Interlobar Venous Flow Is Different between Left and Right Kidney in Uncomplicated Third Trimester Pregnancy

Abstract

Aim: To investigate Doppler flow patterns of renal interlobar veins (RIV) in left (L) and right (R) kidney in relation to gestational age and to intrarenal pyelocalyceal diameters (PCD). Methods: Cross-sectional study involving 6 groups of women: (1) non-pregnant women, women pregnant between weeks (2) 11–14, (3) 18–23, (4) 28–33, (5) 37–40 and (6) women <5 days post delivery. During standardized renal duplex ultrasound scan, PCD (mm) was measured and venous impedance index (VI = [peak flow (PV) – presystolic flow]/PV) of RIV was defined. Comparison between L and R kidney was performed by repeated-measures analysis of variance for VI and by t tests for PCD. Results: A total of 150 women were examined, 25 in each group. In the early third trimester of pregnancy, L VI was significantly higher than R VI (0.38 ± 0.01 vs. 0.33 ± 0.01, p < 0.0001) and L PCD was significantly lower than R PCD (3.90 ± 3.68 vs. 6.25 ± 4.03, p = 0.03). Conclusion: RIV Doppler flow is different between left and right kidney only in the third trimester of pregnancy. This difference is inversely related to PCD, which may be explained by pelvic compression from the gravid uterus.

Doppler Measurement of Renal Interlobar Vein Impedance Index in Uncomplicated and Preeclamptic Pregnancies

“…By definition, RIVI = DeltaV / MxV, so the different gestational evolutions of these two parameters explains the third trimester interkidney difference of RIVI. An inverse relation between RIVI and PCD was reported both for nonpregnant (1) and pregnant individuals (3,4). Our observed evolution of right kidney PCD and RIVI (Figure 2d) during pregnancy and postpartum, is consistent with this.…”

“…Standardisation of scanning methodology therefore is mandatory. We already reported elsewhere a low intra-class correlation coefficient of 0.31 to 0.35 between individual RIVI measurements according to our scanning protocol (4). However, the use of mean values from three consecutive RIVI measurements produced more stable data, represented by an intra-kidney correlation coefficient of 0.88.…”

“…Therefore, the functional meaning of Doppler flow characteristics in the venous system is totally different from those on the arterial side, and are currently not yet well understood. In this study, we have tried to unravel some of the hemodynamic background mechanisms behind the gestational evolution of intrarenal venous flow and behind a reported interkidney difference of RIVI (3)(4)(5). As presented in Figure 2a, the gestational evolution of MxV shows an increase in the first trimester to a maximum at 16 weeks, after which there is a gradual decrease until term.…”

“…Application of this parameter to renal interlobar veins (RIV) was reported to be useful in obstructive uropathy (1,2). In uncomplicated pregnancies (UP), a decrease of renal interlobar venous impedance index (RIVI) was observed, and this decrease was more pronounced in the right kidney (RK) than in the left one (LK) (3,4). It was hypothesized that this observation resulted from retro peritoneal compression 24 Gyselaers et al by the gravid uterus (3,4).…”

“…In uncomplicated pregnancies (UP), a decrease of renal interlobar venous impedance index (RIVI) was observed, and this decrease was more pronounced in the right kidney (RK) than in the left one (LK) (3,4). It was hypothesized that this observation resulted from retro peritoneal compression 24 Gyselaers et al by the gravid uterus (3,4). In pre-eclampsia (PE) however, higher values of RIVI were reported as compared to UP (5).…”