Comparison of Renal Toxicity after Injection of CT Contrast Medium and MR Contrast Medium: Change of Renal Function in Acute Renal Failure Rat Models

PURPOSE: To determine renal toxicity through changes in renal function after the injection of CT and MRI contrast media into rats in which acute renal failure (ARF) was induced. MATERIALS AND METHODS: To cause acute renal failure, the abdominal cavity of 110 male rats each weighing 250-300 gm was opened via a midline incision under anesthesia. Microvascular clamps were placed on both renal arteries and veins to completely block renal blood flow for 45 minutes, and were then removed, allowing blood flow to return to the kidneys. ARF, defined as a two-fold difference in the creatinine level before ARF and 48 hours after, was successfully induced in 60 of the rats. These were divided into two groups: one was injected with CT contrast medium and the other with MRI contrast medium. Each CT and MRI group was divided into a low dose (0.5 cc/kg, 0.2 ml/kg), standard dose (2 cc/kg, 0.8 ml/kg), and high dose (8 cc/kg, 3.2 ml/kg) sub-group; thus, there was a total of six groups with ten rats in each. Blood samples were obtained before ARF, 48 hours after, and 48 hours after contrast injection, and CT scanning and MRI were performed after blood sampling at 48 hours. In each group, creatinine levels 48 hours after contrast injection were compared by means of the ANOVA test. RESULTS: There were no significant differences in creatinine levels between the CT and MRI contrast medium groups (p=0.116), nor between the animals to which different doses of CT and MRI contrast medium, were administered. After both standard and high doses, CT and MRI provided good images. CONCLUSION: In rats in which acute renal failure was induced, renal function did not change according to whether CT or MRI contrast medium was injected. Thus, the two media induce similar levels of toxicity.

Contrast-Enhanced Three-Dimensional MR Imaging Using a Volumetric Interpolated Breath-hold Examination (VIBE): Clinical Utility in the Evaluation of Renal Tumors

PURPOSE: To compare, in terms of technical feasibility, image quality and clinical efficacy, contrast-enhanced three-dimensional (3D) MR imaging using volumetric interpolated breath-hold examination (VIBE) with twodimensional gradient-echo MR imaging for the evaluation of renal masses. MATERIALS AND METHODS: Twenty-three patients with 25 renal masses underwent dynamic MR imaging using a 1.5-T MR system and the 3D VIBE, 2D fast low angle shot (FLASH), and combined fat saturation techniques after the injection of 20 ml of Gd-DTPA. We compared postcontrast 2D FLASH and 3D VIBE images with precontrast 2D FLASH images. For quantitative analysis, the signal-to-noise and lesion to kidney contrast-to-noise ratio of the images were calculated using the three different techniques. For qualitative analysis, two experienced radiologists analyzed the images in terms of artifacts, lesion conspicuity and delineation, and general image quality. Delineation of the anatomy of renal vasculature and pelvocalyceal systems on reconstructed 3D VIBE MIP images was also assessed. RESULTS: Quantitative analysis showed that the SNR of a renal mass was slightly higher at postcontrast 2D FLASH than at 3D VIBE imaging, and the SNR of renal cortex was higher at 3D VIBE than at postcontrast 2D FLASH imaging. The differences were, though, statistically insignificant (p>0.05). The CNR of a renal mass was, however, significantly higher at 3D VIBE than at 2D FLASH imaging (p<0.05). Qualitative analysis showed that general image quality was best at postcontrast 3D VIBE, followed by 2D FLASH and precontrast 2D FLASH imaging, and image artifacts were worst at post-contrast 2D FLASH image (p<0.05). In terms of lesion conspicuity and delineation, 3D VIBE gave the best results and postcontrast images were better than precontrast (p<0.05). Reconstructed angiographic and urographic images using the VIBE technique provided information about the anatomy of the renal vasculature and pelvocalyceal system. CONCLUSION: 3D VIBE MR imaging offers comparable or superior image quality to 2D FLASH, and because it can provide angiograms and urograms may be more useful in the staging work-up of renal malignancies.

Calcified Mesoblastic Nephroma in an Adult: A Case Report

Mesoblastic nephroma is an uncommon renal tumor reported in infants but rarely in adults. We describe a case of calcified mesoblastic nephroma occurring in an adult. It is difficult, on the basis of radiologic images, to differentiate between calcified mesoblastic nephroma and calcified renal cell carcinoma.

