Magnetic resonance imaging as a sole method for the morphological and functional evaluation of live kidney donors

Comparison of magnetic resonance imaging with radionuclide methods of evaluating the kidney

Nuclear medicine and MRI provide information about renal perfusion, function (glomerular filtration rate), and drainage. Some tracers that are used in nuclear medicine (technetium-diethylene triamine pentaacetic acid ([(99m)Tc-DTPA] and (51)chromium-EDTA) and some contrast media (CM) that are used for MRI (gadolinium-DTPA for instance) share the same pharmacokinetic properties, though, detection techniques are different (low-spatial resolution 2-dimensional projection with a good concentration-to-signal linearity for nuclear medicine and high-resolution 3-dimensional localization with nonlinear behavior for MRI). Thus, though based on the same principles, the methods are not the same and they provide somewhat different information. Many MRI perfusion studies have been conducted; some of them were compared with nuclear medicine with no good agreement. Phase contrast can reliably assess global renal blood flow but not perfusion at a tissular level. Arterial spin labeling has not proven to be a reliable tool to measure renal perfusion. Techniques using CM theoretically can assess perfusion at the tissular level, but they have not proven to be precise. To assess renal function, many models have been proposed. Some MRI techniques using CM, both semiquantitative (Patlak) and quantitative, have shown ability to roughly assess relative function. Some quantitative methods (Annet's and Lee's methods) have even showed that they could roughly estimate absolute renal function, with better results than estimated glomerular filtration rate. Quantification of drainage has not been much studied using MRI.

Contrast-enhanced magnetic resonance urography at 3T: clinical feasibility

OBJECTIVE

The objective of this study was to assess the feasibility of performing diagnostic-quality contrast-enhanced excretory magnetic resonance urography (eMRU) at 3T, examining both image quality and diagnostic accuracy for a range of urinary tract abnormalities.

METHODS

The diuretic-enhanced 3T eMRUs of 37 patients were reviewed to assess for the diagnostic conspicuity of urinary tract abnormalities, extent of urinary tract visualization on excretory images, and presence and severity of image artifacts.

RESULTS

Excretory images allowed greater than 75% visualization in 90.8% of renal collecting systems, 90.8% of ureters, and 82.3% of bladders. Common artifacts included susceptibility (21.3%), contrast mixing (21.3%), patient motion (20.4%), signal inhomogeneity (19.4%), and peristaltic motion (17.6%). Severe artifacts occurred in 21.6% of studies. Five of 8 urothelial neoplasms were detected, with 1 false-positive lesion in the bladder. Urolithiasis was correctly diagnosed in 7 of 9 patients.

CONCLUSIONS

Although image artifacts can hamper eMRU at 3T, initial results are promising for evaluation of the urothelium.

Multidetector computed tomography with triple-bolus contrast medium administration protocol for preoperative anatomical and functional assessment of potential living renal donors

OBJECTIVE

To evaluate multidetector computed tomography (MDCT) with a triple-bolus contrast administration protocol for preoperative anatomical and functional assessment of living renal donors.

METHODS

Fifty-five potential living renal donors underwent MDCT of which 27 proceeded to donor nephrectomy. A triple-bolus contrast administration protocol was used for simultaneous acquisition of arterial, nephrographic, and excretory phases. MDCT images were independently reviewed in random order by two radiologists blinded to surgical anatomy findings. Diagnostic accuracy for anatomical variants was quantified by sensitivity and specificity. Differential renal function (DRF) was derived from MDCT for 54 patients and compared with technetium-99 m dimercaptosuccinic acid renography (Tc-99 m DMSA).

RESULTS

All triple-bolus MDCT examinations were technically adequate. Accessory renal arteries and veins were identified at surgery in 33% (n = 9/27) and 22% (n = 6/27) of donor kidneys. The mean difference between MDCT-derived DRF and DMSA was 0.8% (95% CI 0.1-1.6) with 95% limits of agreement of -4.6% (95% CI -3.3 to -5.9) to 6.3% (95% CI 5.0-7.6). MDCT delivered a mean (SD, range) radiation dose of 9.5 (3.6, 3.6-17.3) mSv.

CONCLUSION

MDCT with a triple-bolus contrast administration provides accurate anatomical and functional evaluation of living renal donors.

Time-resolved dynamic contrast-enhanced MR urography for the evaluation of ureteral peristalsis: initial experience

PURPOSE

To determine the feasibility of time-resolved dynamic contrast-enhanced magnetic resonance urography (MRU) for the evaluation of ureteral peristalsis using a data-sharing 3D gradient echo sequence with spiral k-space filling.

