Surgical validation of functional magnetic resonance urography in the study of ureteropelvic junction obstruction in a pediatric cohort.

INTRODUCTION: Ureteropelvic junction obstruction (UPJO) is one of the most common urological diseases in children. The etiology can be intrinsic, extrinsic (crossing vessel [CV] or adhesions), or mixed. To date, ultrasonography and scintigraphy are considered gold-standard imaging techniques for the study of UPJO. Functional magnetic resonance urography (fMRU) combines anatomical and functional information and has been recently evaluated for the detection of CVs in UPJO. OBJECTIVE: The objective of the study was to evaluate the concordance between fMRU and surgery in determining the etiology of UPJO and the presence of obstructing/non-obstructing CVs. STUDY DESIGN: Patients with unilateral hydronephrosis who underwent surgery after an fMRU were included in the sample. Surgical data regarding the etiology of UPJO were compared with radiological results. The etiology was divided into intrinsic, extrinsic due to CV, extrinsic due to adhesions, and mixed or cicatricial (postoperative). The concordance was calculated by means of the Cohen's kappa coefficient. RESULTS: The observed agreement between fMRU and surgical findings regarding the etiology and the presence of CV were 83.2% and 89.4%, respectively (with substantial Cohen's kappa coefficient). The sensitivity and specificity of fMRU were 0.84 and 0.93, respectively; the positive predictive value (PPV) and negative predictive value (NPV) were 0.889 and 0.897, respectively. The observed agreement regarding the type of vessel was 88.3% with a Cohen's kappa coefficient of 0.787 (substantial). DISCUSSION: In children with hydronephrosis, it is very important for the surgeon to quantify the extent of dilation, define the etiology of the obstruction, and the presence or absence of CVs. fMRU is a 'one-stop-shop' technique which provides both anatomical and functional information showing a high concordance with surgical findings, avoiding radiation exposure. CONCLUSIONS: fMRU should be considered a valid imaging technique in the study of pediatric UPJO, as it provides the surgeon with important information regarding the etiology of the obstruction for the preoperative planning.

Hydronephrosis and crossing vessels in children: Optimization of diagnostic-therapeutic pathway and analysis of color Doppler ultrasound and magnetic resonance urography diagnostic accuracy.

INTRODUCTION: Ureteropelvic junction obstruction (UPJO) is one of the most frequent urological diseases affecting the pediatric population. It can be due to both intrinsic stenosis of the junction and extrinsic causes such as the presence of crossing vessels (CVs), which can be detected by color Doppler ultrasound (CD-US). Magnetic resonance urography (MRU) is a good alternative, but sedation and infusion of a contrast agent are required. OBJECTIVE: The aim of this study was to analyze the diagnostic accuracy of CD-US and MRU in visualizing CVs in pediatric hydronephrosis, in order to decide the correct diagnostic pathway in the pre-operative phase. MATERIAL AND METHODS: A retrospective review was performed of medical records for all patients who underwent surgical treatment for hydronephrosis from August 2006 to February 2016. Ultrasound and scintigraphy had been performed on all patients. Data about CD-US and MRU were collected. A high-level technology ultrasound scanner and a 1.5 T MR scanner were used. The presence of CVs at surgery was considered the gold standard. Sensitivity, specificity, positive and negative predictive values (NPV) were calculated and reported for both of the imaging techniques. RESULTS: A total of 220 clinical charts were reviewed. Seventy-three CVs were identified at surgery (33.2% of UPJO). The median age was statistically higher in the group with CVs compared to the group without CVs (P < 0.001). The sensitivity and NPV of CD-US in detecting CVs were higher than MRU (sensitivity 93.3% vs. 71.7%, NPV 95.7% vs. 77.6%, respectively). DISCUSSION: According to the data, CD-US had higher sensitivity and NPV than MRU, resulting in superior detection of CVs. It is important for a surgeon to know that a child has a CV, especially in older children in which the incidence of extrinsic UPJO is higher. The main limitation of this study was the presence of incomplete data, due to the retrospectivity. CONCLUSIONS: In the pre-operative phase, the CD-US should be considered as the investigation of choice to detect CVs in children with hydronephrosis (Summary Fig). Moreover, CD-US has lower costs than MRU, and sedation with infusion of contrast agent is unnecessary. For the future, it could be useful to lead a prospective comparison between the two imaging techniques.