Indications

Indications for PCN may be grouped into the following general categories: relief of urinary obstruction, urinary diversion, and access for diagnostic and therapeutic procedures (Table 146-1).

Urinary obstruction is most frequently caused by pelvic malignancy or renal stone disease (Table 146-2). PCN is performed for rapid decompression of an obstructed renal collecting system when retrograde drainage is not feasible, and may be life saving in patients with urosepsis or acute renal failure. PCN may even be preferred over retrograde stenting in patients with obvious infection, because it accomplishes more rapid drainage.² In patients who have hypotension and leukocytosis, mortality from urosepsis may be reduced from 40% to 8% with emergency PCN.³

Placement of a PCN for urinary diversion may be indicated in several different clinical situations. A urine leak may occur as the result of a traumatic or iatrogenic injury to the renal collecting system, or a leak may arise at a surgical anastomotic site. A urinary fistula may develop in patients with a pelvic malignancy, a pelvic inflammatory process, or a history of irradiation of the pelvis. Another indication for emergency PCN for urinary diversion is the presence of severe refractory hemorrhagic cystitis, which is most commonly due to intravesical chemotherapy or external beam radiation and has a mortality rate of up to 4%.⁴ In all these scenarios, placement of a PCN alone may not accomplish sufficient urinary diversion to allow healing of the underlying process, and ureteral occlusion may ultimately be necessary.⁵

Although PCN may still be performed for a wide variety of diagnostic purposes, antegrade pyelography has been replaced in most instances by noninvasive imaging. In a recent series of patients with renal impairment from ureteral obstruction, non–contrast-enhanced computed tomography (CT) was determined to be the best imaging modality for evaluating calculus disease, and magnetic resonance (MR) urography was thought to be optimal for identifying noncalculous causes of obtstruction.⁶ In cases in which noninvasive imaging is inconclusive, antegrade pyelography can help determine the severity of an obstruction and can provide very detailed information about stenoses, particularly those at ureteroenteric anastomoses. The access established for antegrade pyelography can also be used for further diagnostic testing, such as brush biopsy of urothelial lesions.

Diagnostic PCN can be definitive in other situations in which noninvasive imaging is unreliable. In the setting of chronic obstruction, the finding of mild to moderate cortical atrophy on CT or ultrasound cannot be used to predict whether renal function will recover after decompression, so PCN should be performed before functional testing. If a kidney contributes greater than 20% of overall renal function after percutaneous drainage, it is generally considered worth salvaging. It may also be impossible to determine whether hydronephrosis is due to functional or mechanical obstruction with noninvasive imaging. The Whitaker test, which measures the pressure gradient between the renal pelvis and the bladder, was devised to answer this question (Fig. 146-1).⁷ This test is most commonly performed either before or after pyeloplasty in patients with UPJ obstruction to determine whether surgical or endourologic treatment is indicated or to determine whether it was successful (Table 146-3).

Finally, PCN is frequently performed prior to other interventional procedures, especially in centers with active endourologic surgeons. A wide variety of procedures may be performed via percutaneous access of the kidney, including stone removal, dilation or stenting of a ureteral stricture, endopyelotomy, and foreign body retrieval. Among these procedures, access for treatment of stone disease with percutaneous nephrostolithotomy (PCNL) is by far the most common (Fig. 146-2).²

Contraindications

The strongest contraindication to PCN is severe coagulopathy, with most authors in agreement that an international normalized ratio (INR) less than 1.5 and a platelet count greater than 50,000 should be achieved before the procedure.8–10 Severe hyperkalemia (potassium level > 7 mEq/L) should be corrected with dialysis before the procedure,⁹ and systolic blood pressure less than 180 mmHg is desirable. If the PCN is elective, antiplatelet agents or anticoagulants should be withheld for 5 days before the procedure when feasible.¹⁰ Patients who are allergic to contrast media should receive premedication with either oral or intravenous (IV) steroids. Rarely, patients will have an anatomic variant such as a retrorenal colon that precludes safe percutaneous access to the kidney (Table 146-4).

Equipment

Equipment for PCN is listed in Table 146-5. Image guidance for PCN may be accomplished with ultrasound, CT, fluoroscopy, or some combination of these modalities, most commonly ultrasound and fluoroscopy. For ultrasound-guided access to the renal collecting system, a low-frequency transducer, usually 3.5 MHz, is necessary for sufficient penetration of the retroperitoneal soft tissues to allow good visualization of the kidney. Any multislice CT scanner should provide adequate imaging to identify an appropriate access site and guide needle placement, and combined CT-fluoroscopy can provide real-time guidance for placement of the PCN. If CT-fluoroscopy is not available, it may be necessary to establish needle access to the kidney and then transfer the patient to a fluoroscopy unit for the remainder of the procedure. In the fluoroscopy suite, a rotating image intensifier is extremely helpful because oblique positioning of the tube allows real-time visualization of wire and catheter manipulations while keeping the operator’s hands outside the field of view.

