Diagnostic value of combined static-excretory MR Urography in children with hydronephrosis

The Emerging Role of MR Urography in Imaging Megaureters in Children

INTRODUCTION

Megaureter, described as ureter dilatation more than 7 mm in diameter, commonly associated with other anomalies, is still a diagnostic and therapeutic challenge. Magnetic resonance urography (MRU) appears as a promising method in urinary tract imaging, providing both anatomical and functional information. There are several postprocessing tools to assess renal function (including differential renal function) and severity of ureteral obstruction based on MRU. Still, the place of this method in the diagnostic algorithm of ureteropelvicalyceal dilatation with megaureter remains underestimated. Analysis of imaging findings in a group of children diagnosed with megaureter was done.

MATERIAL AND METHODS

A retrospective analysis of magnetic resonance urography (MRU) was performed in 142 consecutive patients examined from January 2013 to September 2019. Twenty-five patients meeting the criteria of megaureter (dilatation more than 7 mm) in MRU were included in the further analysis. The MRU, ultrasound (US), and scintigraphy results were compared and analyzed together and compared with clinical data.

RESULTS

The sensitivity and specificity of US was comparable to the MRU in the assessment of upper urinary tract morphology (p > 0.05). In five out of 25 children, megaureter was found in each kidney; in a single case, both poles of a duplex kidney were affected. In the diagnosis of ureter ectopia, the MRU was superior to the US for which sensitivity did not exceed 16%. The US showed limited value in the diagnostics of segmental ureter dysplasia as a cause of primary megaureter when compared with MRU. Four cases were visualized in MRU studies, whereas the US examination was negative (all confirmed during surgery). There was a moderate correlation between relative renal function between fMRU and scintigraphy (t = 0.721, p = 0.477) and in the severity of obstruction assessment between both methods (r = 0.441, p < 0.05). However, in 10 kidneys with megaureter, the results in scintigraphy were inconclusive due to the signal from the megaureter imposing on the renal field.

CONCLUSIONS

MRU seems to be a preferred method in the diagnostic algorithm for megaureter, providing both anatomical and functional information. MRU is superior to US and scintigraphy in diagnosing urinary tract anomalies with megaureter.

Coexisting congenital mid-ureteral stricture and megaureter due to ureterovesical junction obstruction: A case report

Congenital mid-ureteral strictures (CMS) are rare. Most congenital strictures occur at the ureteropelvic junction or ureterovesical junction, with mid-ureteral strictures accounting for only 4–5% of all cases of ureteral obstruction in children. Furthermore, there are very few reports of coexisting mid-ureteral stricture and ureterovesical junction obstruction (UVJO). Here, we report a case of coexisting UVJO and CMS. CMS was not detected on preoperative magnetic resonance imaging, and hydronephrosis remained after ureteroneocystostomy. Therefore, MRI was repeated and CMS was diagnosed, for which we performed ureteroureterostomy. Intraoperative retrograde pyelography (RGP) aids definitive diagnosis of UVJO.

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Ureteral strictures (CMS) are rare.

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Few reports of coexisting CMS and ureterovesical junction obstruction (UVJO) exist.

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In such cases, CMS can be overlooked on magnetic resonance imaging.

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Intraoperative retrograde pyelography is important for accurate diagnosis.

Pediatric congenital hydronephrosis (ureteropelvic junction obstruction): Medical management guide

The prevalence of asymptomatic hydronephrosis, now detected by ultrasonography, has increased. However, definitive management guidelines for the management of congenital hydronephrosis have not been established. The Japanese Society of Pediatric Urology created a "medical management guide" based on new findings for physicians practicing pediatric urology. We developed a medical management guide focused on congenital hydronephrosis caused by ureteropelvic junction obstruction. This medical management guide consists of the definition, pathophysiology, epidemiology, diagnosis, classification, treatment using a clinical management algorithm of hydronephrosis and the long-term course of the disease. The aim of hydronephrosis management is to determine whether surgery should be carried out to avoid renal dysfunction, as there is a possibility for improvement without intervention. Ultrasonography is essential to make treatment decisions. Management is determined by a comprehensive assessment, including the degree of hydronephrosis, anterior-posterior diameter of the renal pelvis and, if necessary, a nuclear medicine evaluation of the status of urine drainage and renal function.

