Multidetector CT Urography with Abdominal Compression and Three-Dimensional Reconstruction

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1 Pictorial Essay Multidetector T Urography with bdominal ompression and Three-imensional Reconstruction ownloaded from by on 04/28/18 from IP address opyright RRS. For personal use only; all rights reserved P ainless hematuria is one of the most important warning signs of urologic malignancy, and whereas its causes are numerous, including benign entities, more ominous diagnoses must be excluded by urologic and radiologic evaluation. With the development of helical and, more recently, multidetector T, unenhanced T has largely replaced excretory urography in the evaluation of patients presenting with possible renal colic. Fig year-old man, otherwise healthy, with 1-week history of gross hematuria while on considerable dose of nonsteroidal antiinflammatory medication., Scout image from T scan with abdominal compression shows normal findings on bilateral nephrograms and good distention of collecting systems, despite balloon being slightly off center. This image provides overview of genitourinary tract similar to traditional excretory urogram., Scout image from T scan after release of compression shows opacification of ureters., Twenty-millimeter-thick maximum-intensity-projection T image through both kidneys and proximal ureters from enhanced T data with compression shows distention and opacification of collecting systems. alices, fornices, infundibula, and renal pelves are shown. Slight kinking of proximal ureter of no clinical significance can be seen on right., ouble-oblique maximum-intensity-projection T image shows right kidney in plane that is truly coronal to kidney rather than to patient. Lawrence. how 1 and F. Graham Sommer In most institutions, however, excretory urography remains the mainstay in evaluating patients who present with painless hematuria. Multidetector T is ideally suited for dynamic multiphase scans and allows the acquisition of Received February 6, 2001; accepted after revision pril 24, oth authors: epartment of Radiology, Stanford University Medical enter, 300 Pasteur r., Rm. H1307, Stanford, ddress correspondence to L.. how. JR 2001;177: X/01/ merican Roentgen Ray Society JR:177, October

2 how and Sommer ownloaded from by on 04/28/18 from IP address opyright RRS. For personal use only; all rights reserved isotropic or near-isotropic image data sets, making true multiplanar reconstruction of T data a reality. These attributes, in conjunction with the traditional strengths of T in the imaging of the renal parenchyma, make multidetector T well suited for evaluation of patients with hematuria and provide a single examination capable of imaging both the renal parenchyma and collecting systems. t our institution, T urography has virtually replaced conventional excretory urography in the evaluation of patients with hematuria and has proven successful in depicting a wide range of disease affecting the urinary tract. Technique of ata cquisition and Postprocessing T urography is performed with a Light- Speed T scanner (General Electric Medical Fig year-old woman being evaluated for episodic asymptomatic gross hematuria. Maximum-intensity-projection T image generated from postcompression-release T data shows exquisite detail of normal distal ureters bilaterally. Note ureteral jets and cloudlike appearance of contrast agent mixing with urine in bladder. Systems, Milwaukee, WI) and the following protocol: scans are obtained in three phases unenhanced, enhanced with abdominal compression, and postrelease. Initial unenhanced images are obtained from the diaphragm to the symphysis pubis with 5-mm collimation and 2.5-mm reconstruction interval. Subsequently, a 40-mL bolus of Omnipaque 300 (Nycomed-mersham, Princeton, NJ) is administered at 2 ml/sec via an antecubital IV with an Envision T power injector (Medrad, Indianola, P), and abdominal compression is applied. fter a 2-min delay, the remaining 80 ml of contrast agent is administered at an injection rate of 2 ml/sec. T scans are obtained after a 90-sec delay from the diaphragm to the iliac crests with 2.5-mm collimation and a 1.25-mm reconstruction interval. scout image is then obtained of the abdomen and pelvis. ompression is released, and a T scan is immediately obtained from the iliac crests to the symphysis pubis with 2.5-mm collimation and 1.25-mm interval. final scout image of the abdomen and pelvis is then obtained. ll T images are obtained helically in HiSpeed mode (pitch, 6:0). Three-dimensional (3) reconstruction of the data includes both thin- and thick-slab maximum-intensity-projection images. Slid- Fig year-old man being evaluated for possible mass seen in left kidney on sonogram at another institution. and, Maximum-intensity-projection () and average-projection () T images of left kidney generated from same contrast-enhanced T with compression show duplication of collecting system and ureters. verage-projection T image () is more conventional in appearance, resulting from summation of overlapping structures, but at cost of contrast resolution between opacified collecting system and adjacent structures., Maximum-intensity-projection T image of duplicated distal left ureters shows orthotopic insertion of both ureters into bladder. Vascular calcification is incidentally seen. 850 JR:177, October 2001

