Computerized Tomography Guided Access for Percutaneous Nephrostolithotomy

0022-5347/03/1701-0045/0 THE JOURNAL OF UROLOGY® Copyright © 2003 by AMERICAN UROLOGICAL ASSOCIATION

Vol. 170, 45– 47, July 2003 Printed in U.S.A.

DOI: 10.1097/01.ju.0000065288.83961.e3

COMPUTERIZED TOMOGRAPHY GUIDED ACCESS FOR PERCUTANEOUS NEPHROSTOLITHOTOMY BRIAN R. MATLAGA, OJAS D. SHAH, RONALD J. ZAGORIA, RAYMOND B. DYER, STEVAN B. STREEM* AND DEAN G. ASSIMOS†, ‡ From the Departments of Urology (BRM, ODS, DGA) and Radiology (RJZ, RBD), Wake Forest University School of Medicine, Winston-Salem, North Carolina, and Urological Institute (SBS), Cleveland Clinic Foundation, Cleveland, Ohio

ABSTRACT

Purpose: Access for percutaneous nephrostolithotomy (PNL) using conventional fluoroscopic guidance may carry an increased risk of damage to surrounding organs in patients with renal calculi and aberrant anatomy. In these situations cross-sectional anatomical imaging may facilitate safe percutaneous access. We describe our experience with computerized tomography (CT) guided percutaneous access for such patients undergoing PNL. Materials and Methods: Between June 2000 and December 2001, 154 patients underwent PNL at our institution. Five of these patients (3%) required a total of 6 percutaneous access tracks under CT guidance. All patients in this group had anatomical abnormalities precluding standard access to the collecting system without risk to adjacent organs. These abnormalities included a retrorenal colon in 2 and a severely distorted body habitus due to spinal dysraphism in 3. Results: Percutaneous access was achieved without complication in all cases. At subsequent PNL 5 of the 6 renal units (83%) were rendered completely stone-free. Conclusion: CT guided percutaneous access is infrequently required for PNL. However, there is a select group of patients with anatomical anomalies that may predictably require this procedure to facilitate safe and efficacious PNL. KEY WORDS: kidney; kidney calculi; nephrostomy, percutaneous; tomography, x-ray computed

colon had previously undergone percutaneous nephrostomy tube placement under fluoroscopic guidance, resulting in transcolonic tube placement. After providing informed consent the patients were placed prone on the table of a standard helical CT scanner. The access procedure was performed under the direction of the radiologist (RBD or RJZ). Mild sedation and appropriate parenteral antibiotic coverage was administered. Initially an uninfused CT image was obtained to localize the targeted aspect of the collecting system. Renal position, specifically in relation to the surrounding structures and orientation of the collecting system, was the primary factor that guided the choice of the point of access. A skin marker was placed to mark the puncture site. The patient was then re-imaged and the marker was repositioned as necessary to ensure that it corresponded to the selected access point. Following standard skin preparation and sterile draping 1% lidocaine was injected at the selected puncture site. A 21 gauge needle was then introduced at the skin site and advanced subcutaneously. A localizing CT image was obtained and the needle was realigned as necessary to optimize its trajectory toward the intended target calix. After this needle was positioned in the correct trajectory an 8Fr trocar with an attached cope loop nephrostomy tube was advanced in tandem parallel to the needle track until urine could be aspirated. The nephrostomy tube was then advanced over its metal stiffener into the pelvocaliceal system, so that the loop portion of the nephrostomy tube was reconstituted. Contrast medium was injected to confirm placement as necessary and the tube was then sutured into place. PNL was subsequently performed as a separate procedure.

In 1955 Goodwin et al described percutaneous puncture of the intrarenal collecting system without the assistance of radiographic guidance as a means of supravesical urinary diversion.1 Since that time, percutaneous renal surgery has evolved into a technique that is routinely used for a wide variety of clinical applications.2 Percutaneous nephrostolithotomy (PNL) is a particularly effective procedure that is used to treat patients with large or otherwise complex stones. For most patients in the United States fluoroscopy or sonography is done to monitor access into the renal collecting system for subsequent PNL.3 However, despite the application of these imaging techniques patients with certain types of anatomical anomalies are at significant risk for adjacent organ puncture, including the colon, small bowel, liver, spleen or lung. We describe our use of computerized tomography (CT) guidance alone to achieve access for PNL in such complicated cases. MATERIALS AND METHODS

From June 2000 through December 2001, 154 patients underwent a PNL procedure at Wake Forest University Medical Center. During this time 5 patients (3%), including 4 men and 1 woman 25 to 48 years old (mean age 38.8 years), underwent a total of 6 percutaneous access procedures under CT guidance. The indication for PNL in all cases was large or otherwise complex symptomatic calculi. All 5 patients had anatomical anomalies detected on pretreatment imaging that precluded safe access for PNL using conventional fluoroscopic imaging techniques. A patient with a retrorenal Accepted for publication February 14, 2003. * Financial interest and/or other relationship with Bard Urology and Boston Scientific. † Corresponding author: Department of Urology, Wake Forest University School of Medicine, Medical Center Blvd., WinstonSalem, North Carolina 27157. ‡ Financial interest and/or other relationship with Ixion, Olympus and Boston Scientific.