What is the Best MR Sequence to Evaluate

PURPOSE: To determine the best MR sequence for evaluation of the anatomical structures of normal kidney. MATERIALS AND METHODS: Twenty normal volunteers (M:F=15:5) took part in this study, and for each, seven sequences were performed. The T1 weighted sequences were conventional spin echo T1 (Conv-SET1), turbo spin echo T1 (TSET1), and fast low angle shot (FLASH), while the T2 weighted sequences were turbo spin echo T2 (TSET2), half-Fourier acquisition single-shot turbo spin echo (HASTE), true-fast imaging with steady-state precession (True-FISP), and echoplanar imaging (EPI). The study involved quantitative and qualitative analysis. In quantitative analysis, CNRs between cortex and adjacent fat tissue, and between cortex and medulla were calculated from SNR (signal to noise ratio), and the CNRs of sequences were statistically compared. In quantative analysis, three radiologists collectively evaluated kidney outline, corticomedullary division, the renal vessels, the pelvis/ureter, and artifacts. For each sequence a grade was assigned, and for each parameter the grades were compared. RESULTS: Between cortex and adjacent fat, the highest CNR was shown by TSET1, followed by Conv-SET1,while among T2 sequences, the CNR shown by TSET2 was highest. Between cortex and medulla, the CNR demonstrated by the three T1 sequences showed no statistically significant difference. Among T2 sequences, however, HASTE showed the highest CNR, followed by EPI, and statistically, the findings for these two were significantly different from those of other T2 sequences. Among T1 sequences, FLASH provided the best kidney outline, though among T2-sequences there was no statistically significant difference. FLASH was also the best for cortico-medullary distinction, while for this purpose the best T2 sequence was HASTE. True-FISP was best for the evaluation of renal vessels, and HASTE for evaluating the pelvis and ureter. Artifacts were most prominent on Conv SET1. CONCLUSION: For evaluating the shape of the kidney, the best T2 sequence was TSET2, but the best T1 sequence could not be determined. For cortico-medullary differentiation, the best T1 sequence was FLASH and the best T2 sequence was HASTE. For the evaluation of renal vessels, True-FISP was best, and for the pelvis and ureter, HASTE. Artifacts were most prominent on Conv-SET1.

Magnetic Resonance Voiding Cystography in the Diagnosis of Vesicoureteral Reflux: Comparative Study with Voiding Cystourethrography

PURPOSE: To evaluate the availability of magnetic resonance (MR) voiding cystography for the diagnosis of vesicoureteral reflux (VUR) and to compare the sensitivity of MR voiding cystography (MRVC) with that of radiographic voiding cystourethrography (VCUG) in the detection of VUR. MATERIALS AND METHODS: MRVC was performed upon 20 children referred for investigation of VUR. Either coronal T1-weighted spin-echo or spoiled gradient-echo images were obtained before and after transurethral administration of a mixture of normal saline and gadopentetate dimeglumine, and immediately after voiding. The findings of MRVC were compared with those of VCUG performed within 6 months of MRVC. RESULTS: VUR was detected in 23 ureterorenal units (16 VUR's by both methods, five VUR's by VCUG, and two VUR's by MRVC). The sensitivity of VCUG and MRVC in detecting VUR was 91.3% (21/23) and 78.3% (18/23), respectively. MRVC detected renal scarring in 15 out of 17 kidneys with scintigraphically detected renal scarring. CONCLUSION: Although MRVC is slightly less sensitive than VCUG in the detection of VUR, it can be used for the diagnosis of VUR and renal scarring simultaneously, and thus will reduce the radiation hazard.

Effectiveness of MR Urography in the Evaluation of Kidney which Failed to Opacify during Excretory Urography: Comparison with Ultrasonography

OBJECTIVE: The purpose of this study was to compare the effectiveness of MR urography (MRU) with that of ultrasonography (US) in the evaluation of urinary tract when this failed to opacify during excretory urography (EXU). MATERIALS AND METHODS: Twelve urinary tracts in 11 patients were studied. In each case, during EXU, the urinary system failed to opacify within one hour of the injection of contrast media, and US revealed dilatation of the pelvocalyceal syytem. Patients underwent MRU, using a HASTE sequence with the breath-hold technique; multi-slice acquisition was then performed, and the images were reconstructed using maximal intensity projection. Each set of images was evaluated by three radiologists to determine the presence, level, and cause of urinary tract obstruction. RESULTS: Obstruction was present in all twelve cases, and in all of these, MRU accurately demonstrated its level. In this respect, however, US was successful in only ten. The cause of obstruction was determined by MRU in eight cases, but by US in only six. In all of these six, MRU also successfully demonstrated the cause. CONCLUSION: MRU is an effective modality for evaluation of the urinary tract when this fails to opacify during EXU, and appears to be superior to US in demon-strating the level and cause of obstruction.

