Delivery of renal ablative technology


Due to the increased use of cross-sectional imaging coupled with advances in imaging technologies, the incidence of renal tumors, particularly small renal masses (SRM), has increased significantly. , Historically, surgical extirpation including radical nephrectomy (RN) and later partial nephrectomy (PN) became the standard of care for the management of renal masses. PN allows for preservation of renal function while also delivering oncologically equivalent outcomes. According to the 2017 guidelines of the American Urological Association, PN should be prioritized for the majority of pT1a tumors when intervention is indicated. In an effort to improve patient procedural tolerance but still achieve the equivalent efficacy of PN, alternative less invasive modalities such as cryoablation (CA) or radiofrequency ablation (RFA) are recommended, particularly in patients with major comorbidities. Recent studies have shown that CA can achieve good oncological outcomes similar to those of PN for SRM. Ablation has become more popular as a nephron-sparing/minimally invasive treatment for SRM, particularly in centers with adequate resources and experience. Despite concern about the difficulty of salvage surgery after ablation , , patients are often treated effectively after failed ablation therapy with repeat ablation.

With the introduction of liquid nitrogen and 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. In contrast, coagulative necrosis in RFA is achieved by heating soft tissue to temperatures exceeding 60°C. RFA achieves temperatures in this range by delivering a monopolar or bipolar electrical current via a needle electrode. , The first attempts at percutaneous CA (PCA) were reported in 1995 , and Gill and associates reported their initial series of laparoscopic renal CA (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).

In this chapter, we discuss indications and contraindications, preoperative evaluation and preparation, and procedural details of both laparoscopic and percutaneous ablative modalities such as CA and RFA. In addition, we review postoperative management and follow-up as well as oncologic outcomes of both ablative modalities.

Indications and contraindications

The indications for ablative procedures have been widely described and are similar to the indications for nephron-sparing extirpation surgery for SRM. Patients who have tumors >4 cm who have typically been candidates for RN are not generally considered candidates for ablative therapy. In the modern era, patients with clinical T1a SRM should be evaluated with high-quality cross-sectional imaging with computer tomography (CT) or magnetic resonance imaging (MRI) to guide the management plan. According to the 2017 American Urological Association guidelines, renal biopsy, whether ultrasound (US)-guided or CT guided, should be performed prior to or during CA to provide pathologic diagnosis and guide subsequent management and surveillance. Contemporary trends for the pretreatment needle biopsy have changed in recent years. We strongly believe that the vast majority of T1a renal cortical neoplasms should be biopsied prior to discussing management options with the patient. Indeed, patients with cT1a indolent renal cell carcinoma (RCC) subtypes such as papillary type I and chromophobe RCC are optimal candidates for ablative therapies as they can enjoy the benefits of the minimally invasive approach with little risk of disease-related mortality. We believe that the implementation of routine renal biopsy leads to a significant reduction in the rate of surgical intervention for benign tumors. In our recent multicenter analysis, the excision of benign tumors was fivefold less in the group of patients who underwent pretreatment renal biopsy compared with the control group who underwent surgery without a renal biopsy. Moreover, the rate of active surveillance in the renal biopsy group was three times higher than that of the control group (34.5% vs. 12.5%, p=0.0006). 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 SRM, should always be discussed as an option. Discussion of RN versus nephron-sparing treatment modalities (PN/ablation) should include a comprehensive discussion about oncological outcomes, renal function outcomes, possible complications, and potential morbidities. Urologists should discuss the potential advantages of nephron-sparing surgery (NSS)/ablation in imperative and elective settings, including decreasing the risk of chronic kidney disease (CKD), dialysis and associated Cardiovascular system (CVS) events. ,

Patients with clinically T1a (<4 cm) contrast-enhancing SRM 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.

Particularly challenging patients with recurrent tumors are often good candidates for ablation due to their need for multiple procedures. Patients with inherited diseases with a propensity for multifocal and recurrent tumors, such as von Hippel-Lindau disease, are well suited for ablative procedures because of the less invasive nature of the procedure. 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 PCA.

Patients with a shorter life expectancy, such as those with advanced age and impaired performance status, are candidates for CA. These patients are more likely to benefit from a less-invasive treatment modality like CA or RFA or choose active surveillance as they may not be fit for surgery. Again, in these cases a preprocedure biopsy allows for more precise shared decision making because only the most aggressive RCC variants would require active treatment in older patients with multiple comorbidities and avoid any intervention altogether in the more indolent RCC variants.

