostly because of increased use of and advances in cross-sectional imaging. Historically, radical nephrectomy (RN) was the standard of care for management of renal masses. Later, partial nephrectomy (PN) was found to be oncologically equivalent, with the added benefit of preserving renal function. In 2009, the American Urological Association (AUA) guidelines described PN as the standard of care for the majority of pT1a tumors. Cryoablation (CA) and radiofrequency ablation (RFA) are recommended as alternative less-invasive treatment modalities, particularly in patients with major comorbidities. Reasons cited have included the following: Local tumor recurrence might be more likely with ablative procedures; measures of success were not defined; and salvage surgical therapy may be difficult. Recent studies have shown that CA can achieve good oncologic outcomes similar to those of PN series for SRMs. Ablation has become more popular as a nephron-sparing or minimally invasive treatment for SRMs, particularly in centers with adequate resources and experience. Despite the concern about difficulty of salvage surgery after ablation, the most commonly used option after failed ablation therapy is repeat ablation.
With the introduction of liquid nitrogen– or argon-cooled probes, targeted renal CA became clinically feasible. Temperatures as low as −195.8° C can be produced, resulting in direct cell injury with intracellular ice crystal formation or secondarily by reperfusion injury during the thawing phase. Histologically, coagulative necrosis is eventually replaced by fibrosis in the targeted tissue. Similarly, coagulative necrosis can also be accomplished by heating soft tissue to temperatures exceeding 60° C. RFA achieves temperatures in this range by delivering a monopolar electrical current via a needle electrode. The first attempts at percutaneous cryoablation (PCA) were reported in 1995, and Gill and associates reported their initial series of renal laparoscopic cryoablation (LCA) in 1998. Zlotta and colleagues reported the first percutaneous renal RFA in 1997, and laparoscopic RFA was first used clinically as a hemostatic measure preceding laparoscopic partial nephrectomy (LPN).
Indications and Contraindications
The indications for ablative procedures are similar to the indications for nephron-sparing surgery (NSS) for SRMs in general. Patients who have typically been candidates for RN are not generally considered candidates for ablative therapy. In the modern era, patients with a clinical T1a renal mass should be evaluated with high-quality cross-sectional imaging modalities such as computed tomography (CT) or magnetic resonance imaging (MRI). Renal biopsy, whether ultrasound guided or CT guided, should be discussed. Although pretreatment needle biopsy has been rarely used in the past, we now believe that the vast majority of T1a renal cortical neoplasms should undergo biopsy before management options are discussed with the patient. Indeed, patients with cT1a indolent renal cell carcinoma (RCC) subtypes such as papillary type 1 and chromophobe RCC are optimal candidates for ablative therapies because they can enjoy the benefits of the minimally invasive approach with little risk of disease-related mortality. Similarly, pretreatment renal tumor biopsy has allowed us to almost eliminate the need for any procedure in patients with benign renal cortical neoplasms. The natural history and the relative risk of benign versus malignant pathology should be an essential part of patient counseling. Active surveillance and its role, particularly in the management of SRMs, should be one of the options always discussed. Discussion of radical versus nephron-sparing treatment modalities (PN and ablation) should include a comprehensive discussion about oncologic outcomes, renal function outcomes, possible complications, and potential morbidities. Urologists should discuss the potential advantages of NSS and ablation in imperative and elective settings, including decreasing the risk of chronic kidney disease (CKD), dialysis, and associated cardiovascular (CVS) events.
Patients with a cT1a small (<4 cm) contrast-enhancing renal mass or a complex renal cyst suspicious for RCC and imperative indications for NSS (anatomically or functionally solitary kidney) are good candidates for ablative technologies. Relative indications occur in the presence of diseases that may impair the normal contralateral kidney, such as diabetes mellitus, hypertension, nephrolithiasis, and renal artery stenosis.
Patients with inherited diseases that have a propensity for multifocal and recurrent tumors, such as von Hippel-Lindau disease, are well suited for ablative procedures. In this patient population, recurrent tumors can be treated in a minimally invasive manner on multiple occasions. In our experience, repeated laparoscopic treatment of tumors with CA is feasible because the laparoscopic approach causes minimal scarring. Indeed, a percutaneous ablative approach is even more easily repeated, and, in our experience, offers very little additional challenge over a primary percutaneous ablation.
Patients with a shorter life expectancy, such as older patients with impaired performance status, are more likely to be treated with a less invasive treatment modality such as CA or to choose active surveillance because they may not be fit for surgery. Again, in these patients a preprocedure biopsy allows for more precise decision making because only the most aggressive RCC variants would require active treatment in older patients with multiple comorbidities.
