Objective Methods of Assessing Fluid Status to Optimize Volume Management in Kidney Disease and Hypertension: The Importance of Ultrasound

Abstract

Fluid overload, a prevalent complication in patients with renal disease and hypertension, significantly impacts patient morbidity and mortality. The daily clinical challenges that clinicians face include how to identify fluid overload early enough in the course of the disease to prevent adverse outcomes and to guide and potentially reduce the intensity of the diuresis. Traditional methods for evaluating fluid status, such as pitting edema, pulmonary crackles, or chest radiography primarily assess extracellular fluid and do not accurately reflect intravascular volume status or venous congestion. This review explores the rationale, mechanism, and evidence behind more recent methods used to assess volume status, namely, lung ultrasound, inferior vena cava (IVC) ultrasound, venous excess ultrasound score, and basic and advanced cardiac echocardiographic techniques. These methods offer a more accurate and objective assessment of fluid status, providing real-time, non-invasive measures of intravascular volume and venous congestion. The methods we discuss are primarily used in inpatient settings, but, given the increased pervasiveness of ultrasound technology, some could soon expand to the outpatient setting.

Keywords: echography; fluid overload; sonography; ultrasound; volume overload.

Figure 1

Normal lung ultrasound, A-line pattern.

Figure 2

(A) Abnormal lung ultrasound, with B-line pattern reflecting possible interstitial edema. (B) Abnormal lung ultrasound, with B-line pattern indicating moderate interstitial edema. (C) Abnormal lung ultrasound, with B-line pattern indicating severe interstitial edema.

Figure 3

IVC ultrasound showing a diameter >2.1 cm with <50% change during the respiratory cycle.

Figure 4

Doppler of hepatic vein showing flow reversal.

Figure 5

Doppler of portal vein showing >50% pulsatility index.

Figure 6

Doppler analysis showing mitral valve inflow including E (passive filling during early diastole) and A (active filling during late diastole as the LA contracts) waves with a normal E/A ratio.

Figure 7

Tissue Doppler image (TDI) showing E’ and elevated E/E’ ratio implying elevated filling pressures. E wave calculated from Doppler analysis over MV inflow (not shown).