Subcutaneous Tissue Depth Associated With Hospital Admission in Cellulitis: A Retrospective Study

We conducted a single-site retrospective cohort study of ED patients who underwent soft-tissue PoCUS for suspected cellulitis of the face, neck, axilla, posterior arm, abdomen, buttocks, or thigh from 1/1/2020 to 12/31/2024. Exclusion criteria included alternative soft tissue diagnoses (abscess, hematoma, seroma, venous thrombus), recent surgery at the affected site, tick bite, animal bite, chronic wound, foreign body, or inadequate PoCUS image quality. The primary outcome was hospital admission. Maximal superficial fatty layer thickness was independently measured on PoCUS by three blinded reviewers. Normal superficial fatty layer thickness was calculated using a validated formula incorporating age, sex, and body mass index (BMI). A measured-to-normal thickness ratio was calculated, with a ratio ≥1.5 selected a priori to represent a clinically meaningful increase in subcutaneous tissue thickness. The association between a ratio ≥1.5 and hospital admission was evaluated using bivariate analyses and multivariable logistic regression controlling for diabetes, intravenous drug abuse, and immunocompromised state.

Emergency physicians often face uncertainty when determining which patients with cellulitis require hospital admission. While point-of-care ultrasound (PoCUS) is commonly used to exclude abscess, it can also quantify affected subcutaneous tissue depth not apparent on physical examination. This study evaluated whether PoCUS-measured subcutaneous tissue depth independently predicts hospital admission in Emergency Department (ED) patients with cellulitis.

Of 975 patients who had soft tissue PoCUS, 61 had suspected cellulitis at eligible sites after applying exclusion criteria. Among these, 10/61 (16.4%) were admitted to the hospital, 36/61 (59.0%) had ratios

PoCUS-measured superficial fatty layer thickness may provide objective information beyond physical examination to help risk stratify patients and inform disposition decisions, warranting further prospective validation.