**Background:** Sarcopenia, defined as loss of muscle mass and quality, is prevalent in up to 70% of patients awaiting liver transplantation (LT) and contributes to adverse outcomes. While low muscle mass has been associated with waiting list and post-transplant mortality, the impact of muscle quality (myosteatosis) on short- and long-term survival remains insufficiently understood. CT is the reference standard for assessing both muscle quantity (skeletal muscle index, SMI) and quality (muscle radiodensity attenuation, MRA). This study aimed to evaluate the course of CT muscle parameters after LT and their impact on short-term and long-term survival.
**Methods:** This retrospective observational study included 152 patients (109 male, 43 female; mean age 55±10 years) who underwent LT between 2011 and 2015 and had a pre-transplant CT scan within 8 months prior to LT. CT scans at the level of L3 were analyzed using ImageJ software. SMI was calculated as skeletal muscle area (SMA) divided by height squared, with sarcopenia defined by Carey et al. cut-offs (male <50 cm²/m², female <39 cm²/m²). MRA in Hounsfield units (HU) was assessed exclusively on venous-phase CT scans to avoid contrast-agent bias. Short-term follow-up (FU) was defined as 6–18 months post-LT (median 11 months, n=50 for muscle mass, n=38 for muscle density), and long-term FU as ≥19 months (median 56 months, n=52 for muscle mass, n=35 for muscle density). Changes in muscle parameters were analyzed using univariate linear regression with baseline adjustment. Survival was assessed using Kaplan-Meier estimators and multivariable Cox proportional hazards regression adjusting for sex, age, MELD score, BMI, and Clavien-Dindo classification.
**Key Results:** Pre-transplant, 93/152 (61%) patients had sarcopenia by SMI cut-offs. Mean SMI was 44.59±9.06 cm²/m² and mean MRA was 38±8 HU. At short-term FU, SMI decreased by −2.65 cm²/m² (95% CI [−4.52, −0.77], p=0.007) and MRA decreased by −3 HU (95% CI [−6, −1], p=0.007) compared to pre-LT values. At long-term FU, SMI decreased by −2.96 cm²/m² (95% CI [−4.7, −1.23], p=0.001) and MRA showed a non-significant decrease of −2 HU (95% CI [−4, 0], p=0.069). The prevalence of sarcopenia increased from 61% pre-LT to 70% at short-term FU and 67% at long-term FU. Patients with pre-LT MRA below the mean (38 HU) had significantly worse survival: 3-month survival 72% vs. 95%, 1-year survival 63% vs. 90%, and 5-year survival 54% vs. 84% (p<0.001). In multivariable Cox regression, pre-LT muscle density below the mean was an independent predictor of mortality (HR 2.985, 95% CI [1.365–6.528], p=0.006), as was underweight (BMI <18.5 kg/m²; HR 3.185, 95% CI [1.023–9.919], p=0.046). Pre-LT muscle mass below the sarcopenia cut-off was not associated with survival (HR 0.979, 95% CI [0.481–1.990], p=0.953). Patients with low muscle density also had higher rates of infectious causes of death (p=0.035). Neither muscle mass nor density was associated with length of ICU stay in multivariable models. Patients with low MRA had more severe post-operative complications (Clavien-Dindo ≥IIIb: 71% vs. 48%, p=0.008).
**Clinical Implications:** This study demonstrates that both muscle mass and quality do not improve after liver transplantation and instead continue to decline. Crucially, muscle quality (MRA) — not muscle mass — was a strong independent predictor of short-term and long-term survival, with the highest mortality risk in the first 3 months post-transplant. These findings suggest that CT-assessed muscle density should be routinely evaluated alongside muscle mass in pre-transplant assessment to identify high-risk patients who may benefit from targeted nutritional and physical therapy interventions. The study supports EASL guidelines recommending optimization of muscle status prior to LT, as this may improve not only waiting list survival but also post-transplant outcomes. Limitations include the reduced number of patients with available post-transplant CT scans and the lack of data on physical performance measures.