Treatment of patients with centrally located renal tumors or with cystic lesions remains controversial. LPN is particularly challenging in patients with endophytic tumors. Accordingly, ablative technologies, which can be targeted by imaging modalities, are ideally suited for these tumors. In the University of California, Irvine experience, approximately one third of all tumors treated have been endophytic. With short follow-up, we have had excellent results. Management of cystic lesions has been similarly controversial.
Contraindications for laparoscopic ablative procedures include coagulopathy, history of peritonitis or multiple adhesions, and severe obstructive airway disease. Contraindications for percutaneous ablative procedures include the presence of overlying structures such as bowel, liver, or spleen that interfere with probe placement. In general, tumors within 1 cm of bowel structures, the ureteropelvic junction, or the hilar vasculature are contraindicated. These tumors are more safely approached laparoscopically to allow for mobilization of these sensitive structures to protect them during tumor ablation.
Patient Preoperative Evaluation and Preparation
Informed consent is gained from the patient after a full discussion of the risks, benefits, and alternatives. Routine serum hematology, chemistries, liver function tests, coagulation studies, and a type and screen are performed. For all ablative renal procedures we require a high-quality and recent (within 3 months) CT scan or MRI with and without intravenous contrast. Exceptions are made for patients with chronic kidney disease who have a bona fide risk from contrast material (e.g., glomerular filtration rate [GFR] <30). For percutaneous procedures, we occasionally require imaging with the patient in the prone position to reveal exact intra-abdominal organ position when probe placement is attempted. Indeed, patients with upper pole tumors near the pleural reflections, and those with tumors close to bowel structures should be considered for prone axial imaging because the anatomic changes associated with the positional changes may result in inability to successfully execute the procedure. A standard metastatic evaluation including a chest radiograph is performed.
For laparoscopic procedures, the selection of transperitoneal or retroperitoneal approach is based on tumor location, the patient’s surgical history, and preference. However, the majority of tumors that historically were treated with a retroperitoneal approach are not managed via the less invasive outpatient percutaneous approach.
High-quality and recent (within 3 months) axial imaging is a critically important part of preoperative preparation. For laparoscopic procedures, axial imaging studies can help expedite identification of the tumor. In addition, probe targeting is critically important and is greatly facilitated by high-quality imaging; probe deployment can be optimized by coordinating the gestalt picture of the laparoscopic view, the laparoscopic ultrasound image, and the preoperative imaging.
Operating Room Configuration and Patient Positioning
For laparoscopic procedures, position the monitor on the opposite side of the patient from the surgeon. The insufflation pressure and CO 2 flow rate should be easily visible by the surgeon. The scrub nurse stands beside the surgeon. The equipment specific to the ablation procedure is best positioned at the feet of the patient, allowing these connections to pass perpendicular and over the top of the cords from the monitor. The same considerations apply for percutaneous procedures. With the patient prone, stand on the same side as the lesion and, ideally, have a straight-line view of the imaging monitor. The anesthesiologist occupies the room at the head of the patient, leaving room at the patient’s feet for ablation equipment ( Fig. 23-1 ).
For laparoscopic transperitoneal procedures, position the patient in a 70-degree flank position with the patient’s ventral surface aligned with the edge of the operating table. For retroperitoneal procedures, use a 90-degree flank position, typically with the patient centered in the middle of the operative table. With the patient’s iliac crest at the break in the table, flex the table. Flex the contralateral knee. Place an axillary roll, and carefully pad all pressure points. Position the arms to prevent brachial plexus tension ( Fig. 23-2 ). After the patient is adequately positioned, secure the patient to the table at the chest, hip, and knee in case rotation of the table is needed during the procedure. For percutaneous procedures, place the patient in the prone position.
Trocar Placement
Laparoscopic ablative technology can be applied via a transperitoneal or retroperitoneal approach. Anterior renal tumors are best approached transperitoneally, whereas posterior tumors are accessed retroperitoneally. Preference dictates the approach for lateral tumors. However, imposing the wrong approach results in the need for additional renal mobilization and can result in suboptimal angles of ablation. Whenever possible, treat anterior tumors with a transperitoneal approach and treat posterior tumors with a retroperitoneal approach ( Fig. 23-3 ).