RESULTS

A total of 6 percutaneous nephrostomy tubes were placed under CT guidance in 5 patients. Two percutaneous nephros45

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COMPUTERIZED TOMOGRAPHY GUIDED ACCESS FOR NEPHROSTOLITHOTOMY

FIG. 1. CT guided access in patient with retrorenal colon. A, initial access into collecting system with 21 gauge needle. B, subsequently placed nephrostomy tube located in collecting system.

DISCUSSION

data set may be formatted to display the anatomical region from a cross-sectional perspective, or in single or multiple planes, thus, facilitating the identification of adjacent structures. In fact, MR and CT have been applied as radiographic guidance modalities in interventional radiology for percutaneous biopsy and tissue ablation procedures.6 –9 However, there are only a few reports regarding the use of CT for percutaneous access guidance for subsequent nephrostolithotomy. In a porcine model Nolte-Ernsting et al successfully entered nondilated pelvocaliceal systems under MR guidance10 and Hagspiel et al reported a single case of MR guided percutaneous nephrostomy in a human.11 In 1977 Haaga et al reported the first case of CT guided percutaneous nephrostomy.12 Barbaric et al subsequently reported a series of 129 patients undergoing placement of a percutaneous nephrostomy using an especially built unit that combined CT and fluoroscopy.13 However, this equipment is only available at a few centers. There are some patients who are not appropriate candidates for CT guided percutaneous access. Skoog et al reported on a patient with a retrorenal colon identified by preoperative CT who subsequently required open pyelolithotomy due to inability to access safely the collecting system percutaneously.14 Similarly patients with pelvic kidneys may require laparoscopically assisted PNL.15 Sonography is another alternative imaging modality that has been used in such patients. However, it is not as precise as CT, and may be difficult to perform in patients who are obese or in

Goodwin et al introduced the technique of percutaneous nephrostomy in 1955 as a blind puncture performed without the aid of real-time radiographic guidance.1 It was not until 2 decades later, when Pedersen described adjunct radiographic guidance,4 that this procedure gained widespread clinical use. Although it was initially performed as a means of supravesical urinary diversion, percutaneous nephrostomy was subsequently used to treat renal calculi after Fernstrom and Johansson first described in 1976 the technique of establishing a percutaneous nephrostomy tract specifically to remove a stone.5 At most centers in the United States PNL is performed under fluoroscopic guidance for access and subsequent manipulation, although some groups use sonography at least to facilitate and direct initial access. The primary disadvantage of the fluoroscopic technique for access is the inability to delineate adequately the perinephric anatomy. As such, in patients with known anomalous retroperitoneal anatomical relationships percutaneous access under fluoroscopic guidance may place the patient at increased risk for adjacent organ injury. In these instances accurate cross-sectional imaging can facilitate safe, accurate access into the renal collecting system. Magnetic resonance (MR) imaging and CT acquire the volumetric data set of an anatomical region of interest. This

FIG. 2. Patient with large renal calculus in renal transplant graft with overlying bowel. After CT guided access PNL was performed successfully at Cleveland Clinic Foundation.

tomy tubes were placed under CT guidance due to a retrorenal colon (fig. 1). In these 2 cases the retrorenal colon had been identified on pretreatment CT images. These 2 patients had large volume renal calculi and nephrostomy placement was performed to allow subsequent PNL. In each case the nephrostomy tubes were placed in infracostal lower pole positions. Four percutaneous nephrostomy tubes were placed under CT guidance due to severely distorted patient anatomy associated with spinal dysraphism. These patients had large volume complex calculi. Two tubes were placed in upper pole positions, 1 was placed in a mid pole position and 1 was placed in a lower pole position. All access points were infracostal. A single patient underwent 2 separate access procedures using 2 distinct access points. In all 6 attempts at percutaneous nephrostomy placement under CT guidance the kidney, intrarenal collecting system and perinephric structures were well visualized. The percutaneous nephrostomy drain was placed successfully in each case. Furthermore, no complications related to nephrostomy tube placement were noted. At the completion of PNL 5 of the 6 renal units (83%) were rendered stone-free. The patient who was not rendered stone-free had residual calculi in a caliceal diverticulum and repeat CT guided access was recommended, which he refused. There were no complications associated with any PNL procedures.