MATERIALS AND METHODS

Eight patients (M=3, F=5, mean 48.1 years) were referred for MRU for the evaluation for renal mass (n=3), hematuria (n=2), urinary tract tuberculosis (n=1), postoperative bladder cancer (n=1), and postoperative ureteric reimplantation (n=1). Dynamic MRU was performed for 120 seconds at 1.5T after intravenous furosemide and gadolinium administration using an oblique sagittal, time-resolved T1 3D gradient echo sequence with 1 second effective temporal resolution. Study quality was assessed based on artifacts and extent of ureteric visualization. Frequency of peristalsis from the renal pelvis to urinary bladder was evaluated for each subject.

RESULTS

A total of 16 ureters were examined. Image quality was good in four ureters, satisfactory in 11 ureters, and poor in one ureter. Mean peristaltic frequency was 3.5 waves per minute (range, 2.5-6.5 waves/minute) in normal ureters (n=11). Five ureters were considered abnormal (one urinary tract tuberculosis and four postsurgical ureters), and all had decreased or no peristalsis (0-1.5 waves per minute).

CONCLUSION

MRU using a time-resolved, data-sharing 3D contrast-enhanced technique is able to demonstrate ureteral peristalsis and permits quantification of ureteral peristaltic frequency.

Magnetic resonance imaging in the evaluation of pelvi-ureteric junction obstruction: an all-in-one approach

OBJECTIVE

To study the ability of comprehensive magnetic resonance imaging (MRI) to replace multiple imaging methods in the evaluation of patients with pelvi-ureteric junction obstruction (PUJO).

PATIENTS AND METHODS

Between May 2003 and November 2005, 46 consecutive patients (22 male and 24 females; mean age 31.6 years) with symptomatic primary PUJO were included. All had comprehensive MRI, including MR urography (MRU), dynamic MRI and MR angiography (MRA). Morphological results of MRU were compared with that of renal ultrasonography or intravenous urography, while the anatomical results of MRA were compared with the operative findings. A correlation between MR clearance and radioisotope clearance was done using linear regression analysis.

RESULTS

MRU showed the morphology of the collecting system in all patients, and the ureter below the PUJ in 31 of 46 (67%), but renal stones were missed in three of 10 patients. MRA showed crossing vessels in 22 patients (48%). There was a strong correlation between MR clearance and radioisotope clearance (r = 0.823, P < 0.001). From the MRI results, 35 patients (19 with crossing vessels and 16 with marked hydronephrosis) had pyeloplasty and 11 had an endopyelotomy. Findings during pyeloplasty showed one false-negative and one false-positive result of the preoperative MRI. Therefore, the sensitivity, specificity and accuracy of MRA were 95%, 94% and 94%, respectively. The outcome was successful in 44 (96%) patients. One failure after pyeloplasty was managed with endopyelotomy and the other was treated with pyeloplasty after endopyelotomy.

CONCLUSION

Comprehensive MRI is a valuable and accurate single-imaging method for evaluating patients with PUJO.

Renal Effects of Long-Term Ciclosporin A Treatment in a Large Animal Model

BACKGROUND

Most experimental studies of chronic ciclosporin A (CsA) nephrotoxicity have been performed in rodents; however, the pig possesses several advantages. The aim of this study was to investigate renal functional and structural changes during CsA treatment with 20 mg/kg/day for 6 months in a pig model.

METHODS

Gottingen minipigs were randomized to oral CsA treatment or as controls. At 0, 5, 10, 15, 20 and 25 weeks body weight, blood pressure, serum creatinine, and whole blood CsA levels were measured. Magnetic resonance imaging was used to estimate relative glomerular filtration rate (rGFR), renal blood flow (RBF), kidney length and volume. Renal vascular resistance (RVR) was calculated. Kidney tissue biopsies were taken and volume fraction of cortical interstitial tissue estimated by a stereology-based method.

RESULTS

CsA induced significant increases in serum creatinine, blood pressure, RVR, and a significant decrease in RBF. Furthermore, renal volume increased significantly. This finding was inversely related to the decrease in RBF and initially followed by an increase in rGFR, which then decreased. No significant histopathological kidney changes were observed.

CONCLUSION

CsA treatment with 20 mg/kg/day for 6 months causes increased serum creatinine, blood pressure, RVR, and renal volume along with a decrease in RBF in accordance with data obtained in humans. The initial temporal changes in renal volume and function during CsA administration have similarities to the functional changes seen in early diabetes.

