Cine magnetic resonance urography and Whitaker test: dynamic visualized and quantified tools in ileal ureter replacement

BACKGROUND: To assess the feasibility and usefulness of cine magnetic resonance urography (MRU) and Whitaker test as postoperative evaluation tools of ileal ureter replacement. METHODS: We retrospectively collected the medical records of 42 patients who underwent ileal ureter replacement between August 2015 and August 2020. The morphology, luminal diameter, amplitude, contraction ratio, peristaltic frequency, ureteral jets and peristalsis efficiency were recorded in cine MRU. Under different perfusion loads, image and pressure changes of the reconstructed upper urinary tract were recorded in the Whitaker test. Patients were categorized into normal pressure and elevated pressure groups. RESULTS: A total of 42 patients underwent cine MRU, and 20 of them finished the Whitaker test successfully. The mean amplitude was 9.29±3.51 mm, and the contraction ratio was 0.607 (0.247–0.790). The median peristaltic efficiency was 0.75 (0.29–1). Three patients presented an unusual rise in renal pelvis pressure, which was 54, 26, 57 cmH(2)O respectively. The amplitude of the ileal graft in the elevated pressure group was larger (13.80±5.73 vs. 8.09±3.38 mm, P=0.024), the contraction ratio was higher [0.68 (0.59–0.79) vs. 0.59 (0.25–0.79), P=0.028], the peristaltic frequency was more active [7 (6–8) vs. 4 (3–8), P=0.025], but the peristaltic efficiency was lower [0.50 (0.29–0.50) vs. 0.75 (0.33–1), P=0.029] compared to the normal pressure group. There were no significant differences in the ureteral jets [3 (2–4) vs. 3 (1–7), P=0.840), creatinine (97.3±7.3 vs. 103.2±30.7 µmol/L, P=0.753), and estimated glomerular filtration rate (eGFR) (76.4±14.1 vs. 68.5±28.7 mL/min·1.73 m(2), P=0.663). CONCLUSIONS: Cine MRU provides morphological and peristaltic motility of the ileal graft, cine MRU after ileal ureter replacement was recommended as a routine examination. The Whitaker test represents a complementary investigation to evaluate pressure changes to reveal the ability to transport urine, and it can be used as a supplementary examination to clarify equivocal cases.