Preoperative Details
A thorough history should be obtained and a physical examination should be performed prior to any procedure. Special attention should be paid to the following historical factors: anticoagulation, bleeding disorders, contrast medium reactions, malignancy, obesity, spinal cord injury, and history of urinary tract infections. Essential laboratory data include a coagulation profile, complete blood cell count, electrolytes, blood urea nitrogen, creatinine, platelet count, urinalysis, and urine culture. Appropriate antibiotic coverage before and on call during the procedure is useful in preventing intraoperative sepsis.
Simple percutaneous renal access procedures are performed with the patient in the prone position while under a combination of local anesthetic and intravenous sedation. This position may be hazardous to patients with severe cardiopulmonary disease (eg, chronic obstructive pulmonary disease) or those who are morbidly obese. Consultation with a pulmonologist or intensivist may be required. If more than a simple drainage procedure is planned, then a general endotracheal anesthetic should be used to protect the airway from aspiration (ie, vasovagal reaction).
Intraoperative Details
Initial access
The ideal percutaneous nephrostomy tract should avoid surrounding organs and provide straight access to the desired calyx. Nephrostomy placement is usually performed under fluoroscopy or with the assistance of real-time ultrasonography. For percutaneous puncture of the renal collecting system, the patient should be placed on the fluoroscopy table in the prone position. The collecting system is then opacified via 1 of 3 techniques: (1) intravenous pyelography, (2) retrograde pyelography, or, if needed, (3) an antegrade ureteropyelography (ie, a 2-stick technique where a small needle is passed first and then a larger needle used for guidewire access.).
A standard lower-pole puncture site is along the posterior axillary line midway between the 12th rib and the iliac crest in the lumbar triangle (Petit triangle). Posterior calices, which project more medially than anterior calices, are preferred. Even though lower-pole access is often useful and may be adequate for drainage, upper-pole access is preferred for ureteral procedures. It is commonly performed above the 12th rib with a low rate of pneumothorax (< 3%). The first maneuver is positioning the access needle (18- to 21-gauge) over the desired calyx with posteroanterior fluoroscopy. The fluoroscope's image intensifier is then rotated 30° toward the operating surgeon so that the axis of the posterior calyx is parallel to the fluoroscopic beam. With the shaft of the access needle also in line with the oblique fluoroscopic beam, the tip of the needle is adjusted so it remains on the selected calyx. The needle is then advanced into the posterior calyx. See image below.
Direct percutaneous access to the renal pelvis should be avoided to prevent hilar injury. Successful puncture is determined by urine dripping from the sheath after the needle's stylet has been removed. Contrast is then injected through the sheath to opacify the collecting system. A guidewire is then passed through the sheath and coiled in the collecting system, as shown below. Narrow dilators and subsequently a small nephrostomy tube (6-12F) may then be placed over the guidewire if only simple renal drainage is desired. If a more invasive procedure is planned, dilation with either serial or balloon dilators may be performed to obtain a tract 24-30F in diameter.
After initial needle access is obtained, a guidewire is coiled in the renal pelvis prior to tract dilation.
Endoscopic intrarenal instrumentation
Nephroscopes are instruments that are inserted percutaneously through a nephrostomy tract. Standard rigid instruments are 19.5-26F in diameter and have rod lenses or fiberoptic imaging with offset eyepieces. Endoscopic lithotripsy is performed by applying a lithotrite through the central working channel. Available instruments include mechanical graspers and various lithotrites (eg, holmium laser, electrohydraulic, hollow-core ultrasonic or lithotriptors) and are complementary to the endoscope as long as they pass through the central channel. Actively deflectable, flexible nephroscopes are also used percutaneously through nephrostomy tracts. They are used to access calculi in calyces that cannot be reached by the rigid instruments and frequently can be deflected into most of the intrarenal collecting system. See images below.
After tract dilation, the calculi are treated with a rigid nephroscope and ultrasonic lithotriptor. A 7.5F flexible nephroscope and a laser lithotriptor are used to treat stones in tangential calyces. All aspects of the intrarenal collecting system are accessible, which requires both primary and secondary deflection.
Following treatment of the large stone burden, the remainder of the collecting system is examined in an antegrade manner via flexible ureteroscopy.
Percutaneous treatment of renal stones
In the era of extracorporeal shockwave lithotripsy (ESWL), the indications for percutaneous treatment include (1) urinary obstruction not caused by the stone itself (eg, calyceal diverticulum, UPJ obstruction), (2) large-volume stones that are larger than 2.5 cm (eg, staghorn calculi), (3) stones that are not amenable to ESWL or ureteroscopic treatment (eg, anomalies of the kidney, pelvic kidney, obesity), (4) infectious stone burdens (eg, staghorn calculi), and (5) lower-pole calculi that are deemed inappropriate for ESWL.
