Combined static-dynamic MR urography for the simultaneous evaluation of morphology and function in urinary tract obstruction

Objective. A new approach, combined static-dynamic MR urography is evaluated to determine its potential utility for the functional-morphological diagnosis of paediatric urinary tract obstruction. In this initial investigation we sought to evaluate the procedure by imaging the urinary tract of piglets. Materials and methods. Twenty-nine healthy piglets were studied with MR urography (MRU), 99 mTc-MAG3 diuretic renal scintigraphy (DRS), ultrasound (US) and excretory urography (EU). The functional and morphological findings were compared. For MRU we combined a respiration-triggered 3D-IR-TSE sequence and a dynamic 2D-FFE sequence after Gd-DTPA injection. Results. MRU depicted the complete urinary tract with superior image quality compared to EU. Calculation of time-intensity curves from the dynamic sequence permitted determination of single kidney function from parenchymal ROIs and urinary excretion using the whole kidney ROI. MRU and DRS showed significant agreement in the assessment of both single kidney function and urinary excretion. Disturbances of urinary drainage were generally caused by an overfilled bladder. Conclusions. Combined static-dynamic MRU is well suited for the depiction of the complete urinary tract and for the determination of individual kidney function and urinary excretion in the piglet.