3 Multidetector T Urography ownloaded from by on 04/28/18 from IP address opyright RRS. For personal use only; all rights reserved ing thin-slab (5-mm) maximum-intensityprojection coronal oblique images in a plane as en face to the kidney as possible are generated from both unenhanced and enhanced data for each kidney individually. dditionally, anteroposterior thick-slab (35 50 mm) maximum-intensity-projection images are generated of the kidneys individually and collectively from the enhanced compression data. Finally, a maximum-intensity-projection image of the distal ureters and urinary bladder from the third phase is generated. dditional maximum-intensity-projection, minimum-intensity-projection, average-projection, and curved planar reformation images are generated on an individual as-needed basis. ll 3 reconstructions are generated on an dvantage Windows 3.1 dedicated workstation (General Electric Medical Systems). Final image adjustment is performed with Photoraw 1.0 image software (Microsoft, Redmond, W). Fig year-old boy with hematuria. Right renal lesion was identified at another institution, and he was referred for further evaluation., Longitudinal sonogram of right kidney from another institution shows 1.3-cm mildly complex nearly anechoic upper pole structure (arrows ) with acoustic enhancement and slight irregularity of its margins., Unenhanced T scan from another institution shows fluid-attenuation (8 H) structure (arrow) in upper pole of right kidney., ontrast-enhanced T scan from another institution shows enhancement of this structure (arrow, and ) to 39 H, suggesting that it is solid in nature., elayed image from repeated contrast-enhanced T scan at our institution shows dependent layering contrast agent (arrow) in this structure (), implying communication with collecting system and showing that it is not solid. E, ouble-oblique maximum-intensity-projection T image of right kidney shows that communication with E upper pole collecting system is now clearly visible (arrow ). aliceal diverticula are narrow-necked outpouchings of renal collecting system ranging in size from few millimeters to several centimeters, which most commonly arise from fornix. Normal natomy The benefit of T urography is its ability to depict the normal urinary tract anatomy, including both the renal parenchyma and the collecting structures and ureters. Unenhanced images are obtained to evaluate the presence of calcifications and to allow determination of unenhanced attenuation values for any focal lesions in the kidneys. To simplify the procedure and to reduce the number of phases necessary, a splitbolus technique of contrast administration is used, resulting in scanning during a simultaneous nephrographic and excretory phase. Nephrographic and excretory phase images have previously been shown to be superior to corticomedullary phase images in the detection and characterization of renal masses [1]. With abdominal compression, good contrast distention of the collecting system can be achieved that is comparable to or superior to that of conventional excretory urography [2, 3] (Figs. 1 and 2). Three-dimensional reformation of T data in the coronal plane provides a more familiar representation of the collecting system, showing the calices, fornices, infundibula, renal pelvis, and ureters in continuity. To our knowledge, in at least one study, 3 reformatted images have been shown to be acceptable alternatives to or preferable to conventional excretory urography images when judged by experienced urologists [2]. nomalies and bnormalities ecause T urography can image both the renal parenchyma and urothelium, a wide range of disease can be identified. In our experience, T urography has been successful in clearly depicting anatomic variants, stone disease, inflammatory processes, and benign and malignant neoplasms. s with traditional T, congenital anomalies of renal position, number, and form are easily ap- JR:177, October

