The Potential of Magnetic Resonance Urography in the Diagnosis of Ureteral Strictures

The aim of the study was to assess the sensitivity of magnetic resonance urography (MRU) — both native and contrast-enhanced examinations — in the diagnosis of ureteral strictures and to evaluate its importance in the diagnostic algorithm in patients with different causes of urinary obstruction.

Materials and Methods. MRU was performed in 62 patients with ureteral strictures, whose average age was 47±9.8 years, using high-field MRU devices Vantage Atlas (Toshiba, Japan) and Ingenia (Philips, the Netherlands) with magnetic field intensities of 1.5 and 3.0 T, respectively. The strictures were primary in 6 cases and secondary (acquired) in 56. In 42 cases (67.7%), excretory MRU was carried out: the procedure involved intravenous administration of contrast agent. The detected strictures were evaluated in terms of localization, shape, extension and suprastenotic dilatation extent. The technique sensitivity in detecting the changes in surrounding structures was also estimated: ureteral wall thickening and paraureteral tissue infiltration were evaluated, the spread of tumor process was assessed when appropriate. The results obtained by computed tomography urography (CTU) and confirmed by surgical intervention were considered as reference values.

Results. MRU sensitivity in the diagnosis of ureteral strictures was 96.3%. The technique showed the best results in the lower third of the ureters: 100% of strictures were identified regardless of their origin. In the upper third, MRU confirmed the strictures detected on CTU in 97.2% of cases. As for the middle third of the organ, the results were lower than on CTU: 87.4% of strictures were detected. According to excretory MRU data, the following pathological symptoms were revealed: organ obstruction — in 62 cases (100%), filling defect — in 9 cases (14.5%), suprastenotic dilatation — in 56 cases (90.3%), hydronephrosis — in 52 cases (83.9%), pelvicalyceal system dilation — in 58 cases (93.5%). Besides, traditional MR sequences, especially the series with suppression of the signal from adipose tissue, are highly sensitive to edema manifestations and revealed infiltrative changes in the surrounding tissue in 34 (54.8%) and ureteral wall thickening in 45 cases (72.5%). Accumulation of fluid in the pelvis was found in 8 cases (12.9%). MRU also made it possible to detect changes in parenchymal organs, the liver, adrenal glands and to suspect the presence of secondary pelvic bone lesions.

Conclusion. Contrast-enhanced MRU demonstrates high efficacy in detection of ureteral strictures similarly to CTU and, in case of obstruction located in the lower third of the organ, it is superior to CTU and provides additional information about the condition of the organ wall and the surrounding tissues. Non-contrast MRU provides the possibility to clearly localize the level of obstruction and identify its cause. The absence of ionizing radiation makes the technique successfully applicable in patients with contraindications to CTU.

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Davydova E.S., Egorova E.A. The Potential of Magnetic Resonance Urography in the Diagnosis of Ureteral Strictures. Sovremennye tehnologii v medicine 2018; 10(4): 122, https://doi.org/10.17691/stm2018.10.4.14