[Comparison of functional magnetic resonance urography and dynamic renal scintigraphy in the functional assessment of ureteropelvic junction obstruction in children].

PURPOSE: In order to determine the role and significance of functional magnetic resonance urography (fMRU) in the diagnosis of ureteropelvic junction obstruction (UPJO), a comparative analysis of the results of fMRU and dynamic renal scintigraphy (DRS) was carried out. MATERIALS AND METHODS: From January 2017 to December 2019, fMRU and diuretic DRS were performed in 36 patients (mean age 89+/-63 months). Boys - 26 (72.2%), girls - 10 (27.8%). Left-sided hydronephrosis was detected in 23 (63.9%) children, right-sided in 12 (33.3%) patients, and bilateral lesions in 1 (2.8%) patient (2 renal units (RU)). Antenatal hydronephrosis was detected in 9 (25%) patients, and postnatally in 27 (75%) patients. According to ultrasound data, grade II hydronephrosis occurred in 11 (29.8%) RU, grade III - in 21 RU (56.7%), and grade IV - in 5 RU (13.5%) according to the SFU classification. A diuretic test was performed in 26 patients. RESULTS: Median and quartiles of differential renal function (DRF) according to fMRU data on the affected side were 37% [29; 43], and according to DRS - 46% [40;49]. When performing fMRU, a positive diuretic test was detected in 20 patients, 5 patients - negative and 1 patient - doubtful, and according to the DRS data, 12 patients had a positive test, 10 patients - negative and 4 patients - doubtful. Differences in DRF between fMRU and DRS varied between 0.7-33%. The average value of differences in DRF on the affected side was 11.3+/-8.5%. When comparing the results of DRF on the affected side, a moderate correlation was found on the Cheddock scale (r=0.59, p<0.05) between fMRU and DRS data. In comparison of the DRF using the Wilcoxon test, statistically significant differences were revealed (p<0,05). SUMMARY: Our experience demonstrates the high potential of fMRU in terms of replacing the classical methods of diagnosis of UPJO in children, taking into account the high correlation coefficients between the results of fMRU and DRS. Standardization of the fMRU protocol will increase the diagnostic relevance of information and in the future will make fMRU the only necessary study to determine management tactics for patients with UPJO.

Functional magnetic resonance urography in infants: feasibility of a feed-and-sleep technique.

BACKGROUND: Functional magnetic resonance (MR) urography has been well established in the diagnostic workup of congenital anomalies of kidneys and urinary tract, though long acquisition time requires sedation or general anesthesia in infants. OBJECTIVE: To evaluate the success rate of an optimized functional MR urography protocol in infants carried out in natural sleep. MATERIALS AND METHODS: We retrospectively evaluated all functional MR urographies performed under general anesthesia or during natural sleep in infants younger than 1 year between 2010 and 2017 and rated image quality in both cohorts using a 3-point Likert scale. We tested the analyzability of functional sequences using a free available software. We also calculated examination time. Finally, we compared examinations in natural sleep and those with general anesthesia using independent t-test for continuous data and Mann-Whitney U test for categorical data. RESULTS: Functional MR urography could be performed successfully during natural sleep in 38 of 42 (90%) infants younger than 10 months. Four examinations were aborted before contrast medium was administrated. In the same period, 19 functional MR urographies were performed successfully under general anesthesia. Although image quality was significantly better in this group (P<0.0001), image quality was at least diagnostic in all finished examinations in natural sleep, and the functional analyzability was given in all completed examinations. There was a significant saving in examination time during natural sleep (P<0.001). CONCLUSION: Functional MR urography can be successfully performed in natural sleep in infants younger than 10 months.

Role of magnetic resonance urography in pediatric renal fusion anomalies.

Renal fusion is on a spectrum of congenital abnormalities that occur due to disruption of the migration process of the embryonic kidneys from the pelvis to the retroperitoneal renal fossae. Clinically, renal fusion anomalies are often found incidentally and associated with increased risk for complications, such as urinary tract obstruction, infection and urolithiasis. These anomalies are most commonly imaged using ultrasound for anatomical definition and less frequently using renal scintigraphy to quantify differential renal function and assess urinary tract drainage. Functional magnetic resonance urography (fMRU) is an advanced imaging technique that combines the excellent soft-tissue contrast of conventional magnetic resonance (MR) images with the quantitative assessment based on contrast medium uptake and excretion kinetics to provide information on renal function and drainage. fMRU has been shown to be clinically useful in evaluating a number of urological conditions. A highly sensitive and radiation-free imaging modality, fMRU can provide detailed morphological and functional information that can facilitate conservative and/or surgical management of children with renal fusion anomalies. This paper reviews the embryological basis of the different types of renal fusion anomalies, their imaging appearances at fMRU, complications associated with fusion anomalies, and the important role of fMRU in diagnosing and managing children with these anomalies.

Intra- and inter-observer variability of functional MR urography (fMRU) assessment in children.