4 how and Sommer ownloaded from by on 04/28/18 from IP address opyright RRS. For personal use only; all rights reserved preciated with T urography. uplications of the collecting system, however, are more difficult to appreciate on conventional T and can easily be missed because opacification of the ureters is usually incomplete. Furthermore, the findings of a duplicated system are more obvious on a single coronal image that depicts the collecting system in its entirety (Fig. 3). lthough duplications of the collecting system are relatively rare, with an autopsy incidence of partial duplications in one in 150 cases and complete duplications, one in 500 cases [4], knowledge of the presence of a duplication before a procedure or intervention is invaluable to the urologist. Similarly, coronally reformatted T urograms can provide good delineation of a caliceal diverticulum and show its communication with the collecting system (Figs. 4 and 5). lthough urinary tract stone disease generally presents with a classic clinical scenario of colicky flank pain and hematuria, for which the appropriate initial and often only imaging Fig year-old man with microhematuria. Patient is on warfarin sodium for atrial fibrillation., onventional radiographic tomogram shows no abnormal calcifications., Tomogram from excretory urography shows round contrast-filled structure in upper pole of left kidney that contains round filling defect (arrow) not seen on unenhanced image, consistent with radiolucent stone. and, Maximum-intensity-projection images from T scans before () and after () contrast administration show to better advantage upper pole caliceal diverticulum, containing calculus (arrow, ). Two smaller calculi are also seen in interpolar region. Most commonly, caliceal diverticula are asymptomatic, but because of urinary stasis, complications can include both infection and formation of stones, which may become entrapped in diverticula. evaluation required is unenhanced helical T, T urography can be useful in the evaluation of chronic stone disease by providing information regarding the number and size of calculi and their relationship to and effect on the collecting system (Figs. 5 7). Various infectious and noninfectious inflammatory entities can result in hematuria. lthough imaging is usually not indicated in acute bacterial pyelonephritis or cystitis, T urography could be helpful in the evaluation of 852 JR:177, October 2001

5 Multidetector T Urography ownloaded from by on 04/28/18 from IP address opyright RRS. For personal use only; all rights reserved more chronic infectious processes such as renal tuberculosis, chronic pyelonephritis, and xanthogranulomatous pyelonephritis (Fig. 7), in which long-term sequelae involve both renal parenchyma and the collecting system. Malignancy of both the urothelium and the renal parenchyma may present with hematuria. pproximately 7 8% of renal malignancies develop in the collecting system. Transitional cell carcinoma most commonly presents as an intraluminal filling defect or with obstruction (Fig. 8), in which case renal function may be inadequate to allow visualization with excretory urography. In any patient in whom transitional cell carcinoma is suspected, the entire urothelium must be examined because of the multicentric nature of the tumor. In the bladder, cystoscopy provides the most direct and most thorough examination. The renal collecting systems and ureters, however, have traditionally been examined by excretory urography. T urography allows reconstruction of images in any plane at user-definable slice thicknesses. Maximum-intensity-projection T images provide superior contrast resolution in visualizing the opacified collecting structures. Hematuria is the most common sign of renal adenocarcinoma, occurring in more than Fig year-old woman with one episode of crampy lower abdominal pain and gross hematuria 1 month earlier. Sonogram (not shown) at another institution revealed hydronephrosis but no definite stone. Patient is now asymptomatic but with persistent microhematuria., Twelve-millimeter-thick double-oblique minimum-intensity-projection T image of right kidney shows moderate hydronephrosis (asterisk) well. Small simple cyst (arrow) is incidentally seen in upper pole., Maximum-intensity-projection T image of distal ureters from postrelease T scan shows normal course and caliber of distal left ureter but no opacification of right ureter. alculus (arrow) is identified along course of distal right ureter., urved planar reformation of right kidney and ureter from enhanced T shows moderate hydroureteronephrosis resulting from obstructing calculus (arrow) in distal ureter. elay in contrast excretion from right kidney is evident. In this patient, T urography provided efficient complete examination of obstructed right urinary tract, obviating serial follow-up images over ensuing hours, which would have been necessary with conventional excretory urography. half of patients [4]. Excretory urography is an insensitive test for the detection of small renal neoplasms [5, 6], and T can detect a substantial number of renal parenchymal masses missed by excretory urography [7]. T urography provides information similar to conventional T in the assessment of renal masses (Figs. 9 and 10). Unenhanced images ensure evaluation of the enhancement characteristics of solid renal lesions, and coronal reformatted images are useful in visualizing the relationships of renal lesions with adjacent anatomy and as an aid to surgical planning. Future irections Whereas T urography can clearly provide exquisite depiction of the kidneys, collecting systems, and ureters, it is an evolving technique and, like all new strategies, is subject to controversy. The optimal method is still subject to debate, and as many different protocols are probably being used as there are institutions that perform T urography. Several concepts remain universally important, however, despite the specific protocol being used. Evaluation of the collecting system requires abdominal compression to achieve adequate distention. dditionally, it is important to interpret the images with different window and level settings appropriate for the target structure being examined. This interpretation is particularly relevant in evaluating the collecting system because small filling defects or urothelial lesions can be obscured by dense intraluminal contrast agents. Furthermore, despite the usefulness and simplicity of 3 reformatted images, careful interpretation of the axial source images remains imperative. lthough it seems evident, in theory, that T urography would be an ideal method to study patients with hematuria, its ability to detect disease has not yet been proven by prospective studies. ritics would argue that T still lacks the spatial resolution of conventional radiography, and although this argument is true, recent advances in multidetector T technology now allow section thicknesses as narrow as 0.5 mm. dditionally, forthcoming advances hold promise for improving the information provided by scout images. Perhaps it is premature to dismiss the conventional excretory urogram completely, but we are optimistic about the future of T urography because of the technologic advances and research that are quickly bringing this technique into the mainstream. JR:177, October

