Can We Measure Renal Tissue Perfusion by Ultrasound?

Abstract

BackgroundPerfusion of any organ is a necessary prerequisite of its normal function and reflects disease and functional activity. Easily applicable methods to quantify tissue perfusion are therefore urgently wanted. Widely used single vessel resistance index (RI) calculations have profound conceptual and practical limitations rendering them an often unreliable tool. This paper presents the novel technique of dynamic sonographic tissue perfusion measurement (DTPM) to overcome RI's constrictions.Basic AssumptionIn contrast to using RI calculations we consider perfusion as a product of mean blood flow velocity and mean perfused vascular area inside a tissue during a complete heart cycle.MethodColor pixels in a standardized region of interest in standardized recorded color Doppler sonographic videos are evaluated by the PixelFlux-software. Mean blood flow velocity and mean perfused area are calculated automatically image by image from the beginning to the end of a complete heart cycle. The product is the mean perfusion intensity of the entire region of interest, the pulsation of all parameters allows calculation of so called tissue pulsatility and resistance indices.MaterialDTPM is demonstrated in examples of healthy and transplanted kidneys with normal and compromised function as well as in an apparently healthy kidney from a diabetic individual.ResultsDTPM permits a more realistic appreciation of tissue perfusion compared to RI. DTPM describes quantitatively the microvascular state of the renal cortex in millimetre-thin slices. Functional and morphologic changes can be detected very early this way. Future studies have to plumb the full potential in detection and intervention in acute and chronic renal disease