BACKGROUND: Functional MR urography (fMRU) provides comprehensive functional data that can be subject to variability. To interpret the results of fMRU, it is essential to know the intra- and inter-observer variability of the measured parameters. OBJECTIVE: To define the range of variability in fMRU, particularly that of the differential renal function based on volume (volumetric differential renal function) and Patlak differential renal function measurements in children. MATERIALS AND METHODS: We included 15 fMRU studies, 10 of non-duplicated and 5 of unilateral duplex kidneys. We recruited six observers with a range of fMRU experience, including two MRI technologists, one resident, one fellow, one pediatric radiologist and one pediatric urologist. The observers underwent intensive training in using the Children's Hospital of Philadelphia (CHOP)-fMRU freeware for analysis. They conducted the fMRU analysis on each case twice, at least 1 week apart. Mean and standard deviation were calculated for each set of absolute volume, absolute Patlak, volumetric differential renal function and Patlak differential renal function. We calculated the statistical significance of these deviations using the student's t-test. We also calculated interclass correlations for intra-observer and inter-observer agreement of both volume and Patlak measurements using SPSS software. RESULTS: Intra- and inter-observer variability did not differ significantly, measuring 6% and 4% for relative volume (volumetric differential renal function: P > 0.05) and 5% and 3% for relative function (Patlak differential renal function: P > 0.05). Absolute values of parameters showed more variability than the relative values. Intra- and inter-observer agreement was well above 0.90 (P < 0.001) for all volume measures except for duplex upper pole intra-observer measurements (0.80, P < 0.01). Intra- and inter-observer agreement for Patlak values were also above 0.90 (P < 0.001) except for duplex upper pole measurements, which were 0.54 (P = 0.13) and 0.81 (P < 0.01), respectively. CONCLUSION: Functional MRU analysis using CHOP-fMRU software is reproducible, with overall intra- and inter-observer variability rates of 5% for volumetric differential renal function and 4% for Patlak differential renal function. There was higher variability in volume and function measurements between upper and lower pole moieties of duplicated kidneys and for absolute volume and function values overall. A range of 45-55% for relative values of volumetric differential renal function and Patlak differential renal function could serve as the normal range.

Comparative Study Between Functional MR Urography and Renal Scintigraphy to Evaluate Drainage Curves and Split Renal Function in Children With Congenital Anomalies of Kidney and Urinary Tract (CAKUT).

Background: Obstructive congenital anomalies of the kidney and urinary tract have a high risk of kidney failure if not surgically corrected. Dynamic renal scintigraphy is the gold standard technique to evaluate drainage curves and split renal function (SRF). Objectives: To compare functional magnetic resonance (MR) urography with dynamic renal scintigraphy in measuring volumetric SRF and in the classification of drainage curves in patients with congenital anomalies of the kidney and urinary tract. Materials and Methods: We retrospectively collected patients with hydroureteronephrosis or pelvicalyceal dilatation at renal ultrasound, who underwent both functional MR urography and dynamic renal scintigraphy (DRS) within 6 months. DRS studies were evaluated by a single nuclear medicine physician with a double reading. Functional MR urography renograms were blind evaluated twice by two radiologists. The functional MR urographyintra- and inter-reading agreements as well as the agreement between the two imaging techniques were calculated. SRF was evaluated by Area Under the Curve and Rutland-Patlak methods. Drainage curves were classified as normal, borderline or accumulation patterns by both the techniques. Results: Fifty-two children were studied, 14 with bilateral involvement. A total of 104 kidney-urinary tracts were considered: 38 normal and 66 dilated. Considering Area Under the Curve and Rutland-Patlak for SRF, the intra- and inter-reader agreements of functional MR urography had excellent and good results, respectively, and the two techniques demonstrated a good concordance (r2: 67% for Area Under the Curve and 72% for Rutland-Patlak). Considering drainage curves, the inter-readers agreement for functional MR urography and the concordance between the two techniques were moderate (Cohen's k, respectively, 55.7 and 56.3%). Conclusions: According to our results, there are no significant differences between functional MR urography and DRS in measuring volumetric SRF and in the classification of drainage curves in patients with congenital anomalies of the kidney and urinary tract.

Detection of crossing vessels in pediatric ureteropelvic junction obstruction: Clinical patterns and imaging findings.

BACKGROUND: Pediatric ureteropelvic junction obstruction (UPJO) is caused by congenital intrinsic narrowing and/or a lower pole-crossing renal artery. When a crossing renal vessel (CRV) is missed at the time of pyeloplasty, a redo-pyeloplasty is often required. OBJECTIVES: The aims were to analyze clinical predictors for the presence of a CRV in UPJO and the utility of functional magnetic resonance urography (fMRU) in preoperative identification of a crossing vessel. METHODS: Using an Institutional Review Board approved registry database, we identified 166 patients from July of 2007 until January of 2014 who had undergone open, laparoscopic, or robotic assisted laparoscopic pyeloplasty at our institution. We abstracted data including age at surgery, preoperative symptoms, preoperative imaging findings, and whether or not a CRV was identified intraoperatively. Statistical analysis was performed on SPSS using the Mann-Whitney U test. RESULTS: Of the 166 patients identified, 78 were found to have a CRV at the time of surgery and 88 did not. The surgical approach was distributed as 104 robotic assisted laparoscopic, 51 open, and 11 pure laparoscopic. On univariate analysis, older age at presentation and pain at presentation predicted the presence of a CRV; antenatal hydronephrosis was a negative predictor, though 20 of 68 (25.6%) infants diagnosed with UPJO antenatally did have a CRV. Subgroup analysis of patients undergoing preoperative MRU showed a sensitivity of 88.2% and specificity of 91.7% for the detection of CRVs. DISCUSSION: This study confirmed the importance of looking for a crossing vessel in all cases, with the knowledge that increased age and pain at presentation were more likely to be associated with a crossing vessel. In addition, fMRU is a valuable source of information in the preoperative identification of the presence of a crossing vessel. The study has limitations including being retrospective in nature, and that the sensitivity of fMRU to identify CRVs was based on the read of an experienced uroradiologist who specializes in MRU, so may not correlate with the standard clinical read of an fMRU. CONCLUSION: This study confirms the need to maintain a high index of suspicion for the presence of a CRV when intervening in a clinically symptomatic older child, although 25% of infants with antenatally detected UPJO did have one too. Our subset analysis demonstrated that MRU is a reliable method of detecting crossing vessels.