Excretory MR Urography Using Breathhold Three-dimensional FISP: Comparison with MR Urography Using HASTE Technique

PURPOSE: To compare the usefulness of gadolinium-enhanced excretory MR urography using breath-hold three-dimensional fast imaging with steady state precession (3-D FISP) with conventional MR urography using the half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequence in the evaluation of obstructive uropathy. MATERIALS AND METHODS: Twenty-three patients in whom ultrasonography (US) and/or intravenous urography(IVU) revealed signs of urinary obstruction were enrolled in this study. Fifteen were men and eight were women, and their mean age was 54 (range, 21 -80) years. All MR images were obtained using a 1.5-T MR unit. MR urography using the HASTE technique (MRU) and gadolinium-enhanced excretory MR urography using the 3D-FISP technique were performed, and in all cases, reconstructions involved maximum intensity projection. For contrast-enhanced MR urography (CEMRU), images were obtained 3, 5, 20, and 30 minutes after the administration of intravenous contrast media, and for selected cases, additional images were obtained until 24 hours after contrast media injection. For qualitative analysis, two experienced radiologists compared CEMRU and MRU in terms of their diagnostic value as regards the level and cause of urinary obstruction, and morphologic accuracy. In addition, signal to noise ratio (SNR) and contrast to noise ratio (CNR) of the urinary tract at each anatomic level were quantitatively analysed. RESULTS: Quantitative analysis showed that in terms of SNR and CNR of the urinary tract at the level of the mid and distal ureter, CEMRU using 3-D FISP was better than MRU using HASTE (p<0.05). Qualitative analysis indicated that for the depiction of the whole length of normal ureter, and detection of the level of obstruction, anatomic anomalies and intrinsic tumors, 3-D FISP was superior to HASTE. There was, however, no difference between these two modalities in the diagnosis of ureteral stone and the degree of hydronephrosis. In addition, 3-D FISP was better than HASTE for the assessment of filling defect, but the difference was not statistically significant. CONCLUSION: Breath hold 3-D FISP is a very valuable tool in the evaluation of obstructive uropathy. It not only depicts very clearly the anatomy of the urinary tract system, but also provides qualitative information on renal function. We believe that CEMRU using 3-D FISP is a valuable diagnostic approach which can be added to those already available for the workup of obstructive uropathy.

Gadolinium-enhanced Excretory MR Urography: Comparison with MR Urography Using HASTE Technique

PURPOSE: To compare the feasibility of gadolinium-enhanced excretory MR urography(GEMRU) and conven-tional MR urography using the half-Fourier acquisition single-shot turbo spin-echo(HASTE) sequence in pa-tients with hydronephrosis or non-visualized kidney. MATERIALS AND METHODS: Fifteen patients with hydronephrosis or non-visualized kidney, as demonstrated by ul-trasonography or intravenous urography, were enrolled in this study. Nine were men and six were women, and their age ranged from 18 to 77 (mean, 60.6) years. For all MR examinations, a 1.5-T MR unit was employed. For breath-hold MR urography, the HASTE technique(MRU) was used, and reconstruction involved the use of a maximum intensity-projection (MIP) algorithm. For gadolinium-enhanced excretory MR urography, the fast low angle shot(FLASH) 3-D method was used and images were obtained at 5, 10, 20, and 30 minutes, and recon-struction again involved the use of an MIP algorithm. In some cases, additional GEMRU was obtained 24 hours after contrast material injection, and an MIP algorithm was used for reconstruction. MRU and GEMRU were independently interpreted by two radiologists who for quantitative analysis compared SNR with CNR, and at each anatomic level qualitatively analysed morphologic accuracy and diagnostic value of the lesions. RESULTS: In quantitative analysis, SNR and CNR differences between the two sequences at the renal pelvis and the level of the ureter were not significant (p>0.05). In qualitative analysis, GEMRU was superior to M-RU for the assessment of evaluated ureter at each level(p<0.05), anatomic anomaly and intrinsic tumor. Ureteral stones, however, were more easily diagnosed with MRU. CONCLUSION: For assessment of the ureter GEMRU is superior to MRU and has the advantage of evaluating renal function. We believe that for evaluation of the urinary tract, especially the distal ureter, GEMRU may be a valuable adjunct to routine MR urography.

