Reliability of bedside ultrasound for measurement of quadriceps muscle thickness in critically ill patients with acute kidney injury

Main problem

In patients with Acute Kidney Injury there is a lack of nutritional variables that can assess nutritional status, more specifically lean body mass (LBM), at the individual level (Fiaccadori E et al, 2013 [1]). In this clinical setting, ultrasound (US) of the quadriceps femoris could represent a widely available, non-invasive, affordable, and reliable tool to evaluate skeletal muscle, a clinical surrogate of LBM (Connolly B et al, 2015 [2]Segers J et al, 2015 [3]Arbeille P et al, 2009 [4]).


We performed a cross-sectional observational study in adult critically ill patients with KDIGO stage 3 AKI on dialysis. Quadriceps rectus femoris and vastus intermedius thickness (QRFT and QVIT) were measured by two assessors. Intra-, interobserver  and test-retest reliability was evaluated using the intraclass coefficient correlation (ICC). The same US measures were obtained before and after dialysis for the test-retest reliability study.


We enrolled 34 patients, 22 (65%) were male and the mean APACHE II score was 22.7 (± 5.6) (Figure 1).  In the intraobserver reliability study, assessor 1 performed 288 paired measurements and assessor 2 performed 430 paired measurements in 34 patients, with an ICC equal to 0.99 and 1.00, respectively (Figure 2). There were 238 paired measurements (34 patients) in the interobserver reliability study, with an ICC = 0.92 (Figure 3). No difference was found in the measurements obtained before and after dialysis (11.5 (4.2) vs 11.4 (4.1) mm, P = 0.2498), independently from acute body weight changes due to fluid removal. In the test-retest reliability study, assessor 1 performed 294 paired measures and assessor 2 performed 306 paired measures, the ICC for the test-retest reliability was 0.97 for assessor 1 (range from 0.95 to 0.95 for all sites) and 0.95 for assessor 2 (range from 0.93 to 0.96 for all sites) (Figure 4).


In patients with AKI, US of quadriceps femoris could represent a simple, accurate, and non-invasive method to evaluate quantitative changes in skeletal muscle.