Spiral computed tomography for staghorn calculi

ADULT

UROLOGY

ELSEVIER

SPIRAL COMPUTED TOMOGRAPHY FOR STACHORN CALCULI STUART

N. LIBERMAN,

ETHAN

J. HALPERN,

KEVIN

SULLIVAN,

AND DEMETRIUS

H. BAGLEY

ABSTRACT Objectives. To assessthe utility of spiral computed tomography (CT) with three-dimensional reconstruction for preoperative planning of percutaneous nephrostolithotomy in patients with complex branched calculi (full staghorns). Methods. Patients with complex branched stones were imaged with spiral CT with three-dimensional reconstruction. These images were compared with standard imaging modalities, including excretory urography and plain radiographs, for planning percutaneous access for nephrostolithotomy. The utility of the scan was evaluated. Results. Ten patients with branched calculi were studied. Anatomic abnormalities were present in 5 patients. Excellent three-dimensional images were obtained in all patients without any complications related to the study. In 1 patient with multiple calculi in a horseshoe kidney, the three-dimensional image indicated a branched stone. The spiral CT scan was not helpful in directing percutaneous access in any patient. In a single patient, residual fragments noted during nephrostolithotomy were located by reference to the spiral CT scan. Conclusions. Spiral CT scans with three-dimensional reconstruction provide three-dimensional imaging of branched renal calculi. This modality provides minimal additional information over that obtained from standard radiographic studies for guiding nephrostolithotomy and cannot be recommended as a routine preoperative study. It was helpful in 1 patient to locate a residual fragment. UROLOGY 50: 519-524, 1997. 0 1997, Elsevier Science Inc. All rights reserved.

P

ercutaneous nephrostolithotomy alone or in combination with shock wave lithotripsy has become the treatment of choice for the treatment of struvite staghorn calculi.’ Accurate calyceal puncture is essential for successful percutaneous stone removal. These procedures must achieve a stone-free state, since residual fragments may result in recurrent urinary tract infections and stone regrowth.2’3 For percutaneous access and stone removal to be performed safely and efficiently, it is essential for the endourologist to have an accurate threedimensional mental image of the pelvicaliceal system and a clear understanding of the stone’s location with respect to infundibular and caliceal

From the Departments of Urology and Radiology, Thomas Jeffevson University, Philadelphia, Pennsylvania Dr. Libeman is currently at MlMA Urology, Melbourne, Florida. Reprint requests: Demetrius H. Bagley, M.D., Department of Urology, Jefferson Medicul College, 1025 Wulnut SLreetlRuum 1108, Philadelphia, PA 19107-5083. Submitted: February 17, 1997, accepted: Aprd 21, 1997 0 ALL

1997, RIGHTS

ELSEVIER SCIENCE INC. RESERVED

anatomy. To complicate this approach further, patients with various anatomic abnormalities such as morbid obesity, kyphoscoliosis, organomegaly, and ectopic or malrotated kidneys are all at a greater risk for unsuccessful or nonideal access, difficult or incomplete stone removal, and injury to other organs4 Spiral computed tomography (CT) was first introduced into clinical practice in the late 1980~.~ Since then, it has been applied successfully to the three-dimensional imaging of many areas of the human body, including blood vesselse9 osseous structures,lO~ll and soft tissue.12-16Spiral or helical CT involves continuous translational motion of the patient through the gantry during simultaneous continuous rotation of the x-ray source in a spiral or helical path around the patient, providing rapid acquisition of a three-dimensional data set in a single breath hold.17,18 To assessthe utility of the spiral CT scan in planning the treatment of complex branched calculi, 10 patients with staghorn stones were imaged prior to percutaneous nephrostomy tube placement and endoscopic lithotripsy. The three-di0090-4295/97/$17.00 PII s0090-4295(97)00300-2

519

TABLE Patient No.

1.

