Methodological Approaches for Ultrasound Assessment of Peripheral and Abdominal Muscle Thickness in Intensive Care: A Scoping Review and Proposed Reporting Framework.

OBJECTIVE

To map and synthesize methodological approaches used for ultrasound (US) assessment of peripheral (upper- and lower-limb) and abdominal muscle thickness in critically ill patients, and to propose a preliminary Standard Operating Procedure (SOP) as a structured reporting framework.

METHODS

A review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews checklist, using systematic searches on PubMed, BIREME (including MEDLINE, LILACS and IBECS) and Embase. Two reviewers independently screened, selected, and extracted data from studies published between 2015 and 2025. Extracted data included muscle groups assessed, thickness measurement criteria, patient and probe positioning, operational US parameters, and reliability information. The proposed SOP was developed based on recurring methodological patterns identified in the literature and subsequently refined through external expert review and pilot feasibility testing in ICU settings.

RESULTS

Of 2.293 identified records, 29 studies (1.736 patients) were included. B-mode imaging and linear transducers were the most frequently reported US parameters, and the supine position with the head of the bed elevated to 30° was the predominant patient position. Although 79.3% of studies described muscle thickness measurement criteria, important methodological details such as depth, gain, and anatomical landmarks were inconsistently reported. Lower-limb muscles were the most frequently assessed, whereas upper-limb and abdominal muscles remained comparatively underrepresented. Considerable variability was identified across acquisition procedures, anatomical landmarks, measurement criteria, and reporting practices.

CONCLUSIONS

Ultrasound assessment of muscle thickness in critically ill patients shows substantial methodological and reporting variability. A preliminary SOP was developed and pilot-tested to improve consistency and comparability. Standardization may support bedside monitoring and inform physiotherapy assessment and rehabilitation decisions, although multicenter validation is required.

TRIAL REGISTRATION: Open Science Framework: https://doi.org/10.17605/OSF.IO/S95MJ.