Routine Screening for the Functional Asymmetry of Potential Kidney Donors

The functional capacity of each kidney of a healthy donor may change under the influence of genetic and environmental factors. An assumption that the donor kidneys show equal function is not always true. As part of the pre-nephrectomy evaluation of potential donors, radioisotope renal scintigraphy using technetium-99m diethylenetriaminepentaacetic acid (99mTcDTPA) was routinely included to evaluate renal functional asymmetry of undetermined etiology. The functional ratios of each kidney using 99mTcDTPA as well as serum creatinine (Scr) and creatinine clearance (Ccr) in a 24-hour urine were measured and calculated from a hundred donors. The left kidneys showed greater function (51.67%-53.35% under 95% confidence interval [CI]) and the average left versus right ratio was 52.5 versus 47.5. The average fraction of Ccr of left kidneys was 57.8 mL/min/1.73 m +/- 10.99 compared with right kidneys at 52.6 mL/min/1.73 m +/- 11.63. Seventy-three healthy volunteers donated their left kidneys, and 27, their right kidney. The average fraction of Ccr of the donated kidneys was 55.9 mL/min/1.73 m +/- 11.78 compared with that of the remnant kidneys (54.5 mL/min/1.73 m +/- 11.39). After kidney donation, the Scr of the donors increased from 0.85 mg/dL +/- 0.17 to 1.33 mg/dL +/- 0.27. The average postnephrectomy Ccr was 68.0 mL/min/1.73 m +/- 14.29. Even though the Ccr after kidney donation was higher than that of the remnant kidney estimated before the donation, one must pay attention to possible functional kidney asymmetry to select the nephrectomy site.

Magnetic Resonance Urethrography in Comparison to Retrograde Urethrography in Diagnosis of Male Urethral Strictures: Is It Clinically Relevant?

OBJECTIVE

To compare the clinical relevance of retrograde urethrography (RUG) and magnetic resonance (MR) urethrography in evaluating male urethral strictures.

METHODS

Between January and April 2004, 20 men were referred to our institute for management of urethral strictures. The patients were investigated by conventional RUG and multiformat MR urethrography. The patients were examined by urethroscopy under anesthesia to be followed by definitive endoscopic or open operative intervention. The radiologic data were compared by endoscopic as well as operative findings in all the patients.

RESULTS

Ten patients were managed by visual internal urethrotomy (VIU) and two by dilatation under anesthesia; two showed normal urethral caliber. Four patients required open urethral reconstructive procedures. Two patients underwent radical cystectomy and cutaneous diversion because of associated bladder or urethral malignancy. Although overall accuracy for diagnosis of urethral strictures was equal between both modalities (85%), MR urethrography provided extra clinical data in seven patients (35%). It was superior to RUG in judging the urethral stricture length in three patients, diagnosing a urethral tumor in one, detecting associated bladder mass in one, characterizing the site of urethra-rectal fistula in one, and accurately delineating the proximal urethra in the last patient. Unlike RUG, MR urethrography provided adequate information about the degree of spongiofibrosis in all patients.

CONCLUSION

MR urethrography is a promising tool for defining male urethral strictures and can provide extra guidance for treatment planning that cannot be obtained with RUG.

Deceased donor renal transplantation--does side matter?

BACKGROUND

The aim of the present study was to determine whether the deceased donor kidney side (left or right kidney) was predictive of subsequent kidney transplant outcomes.

METHODS

A retrospective analysis was undertaken of the left-right deceased donor kidney pairs transplanted into recipients with end-stage renal failure in Queensland between 1 April 1994 and 31 March 2004.

RESULTS

A total of 201 left-right deceased donor kidney pairs were transplanted into 402 patients. The baseline characteristics of the recipients in the two groups were comparable, except that the patients receiving right kidneys had lower body mass indices and shorter cold ischaemic times. No differences were seen between the left and right kidney recipient groups with respect to operative duration (3.02 +/- 0.67 vs 3.12 +/- 0.72 h, P = 0.16), warm ischaemic time (0.62 +/- 0.18 vs 0.65 +/- 0.21, P = 0.09), delayed graft function (4 vs 6%, respectively, P = 0.26) or a composite vascular, haemorrhagic, ureteric and infective post-operative complication end-point (22 vs 22%, P = 0.90). Estimated glomerular filtration rates were almost identical at 1 month (52.7 +/- 39.6 vs 51.0 +/- 24.0 ml/min/1.73 m(2), P = 0.34) and remained comparable thereafter. Respective death-censored graft survival rates for left and right kidney recipients were 100 and 100% at 1 year, 99.4 and 96.4% at 3 years and 96.3 and 95.5% at 5 years, respectively (P = 0.67).

CONCLUSIONS

Although left and right deceased donor kidneys present different operative challenges, the present results suggest that the probability of early post-operative complications, delayed graft function, impaired early and medium-term renal allograft function or death-censored graft failure is comparable between left and right kidney recipients.