Clinical

history

Anatomic Abnormality

Age WI

Side

52 39 56 32

L R L R

None None None None

5 6

44 39

R L

7

54

R

None Solitary L kidney, scoliosis Kyphoscoliosis, duplicated collecting system Nonfunctioning R kidney (bilateral staghorns) Horseshoe kidney Morbid obesity

Gender

8

M

74

B

9

F

63

R

10

F

34

L

KEY: B = bilateral; CHF = congestive heart failure; NIDMM = non-insulin-dependent diabetes melhtus;

AND

METHODS

Patients with complex branched calculi were included in the study. Preference was given to patients with the most difficult calculi, particularly full staghorn stones filling the entire collecting system and bilateral stones, and those patients with anatomic deformities. Imaging of the calculi was performed with a 9800 Hi Speed Advantage spiral CT scanner (General Electric, Milwaukee, Wis). A scout view of the abdomen was first obtained to localize the stones. Helical images were obtained through the level of the calculi during a single breath hold. Images were obtained with 3-mm collimation at a table pitch of 1. The duration of the breath hold varied; a 20-second breath hold was required for a 6-cm scan length and a 30-second breath hold was required for a 9-cm scan length. No contrast material was administered. Three-dimensional shaded surface display images of the calculi were rendered with the Windows Advantage Workstation (General Electric) and filmed in multiple different projections. The raw helical CT data were reconstructed at 1.5mm intervals with a 22-cm field of view for the purpose of three-dimensional rendering. Three-dimensional images were rendered first with both the staghorn calculi and the spine included to provide a frame of reference as to the position of the stone. The spine and ribs were then excluded from the data set and magnified. Three-dimensional images of the calculi were again rendered to demonstrate finer detail. Any plane could be presented for inspection.

RESULTS Over a 16-month period, 10 patients (7 female, 3 male) who were referred for treatment of stag520

in this study

Presentation

Past GU History

Past Medical History

DVT Gross hematuria Low back pain R flank pain, T 102 R flank pain Proteus UTI

None Passed R stone Cystitis None

HTN, DVT Uterine fibroids HTN, asthma

None None

Pneumonia

R pyelolithotomy, chronic Foley, L UPJ calculus

NIDDM Sarcoid, CRI, hyper PTH L5-6 para, NIDDM

Pneumonia

None

R flank pain

Passed R stone

R pyelo 2” to obstructing ureteral stone

None

Pneumonia, CHF, M

Sarcoid,

CR1 = chronic renal insufficiency; DVT = deep vein rhrombosis; GIJ = genitourinary; HTN = hypertension; PTH = pamthyroid hornone; R = right; UP/ = ureteropelvicjuncrlon; UT1 = urinary tvwt infection.

mensional surface rendered reconstructions were critically evaluated and compared to standard imaging techniques, and their utility discussed. MATERIAL

of patients

HTN

L = left;

horn calculi were entered into this pilot study. The average age was 48.7 years (range 32 to 74). Four patients presented with stone in the left kidney; 5 had stone in the right kidney; and 1 had bilateral staghorn calculi. Anatomic abnormalities were present in 5 patients, including severe kyphoscoliosis, morbid obesity, horseshoe kidney, duplicated collecting system, bilateral stone disease, and a solitary kidney. These problems placed these patients at a higher risk for unsuccessful treatment. Table I reviews the pertinent clinical history. As part of their preoperative evaluation, all patients had successful spiral CT scans prior to undergoing percutaneous nephrostomy tube placement. No complications or adverse side effects were noted as a result of spiral CT scanning. Accurate three-dimensional images of the staghorn calculi were obtained and compared to standard plain films (KUB) and intravenous urograms. All radiographic studies were extensively reviewed and critically evaluated by the interventional radiologists and urologists prior to the operative procedure. Despite the clarity and resolution that these images provided, they did not result in altering the location of the renal access site (Fig. 1). With respect to the lithotripsy procedures themselves, review of the three-dimensional images provided useful information in only one situation. Following initial percutaneous ultrasonic stone debulking, residual fragments in a morbidly obese female were not clearly seen on tomographic imUROLOGY

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the nephrostomy site or subsequent extracorporeal shock wave lithotripsy procedures. The CT scan could rule out posterior perirenal positioning of bowel or lung. Multiple intrarenal calculi could appear on the CT scan as a single branched stone. A patient with five stones in the left kidney had a three-dimensional CT reconstruction that indicated a complex branched stone (Fig. 2). This failure of resolution could be a source of error in other patients with multiple calculi. COMMENT