When performing a PCNL (see video below), smaller mobile stones are removed via graspers, forceps, or flexible/rigid (Perc NCircle) wire baskets. Large dense stones are fragmented using ultrasonic, electrohydraulic, laser, or pneumatic energy. Ultrasonic techniques are preferred because they allow for stone fragmentation with simultaneous in-line suction through a hollow cylindrical probe that continuously removes sand and small fragments. However, ultrasonic lithotripsy can be performed only through a rigid endoscope because any deflection of the probe dramatically decreases the power of this lithotrite. Laser lithotriptors such as the holmium:yttrium-aluminum-garnet laser are particularly powerful and also may be used with flexible endoscopes that can access more of the collecting system but without simultaneous suction to clear debris.
The irrigation used during all percutaneous endoscopic treatments should be sterile warm isotonic sodium chloride solution. Irrigant may be absorbed during treatment via small veins. If significant fluid absorption is suspected, then diuretics (eg, mannitol, furosemide [Lasix]) should be administered intraoperatively.
Following completion of percutaneous endoscopic treatment, a nephrostomy tube should be placed through the tract, as shown below. The tube type selected depends on the need for future interventions. If repeat procedures are planned, then a reentry Malecot may be used. Other drainage tubes include Foley catheters and regular Malecot drainage catheters.
Following the procedure, a 14F Malecot nephrostomy tube and a 5F nephroureteral stent are placed for renal drainage.
Success rates have been reported to be as high as 98-99% with PCNL. However, as the size of the stone burden increases, the stone-free rate with a single session drops. Repeat procedures or multiple nephrostomy access tracts may be required for large stone burdens. Repeat or staged surgery often is performed 36-48 hours following the initial procedure, after any bleeding has subsided and endoscopic visibility has improved.
Postoperative Details
Following percutaneous endoscopic procedures involving a significant amount of manipulation of the collecting system (eg, laser lithotripsy, endopyelotomy), urinary drainage is ensured with a nephrostomy drainage catheter and, on occasion, an additional internal ureteral stent. The catheters should be large enough to provide adequate drainage of the kidney and should be chosen relative to the size of the percutaneous access tract used for the surgical intervention. Venous sinus or access tract bleeding can be minimized with the tamponading nature of a large-caliber nephrostomy tube. Simple Foley drainage catheters may be left as a nephrostomy postoperatively, especially if no further endoscopic treatments are required. If staged endoscopic procedures are anticipated and a mature straight nephrostomy tract is required, then a reentry Malecot that combines a nephrostomy with a short ureteral stent is often used.
Postoperatively, patients should be monitored for bleeding, especially in the recovery room. If significant parenchymal bleeding occurred intraoperatively, the hematocrit should be checked and the patient should be appropriately resuscitated. Renal parenchymal bleeding can often be controlled postoperatively by clamping the nephrostomy tube for a short period in the recovery room. The simultaneous administration of diuretics (eg, mannitol, Lasix) and intravenous fluid increases the intraluminal collecting system pressure. If the bleeding is venous in origin, this maneuver stops it once the intrarenal pressure exceeds central venous pressure. Later, urine begins to drain from the nephrostomy as urokinase begins to slowly act on the intrarenal clot. Vigorous attempts at catheter irrigation in the immediate postoperative period only lead to blood loss and should be avoided, if possible.
Chest radiography should be part of the routine postoperative management due to the risk of a pleural tear or perforation when supracostal percutaneous access is obtained. If a pneumothorax or hydrothorax is present, pleurocentesis or placement of a small-diameter thoracostomy tube may be required.
Prophylactic antibiotics routinely are continued postoperatively until all tubes are removed and all puncture sites are healed.
Follow-up
Follow-up imaging and nephrostography are performed routinely after most therapeutic maneuvers, prior to nephrostomy removal. Antegrade studies allow assessment of most treatment outcomes. For example, the presence and location of residual stone material may be assessed, and the patency of the entire collecting system also may be assessed. Mild extravasation may be present at the nephrostomy site and along the tract, but other sites of extravasation secondary to perforations in the collecting system should be allowed to heal with catheter drainage prior to nephrostomy tube removal.
For excellent patient education resources, see eMedicineHealth's patient education article Kidney Stones.