A template for transperitoneal renal surgery trocar positions is presented in Figure 23-4 . With no history of abdominal surgery, place a Veress needle, if needed, at the anterior superior iliac spine trocar site to establish a pneumoperitoneum of 15 mm Hg. If the AirSeal insufflation technology (SurgiQuest, Milford, Conn.) is used, after initial access at 15 mm Hg, most procedures are performed at 10 mm Hg. If there has been prior lower abdominal surgery, obtain initial access at the subcostal trocar site. Place the lower trocar approximately 1 inch medial and superior to the anterior superior iliac spine, and place the subcostal trocar in the midclavicular line. Use a visual dilating trocar with a 0-degree lens for optimal initial trocar placement. Subsequently, introduce the remaining trocars under laparoscopic vision via the initial trocar site. Place the third trocar between the two working trocars at the midline or just lateral to the rectus muscle. The third trocar can also be deployed at the umbilicus. This trocar serves as the primary access site for the laparoscope. Place an optional fourth 5-mm trocar at the posterior axillary line, if needed, to optimize tumor position for probe entry or, for right-sided tumors, place the trocar just inferior to the xiphoid to introduce a locking grasper for liver retraction. Shift transperitoneal trocar positions laterally for obese patients or cephalad for upper pole tumors.
Figure 23-5 demonstrates a suggested trocar template for retroperitoneal surgery. Obtain initial access with the Hasson technique at the tip of the 12th rib. Then position a trocar-mounted balloon dissection device posterior to the kidney and inflate it. This device creates a working space to allow placement of the next trocar. Place the second trocar at the lateral border of the erector spinae muscle just below the 12th rib. Place the third trocar at the intersection of the anterior axillary line and the downward sloping line made by the extension of the first two trocars.
Procedure
Laparoscopic Tumor Exposure
If transperitoneal access has been gained, take a brief survey of the intraperitoneal organs. Inspect the bowel for injury, and look at the liver for evidence of mass lesions. Deflect the colon with gentle medial traction provided by an atraumatic laparoscopic grasper. Incise the thin layer of mesentery lateral to the edge of the colon but medial to the actual line of Toldt to expose the bloodless plane between the mesentery and Gerota fascia. On the right, expose the duodenum and cauterize. These steps provide visualization of the anterior surface of the Gerota fascia overlying the kidney and anterior hilum. For the retroperitoneal approach, the psoas muscle and the pulsations of the renal artery are usually immediately visible and serve as important anatomic landmarks.
Regardless of approach, enter the Gerota fascia 1 to 2 cm away from the tumor. The application of laparoscopic ultrasound with a flexible probe is of extraordinary value in expediting the identification of tumor location and selecting the location for entry through the Gerota fascia. Excise the fat overlying the tumor, and send it for histopathologic examination. If the fat is densely adherent to the area over the tumor, we assume possible fat invasion (T3a disease), and the fat is left over the tumor and ablated with the tumor. Extensively mobilize the kidney within the Gerota fascia. Renal mobilization allows for passage of a flexible laparoscopic ultrasound probe on the surface of the kidney opposite the tumor to optimize imaging and targeting of the tumor. Note the tumor size, margins, vascularity, and proximity to collecting system or hilar structures. Next, if preprocedure biopsy has not been performed, percutaneously pass a biopsy device with a 15-gauge Tru-Cut needle (ASAP Biopsy System, Microvasive; Boston Scientific, Watertown, Mass.) into the tumor and obtain a tissue sample for histopathology.
Laparoscopic Cryoablation
We select the skin site for probe deployment by passing a small-gauge spinal needle. This “finder” needle is minimally traumatic and allows the surgeon to test several sites to achieve optimal skin site selection. Ideally, the CA probes are placed such that the needles are passed perpendicular to the surface of the kidney. Once a skin site has been selected, we percutaneously introduce the probes and visually guide them into the tumor. Because the temperature extremes are realized only at the distal aspect of the probes for CA and RFA, skin complications are rare with the laparoscopic approach. Targeting tumors is the most challenging component of the procedure and will differentiate success from failure. Intraoperative real-time laparoscopic ultrasound is essential for tumor targeting and, during CA, for monitoring of iceball progression. Depending on tumor size, the number of cryoprobes can vary from one to four. We prefer 1.47-mm IceRod Plus ablation probes (Galil Medical, Plymouth Meeting, Pa.) for the majority of cases. These probes have been characterized to have an ablative diameter of 1.9 cm in an animal model. Typically, a cluster of cryoprobes are positioned 1.5 cm apart in a triangular or quadratic configuration to ensure cryolesion overlap. Alternatively, for a larger ablation zone, we occasionally use 3-mm IceEdge probes (Galil Medical), which result in a larger zone of ablation.