C FIGURE 1. (A) A complete staghorn calculus is seen filling the collecting system of the right kidney. Two smaller stones are present in the left kidney. (B) A cross-sectional CT image demonstrates the right renal calculus at the level of the renal pelvis. (C) Three-dimensional reconstruction of the spiral CT scan is presented as the anterior-posterior projection. Other planes can also be viewed.

ages. In this situation, we did refer back to the spiral CT scan to help locate two small posterior midrenal calyces and the fragments within them. In the patients with various other anatomic abnormalities or complicating medical conditions, the spiral CT images did not alter positioning of UROLOGY

50 (4), 1997

Staghorn calculi are defined as stones that fill the majorvportion of the collecting system; they typically occupy the renal pelvis and branch into most of the calyces. The majority of staghorn stones are composed of struvite (magnesium ammonium phosphate) and calcium phosphate. Struvite stones occur only in the presence of urease-producing bacteria. Although relatively uncommon, these stones can be the cause of serious morbidity and even mortality. Recent guidelines from the American Urological Association Nephrolithiasis Panel recommend percutaneous nephrolithotomy alone or in combination with shock wave lithotripsy for the treatment of struvite staghorn calculi.’ The association of residual fragments after treatment and persistent urinary tract infections with stone regrowth emphasizes the importance of rendering the patient stone-free.19-21 For percutaneous lithotripsy to be successful, a carefully chosen renal entry site is critical to assure optimal access to the calculus through the collecting system. This requires an unobstructed retroperitoneal approach to the kidney. Patients with anatomic abnormalities such as morbid obesity, kyphoscoliosis, organomegaly, and ectopic or malrotated kidneys are all at a greater risk for unsuccessful or nonideal access or injury to other organs4 For endourologic removal of renal calculi to be performed safely and efficiently, it is important for the urologist to have an accurate three-dimensional mental image of the location of the stone with respect to infundibular and calyceal anatomy, as well as the orientation of the kidney within the body. Standard intravenous urography displays the collecting system only in the anterior-posterior and oblique planes, making it somewhat difficult to visualize the pelvicaliceal system in three dimensions. Caliceal position relative to the lateral kidney margin is a controversial subject and can differ considerably. In 1901, Brodel” showed in schematic illustrations that the anterior calyces are located more medially, whereas the posterior calyces are more lateral (peripheral). For many years, 521

B FIGURE 2. (A) This horseshoe kidney contains five calculi on the left and one on the right. (B) Three-dimensional reconstruction of the spiral CT scan suggests a branched stone on the left rather than individual calculi.

B FIGURE 3. (A) A patient with severe kyphoscoliosis has multiple calculi with a branched configuration in the left kidney. (B) Three-dimensional reconstruction with a spiral CT scan presents the multiple and branched calculi.

this classic study had been the anatomic basis for endourologic manipulations. In 1972, however, Hodson presented a schematic illustration that was nearly a mirror image of that recorded by Brodel. In 1983, Kaye24 affirmed that on a standard intravenous urogram, the anterior row of calyces is usually seen more peripherally and laterally as cup-shaped structures, whereas the posterior row is seen more medially and frontally as round concentrations of contrast. To solve this problem during endourologic procedures, with the patient in the prone position, introduction of gas into the collecting system has been proposed to determine which calyces are positioned posteriorly.25 In the late 1980s spiral CT was introduced into clinical practice. Spiral CT involves continuous translational motion of the patient through the gantry during simultaneous continuous rotation of the x-ray source in a spiral or helical path around the patient. In contrast to conventional dynamic CT scanning, in which each individual slice is interrupted by table incrementation and an interscan time delay, spiral CT involves the continuous ac-