A Comparative Study of MRI Findings of Experimentally Induced Rapid Progressive Glomerulonephritis (RPGN) and Acute Tubular Necrosis (ATN) in Rabbits

PURPOSE: To evaluate the usefulness of MR imaging in the differential diagnosis of the underlying causes of early-stage acute renal failure (ARF) by comparing the MRI findings of experimentally-induced crescentic glomerulonephritis (CGN) and acute tubular necrosis (ATN) in rabbits. MATERIALS AND METHODS: Experimental CGN was induced by injecting anti-glomerular basement membrane antibody into six rabbits, and ATN by injecting glycerol solution into six rabbits. A normal control group of three rabbits was also used. Renal MR imaging (T1-and T2-weighted coronal images and dynamic MRI : DMRI) was performed the day before, and one, four, and seven days after the induction of CGN; and immediately before, and four, and eight hours, and one, four, and seven days after the induction of ATN. Sequential renal gun-biopsies and blood sampling (serum creatinine, sCr) were performed. Renal area, corticomedullary differentiation(CMD), and the passage of Gd-DTPA (pattern of dark band), as seen on MRI, were analyzed and correlated with serial change of sCr. RESULTS: In normal kidneys, CMD was clearly apparent on both T1- and T2-weighted images. DMRI demonstrated a progressively inwardly migrating dark band in the kidneys. CMD was relatively clearly demonstrated in the ATN group but less clearly identified in the CGN group. Renal size (area) and sCr gradually increased in both the CGN and ATN groups, and dark bands were moderately to poorly defined in both. CONCLUSION: We conclude that DMRI could be used to differentiate and evaluate disease processing and compromised renal function in cases of CGN and ATN. On T1- and T2-weighted images, CMD was relatively well preserved in the ATN group, but was less clear in the CGN group. These MRI findings may be helpful for differentiation of the underlying causes of early-stage ARF, particularly between CGN and ATN.

MR Imaging Findings of Renal Infarction Induced by Renal Artery Ligation in Rabbits: The Usefulness of Diffusion-weighted Imaging

PURPOSE: To assess the usefulness of diffusion-weighted imaging(DWI) in evaluating serial parenchymal changesin renal infarction induced by renal artery ligation, by comparing this with the conventional spin echo techniqueand correlating the results with the histopathological findings. MATERIALS AND METHODS: In 22 rabbits, renalinfarction was induced by ligation of the renal artery. Spin-echo T1-weighted imaging(T1WI), turbo spin-echo(TSE)T2-weighted imaging(T2WI), and DWI were performed, using a 1.5-T superconductive unit, at 30 minutes, 1 hour, 2,3, 6, 12 and 24 hours, and 2, 3, 7 and 20 days after left renal artery ligation. Changes in signal intensity onT1WI, T2WI, and DWI were correlated with histopathologic findings. RESULTS: On MR images obtained 30 minutesafter ligation, the signal intensity of affected kidney was not significantly different from that of contralateralkidney, as seen on T1WI and T2WI, but was noticeably higher on DWI. On T2WI, the signal intensity ratio(SIR) wasslightly higher over time from 30 minutes to 2 days after ligation, and then decreased slightly. The SIR on DWIincreased abruptly at 30 minutes, remained high until 12 hours, and then fell, returning to close to the normalrange at between 2 and 3 days. It fell further, below the normal range, until 20 days after ligation. The mainhistopathologic findings after ligation were congestion and swelling of renal tubules (1-6 hours after ligation),degeneration and necrosis of renal tubules (12 hours - 2 days), coagulation necrosis of renal tubules(3 days),collection of cellular debris between renal tubules (7 days), and proliferation of fibroblast between renaltubules (20 days). CONCLUSION: Diffusion-weighted imaging is useful for the detection of hyperacute renalinfarction, and the apparent diffusion coefficient may provide additional information concerning its evolution.

