1. Renal parenchymal perfusion measurement with the PixelFlux method to evaluate the effect of the so called Nutcracker-Syndrome
Thomas Scholbach
Leipzig Ultrasound Institute

2. Background
Compression of the left renal vein is the hallmark of the Nutcracker Syndrome. It is often difficult to correlate the diameter reduction to the patient’s symptoms, mainly left flank and mid-abdominal and pelvic pain.
Moreover, left renal vein compression may occur without compression by the superior mesenteric artery or away from the aorta.
Nevertheless, any compression may cause a relevant pressurization and thus pain in the left flank and in the collateral pathways.
To evaluate the functional extent of left renal vein compression we measure the parenchymal perfusion of both kidneys with the PixelFlux technique.

3. Material and Methods
measurements
patients 1
158 2 28 3 10 4 5 7 9
Patients: 285 PixelFlux measurements were carried out in 204 patients with NKS from 2016 til 2018 Method: Dynamic Color Doppler sonographic PixelFlux perfusion measurement Descpition of the method: PixelFlux software calculates blood flow intesity in renal cortex in standardized color Doppler videos Statistics: Mann-Whitney-U-Test

4. Color Doppler example of severe Nutcracker-Syndrome
V. ren. sin
Aorta
A. mes. sup.
V. ren. sin
Aorta
A. mes. sup.
Click to start video
Click to start video

5. Perfusion suppression of the left kidney can now be measured
For entire cortex:
1. H0 hypothesis Since p-value<α, H0 is rejected. The value of the Group1's population is considered to be not equal to the value of the Group2's population. In other words, the difference between the value of the Group1 and Group2 populations is big enough to be statistically significant.
2. P-value p-value equals , ( p(x≤Z) = ). This means that the chance of type1 error (rejecting a correct H0) is small: (1.98%) The smaller the p-value the more it supports H1 3. The statistics The test statistic Z equals , is not in the 95% critical value accepted range: [ : ] U= , is not in the 95% accepted range: [ : ]
For proximal cortex: Two sample mann-whitney u test, using Normal tables (n=562) (two-tailed)
Since n1 > 20 or n2 > 20, normal approximation is used.
2. P-value p-value equals , ( p(x≤Z) = ). This means that the chance of type1 error (rejecting a correct H0) is small: (0.52%) The smaller the p-value the more it supports H1 3. The statistics The test statistic Z equals , is not in the 95% critical value accepted range: [ : ] U= , is not in the 95% accepted range: [ : ]
For distal cortex: Two sample mann-whitney u test, using Normal tables (n=559) (two-tailed)
2. P-value p-value equals , ( p(x≤Z) = ). This means that the chance of type1 error (rejecting a correct H0) is small: (0.077%) The smaller the p-value the more it supports H1 3. The statistics The test statistic Z equals , is not in the 95% critical value accepted range: [ : ] U= , is not in the 95% accepted range: [ : ]
The suppression of left kidney‘s perfusion in Nutcracker-Syndrome patients can be measured reliably with the PixelFlux-method. Perfusion loss is 30% in median.

6. PixelFlux measurements demonstrate treatment effect in Nutcracker-Syndrome

7. Conclusion
PixelFlux measurements allow for the first time an objective evaluation of the impact of Nutcracker-Syndrome onto renal perfusion.
Examination lasts less than 1 minute. Results correlate to patient's complaints (not outlined here).
In Nutcracker-Syndrome significant suppression of the left renal perfusion is found.
This improves after surgical or medical treatment.
Treatment effect can be precisely evaluated.
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