Fig. 7: Comparison of kidney parameters in hydronephrosis measured by hyperpolarized ¹³C-MRI using Z-OMPD and clinical standard techniques.

a 3D dynamic perfusion imaging of hydronephrotic kidneys shows poor filtration of Z-OMPD towards the renal pelvis (grey arrows) despite strong cortical perfusion (white arrows). This is quantitatively reflected by normal tRBF (b, n = 9 healthy and n = 8 hydronephrotic individual kidneys) but strongly reduced tGFR (c, n = 8 healthy and hydronephrotic individual kidneys). Four-fold interpolated pH compartments for the cortex (d, e) and the medulla (f, g) appear homogeneous and at physiological pH while the pelvis exhibits strong, pathologic acidification (h, i) (n = 10 healthy kidney values from Fig. 3f, n = 12 individual hydronephrotic kidney cortex and medulla and n = 9 pelvis compartments). The left kidney pH compartments in d, f and h exhibit reduced cross-section due to inclined CSI slice placement. Conventional MRI for renal disease status assessment shows a moderate increase j in ADC (diffusion-weighted MRI) and a substantial volume (k) increase of hydronephrotic kidneys (T₂-weighted MRI, j, k: n = 14 healthy, n = 16 hydronephrotic individual kidneys) compared to healthy controls. Renal biomarkers in blood serum reveal mildly increased creatinine- (l) and strongly elevated urea levels (m), while SDMA values are not clinically evident (n) (l, m, n: n = 8 individual blood samples). Reference ranges (dashed lines) were obtained from animal suppliers for creatinine and urea⁹⁷ or literature for SDMA^98,99,100. o Urine pH is unobtrusive in hydronephrotic models (n = 10 healthy and n = 11 individual hydronephrosis urine samples). p Comparison of significant parameters using Cohen’s d indicates pelvic pH and tGFR measured by hyperpolarized imaging Z-OMPD to be most sensitive to this kidney disease. Scale bars and white squares in a and d indicate 10 mm and native acquisition resolution respectively. Values in b, c, e, g, i—o are presented as means ± SD. Two-tailed, unpaired Student’s t tests were used in b, c, e, g, i, j, k, o, One-sided Student’s t tests against the upper reference interval boundary were used in l, m.