Ultrasound Assessment of Diaphragm Structure and Function in Dialysis-Dependent Chronic Kidney Disease: A Systematic Review

Abstract

Background: Respiratory muscle dysfunction is common in dialysis-dependent chronic kidney disease (CKD), but the structural and functional status of the diaphragm and its responsiveness to rehabilitation have not been consistently characterised using ultrasound.

Objective: To synthesise evidence on ultrasound-derived diaphragm thickness, thickening fraction, excursion, and stiffness in adults receiving dialysis and to examine whether rehabilitation interventions are associated with changes in these imaging outcomes.

Methods: A systematic review was conducted in accordance with PRISMA 2020. MEDLINE, Embase, CENTRAL, CINAHL, Web of Science Core Collection, Scopus, and PEDro were searched from inception to the final search date, supplemented by trial registries, citation tracking, reference list screening, and grey literature searches. Eligible studies included adults with dialysis-dependent CKD or advanced CKD reporting ultrasound-derived diaphragmatic outcomes. Two reviewers independently screened studies and extracted data. Randomised trials were assessed using RoB 2, and observational studies using design-appropriate Joanna Briggs Institute appraisal tools. Because of substantial clinical and methodological heterogeneity, findings were synthesised narratively in accordance with SWiM principles, and certainty was assessed using GRADE.

Results: Four studies involving 478 participants were included. Three were observational, and one was a small randomised trial. Ultrasound-derived diaphragm thickness during deep inspiration was lower in haemodialysis populations than in healthy controls or preserved-function subgroups. The thickening fraction was also consistently lower in the two studies reporting it. Excursion and velocity were directionally reduced, although statistical significance was not consistent. One study using shear-wave elastography reported substantially lower diaphragmatic stiffness in haemodialysis patients than in healthy controls, with excellent diagnostic discrimination, but this finding has not been replicated. The only interventional study evaluated intradialytic cycle ergometry rather than targeted respiratory muscle training and found no significant change in diaphragm thickness after four weeks, despite reported improvements in respiratory muscle strength. Overall certainty was low to very low for the principal outcomes.

Conclusion: Ultrasound provides convergent descriptive evidence of impaired diaphragmatic structure and function in dialysis-dependent CKD. However, evidence that targeted respiratory muscle training reverses ultrasound-defined structural abnormalities is absent. Future multicentre studies should harmonise ultrasound acquisition, validate diagnostic thresholds, and evaluate targeted respiratory muscle training with serial imaging alongside functional and patient-reported outcomes.