Can We Measure Renal Tissue Perfusion by Ultrasound?

Ultrasound Doppler Flow Parameters Are Independently Associated with Renal Cortex Contrast-Enhanced Multidetector Computed Tomography Perfusion and Kidney Function

BACKGROUND

The assessment of kidney perfusion has an emerging significance in many diagnostic applications. However, whether and which of the ultrasound Doppler parameters better express renal cortical perfusion (RCP) was not shown. The study aimed to prove the usefulness of Doppler ultrasound parameters in the assessment of RCP regarding low-dose contrast-enhanced multidetector computer tomography (CE-MDCT) blood flow.

METHODS

Thirty non-stenotic kidneys in twenty-five hypertensive patients (age 58.9 ± 19.0) with mild-to-severe renal dysfunction were included in the study. Resistive index (RI) and end-diastolic velocity (EDV) in segmental arteries, color Doppler dynamic RCP intensity (dRCP), RI (dRI), pulsatility index (dPI), and CE-MDCT blood flow (CBF) in the renal cortex were estimated.

RESULTS

CBF correlated significantly with age, estimated glomerular filtration rate (eGFR), RI, EDV, dRI, dPI, and dRCP. In separate multivariable backward regression analyses, RI (R² = 0.290, p = 0.003) and dRCP (R² = 0.320, p = 0.001) were independently associated with CBF. However, in the common ultrasound model, only dRCP was independently related to CBF (R² = 0.317, p = 0.001). Only CBF and EDV were independently associated with eGFR (R² = 0.510, p < 0.001).

CONCLUSIONS

Renal cortical perfusion intensity is the best ultrasound marker expressing renal cortical perfusion. In patients with hypertension and kidney dysfunction, renal resistive index and end-diastolic velocity express renal cortical perfusion and kidney function, respectively.

Renal perfusion index reflects cardiac systolic function in chronic cardio-renal syndrome

BACKGROUND

Cardiac dysfunction can modify renal perfusion, which is crucial to maintain sufficient kidney tissue oxygenation. Renal cortex perfusion assessed by dynamic ultrasound method is related both to renal function and cardiac hemodynamics. The aim of the study was to test the hypothesis that Renal Perfusion Index (RPI) can more closely reflect cardiac hemodynamics and differentiate etiology of chronic cardio-renal syndrome.

MATERIAL AND METHODS

Twenty-four patients with hypertension and chronic kidney disease (CKD) at 2-4 stage (12 with hypertensive nephropathy and 12 with CKD prior to hypertension) were enrolled in the study. Blood tests, 24-h ABPM, echocardiography, and ultrasonography with estimation of Total renal Cortical Perfusion intensity and Renal Perfusion Index (RPI) were performed.

RESULTS

In the group of all patients, RPI correlated with left ventricular stoke volume (LVSV), and cardiac index, but not with markers of renal function. In multiple stepwise regression analysis CKD-EPI(Cys-Cr) (b=-0.360), LVSV (b=0.924) and MAP (b=0.376) together independently influenced RPI (R2=0.74; p<0.0001). RPI<0.567 allowed for the identification of patients with chronic cardio-renal syndrome with sensitivity of 41.7% and specificity of 83.3%.

CONCLUSIONS

Renal perfusion index relates more strongly to cardiac output than to renal function, and could be helpful in recognizing chronic cardio-renal syndrome. Applicability of RPI in diagnosing early abnormalities in the cardio-renal axis requires further investigation.

Correlation of histopathologic and dynamic tissue perfusion measurement findings in transplanted kidneys

Background

Cortical perfusion of the renal transplant can be non-invasively assessed by color Doppler ultrasonography. We performed the Dynamic Tissue Perfusion Measurement (DTPM) of the transplant’s renal cortex using color Doppler ultrasonography (PixelFlux technique), and compared the results with the histopathological findings of transplant biopsies.

Methods

Ninety-six DTPM studies of the renal transplant’s cortex followed by transplant biopsies were performed in 78 patients. The cortical perfusion data were compared with the parameter of peritubular inflammatory cell accumulation (PTC 0 to 3) based on Banff-classification system.

Results

A significant decrease of cortical perfusion could be demonstrated as the inflammatory cells accumulation in peritubular capillaries increased. Increasing peritubulitis caused a perfusion loss from central to distal layers of 79% in PTC 0, of 85% in PTC 1, of 94% in PTC 2, and of 94% in PTC 3. Furthermore, the perfusion loss due to peritubular inflammation was more prominent in the distal cortical layer. The extent of perfusion decline with increasing peritubulitis (from PTC 0 to PTC 3) was 64% in proximal 20% cortical layer (p20), 63% in proximal 50% cortical layer (p50), increased to 76% in distal 50% cortical layer (d50), and peaked at 90% in the distal 20% cortical layer (d20). For those without peritubulitis (PTC 0), the increase in the the Interstitial Fibrosis/Tubular Atrophy (IF/TA) score was accompanied by a significantly increased cortical perfusion. A Polyomavirus infection was associated with an increased cortical perfusion.

Conclusions

Our study demonstrated that the perfusion of the renal transplant is associated with certain pathological changes within the graft. DTPM showed a significant reduction of cortical perfusion in the transplant renal cortex related to peritubular capillary inflammation.

Impact of cardiovascular organ damage on cortical renal perfusion in patients with chronic renal failure

Introduction. Properly preserved renal perfusion is the basic determinant of oxygenation, vitality, nutrition, and organ function and its structure. Perfusion disorders are functional changes and are ahead of the appearance of biochemical markers of organ damage. The aim of this study was to evaluate a relationship between the renal cortex perfusion and markers of cardiovascular organ damage in patients with stable chronic renal failure (CKD). Methods. Seventeen patients (2 F; 15 M; age 47 ± 16) with stable CKD at 2–4 stages and hypertension or signs of heart failure were enrolled in this study. Blood tests with an estimation of renal and cardiac functions, echocardiographic parameters, intima-media thickness (IMT), renal resistance index (RRI), and total (TPI), proximal (PPI), and distal (DPI) renal cortical perfusion intensity measurements were collected. Results. DPI was significantly lower than PPI. TPI significantly correlated with age, Cys, CKD-EPI (cystatin), and IMT, whereas DPI significantly depended on Cystain, CKD-EPI (cystatin; cystatin-creatinine), IMT, NT-proBNP, and troponin I. In multiple stepwise regression analysis model only CKD-EPI (cystatin) independently influenced DPI. Conclusions. Cardiovascular and kidney damage significantly influences renal cortical perfusion. Ultrasound measurement of renal perfusion could be a sensitive method for early investigation of cardiovascular and renal injuries.