The Detection of Lung Pathologies Among Dialysis Patients Using Novel Mobile-Phone Ultrasound - A Feasibility Pilot Study

Background Patients with end-stage renal disease (ESRD) and heart failure (HF) have a high risk to suffer from pulmonary congestion (PC) (1,2). PC in HF and ESRD patients is a common cause of admission, mortality, and cardiac events )3-6(. Extravascular lung water (EVLW), which leads to PC, can be subclinical among normo-hydrated dialysis patients (1,7).

PC exact mechanism in ESRD is under debate )8( but occurs in a combination of two forces mechanism - changes in hydrostatic pressure due to HF and volume overload and increase in lung permeability with retention of uremic product and chronic inflammation (1,2,6,8). Chronic load of extracellular volume and increased LV filling pressure is mainly the cause of EVLW accumulation leading to clinical PC (1,2). Volume overload builds gradually during the interval between the dialysis treatments (6,7) and maybe asymptomatic (1,6). PC can also occur in ESRD patients, even with normal cardiac filling pressure or mild volume overload )8( and can be explained by volume redistribution (2). Untreated or suboptimal treated PC can cause respiratory distress. Volume overload is an independent risk factor for death and cardiovascular events in ESRD patients (2,9). Therefore, volume removal is crucial to prevent PC events (2). Dialysis reduces the severity of PC immediately )8(, and delay in treatment can increase the frequency and the severity of the events (8,9).

Lung ultrasound (LUS) is an effective, bedside, imaging tool for the detection and monitoring of PC (2,7-12). Alveolar interstitial syndrome, which can be caused by an increase of EVLW, is diagnosed by the detection of ultrasonographic B-lines in both lung zones (2,3,5,7,9,10). Lung ultrasound was found at least sensitive and effective as other traditional modalities to diagnose PC (1,4,5,8,10,13).

B-lines are hyperechoic reverberation, relatively simple to teach and conduct (3,8,11), which can be detected by LUS (5,8,14). Some studies quantified B-lines using the B-line score (BLS). The score is calculated by the number of lung zones that are dichotomously positive for B-lines (10,11). Furthermore, B-lines are an important prognostic factor for death, cardiovascular events, and readmission in ESRD and HF patients (2-4,10-12).

Changes in BLS seen during volume removal by dialysis treatment or diuresis (2,7-10) represents the dynamic changes in EVLW (7,9-11). Studies found a distinct real-time decrease in the number of B-line and BLS that correlated with the traditional examination for EVLW (2,9- 11,13). Data suggests that B-lines monitoring is used for the assessment of volume overload removal adequacy (2,4,10,11).