Percutaneous Renal Access





Percutaneous renal access was first described in 1955 by Goodwin and colleagues for the purpose of relieving obstruction in a hydronephrotic kidney. Rapid evolution of the techniques for percutaneous renal access has led to applications beyond simple drainage of the urinary tract. Percutaneous renal surgery now plays a prominent role in the treatment of a variety of urologic conditions. Performance of safe and efficient percutaneous access is the most critical aspect of successful percutaneous renal surgery.


Indications


Percutaneous renal access is performed for both diagnostic and therapeutic interventions. Diagnostic tests using percutaneous access include antegrade pyelography and pressure/perfusion studies (Whitaker test). Common therapeutic indications include drainage of an obstructed kidney, treatment of complex nephrolithiasis, antegrade endopyelotomy for ureteropelvic junction (UPJ) obstruction, endoscopic resection of upper tract transitional cell carcinoma, treatment of ureteral stricture, removal of foreign body (ie, retained stent), and instillation of topical intrarenal agents (chemolytics, chemo/immunotherapy). Percutaneous nephrolithotomy (PNL) is by far the most common operation employing percutaneous renal access. PNL is indicated for the treatment of staghorn calculi, brushite, struvite, or calcium oxalate monohydrate, impacted or large proximal ureteral calculi, calyceal diverticular calculi, ectopic renal calculi (horseshoe kidney, pelvic kidney, or transplant kidney), coexisting UPJ obstruction and renal calculi, lower pole renal calculi greater than 1 cm, and stones that have failed ureteroscopy or shock-wave lithotripsy.




Preoperative Evaluation


A complete medical history and physical examination should be performed in all patients before percutaneous access. Special attention is paid to identifying conditions in which percutaneous access is contraindicated such as bleeding disorders and active urinary tract infection (UTI) unless for obstruction or sepsis. If medically feasible, aspirin and other antiplatelet medications should be discontinued 7 days before surgery. Preoperative laboratory evaluation includes complete blood count, serum electrolytes, and renal function measurement. All patients should have a preoperative urine culture to exclude UTI. This is particularly important in patients with neurogenic bladder and urinary diversion who are often colonized with bacteria, and/or infected with organisms that are resistant to commonly prescribed antibiotics. In patients undergoing PNL, a 1-week course of a broad-spectrum antibiotic is recommended even in the presence of a negative urine culture because the calculi may be harboring bacteria. Cephalosporins are the most appropriate antibiotics for surgical prophylaxis immediately before surgical procedures in noninfected stone patients, because the most common secondarily infecting organism is Staphylococcus epidermidis. High-risk patients can be treated with intravenous ampicillin and gentamicin. Morbidly obese patients warrant special preoperative consideration because they often have cardiac and/or pulmonary disease that can represent a challenge for the anesthesiologist, especially when the patient is placed in the prone position.


Finally, preoperative imaging is essential in planning percutaneous access. Intravenous pyelography (IVP) has largely been supplanted by computed tomography (CT). CT is particularly useful in cases of congenital renal anomalies, transplant kidney, morbid obesity, and spinal cord deformities to allow evaluation of adjacent visceral structures. Although rare (<1%), CT can also identify a retrorenal colon, the incidence of which may be higher in patients with jejunoileal bypass or spinal cord injury. IVP and/or retrograde pyelography remain useful in patients with calyceal diverticulum to define the relationship between the diverticular cavity and the renal collecting system. A three-dimensional CT scan with reconstruction images or CT urogram may be helpful in planning percutaneous access for treatment of a urothelial neoplasm, UPJ obstruction, or calculi in an ectopic kidney.




Anatomic Considerations


Familiarity with basic renal anatomy is essential for safe and efficient percutaneous renal access. The kidneys lie obliquely within the retroperitoneum anterior to the psoas and quadratus lumborum muscles. These muscle layers are thinner superiorly; therefore, the upper pole of the kidney lies more posterior than the lower pole. The right kidney is adjacent to the 12th rib, liver duodenum, and hepatic flexure of the colon, and is positioned 2–3 cm lower than the left because of the position of the liver. Structures bordering the left kidney include the 11th and 12th ribs, pancreas, spleen and splenic flexure of the colon. The pleura normally attaches at the level of the 11th rib and is important to consider, particularly when planning supracostal access.