Gd-DTPA Enhanced Dynamic Renal MR Imaging of Experimentally

PURPOSE: The purpose of this study was to evaluate the utility of Gd-DTPA-enhanced dynamic MRI (DMRI) in earlydiagnosis and the assessment of disease processing in experimentally-induced crescentic glomerulonephritis (CGN)in rabbits. MATERIALS AND METHODS: In six rabbits, CGN was induced by an injection of anti-glomerular basementmembrane Ab. A time-signal intensity curve (TSC) was obtained from DMRI on the day before, and at 1, 4, 7, 15, 45and 113 days after the induction of CGN. Sequential renal biopsies and blood sampling (serum creatinine) wereperformed on the same days, and the results of DMRI and TSC, were compared. RESULTS: In normal kidneys, sequentialDMRI demonstrated the intratubular passage of Gd-DTPA as an inwardly migrating, thin, dark, band pattern. On days1 and 4, the thin dark band appeared but was poorly defined and TSC revealed a delay in peak time. On days 7 and15, movement of the band was seen to be weak and slow, and there was no centripetal migration. The maximal signalintensity of TSC was delayed, and the curves declined very slowly. On days 45 and 113, the dark band pattern wasvery weak and slow, and again there was no centripetal migration. CONCLUSION: GD-DTPA-enhanced DMRI may be ofvalue in the evaluation of disease processing and the severity of CGN.

Effect of Gd-DTPA on Kidneys of the Rats with Acute Renal Failure

PURPOSE: To evaluate the nephrotoxicity of Gd-DTPA in rats with normal renal function and in those with acute renal failure, using 0.1mmol/kg and 0.3mmol/kg in each group. MATERIALS AND METHODS: Sixty rats weighing 200-250gm were divided into two groups: normal (N) and glycerol induced acute renal failure (F) ; this was inducedby intramuscular injection of 50% glycerol(10ml/kg). Each group was divided into three subgroups; subgroup 1 was given physiologic saline (0.15 M NaCl) via the tail vein, while subgroups 2 and 3 were given 0.1 mmol/kg Gd-DTPAand 0.3mmol/kg Gd-DTPA, respectively. Blood and 24-hour urine were collected before and on the first and secondday after intravenous injection of either physiologic saline or Gd-DTPA. In order to obtain pathologic specimens, two additional rats in each group underwent the same experimental procedure, and on the first or second day after intravenous injection of saline or Gd-DTPA, both kidneys were removed for light microscopic examination. Serum creatinine (Cr), urine creatinine, and several urinary enzymes such as alkaline phosphatase (ALP), gammaglutamyl transferase (GGT), N-acetyl-Beta-glucosaminidase (Beta-NAG) and lactic dehydrogenase (LDH) of 24 hour urine were measured, and creatinine clearance (Ccr) was calculated. RESULTS: The results were as follows. 1. In the groupwith normal renal function, levels of serum creatinine and urinary enzymes remained unchanged after infusion of 0.1mmol/kg Gd-DTPA or 0.3mmol/kg Gd-DTPA. 2. Among rats with acute renal failure, no difference in serum creatinine and urinary enzyme levels between the saline injection group and 0.1mmol/kg Gd-DTPA injection group was noted. 3. Among rats with acute uremia, Beta-NAG, LDH and ALP were significantly higher on post-injection days 1 and 2 in the 0.3mmol/kg Gd-DTPA injection group than in the physiologic saline or 0.1mmol/kg Gd-DTPA injection group.4. Light microscopic exammination of rats with normal renal function after Gd-DTPA injection revealed no significant pathologic change. Those with acute renal failure rats revealed some degree of vacuolization and/or necrosis of renal proximal tubular epithelial cells. No difference was found, however, between the saline and Gd-DTPA injection subgroups. CONCLUSION: In conclusion, Gd-DTPA was safe in rats with normal renal function, even when the dose was tripled (0.3mmol/kg), and was safe in those with acute renal failure when the standard dose (0.1mmol/kg) was given. In this latter group, however, a triple dose induced some renal damage.

Fused Cake Kidney Combined with Hypoplastic Thumb: A Case Report

During embryologic development, many renal anomalies, including fusion and ectopia, can occur. Among them, fused cake kidney is a rare developmental anomaly. We report a case in which this condition was combined with hypoplastic thumb. Ultrasonographic, scintigraphic, CT and MRI findings of this rare condition are presented.