COMPUTERIZED TOMOGRAPHY GUIDED ACCESS FOR NEPHROSTOLITHOTOMY

those with a dysmorphic body habitus; that is those who might benefit most from cross-sectional imaging. While it is certainly a reasonable method for accessing a superficial ectopic kidney such as a renal transplant graft, even some of those patients may benefit from CT guidance (fig. 2). Clearly there is a select group of patients who would benefit from CT guided percutaneous access to perform PNL effectively and safely. This group includes certain patients with ectopic kidneys, a retrorenal colon or any form of megacolon, severe spinal dysraphism and other causes of an abnormal body habitus as well as select individuals with hepatomegaly, splenomegaly or renal angiomyolipoma. In fact, while a retrorenal colon has been reported to be present in less than 1% of patients, the incidence may be higher in those who have undergone jejunoileal bypass, those in a nursing home (institutional bowel) or those with spinal cord injury.16 It is anticipated that in the future more patients with a retrorenal colon may be identified because helical CT is now performed routinely to evaluate patients with nephrolithiasis. Thus, more patients may require CT guided access. The majority of these patients can be identified preoperatively by physical examination and medical history, and in these patients initial CT should be done. Our series reinforces the contemporary role of percutaneous access achieved exclusively under CT guidance in a select group of patients expressly for elective PNL. As described, the procedure was accomplished in a safe and efficacious manner, and PNL was subsequently performed without difficulty in all cases. As an alternative, MR guidance can eliminate patient exposure to ionizing radiation, although those with metallic implants are excluded. In our series all patients with spinal dysraphism had metallic devices that precluded MR imaging. CONCLUSIONS

CT guided percutaneous access for PNL would not replace the current fluoroscopic standard. However, there is a select group of patients with anatomical anomalies in whom noncross-sectional imaging guidance technology increases the risks inherent in the procedure. For these patients CT guided access for subsequent PNL has proved to be a safe, reliable adjunct. REFERENCES

1. Goodwin, W. E., Casey, W. C. and Woolf, W.: Percutaneous trocar (needle) nephrostomy in hydronephrosis. JAMA, 157: 891, 1955

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2. Dyer, R. B., Assimos, D. G. and Regan, J. D.: Update on interventional uroradiology. Urol Clin North Am, 24: 623, 1997 3. Lange, P. H., Reddy, P. K., Hulbert, J. C., Clayman, R. V., Castaneda-Zuniga, W. R., Miller, R. P. et al: Percutaneous removal of caliceal and other “inaccessible” stones: instruments and techniques. J Urol, 132: 439, 1984 4. Pedersen, J. F.: Percutaneous nephrostomy guided by ultrasound. J Urol, 112: 157, 1974 5. Fernstrom, I. and Johansson, B.: Percutaneous pyelolithotomy. A new extraction technique. Scand J Urol Nephrol, 10: 257, 1976 6. Silverman, S. G., Collick, B. D., Figueira, M. R., Khorasani, R., Adams, D. F., Newman, R. W. et al: Interactive MR-guided biopsy in an open-configuration MR imaging system. Radiology, 197: 175, 1995 7. Vogl, T. J., Muller, P. K., Hammerstingl, R., Weinhold, N., Mack, M. G., Philipp, C. et al: Malignant liver tumors treated with MR imaging-guided laser-induced thermotherapy: technique and prospective results. Radiology, 196: 257, 1995 8. Hagga, J. R. and Alfidi, R. J.: Precise biopsy localization by computed tomography. Radiology, 118: 603, 1976 9. Crowley, J. D., Shelton, J., Iverson, A. J., Burton, M. P., Dalrymple, N. C. and Bishoff, J. T.: Laparoscopic and computed tomography-guided percutaneous radiofrequency ablation of renal tissue: acute and chronic effects in an animal model. Urology, 57: 976, 2001 10. Nolte-Ernsting, C. C., Bucker, A., Neuerburg, J. M., Glowinski, A., Adam, G. B. and Gunther, R. W.: MR imaging-guided percutaneous nephrostomy and use of MR-compatible catheters in the nondilated porcine urinary tract. J Vasc Interv Radiol, 10: 1305, 1999 11. Hagspiel, K. D., Kandarpa, K. and Silverman, S. G.: Interactive MR-guided percutaneous nephrostomy. J Magn Reson Imaging, 8: 1319, 1998 12. Haaga, J. R., Zelch, M. G., Alfidi, R. J., Stewart, B. H. and Daugherty, J. D.: CT-guided antegrade pyelography and percutaneous nephrostomy. AJR Am J Roentgenol, 128: 621, 1977 13. Barbaric, Z. L., Hall, T., Cochran, S. T., Heitz, D. R., Schwartz, R. A., Krasny, R. M. et al: Percutaneous nephrostomy: placement under CT and fluoroscopy guidance. AJR Am J Roentgenol, 169: 151, 1997 14. Skoog, S. J., Reed, M. D., Gaudier, F. A., Jr. and Dunn, N. P.: The posterolateral and the retrorenal colon: implication in percutaneous stone extraction. J Urol, 134: 110, 1985 15. Zafar, F. S. and Lingeman, J. E.: Value of laparoscopy in the management of calculi complicating renal malformations. J Endourol, 10: 379, 1996 16. Sherman, J. L., Hopper, J. D., Greene, A. J. and Johns, T. T.: The retrorenal colon on computed tomography: a normal variant. J Comput Assist Tomogr, 9: 339, 1985