Knowledge of the principal renal vascular structures and their relationships to the renal collecting system can decrease the risk of hemorrhagic events. The main renal artery typically divides into an anterior and a posterior division. The avascular field between the anterior and posterior divisions, known as the Brödel bloodless line, is the ideal point of renal entry. Because of the orientation of the kidney in the retroperitoneum, entry through a posterior calyx usually traverses this line. For this reason, a posterior calyx is the preferred site of entry for percutaneous access in that it is associated with a lower risk of vascular injury and usually allows negotiation of a guidewire out of the calyx and down the ureter ( Fig. 26.1 ). Positioning the patient prone will bring the posterior calyces into an end-on position facilitating puncture into a posterior calyx. Inadvertent puncture beyond the anterior aspect of the collecting system risks vascular injury of the large anterior segmental vessels, which is a problematic complication because these vessels cannot be readily tamponaded with a nephrostomy tube or occlusion balloon.




FIGURE 26.1


A posterior calyx is the preferred site of entry for percutaneous renal access as it normally traverses the Brödel line.


The preferred point of entry into a posterior calyx is through the papilla or fornix. Infundibular puncture or direct puncture into the renal pelvis should be avoided because of the increased risk for significant vascular injury. Furthermore, access directly into the renal pelvis may pose a risk for prolonged urinary leakage or easy tube dislodgment. When percutaneous access is created through the papilla or fornix and aligned with the infundibulum, the rigid nephroscope can be used efficiently without the need for excessive torque, which may cause renal trauma and bleeding. To reduce the risk of colonic injury, the puncture site should be medial to the posterior axillary line because the colon is usually anterior or anterolateral to the lateral most part of the kidney. A very medial puncture should also be avoided because it may traverse the paraspinal muscles, increasing postoperative pain. Finally, when performing supracostal access, the puncture should not be performed too close to the rib because it may injure the intercostal nerve and/or vessels.




Standard Lower Pole Access


Equipment needed for standard lower pole access includes




  • C-arm fluoroscopy



  • 22-French rigid cystoscope



  • 5-Frennch open-ended ureteral catheter or an occlusion balloon catheter



  • 16-French Foley catheter



  • 18-gauge diamond-tip access needle



  • Wires:




    • 0.035-inch straight-tip glidewire



    • 0.035-inch straight removable core wire



    • 0.035-inch Amplatz superstiff wire



    • 0.035-inch removable core J wire




  • 5-French angiographic catheter



  • 8-French fascial dilator



  • 8/10-French coaxial dilator



  • Nephromax balloon dilator



  • LeVeen syringe



  • 30-French Amplatz sheath



Cystoscopy, Ureteral Catheterization


The first step in performing percutaneous renal access is cystoscopic placement of a ureteral catheter for retrograde opacification of the collecting system. Placement of the ureteral catheter is performed in the dorsal lithotomy position to ensure catheter placement is rapid and all anatomic conditions, such as urethral or ureteral strictures, can be easily addressed. A 5- or 6-French open-ended ureteral catheter is routinely used; however, a 7-French occlusion balloon catheter should be considered when stone burden is large, or the proximal ureter is dilated. A Foley catheter ensured bladder drainage during the percutaneous procedure.


Alternatively, some urologists prefer to place the patient in a prone split-leg position. This positioning is most often employed when percutaneous access is performed using a combined antegrade and retrograde approach. An operative table that allows abduction of the legs is necessary. Flexible cystoscopy is then performed to first establish retrograde access to the kidney, often via placement of a ureteral access sheath.


Patient Positioning


The patient is placed in the prone position, with the side to be treated elevated on a foam pad at 30 degrees ( Fig. 26.2 ). This position aids in ventilation of the patient and brings the posterior calyces into a vertical position. All pressure points are padded. The patient’s arm on the side of the stone is flexed at the elbow and placed on an arm board, while the contralateral arm is placed at the patient’s side. For bilateral PNL, the patient is placed in the straight prone position and the more symptomatic side or the side with the larger stone burden is addressed first. Intravenous extension tubing is connected to the ureteral catheter, or the occlusion balloon port, to allow inflation or deflation of the balloon, or the instillation of contrast dye.




