Two primary components in the percutaneous therapy of upper urinary tract calculi are the establishment of an access tract and the actual stone removal itself.

Accurate access is the essential underpinning of a successful PCNL. A well-placed access tract can simplify a complex procedure, and, conversely, a poorly placed track may make it impossible to remove even the most accessible of calculi. Fluoroscopic control is usually preferred for the procedure, especially if the calculi are radio-opaque. CT is useful in preprocedural planning in patients with aberrant anatomy, in that the liver, spleen, colon, and pleural space can be avoided by the proposed tract (238,245).

If the calculus is located in a calyx or diverticulum, access should be obtained through that particular calyx or diverticulum. For large-volume calculi, a lower pole or interpolar calyceal puncture through a subcostal approach offers the advantages of avoiding the pleura while being certain of clearing the dependent lower pole calyces of calculi (Figs. 2 and 3). A stone-free rate of greater than 95% can be achieved using a subcostal approach (246). An intercostal puncture may be performed to access an upper pole calyx, usually to extract upper pole staghorn calculi, for concurrent endopyelotomy, and in patients with a large stone burden (247-252).

Narasimhan et al. (247) used an intercostal approach in 24% of their cases. In two of the three patients in whom access was above the 11th rib, thoracic complications requiring treatment (hydrothorax, pneumothorax) occurred. The authors recorded no clinically significant complications in cases where the puncture was below the 11th rib and into a middle or lower calyx. Fuchs and Forsyth (248) used an intercostal approach in 30% of their patients, of whom 5% had a major thoracic complication. The authors of both series (247,248) recommend that access above the 11th rib be avoided. Hopper and Yakes (57) performed CT on prone patients to estimate the risks associated with a puncture between the 10th and 11th ribs and found that an 11th-12th rib intercostal approach would puncture the right lung in 14% of patients and the left lung in 29% of patients in expiration. The risk of puncturing the liver and spleen was minimal in full expiration. However, the risk to the lungs was considered to be prohibitive with a 10th-11th intercostal approach, regardless of the degree of respiration. Munver et al. (252) used a supracostal approach in 33% of their cases (27% of tracks above the 11th rib and 73% above the 12th rib) and reported complications in 34% of supra-11th rib procedures and 9.7% incidence in supra-12th rib procedures. Intrathoracic complications were 16 times greater with supra-11th rib access, when compared with supra-12th rib, and 46 times greater than with subcostal access (intrathoracic complications in 23.1% of supra-11th rib access vs 1.4% of supra-12th rib and 0.5% of subcostal access). Thoracic complications in these patients include intraoperative hydrothorax/hemothorax, nephropleural fistula, and pneumothorax. Seven of eight intrathoracic complications occurred in supracostal cases in Munver et al.'s series (252). Kekre et al. reported a 10% thoracic complication rate (251).

PCNL is customarily performed with the patient in the prone position but has also been performed with the patient in a lateral decubitus position (253) and with the patient in the supine position when he or she is unable to lie prone (254,255). After the puncture is made, a 0.038-inch guidewire is placed into the collecting system and maneuvered into the ureter. Depending on the circumstances unique to the institution, tract dilation may be performed at the same sitting, in the radiology suite, or in the operating room immediately after the nephrostomy (246,256), with the urologists then extracting the calculus under nephroscopic guidance. Experience has proven that tracts can be dilated acutely to 24 French to 30 French with no adverse effects; this approach considerably shortens hospitalization and physician time (256). In most cases, bleeding associated with the tract dilation does not hamper visibility enough to require postponing the procedure.

Tract dilation is a painful procedure and requires that the patient be under either general anesthesia (preferably) or regional anesthesia. The dilation can be performed with tapered-tip fascial dilators of 10 French to 30 French size or high-pressure tract balloons measuring 10 cm in length and 10 mm in width when inflated. Tract dilation should be performed with fluoroscopic monitoring, with care being taken to avoid perforating the medial aspect of the renal pelvis when the stiff dilators are advanced.

Depending on the size and complexity of a stone, multiple access tracts may be necessary to remove it in entirety (257,258). The addition of SWL to PCNL can reduce the number of tracts required, with SWL being used to fragment the residual stone and the fragments then being extracted through the existing nephrostomy tract.

Simultaneous bilateral PCNL has been described for bilateral staghorn calculi (259), with no significant difference in the results or complication rate when compared with unilateral PCNL (Fig. 11).

Small calculi can be directly extracted through the sheath using forceps or a basket. For larger calculi, some form of lithotripsy is used to break the stone into smaller fragments. Ultrasonic lithotripsy is frequently used. The vibrating probe breaks up the calculus, and the fragments are aspirated through the hollow probe. For particularly hard stones, electrohydraulic lithotripsy or laser is used. Flexible nephroscopy is valuable in identifying and breaking up calyceal and ureteral fragments.

After the procedure, the collecting system is inspected to ensure a stone-free state. It is standard practice to leave in a ureteral catheter and a large-bore nephros-tomy tube (20 French to 24 French Malecot catheters or Foley catheters) after the procedure to provide reliable drainage of urine, tamponade the tract, and allow the renal puncture to heal, and to permit access to the collecting system if additional procedures are required. The nephrostomy catheter is then removed in 48 hours to one week after a nephrostogram demonstrates no leaks from the collecting system and no residual stones. However, the routine placement of nephrostomy tubes after an uncomplicated PCNL with complete calculus clearance is increasingly being questioned due to the discomfort associated with the presence of a large-bore nephrost-omy tube (260,261). In one series (262), 30 patients were randomized to receive a standard (20 French) nephrostomy drainage catheter, small-bore (9 French) nephrostomy drainage catheter, or no nephrostomy drainage. All patients with no postprocedural nephrostomy drainage catheters had antegrade placement of a 6 French double-J stent for four weeks. All three groups had a similar duration of hematuria and decrease in hematocrit postprocedure, but analgesic requirements were the highest in the large catheter group and the lowest in the no-catheter group. The tubeless group also had the shortest hospital stay and the smallest amount of

Figure 11 Patient with bilateral renal calculi (same patient as Fig. 2). After successful percutaneous removal of right renal calculi, left renal stones were removed percutaneously. Although bilateral simultaneous stone removal has been described, we prefer to treat one kidney at a time in patients with bilateral stones.

Figure 11 Patient with bilateral renal calculi (same patient as Fig. 2). After successful percutaneous removal of right renal calculi, left renal stones were removed percutaneously. Although bilateral simultaneous stone removal has been described, we prefer to treat one kidney at a time in patients with bilateral stones.

postoperative percutaneous site urine leak. Totally tubeless PCNL has also been reported elsewhere as a safe and effective procedure (263). Exclusion criteria for a tubeless approach are more than two percutaneous accesses, significant perforation of the collecting system, a large residual stone burden, significant postoperative bleeding, ureteral obstruction, and renal anomaly.

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