quisition of data. Scanning can be done during a single breath hold by the patient, thus reducing motion artifact and data misregistration. Radiation dose to the patient is less than or equal to that for standard CT.i7,18 This latest technological advance in CT imaging has gained widespread acceptance and has been applied successfully to the imaging of many areas of the body for lesions indeterminate on standard CT.14-‘6X26Y27Other applications include the noninvasive diagnosis of pulmonary embolism2* and aortic dissection,29 imaging of acetabular fractures3’ as well as complex craniofacial deformities. lo Preliminary re p orts using spiral CT angiography to detect crossing vessels at the ureteropelvic junction have recently appeared.31 Lam et ~1.~~ have used three-dimensional CT scanning to measure stone surface area accurately and found a close correlation between stone volume and surface area. Complicated stone classification systems such as the PICA33 and ROCCO~~systems have been proposed to guide therapy, but these tend to be cumbersome and are not necessary for the majority of calculi. In general, we use stone surface area, as obtained from KUB films, to help

522

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differentiate patients best treated with extracorporeal shock wave lithotripsy monotherapy from those who can be better treated with percutaneous lithotripsy. We do not believe it is necessary to assess the volume of all complex renal stones with spiral CT prior to surgical intervention. This study was planned to assess the utility of the three-dimensional spiral CT scan in planning the treatment of staghorn calculi. All patients were imaged with a spiral CT scan as well as a standard excretory urogram prior to the procedure. The films were reviewed interactively by the interventional radiologists and urologists and were readily available in the operating room during all procedures. The CT images display the stone within the collecting system with remarkable clarity and resolution. In addition, the threedimensional reconstructions clearly demonstrate the anterior-posterior orientation of the calyces as well as infundibular angulation and stone boundaries within the collecting system (Fig. 1). However, after extensive and critical evaluation, we did not find that imaging modality furnished any additional or helpful information that could not be obtained from the excretory urogram and renal tomography when planning fluoroscopitally guided percutaneous nephrostomy tube placement. The spiral CT scan employed could not accurately differentiate a single, large branched stone from several smaller stones within the collecting system. In 1 case, a KUB clearly demonstrated five separate stones, while the CT scan was interpreted as a single branched stone (Fig. 2). Thus, in some situations, the registration of multiple stones by spiral CT scan using this particular software may not be as sensitive or as accurate as conventional and less expensive radiographic studies. In a single morbidly obese female, residual fragments were not clearly seen on tomographic images obtained after her initial percutaneous debulking. We believed these fragments were located in a posterior calyx, in a region of the kidney very difficult to access percutaneously with a rigid nephroscope from another posterior access site. In this situation, reference to her original CT scan helped locate two small midposterior calyces and the fragments within them. With this information, the fragments were easily retrieved using a flexible nephroscope. In other patients with anatomic abnormalities, the helical CT images did not significantly improve the safety or efficiency of percutaneous nephrolithotomy (Fig. 3). Detailed knowledge of three-dimensional calyteal anatomy and renal rotation is mandatory for percutaneous removal of complex, branched renal stones. We believe that careful interpretation of the plain anterior-posterior film, as well as the UROLOGY