Mobilize the kidney so that the probes enter the renal parenchyma in a perpendicular manner whenever possible. Gently guide the probes with a laparoscopic instrument and insert into the tumor such that they are parallel to one another, thus ensuring proper spacing. Position the flexible laparoscopic ultrasound probe to allow imaging of the deepest margin of the tumor. Introduce the IceRods into the tumor under ultrasound guidance, and advance them just beyond the deepest margin. Next, perform a double freeze cycle, each followed by an active thaw. Continue the first freeze until the iceball extends to a perimeter 1 cm beyond the tumor in every direction. Take care to prevent contact of the iceball with critical structures such as the renal vasculature, ureter, renal pelvis, and bowel structures. Mobilize and retract these structures, as needed, to prevent injury. Freezing intrarenal components of the collecting system does not result in damage or complications. However, freezing the ureteropelvic junction or ureter will result in stricture formation. After an appropriate margin has been achieved, perform an active thaw and deploy a second freeze cycle.
After the second freeze cycle, activate an active thaw and remove the IceRods only when they can be twisted gently without resistance. Exercise care not to apply premature force on the IceRods to avert potential fracture of the iceball from the kidney, which may be associated with significant hemorrhage. After removal of the IceRods, hemostasis is typically good and bleeding has not been a problem with these small-caliber probes. Usually, no hemostatic measures are required, and we no longer use surgical hemostatics (e.g., fibrin glues or FloSeal [Baxter Healthcare, Deerfield, Ill.]). If bleeding does occur, apply gentle pressure for hemostasis.
Laparoscopic Radiofrequency Ablation
Achieve access as described for LCA. Percutaneously introduce the probe and enter the tumor perpendicular to the surface of the kidney. On the basis of tumor size as measured by preoperative CT or MRI and intraoperative ultrasound imaging, deploy the tines to a diameter that ensures ablation of the tumor and a 1-cm margin of normal renal tissue. Multiple impedance-based or temperature-based probes are commercially available. Deploy the probes as per protocols, which are delineated in the manufacturer’s recommendations. The size of the ablated area is dependent on the diameter of the deployed tines and the activation time. Typically, activation times range from 3 to 8 minutes, and two cycles are performed with a brief interval between cycles to allow cooling. After the tumor ablation is complete, ablate the probe tract while removing the probe from the kidney. This technique minimizes the risk of bleeding and tumor seeding.
Percutaneous Ablation
Renal PCA is a procedure best performed in a collaborative manner between urologists and interventional radiologists. It can be done with the patient under general anesthesia. However, more recently our team has performed the majority of procedures with patients under local anesthesia with conscious sedation (LACS). Position the patient prone in an interventional CT or MRI unit. MRI permits acquisition of sagittal or coronal T1 images to assist in spatial orientation. In our practice, we perform the majority of cases as CT-guided procedures. We recently published our experience at University of California, Irvine comparing 82 patients who underwent PCA under general anesthesia versus 153 patients who had LACS. We could not find a significant difference in immediate treatment failure, recurrences, or treatment-related complications. However, LACS was associated with decreased procedure time and hospital stay. In general, general anesthesia can have potential disadvantages including increased monitoring requirements and recovery time, need to change patient position to prone position, and higher cost.
In an effort to minimize ionizing radiation exposure, we typically do initial skin site determination and access sheath (angiocatheter) placement under ultrasound guidance. Certainly, the amount of targeting that can be performed with ultrasound is a function of physician experience. After the ultrasound-guided initial sheath placement, a 20-gauge needle core biopsy device is deployed just within the renal mass and its position confirmed with CT scanning. In our current practice, needle biopsy is typically performed before the procedure and the procedure is initiated by ultrasound-guided deployment of the IceRod Plus CA probe after the biopsy. Cryoprobes are advanced into the lesion as described for laparoscopic procedures. The number of probes depends on the tumor burden. Obtain repeat scans before ablation to check probe position for adequacy. Routinely, CA protocol consists of two freeze-thaw cycles. Perform ablation as described earlier. After ablation, we allow approximately 20 minutes for iceball thawing and then perform a final CT with half-dose intravenous contrast to assess for enhancement and to evaluate for adequacy of ablation and any hemorrhage. In our experience, a half-dose contrast bolus provides excellent image quality to confirm that the tumor and a margin of normal tissue have been ablated. Alternatively, MRI demonstrates cryolesions as a signal void on T1-weighted images. Pass absorbable hemostatic material through an introducer after removing the probe to assist hemostasis.
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