Complications
Complications associated with percutaneous nephrostomy tube placement alone are uncommon and are usually minor in nature. When more extensive endoscopic maneuvers are used through a nephrostomy tract, the associated complications are more common and severe. The potential complications include the following:
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Acute bleeding requiring transfusion (< 5%): Bleeding may result from traumatized renal parenchyma or injury to a perinephric vessel. Intraoperative hemorrhage is best managed by immediate tamponade. Large nephrostomy tube placement is invariably effective. In rare cases, angiography with embolization or open surgery is needed (< 0.1%). Delayed bleeding after nephrostomy removal is uncommon (0.5%).
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Perforation of the collecting system (20-30%): This common finding, which often occurs with tract dilation, is managed by nephrostomy drainage. Within 24-48 hours, the urothelium seals, given that the collecting system is adequately drained.
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Pleurotomy/pneumothorax (< 5%): Usually associated with a supracostal approach, a pleural injury usually results in a hydrothorax and, infrequently, pneumothorax. Generally, it resolves with simple thoracentesis, but rarely, it may require chest-tube placement and drainage for 48 hours. Chest radiography is recommended following all percutaneous procedures in the recovery room.
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Sepsis (< 1%): Higher rates are noted in those with an infected stone burden. Parenteral antibiotics and nephrostomy drainage are required. Usually, a penicillin-derivative antibiotic and an aminoglycoside are used in combination for initial broad-spectrum coverage.
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Adjacent organ injury (< 1%): Injury may occur to the liver, spleen, duodenum, colon, and adjacent structures. Colonic injury is the most common of these and occurs when the nephrostomy is passed through a redundant portion of the colon before entering the kidney. In cases of colonic injury, management includes repositioning the nephrostomy catheter back until it is in the colon (ie, colostomy tube) and placing an external retrograde ureteral catheter to drain the renal pelvis. Generally, colostomy is indicated only for clinical peritonitis.
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Contrast reactions (< 0.2%): If a problem is anticipated, preoperative steroids (eg, prednisone) should be administered. Should a reaction develop, treatment includes termination of the examination, antihistamines, steroids, H1 and H2 blockers, plus epinephrine, if needed.
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Acute loss of the nephrostomy tract: This can usually be avoided with the use of a safety wire. If it occurs, the tract may be probed with a guidewire either in an antegrade or in a retrograde fashion; however, a repeat puncture may be required.
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Leakage from around a nephrostomy tube: Generally, this indicates some type of blockage. This may be caused by a blood clot, a piece of sloughed tissue, or compression of the tube by the flank musculature. Tube compression is more likely with a nephrostomy tube that is too narrow or too soft. Irrigation of the tube usually does not provide a permanent solution; therefore, replacement with a stiffer and/or larger tube is recommended and usually solves the problem.
Outcome and Prognosis
Percutaneous surgery is associated with minimal patient morbidity compared to open surgery.
Future and Controversies
With the advent of percutaneous surgery, many conditions that at one time required major open surgical procedures are now treatable endoscopically. Initial percutaneous procedures were simple and included drainage of the upper tracts in the setting of obstruction and sepsis, along with diagnostic procedures. As the instrumentation has developed along with the techniques, percutaneous surgery is now used as a minimally invasive treatment option for large stone burdens, strictures, UPJ obstructions, and upper tract lesions.
Percutaneous surgery is now commonly used by urologists with minimal morbidity in comparison to open surgery. Because significant complications may occur, percutaneous manipulation should be used by those with experience.
The applications of percutaneous endoscopic renal surgery continue to expand. Advances that minimize morbidity and improve accuracy of percutaneous access are areas of current study. Future investigation involving new real-time imaging modalities, bioimpedance-based access needles, and robotic interface systems may ensure increased accuracy. These and other innovations will continue to develop and shape the field of percutaneous endourology well into the 21st century.
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The patient is a 10-month-old girl with a history of fever and recurrent urinary tract infections. Plain radiograph demonstrates multiple large renal calculi.
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Retrograde ureteropyelogram that demonstrates a severely hydronephrotic kidney with multiple large intrarenal and ureteral calculi.
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Initial percutaneous renal access obtained via a lower-pole puncture.
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After initial needle access is obtained, a guidewire is coiled in the renal pelvis prior to tract dilation.
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After tract dilation, the calculi are treated with a rigid nephroscope and ultrasonic lithotriptor. A 7.5F flexible nephroscope and a laser lithotriptor are used to treat stones in tangential calyces. All aspects of the intrarenal collecting system are accessible, which requires both primary and secondary deflection.
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Following treatment of the large stone burden, the remainder of the collecting system is examined in an antegrade manner via flexible ureteroscopy.
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Following the procedure, a 14F Malecot nephrostomy tube and a 5F nephroureteral stent are placed for renal drainage.
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Percutaneous nephrolithotomy. Video courtesy of Dennis G Lusaya, MD, and Edgar V Lerma, MD.