Management of patients with centrally located renal tumors or with cystic lesions remains controversial. PN, via a laparoscopic or robotic approach, is particularly challenging in patients with endophytic and hilar tumors. As such, ablative technologies may play a heightened role in these cases because real-time imaging with US and CT can be used to perform the procedure safely and accurately. At the University of California, Irvine, approximately one-third of all treated tumors have been endophytic. With short follow-up, we have had excellent perioperative and oncologic results.

Since the inception of the LCA, indications and contraindications have drastically changed. Contraindications for LCA procedures include patients with coagulopathy, history of peritonitis, and multiple severe adhesions. Adhesions may not be as challenging in the hands of advanced laparoscopic surgeons, but in general, these patients maybe better candidates for PCA. Contraindications for percutaneous ablative procedures include the presence of overlying structures such as bowel, liver, or spleen that interfere with probe deployment. In general, tumors within 1 cm of bowel structures, the ureteropelvic junction, or the hilar vasculature are contraindicated. At tertiary institutions with significant expertise, hydrodissection or pneumodissection methods can be safely used to displace the surrounding organs to create a safe path for ablation probes. , Otherwise, these tumors are more safely approached laparoscopically, which will allow for easier mobilization of the surrounding structures.

Preoperative evaluation and preparation

After a full and extensive discussion of the CA procedure details, risks, benefits and alternatives, informed consent is obtained from the patient. Routine laboratory tests such serum hematology, chemistries, liver function tests, coagulation studies, and a type and screen are performed. A standard metastatic evaluation including a chest radiograph is performed. As previously discussed, 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 CKD and an estimate glomerular filtration rate of <30 who have a bona fide risk from contrast material. Indeed, recent changes in gadolinium contrast material have virtually eliminated the risk of nephrogenic systemic fibrosis, and when working in collaboration with an experienced radiologist, almost all patients can now get contrast-enhanced axial imaging. It is preferred that preoperative imaging is performed prior to percutaneous procedures with the patient in the prone position to reveal more typical organ distribution at the time of probe deployment as the renal and surrounding anatomy have characteristic changes associated with movement from the supine to prone positions. In upper pole tumors it is particularly important to consider the pleural anatomy, and the position of bowel structures should be considered to preclude the risk of bowel injury.

For a laparoscopic or robotic-assisted laparoscopic approach, the selection of the transperitoneal or retroperitoneal approach for LCA is based on tumor location, patient’s surgical history, and preference as well as surgeon experience. However, the majority of tumors that historically were treated with a retroperitoneal approach are not managed using the less-invasive outpatient percutaneous approach.

Operating room configuration and patient positioning

For laparoscopic procedures, the monitor is positioned on the opposite side of the patient from the surgeon. The insufflation pressure and carbon dioxide (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 foot of the patient, allowing these connections to pass perpendicularly 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 foot of the patient for ablation equipment ( Fig. 21.1 ).

Fig. 21.1

Operating room configuration for the (A) transperitoneal approach and (B) retroperitoneal approach.

For laparoscopic transperitoneal procedures, the patient is positioned in a 70-degree flank position with the patient’s ventral surface aligned with the edge of the operating table. For retroperitoneal procedures, we typically use a 90-degree flank position, with the patient centered in the middle of the operating 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. 21.2 ). 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.

Fig. 21.2

A, Patient positioned for a transperitoneal approach. B, Patient positioned for a retroperitoneal approach.

Trocar placement

Laparoscopic ablative technology can be used 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, 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 posterior tumors with a retroperitoneal approach ( Fig. 21.3 ).

Fig. 21.3

Anterior tumors ( stars ) are usually best approached using the transperitoneal approach. Posterior tumors ( circles ) are usually best approached using the retroperitoneal approach. The tumor indicated by a square is in a location that can be treated with either approach.

A template for transperitoneal renal surgery trocar positions is presented in Fig. 21.4 . 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 mmHg. If using AirSeal insufflation technology (SurgiQuest Inc, CONMED, Milford, CT, USA), after initial access at 15 mmHg, most procedures are performed at 8 mm Hg. If there has been prior lower abdominal surgery, consider the Palmer point, which is subcostal in the midclavicular line on the left side. Place the lower trocar approximately 2 cm 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 zero-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 xyphoid process to introduce a locking grasper for liver retraction. Shift transperitoneal trocar positions laterally for obese patients or cephalad for upper pole tumors.