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oblique radiographs and the excretory urogram, will provide this information for the large majority of patients. Specific calyceal localization is often not necessary for successful extracorporeal shock wave lithotripsy treatment. We have found that the three-dimensional CT scan does not add significant information. In the interest of cost containment, we do not currently recommend that three-dimensional spiral CT be considered part of the routine preoperative evaluation of patients with complex, branched stones. REFERENCES 1. Segura JW, Preminger GM, Assimos DG, Dretler SP, Kahn RI, Lingeman JE, Macaluso JN Jr, and McCullough DL: Nephrolithiasis Clinical Guidelines Panel summary report on the management of staghorn calculi. J Urol 151: 16481651, 1994. 2. Patterson DE, Segura JW, and Leroy AJ: Long-term follow up of patients treated by percutaneous ultrasonic lithotripsy for struvite staghom calculi. J Endourol 1: 122, 1987. 3. Newman DM, Scott JW, and Lingeman JE: Two year follow up of patients treated with extracorporeal shock wave lithotripsy. J Endourol 2: 163, 1988. 4. LeRoy AJ, Williams HJ Jr, Bender CE, Segura JW, Patterson DE, and Benson RC: Colon perforation following percutaneous nephrostomy and renal calculus removal. Radiology 155: 83-85,1985. 5. Rigauts H, Marchal G, Baert AL, and Hupke R: Initial experience with volume CT scanning. J Comput Assist Tomogr 14: 675-682, 1990. 6. Nape1 S, Marks MP, Rubin GD, Dake MD, McDonnell CH, Song SM, Enzmann DR, and Jeffrey RB Jr: CT angiography with spiral CT and maximum intensity projection. Radiology 185: 607-610, 1992. 7. Rubin GD, Dake MD, Nape1 SA, McDonnell CH, and Jeffrey RB Jr: Three-dimension spiral CT angiography of the abdomen: initial clinical experience. Radiology 186: 147152, 1993. 8. Galanski M, Prokop M, Chavan A, Schaefer CM, and Nschelsky JE: Spiral volumetric CT as a new screening tool for renal artery stenosis. Radiology 185: 181, 1992. 9. Schwartz RB, Jones KM, Chernoff DM, Mukherji SK, Khorasani R, Tice HM, Kikinis R, Hooton SM, Stieg PE, and Polak JF: Common carotid artery bifurcation: evaluation with spiral CT. Radiology 185: 513-519, 1992. 10. Vannier MW, Marsh JL, and Warren JO: Three dimensional CT reconstruction images for craniofacial surgical planning and evaluation. Radiology 150: 179-184, 1994. 11. Ney DR, Fishman EK, Kawashima A, Robertson DD Jr, and Scott WW: Comparison of helical and spiral CT with regard to three-dimension imaging of musculoskeletal anatomy. Radiology 185: 865-869, 1992. 12. Zeman RK, Fox SH, Silverman PM, Davros WJ, Carter LM, Griego D, Weltman DI, Ascher SM, and Cooper CJ: Helical (spiral) CT of the abdomen. Am J Roentgen01 160: 719725, 1993. 13. Wyatt SH, Urban BA, and Fishman EK: Spiral CT of the kidneys: role in characterization of renal disease. Part I: nonneoplastic disease. Crit Rev Diagn Imaging 36: l-37, 1995. 14. Foley WD: Dynamic hepatic CT. Radiology 170: 617622, 1989. 15. Dupuy DE, Costello P, and Ecker CP: Spiral CT of the pancreas. Radiology 183: 815-818, 1992. 16. Costello P, Anderson W, and Blume D: Pulmonary nodule: evaluation with spiral volumetric CT. Radiology 179: 875-876, 1991.

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the kidneys with spiral CT: a potential surgical planning tool. Radiology 185: 136, 1992. 27. Silverman SG, Seltzer SE, Adams DF, Tumeh SS, Allegra DP, and Mellins HZ: Spiral CT of the small indeterminate renal mass: results in 48 patients. Radiology 181: 125, 1991. 28. Remy-Jardin M, Remy J, Wattinne L, and Giraud F: Central pulmonary thromboembolism: diagnosis with spiral volumetric CT with single-breath-hold technique-comparison with pulmonary angiography. Radiology 185: 381-387, 1992. 29. Costello P, Ecker CP, Tello R, and Hartnell GG: Assessment of the thoracic aorta by spiral CT. AJR Am J Roentgenol 158: 1127-1130, 1992. 30. Scott WW Jr, Fishman EK, and Magid D: Acetabular fractures: optimal imaging. Radiology 165: 537-539, 1987. 31. Quillin SP, Brink JA, and Nakada SY: Detection of crossing vessels at the ureteropelvic junction with spiral CT angiography (abstract). J Urol 153(suppl): 367a, 1995. 32. Lam HS, Lingeman JE, Russo R, and Chua GT: Stone surface area determination techniques: a unifying concept of staghorn stone burden assessment. J Urol 148: 1026-1029, 1992. 33. Griffith DP, and Valiquette L: PICA/burden: a staging system for upper tract urinary stones. J Ural 138: 253-257, 1987. 34. Rocco F, Mandressi A, and Larcher P: Surgical classification of renal calculi. Eur Ural 10: 121-123, 1984.

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