Morphologic and functional evaluation of duplicated renal collecting systems with MR urography: A descriptive analysis

PURPOSE

To describe the morphology and function of duplicated collecting systems in pediatric patients undergoing functional MR urography (fMRU).

METHODS

This is a HIPAA compliant IRB approved retrospective study of all patients with duplicated renal collecting systems undergoing fMRU at our institution between 2010 and 2017. Two pediatric radiologists evaluated the studies to determine the presence, morphology and function of duplicated collecting systems using both T2-weighted and dynamic post-contrast fat saturated T1-weighted images. Assessed morphologic features included pelvic and calyceal dilation, partial or complete ureteral duplication, ureteral dilation, ectopic ureteral insertion and ureteroceles. Functional analysis was carried out per moiety.

RESULTS

A total of 86 examinations (63 girls; 23 boys), median age 2.6 years (Standard Deviation 6.4 years, interquartile range: 0.4-10.3 years) and 107 kidneys (39 right; 30 left and 19 bilateral), which yielded 214 evaluable moieties, were included in the final sample. One hundred and sixty-three (76.1%) of the moieties had normal morphological features and normal functional results (average calyceal transit time and renal transit time of 2 min 28 s and 3 min 16 s, respectively). The remaining 51 moieties (23.8%) were hypoplastic or dysplastic. Seventy-seven (35.9%) had pelvic and calyceal dilation. Slightly more than half of the kidneys had complete ureteral duplication (60/107; 56%); 50 (50/107, 46.7%) had ectopic ureters (23 intra- and 27 extravesical) and 9 (9/107, 8.4%) had ureteroceles.

CONCLUSION

fMRU provides comprehensive information regarding the morphology and function of duplicated renal collecting systems in children. In particular, fMRU is useful for assessing barely or non-functioning renal poles and ectopic ureters.

Magnetic resonance urography in the pediatric population: a clinical perspective

Diagnostic imaging in pediatric urology has traditionally relied upon multiple modalities based on availability, use of ionizing radiation, and invasiveness to evaluate urological anomalies. These modalities include ultrasonography, voiding cystourethrography, fluoroscopy and radionuclide scintigraphy. Magnetic resonance urography (MRU) has become increasingly useful in depicting more detailed abdominal and pelvic anatomy, specifically in duplex collecting systems, ectopic ureter, ureteropelvic junction (UPJ) obstruction, megaureter and congenital pelvic anomalies. Here we discuss the clinical role of MRU in the pediatric population and its future direction.

The diagnostic value of magnetic resonance urography using a balanced turbo field echo sequence

OBJECTIVES

The aim of the study was to compare the inter-observer variability and the accuracy of magnetic resonance urography (MRU) using a thin sectional balanced-turbo field echo (B-TFE) sequence for detecting ureteral calculi and to determine the effect of additional factors (size, density and location of the calculus) on the sensitivity and specificity of the MRU.

MATERIALS & METHODS

MRU and CT images were evaluated independently by two radiologists according to presence, density and localization of calculi. The degrees of inter-rater agreement for categorical items were evaluated by the Kappa coefficient.

RESULTS

According to the 1st and 2nd observers, the sensitivity of MRU was 65.9 %, 71.8 % and the specificity of MRU was 95.9 %, 100 %, respectively. Inter-observer agreement was 84.6 % for stone detection. The larger size had a better effect on detectability (p < 0.05). Also, the higher density had a better impact on detectability (p < 0.05).

CONCLUSION

Our study has shown that B-TFE MRU was useful to detect ureteral calculi. However, B-TFE MRU has low sensitivity and high specificity in comparison with CT images. MRU is a reasonable alternative imaging technique for follow-up periods of selective groups like patients with large urinary stones, children or pregnant patients when ionizing radiation is undesirable.

KEY POINTS

• According to 1st and 2nd observers, sensitivity of MRU was 65.9 %, 71.8 %, respectively. • According to 1st and 2nd observers, MRU specificity was 95.9 %, 100 %, respectively. • Interobserver agreement was found to be over 84 % for stone detection. • B-TFE sequence provides calculus follow-up without radiation. • Larger calculi and more dense calculi individually have the better effect on detectability.