Fig. 21.4

Transperitoneal trocar positions.

Fig. 21.5 demonstrates a suggested trocar template for retroperitoneal surgery. Obtain initial access using 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 for 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.

Fig. 21.5

Retroperitoneal trocar positions.


Laparoscopic tumor exposure

After transperitoneal access has been gained, take a brief survey of the intraperitoneal organs. The bowel and spleen should be visually assessed for injury, and the liver should be assessed for evidence of mass lesions. The colon should be reflected with gentle medial traction provided by an atraumatic laparoscopic grasper. To expose the bloodless space between the mesentery and Gerota fascia, the thin layer of mesentery lateral to the edge of colon but medial to the actual line of Toldt should be incised. On the right, the duodenum will be exposed, and the Kocher maneuver is performed. These procedural steps provide visualization of the anterior surface of the Gerota fascia overlaying the kidney and anterior renal hilum. For the retroperitoneal laparoscopic approach, it is important to pay attention to the psoas muscle and the pulsations of the renal artery as they are usually immediately visible and serve as key anatomic landmarks.

For both the transperitoneal and retroperitoneal approaches, the Gerota fascia should be entered 1–2 cm away from the tumor. During laparoscopic ablative procedures, the utilization of laparoscopic US with a flexible probe is of extraordinary value in identifying the tumor location and selecting the location for entry through the Gerota fascia. The fat overlying the tumor should be excised and sent for histopathologic examination and staging purposes. In cases where 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. Then, it is recommended to mobilize the kidney within the Gerota fascia. Renal mobilization allows for passage of a flexible laparoscopic US 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 the collecting system or hilar structures. Next, if a preprocedure biopsy has not been performed, a percutaneous biopsy device with a 15-gauge Tru-Cut needle (ASAP Biopsy System, Microvasive; Boston Scientific, Watertown, MA) can be used to 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 US 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 the 1.47-mm IceRod Plus ablation probes (Boston Scientific, Marlborough, MA) for the majority of cases. These probes have been characterized to have an ablative diameter of 1.9 cm in an animal model. Typically, use a cluster of cryoprobes positioned 1.5 cm apart from one another in a triangular or quadratic configuration to ensure cryolesion overlap. Alternatively, for a larger ablation zone we occasionally employ 3-mm Ice Edge probes that 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 each other, thus ensuring proper spacing. Position the flexible laparoscopic US probe to allow imaging of the deepest margin of the tumor. Introduce the IceRods into the tumor under US guidance, and advance them just beyond the deepest margin. Next, perform a double freeze cycle, with each cycle followed by an active thaw. Continue the first freeze until the iceball extends to a perimeter 1-cm margin 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). If bleeding does occur, apply gentle pressure for hemostasis.

Laparoscopic radiofrequency ablation

The surgical access for laparoscopic RFA is identical to that of LCA. The probe is introduced percutaneously and placed into the tumor perpendicular to the surface of the kidney. Based on tumor size as measured by preoperative CT or MRI and intraoperative US 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 for 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

Image-guided PCA is a procedure performed in a collaborative manner between urologists and interventional radiologists for the best patient outcomes. The patient is placed in the prone position. The PCA procedure can be performed under general anesthetic (GA) or under local anesthesia with conscious sedation (LACS). In our practice, we perform the majority of renal cryoablation cases with CT guidance under LACS. A paper describing our technique and experience with image-guided PCA under LACS at the University of California, Irvine, has been recently published. We compared 82 patients who underwent image-guided PCA under GA versus 153 patients who had LACS. There was no significant difference in immediate treatment failure, recurrences, and treatment-related complications. Both GA and LACS for PCA are viable anesthetic approaches with similar efficacy and safety profiles; however, LACS was associated with decreased procedure time and hospital stay. In general, GA requires increased monitoring during the procedure and is associated with longer postoperative recovery time, the need to change patient position to the prone position, higher cost, and longer operating room time.