Ultrasound-guided access is often performed with a freehand technique, but needle guides are available and may be useful, especially for less experienced operators. A sterile cover is necessary for the transducer and cord. It may also be helpful to place a clear plastic drape over the ultrasound control panel to allow the operator to make adjustments to the settings.

If fluoroscopic guidance alone is used, IV administration of contrast material may be necessary to aid in visualization of the collecting system, especially if it is not dilated. Depending on the patient’s size, an initial injection of 75 to 100 mL of 68% ioversol (Optiray 320) is typically given, and an additional bolus can be administered if needed.

Several different sets are available for percutaneous access to the kidney. The Neff Percutaneous Access Set (Cook Medical, Bloomington, Ind.) and the AccuStick II Introducer System (Boston Scientific, Natick, Mass.) include a 21- or 22-gauge needle with a stylet, a 6F coaxial introducer with a locking cannula, a 0.018-inch mandril wire, and a heavy-duty 0.038-inch J-tipped guidewire (150 cm).

A few other tools may be helpful in certain situations. An 80-cm, 0.018-inch nitinol wire (ev3/Covidien, Plymouth, Minn.) is easier to advance through the access needle into the collecting system than the standard 0.018-inch mandril wire and may be extremely useful when the collecting system is not very dilated. If the patient is obese or has scar tissue in the retroperitoneum, an 18-gauge needle with a stylet is sturdier and less likely to be deflected during initial access, and a stiffer wire like a 0.035-inch Amplatz wire (Boston Scientific) may greatly facilitate dilation of the tract for placement of the drainage catheter.

If placement of a nephroureteral stent or internal double-J ureteral stent is planned, a 5F Kumpe catheter (Cook Medical) and 0.035-inch stiff or regular glidewire (Boston Scientific) will facilitate access into the ureter and bladder. In the presence of a tight ureteral stricture, a 4F Glide catheter (Boston Scientific) or 6.3F or 8F van Andel catheters (Cook Medical), which taper to 3F or 5F, respectively, may be useful to cross the stricture. Occasionally, balloon dilation of a stricture is necessary before placement of a ureteral stent, in which case a noncompliant balloon should be used. Side-port sheaths may also aid in crossing a stricture, and peel-away sheaths are useful for placement of internal ureteral stents.

Nephrostomy, nephroureteral, or double-J ureteral drains are available in many different varieties. Most of the nephrostomy tubes placed by interventional radiologists are 8F, 10F, or 12F all-purpose locking pigtail drains, although mini-pigtail drains may be placed when the renal pelvis is not capacious enough to allow a standard pigtail to form. Nephroureteral drains have a loop in the bladder and a locking pigtail in the renal pelvis and are available in different diameters, usually 8F and 10F, and lengths, typically 20 to 28 cm. Internal double-J ureteral drains are available in essentially the same sizes as nephroureteral drains.

Planning the approach for access is the most crucial step in performing successful uncomplicated PCN placement. Before the procedure, any prior studies or cross-sectional imaging should be reviewed to evaluate the anatomy, location, and orientation of the target kidney. Malrotation or malposition of the kidney, duplication of the collecting system, and any cysts, diverticula, tumor, or stones should be noted.¹¹ The location of the lung, liver, spleen, and colon relative to the kidney should be considered, as well as body habitus, such as morbid obesity or spina bifida.

For routine PCN, the patient should be placed in a prone or prone oblique position with the ipsilateral side elevated 20 to 30 degrees. If ultrasound guidance is planned for access, it is often helpful to scan the patient before sterile preparation to optimize positioning. In some patients, placement of a roll or pillow beneath the lower abdomen will reverse the normal lordotic curvature of the lumber spine and improve sonographic visualization of the approach.

The ideal entry site to the kidney is through a relatively avascular plane known as the Brödel line that lies at an angle of about 30 to 45 degrees from midline when the patient is prone. The collecting system should be accessed peripherally via the tip of the calyx to decrease the likelihood of significant bleeding, and a posterior calyx should be chosen to facilitate placement of a nephrostomy tube or any additional endourologic procedures.

