Mildly Low Serum Sodium Levels in Chronic Liver Disease: At Risk for Sarcopenia and Portal Hypertension

Objective: Hyponatremia and sarcopenia in advanced chronic liver disease (ACLD) are both associated with portal hypertension (PHT) and worse prognosis. This study investigated their interrelationship. Methods: This retrospective study analyzed 751 patients with CLD who underwent magnetic resonance elastography (MRE) at Nippon Kokan Hospital (Kawasaki, Japan). Patients were classified and studied in five groups based on serum sodium (Na) levels: <135, 135-136, 137-138, 139-140, and >140 mEq/L. PHT was assessed by thrombocytopenia, varices, and ascites, and magnetic resonance imaging (MRI) data were used to diagnose sarcopenia. Results: The proportions of the five groups were 3/4/13/32/48 (%), and the mean liver stiffness (LS) was 6.6/5.7/4.2/3.2/3.2 (kPa), with significant progressive increases at Na < 139 (p < 0.01). The incidence of all PHT events and sarcopenia also increased at <139 (each p < 0.01). By contrast, the LS thresholds for predicting thrombocytopenia, varices, and ascites increased from 3.5 to 4.7 and 5.1, respectively, and were the same at 3.4 for low Na (<139) and sarcopenia (all p < 0.01). Multivariate analysis of factors associated with low Na identified LS and sarcopenia as independent factors (p < 0.05 both). In the Cox proportional hazards model, low Na was a significant prognostic factor in ACLD (hazard ratio (HR) 5.33, p < 0.01); however, the albumin-bilirubin (ALBI) score (HR 2.49) and sarcopenia (HR 4.03) were extracted in the multivariate analysis (p < 0.05 both). Conclusions: Studies using MRE imaging showed that low Na levels in CLD are associated with worse prognosis, not only due to elevated LS (i.e., PHT) but also the strong association with sarcopenia.