Percutaneous cryoablation, which is traditionally performed under CT guidance, is a safe and effective ablative technique for the management of renal tumors. In our practice, we have been increasingly utilizing US imaging during PCA. US is a radiation-free tool that is readily available to urologists at significantly lower cost, although its sole use for image guidance for PCA may be suboptimal for targeting and iceball control. When used in conjunction with CT, it may significantly reduce CT time during the procedure and subsequent radiation dosage to the patient and staff. In an effort to minimize ionizing radiation exposure associated with CT, we typically do initial skin site determination and access sheath (angiocath) placement under US guidance. Certainly, the amount of targeting that can be performed with US is a function of physician experience. After the US-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 prior to the procedure and the procedure is initiated by US-guided deployment of the IceRod Plus CA probe after the biopsy. Cryoprobes are advanced into the lesion under US guidance, and we then obtain repeat scans before initiating the ablation to check probe position for adequacy. The number of probes deployed depends on the tumor burden.We generally use one probe per centimeter of tumor. Routinely, CA protocol consists of two freeze-thaw cycles, and ablation is performed as described earlier in this chapter. After two freeze-thaw cycles, we allow approximately 20 minutes for the iceball to thaw and then perform a final CT with half-dose intravenous contrast to assess for tumor enhancement and evaluate the adequacy of ablation and the presence of any local 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 cryo lesions as a signal void on T1-weighted images. Pass absorbable hemostatic material through an introducer after removing the probe to assist in hemostasis.

Postoperative management

Percutaneous CA is typically performed as an outpatient procedure. In our experience, less than 10% of patients require 23-hour admission, and very few patients require inpatient care. Patients are quickly advanced to a regular diet as tolerated. A hematocrit is checked in the recovery room and the morning after surgery if they remain in the hospital. We typically perform follow-up evaluation at 3 months after the initial procedure with contrast CT or MRI. In cases where the tumor has been completely ablated at 3 months, follow-up imaging, CT, or MRI is obtained annually thereafter. Complete loss of contrast enhancement on follow-up CT or MRI is considered a sign of complete tissue destruction. , Indeed, we found that 3-month imaging follow-up evaluation is the most accurate in determining the success of ablation following the initial ablation procedure. The size of the lesion and the ablation zone should progressively decrease, and up to one-third of ablated lesions may become undetectable over time. In addition, decreased stranding, hematomas, and perinephric fluid should be observed. The size of the lesion, stranding, and hematomas should progressively decrease over time on MRI. Although each urologist must develop their own postoperative follow-up plan, initial postoperative imaging at 3 months is considered optimal at this time. Delayed appearance of enhancement after previously negative imaging and highly enhancing images (>35 HU) are highly suspicious for recurrence or incomplete ablation. If there is any suspicion of incomplete ablation or recurrence, then additional imaging points are added to guide further management. While not reported in the literature to date, after 4 or 5 years there is often development of small calcifications in the area of ablation. To date, this has not been associated with evidence of recurrence.

For RFA, at long-term post-ablation follow-up imaging, decreased stranding, hematomas, and perinephric fluid should be observed. A decrease in lesion size will not be as pronounced as with cryoablated tumors, and the primary indicator of ablative success is a lack of linear or nodular tumor enhancement (<10 HU). On post-contrast MRI, RF-treated lesions appear T1 hyperintense and T2 hypointense relative to the renal parenchyma. At longitudinal follow-up scans, the emergence of the peripheral halo in the perinephric fat surrounding the ablated lesion can be seen. Stranding and hematomas should progressively decrease; however, lesion size will not decrease significantly. On post-contrast CT imaging, a residual lesion enhancement <10 HU is considered successful ablation, and no recurrence of tumor and complete necrosis in addition to a well-defined nonenhancing zone indicate ablative success.

Complications and perioperative outcomes

A recent meta-analysis comparing LCA to LPN/robotic (RPN) found that patients who underwent LCA were significantly older (weighted mean difference [WMD] 6.1 years), presented with higher ASA score (OR 2.65), had smaller tumors (WMD 0.25 cm), and had less frequently proven malignant disease. LCA was associated with shorter operating time (WMD 36 minutes), lower estimate blood loss (WMD 130 mL), and shorter length of hospital stay (LOS) (WMD 1.2 days). Table 21.1 summarizes the complications of LCA compared with LPN/RPN. When compared with LPN/RPN, less technically challenging ablative procedures offer lower complication rates.

Aug 8, 2022 | Posted by in UROLOGY | Comments Off on Delivery of renal ablative technology
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