Risk of Severe Acute Kidney Injury According to the Presence of Nephrotic-Range Proteinuria in Patients with Liver Cirrhosis: A Retrospective Cohort Study (2016–2025)

Background and Objectives: Acute kidney injury (AKI) is a frequent and life-threatening complication in patients with liver cirrhosis (LC). Nephrotic-range proteinuria may reflect underlying structural renal vulnerability; however, its association with AKI severity in cirrhosis remains unclear. Materials and Methods: We conducted a retrospective cohort study of 408 adults with LC admitted to a tertiary referral hospital between January 2016 and December 2025. Nephrotic-range proteinuria was defined as a urine protein-to-creatinine ratio (UPCR) ≥3.5 g/g measured within 7 days before or at admission. AKI was staged using serum creatinine-based Kidney Disease: Improving Global Outcomes criteria. Baseline creatinine was defined as the lowest value within 7 days before admission; if unavailable, the lowest stable value within the preceding 3 months was used. Severe AKI was defined as KDIGO stage 2–3. Multivariable logistic regression was performed to evaluate the association between nephrotic-range proteinuria and severe AKI after adjustment for age, sex, diabetes mellitus, hypertension, chronic kidney disease (CKD), sepsis, ICU admission, and Child–Pugh class. Results: Of the 408 patients, 56 (13.7%) had nephrotic-range proteinuria. Severe AKI occurred more frequently in patients with nephrotic-range proteinuria than in those without (39.3% vs. 21.9%), corresponding to an absolute risk difference of 17.4 percentage points (p = 0.008). In the adjusted model, nephrotic-range proteinuria was associated with a higher likelihood of severe AKI (adjusted odds ratio OR, 2.27; 95% confidence interval CI, 1.17–4.41; p = 0.015). CKD (adjusted OR, 2.26; 95% CI, 1.33–3.81; p = 0.002), ICU admission (adjusted OR, 2.03; 95% CI, 1.22–3.39; p = 0.007), and Child–Pugh class C versus A (adjusted OR, 3.50; 95% CI, 1.37–8.93; p = 0.009) were also significantly associated with severe AKI. Conclusions: Among hospitalized patients with LC, nephrotic-range proteinuria was associated with a higher likelihood of severe AKI. Quantitative proteinuria assessment may help identify patients at increased risk of advanced renal dysfunction, although causal inference is limited by the retrospective observational design.