Non-invasive urine flow dynamics characterization of pediatric hydronephrosis based on deep learning and...

Pediatric hydronephrosis is a common disease due to ureteropelvic junction obstruction (UPJO). Non-invasive magnetic resonance urography (MRU) can utilize the water in the urine as a natural contrast agent to image renal pelvis and calyces, which could be used to diagnose UPJO. However, as invasive techniques, MRU fails to provide detailed definitive measurements, such as pressure and velocity. This study aims to provide a non-invasive method to compute urine flow dynamics based on deep learning and computational fluid dynamics (CFD) techniques. The method could gain insights into the urodynamic characteristics of hydronephrosis patients, which facilitates clinical decision-making and further contributes to prognosis.

This work proposed a method to characterize urine flow dynamics with MRU data. Specifically, the method first reconstructs patient-specific three-dimensional renal pelvis mesh models with deep learning techniques. Then, boundary conditions were set according to the mesh models, and the Viscous k-epsilon turbulence model was used to perform CFD simulation of urine. Finally, the method characterizes the dynamics of urinary flows for UPJO diagnosis and prognosis.

Experiments are conducted on MRU data via our proposed method. By comparing the preoperative and postoperative urine pressure cloud maps of patients, we found that the pressure in the renal pelvis was significantly lower in the postoperative period than in the preoperative period. Furthermore, we introduced the urine flow velocity ratio (UFVR) index to assess the obstruction of urine in renal pelvis. We compared the UFVR in the preoperative and postoperative phase, and indicated that the obstruction of urine flow has been mitigated following surgery.

CFD can simulate the urinary flow field within the renal pelvis, offering the possibility of predicting renal pelvic pressure without the need for painful, invasive interventions such as the Whitaker test. Moreover, numerical simulation provides a new definitive way for evaluating the postoperative efficacy of dismembered pyeloplasty.