6 how and Sommer ownloaded from by on 04/28/18 from IP address opyright RRS. For personal use only; all rights reserved Fig year-old woman with long history of bilateral staghorn renal calculi after multiple percutaneous nephrolithotomy and lithotripsy procedures. and, Maximum-intensity-projection images of left kidney from unenhanced () and enhanced () T scans show that contour of kidney is abnormal, and low-attenuation nonenhancing masses (asterisks) associated with abnormal calcifications are seen in upper pole and interpolar portion. ontrast agent fills dilated lower pole calices (arrows) on enhanced image ()., Three-millimeter thin-slab maximum-intensity-projection T image of left kidney shows contrast agent in dilated calices (asterisks) and three rounded filling defects in upper pole (arrows), corresponding to sloughed papillae in collecting system., Maximum-intensity-projection image of right kidney from contrast-enhanced T scan shows severe hydroureteronephrosis and marked cortical thinning at upper and lower poles (arrows). Overall appearance is consistent with chronic atrophic pyelonephritis. Fig year-old man with 15-year history of interstitial cystitis now with asymptomatic, but persistent, microhematuria. and, Postrelease scout images from T scan () and average-projection image () from contrast-enhanced T scan show mild right hydroureteronephrosis to level of distal ureter, with abrupt termination of contrast column and filling defect (arrows) perceptible., Maximum-intensity-projection T image of distal ureters better depicts circumferential irregular thickening of distal right ureter (arrows), that resulted in obstruction. Surgical specimen yielded high-grade transitional cell carcinoma. 854 JR:177, October 2001

7 Multidetector T Urography ownloaded from by on 04/28/18 from IP address opyright RRS. For personal use only; all rights reserved cknowledgments We thank Laura Logan and Mark Sofilos for their valuable technical expertise and effort in generating the 3 reformatted images shown in this manuscript. References 1. Yuh I, ohan RH. ifferent phases of renal enhancement: role in detecting and characterizing renal masses during helical T. JR 1999;173: Fig year-old man with one episode of gross painless hematuria., oronal maximum-intensity-projection image of right kidney from contrast-enhanced T scan with compression shows no abnormal findings. Two-centimeter exophytic upper pole mass was seen on anterior sliding thin-slab maximum-intensity-projection T images (not shown). ecause of anterior location, small size, and lack of deformity of collecting structures, detection with conventional excretory urography would be unlikely., Sagittal maximum-intensity-projection image of right kidney from same contrast-enhanced T scan shows that 2-cm exophytic mass (arrow) is clearly visible, extending from anterior margin of upper pole. Subsequent resection yielded grade 3 clear cell carcinoma with distinct margins. 2. Heneghan JP, Kim H, Howard MH, Leder R, elong M, Nelson R. ompression T urography: comparison of 3 volume rendered images with IVP in evaluation of the collecting system and ureters, and assessment of clinical acceptability by urologists. (abstr) Radiology 1999; 213(P): McNicholas MM, Raptopoulos V, Schwartz RK, et al. Excretory phase T urography for opacification of the urinary collecting system. JR 1998; 170: unnick NR, Sandler M, mis ES, Newhouse JH. Textbook of uroradiology, 2nd ed. altimore: Fig year-old woman with intermittent left-flank pain. Five-millimeter average-projection image of left kidney generated from contrast-enhanced T data shows well-circumscribed 8-mm fat-attenuation mass (arrow) in upper pole, consistent with benign angiomyolipoma. Williams & Wilkins, 1997:26, emos T, Schiffer M, Love L, Waters W, Moncada R. Normal excretory urography in patients with primary kidney neoplasms. Urol Radiol 1985;7: urry NS, Schabel SI, etsill WL Jr. Small renal neoplasms: diagnostic imaging, pathologic features, and clinical course. Radiology 1986;158: Perlman ES, Rosenfield T, Wexler JS, Glickman MG. T urography in the evaluation of urinary tract disease. J omput ssist Tomogr 1996;20: JR:177, October