Assessment and follow up of kidney with directional power Doppler of single kidney patients compared with double kidney patients

Aim: Directional power Doppler (dpD) matched with renal echography reveals little and early changes in renal haemodynamics. This study has examined by dpD, in single kidney patients (SK) the renal haemodynamic characteristics and their changes over time in single kidney patients (SK) compared with double kidney patients with chronic renal failure (DK-CKD).

Methods: 33 SK patients with normal renal function (FG >60ml/min/1.73 m2; SK-NOR), 45 SK patients with reduced renal function (SK-CKD) and 40 double kidney patients with chronic renal failure (DK-CKD) have been examined. All patients have been monitored for at least one year and have been clinically examined and tested by biochemistry and echography at the beginning and at the end of the control period. The echographic renal B-mode study evaluated the renal volume (RV) and the parenchymal thickness (PT); dpD study allowed a Doppler semiquantitative evaluation (resistance index, RI).

Results: The three control groups were similar as regards their sex, age, predominance of diabetes mellitus, hypertension and body mass index. The creatinine clearance resulted to be 84.3±24.7ml/min/1.73m2 in SK-NOR (p<0.001 vs. others), 40.5±11.4 in SK-CKD e 40.3±14.9 in DK-CKD. RV was similar in SK-NOR (210±59ml/1.73m2) and SK-CKD (196±63) and reduced in DK-NOR (132±46; p<0.001 vs. other groups); also PT resulted to be similar in SK-NOR (2.1±0.4cm) and SK-CKD (2.0±0.4) but reduced in DK-NOR (1.6±0.3; p<0.001 vs. other groups). RI, instead, resulted to be normal only in SK-NOR (0.63±0.06) and also reduced in SK-CKD (0.70±0.10; p<0.001 vs. SK-NOR) e DK-NOR (0.74±0.11; p<0.001 vs. SK-NOR). Then SK patients with reduced renal function showed a normal renal volumetry with an increased RI. At the end of the follow-up (52±27 months), in SK-NOR, RV (216±54ml/1.73m2; NS vs. basal measurement), PT (2.1±0.4cm; NS vs. basal value) and RI (0.64±0.07; NS vs. basal value), as well as the renal function remained unchanged (87.6±27.7ml/min/1.73m2; NS vs. basal value). In SK-CKD patients, compared with a decrease in renal function (34.5±22.2; p<0.05 vs. basal value), RV resulted to be unchanged (181±56; NS vs. basal value), while PT resulted to be reduced (1.8±0.5; p<0.001 vs. basal value) and RI resulted to be increased (0.76±0.13; p<0.001 vs. basal value). However, in the DK-CKD group, which during the study showed a similar decrease in renal function (29.8±16.6; p<0.001 vs. basal value, NS vs. SK-CKD), a more marked decrease in RV was found (112±38; p<0.001 vs. basal value and SK-CKD) and in PT (1.3±0.3; p<0.001 vs. basal value and SK-CKD) and a higher increase in RI (0.81±0.12; p<0.001 vs. basal value, p=0.05 vs. SK-CKD). Then, SK patients with a reduced renal function over a monitoring period of over 5 years, show renal volume unchanged, a lower decrease in PT and a lower increase in RI compared with control double kidney patients having renal failure. Similar results were also obtained for the diabetic sub-groups (30%) of the 3 control groups.

Conclusions: SK patients with normal renal function keep normal and unchanged renal haemodynamic patterns over time. SK patients with reduced renal function better keep renal volumetries unchanged and show a lesser compromise of renal haemodynamic patterns over a long period compared with double kidney control patients with renal failure, irrespectively of the presence of diabetes.