The ideal skin entry site is approximately 10 cm lateral to the midline but not beyond the posterior axillary line. If the entry site is too medial, the PCN will cross the paraspinal musculature and make dilation of the tract more difficult and the tube more painful for the patient, and an entry site that is too lateral increases the risk of colonic perforation. The tract should avoid the inferior margin of the rib to decrease the risk of injury to an intercostal artery. If a supracostal approach is necessary for treatment of an upper pole stone, the risk of injury to lung, liver, or spleen is significantly less in the T11-T12 interspace than in the T10-T11 interspace.¹²

Technical Aspects

Numerous techniques for image-guided PCN placement have been described. The renal collecting system can be accessed using a single-stick or double-stick method with ultrasound, fluoroscopy, or CT, alone or in combination. The single-stick method is more likely to be possible in patients with moderate to severe hydronephrosis, because it facilitates visualization of a calyx for direct access. A double-stick method is useful when the collecting system is not dilated, making it initially more difficult to access a calyx. In this technique, the first needle is used to access and opacify the collecting system so a more appropriate site for definitive access can be targeted (Fig. 146-3). There is reportedly no difference in technical success and complication rates for a single- versus double-stick technique.^3,13

If ultrasound is used for guidance, the probe should be oriented along the long axis of the kidney, and the needle tip should be visualized from the skin entry site to the point of entry in the calyx. If fluoroscopic guidance alone is used, the site for access can be chosen on the basis of anatomic landmarks, by targeting a stone, or by opacification of the collecting system with IV contrast material. The C-arm should be rotated initially so that the needle is viewed end on as it is advanced toward the appropriate calyx, then the C-arm can be rotated to the orthogonal view to determine the depth.

CT guidance for PCN may be required when the patient has variant anatomy. In addition, CT guidance can allow the procedure to be performed with the patient in a supine oblique position when the patient is unable to lie prone. In CT-guided cases, it is important to select the calyx that can be approached most easily in the horizontal plane.

Routine Percutaneous Nephrostomy Placement

Once the access site has been chosen, the skin and subcutaneous tissues along the expected path for the nephrostomy are infiltrated with a local anesthetic, and a small dermatotomy is made with a scalpel. After needle access is achieved, a small amount of urine should be aspirated for culture, then a small amount of contrast material should be injected to determine the precise point of entry.

If the needle entry site is not appropriate, the first needle can be used to further opacify the collecting system with contrast material and air if necessary so a more appropriate site can be targeted for entry with a second needle. When opacified, the posterior calyces are typically seen end on, whereas the anterior calyces project more laterally in the anteroposterior projection; however, injection of a small amount of air or CO₂, which will fill the nondependent posterior calyces in a prone patient, may be necessary for confirmation. Care should be taken to aspirate a larger volume of urine than the amount of contrast material injected to avoid overdistention and possible sepsis.

If the needle entry site is appropriate, the 0.018-inch wire is advanced through the needle and coiled in the renal collecting system. If the system is not very dilated, a 0.018-inch nitinol wire may be much easier to manipulate into the renal pelvis. More stable access is obtained when the wire is advanced into the ureter. Fluoroscopic guidance is very helpful to ensure that the wire is in good position and does not become kinked during the subsequent steps of the procedure.

Once the 0.018-inch wire is in appropriate position, the access needle is exchanged over the wire for the 6F coaxial sheath, and the 0.018-inch wire and inner stiffeners are removed. A heavy-duty J-tipped 0.038-inch wire is advanced into the renal collecting system, and serial dilation of the tract is performed over the wire. The percutaneous drainage catheter, usually a locking pigtail drain, is advanced over the wire, and the wire and inner stiffener are removed. The pigtail is formed and locked. All the urine should be aspirated from the collecting system if there is any suspicion of infection, and a small amount of contrast material can then be injected to confirm appropriate position of the drain. The drain should be flushed and secured to the skin with either suture or an adhesive retention device.

Percutaneous Nephrostomy Placement in a Nondilated Collecting System

Occasionally, PCN will be necessary in a patient who has a nondilated system, which can be seen in the setting of a ureteral leak or fistula, hemorrhagic cystitis, or nondilated obstruction. The pathophysiology of obstruction without hydronephrosis is not well understood, but reversal of acute renal failure after PCN in a nondilated system has been well documented.¹⁴ A double-stick technique for fluoroscopically guided access to a nondilated system has been described.¹⁵ Intravenous contrast material is administered to opacify the collecting system, and a 22-gauge needle is quickly advanced directly into the renal pelvis. This needle can be used to distend the collecting system with a small amount of contrast material and air, then PCN can be performed as described previously. If the patient is in renal failure and IV contrast material cannot be given, ultrasound guidance can be used to access the renal pelvis as well.

Nephroureteral Drain Placement

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