FIGURE 26.2


Patient positioning. Chest roll/wedge for 30-degree elevation brings posterior calyces into vertical orientation.


Imaging Setup—Fluoroscopic


Percutaneous renal access is most commonly achieved using biplanar fluoroscopy though there is increasing familiarity and experience using ultrasound-guided techniques as well. CT guidance can also be used, though it is generally unnecessary except in instances of uniquely unfavorable anatomy.


When using a fluoroscopic approach, a biplanar C-arm is favored to help determine the calyceal orientation and select the optimal calyx of entry. A C-arm fluoroscopic unit is preferable to a urotable with a fixed x-ray tube because it permits more active movement between anteroposterior and oblique views of the kidney and reduces operator exposure to radiation scatter in that the x-ray source is under the table rather than over it. A C-arm drape is used during the operation to maintain the sterile field.


Selection of Puncture Site and Needle Access


The determination of calyceal orientation and selection of the optimal calyx of entry is best determined intraoperatively using real-time imaging. As mentioned previously, the preferred access site into the lower pole of the kidney is through a posterior calyx. Radiographic guidance for fluoroscopic percutaneous access is routinely performed using one of two techniques: eye of the needle and triangulation. Both techniques begin with retrograde opacification of the collecting system via instillation of contrast dye through the existing ureteral catheter.


Eye of the needle. An 18-gauge diamond-tip access needle is positioned so that the targeted calyx, the needle tip, and needle hub are all in line with the image intensified, giving a bull’s-eye effect on the monitor ( Fig. 26.3A ). In effect, the surgeon is looking down the needle into the targeted calyx, hence the phrase “eye of the needle.” The needle is advanced in this orientation, with continuous fluoroscopic monitoring to ensure that the needle maintains the proper trajectory. The needle depth is ascertained by rotating the C-arm to a vertical orientation (see Fig. 26.3B ). If the needle is aligned with the calyx in this view, the urologist should be able to aspirate urine from the collecting system, confirming proper positioning.




FIGURE 26.3


Imaging modalities: “eye of the needle.” ( A ) AP plane. Visualize directly over both needle and calyx of puncture. Will see a “bulls-eye” appearance as visualized down the shaft of the needle. ( B ) Oblique plane. Allows evaluation of needle penetration depth.


Triangulation technique. The skin puncture is usually performed approximately 1 cm inferior and 1 cm medial to the tip of the 12th rib ( Fig. 26.4 ). With the C-arm oriented parallel to the line of puncture, adjustments are made in the mediolateral (or left/right) direction ( Fig. 26.5A ). The C-arm is rotated to the oblique position and adjustments are made in the cephalad/caudad (or up/down) orientation of the line of puncture, taking care not to alter the mediolateral orientation of the needle (see Fig. 26.5B ). To reduce radiation exposure to the surgeon, the C-arm is angled away from the line of puncture with the image intensifier angled toward the patient’s head. Once the proper orientation of the line of puncture has been obtained, respirations are suspended in full expiration. Care is taken to ensure that the gas-filled colon cannot be visualized on at least one of two views to ensure no retrorenal colon. An 18-gauge diamond-tipped access needle is advanced toward the desired calyx in the oblique position to gauge the depth of puncture. Maintenance of needle orientation in one plane while making adjustments in the other plane is critical to preserve proper orientation. This maneuver is facilitated by resting the surgeon’s forearm on the torso of the patient to minimize drift and stabilize the line of puncture. Before the renal capsule is entered, final adjustments are made. Manipulating the needle after entering renal parenchyma is discouraged because it may displace the kidney affecting the position of the target calyx. Once the needle is advanced into the collecting system, aspiration of urine will verify proper calyceal puncture.


Jan 2, 2020 | Posted by in UROLOGY | Comments Off on Percutaneous Renal Access
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