The catastrophic coronavirus disease 2019 (COVID-19) pandemic is currently a critical global issue. One well-known complication of COVID-19 in severe cases is acute kidney injury, but no research has given a description of its impact on the kidney in patients with mild symptoms. We explore the renal function changes in mild COVID-19 patients. This retrospective, single-center study included 27 participants with laboratory-detected severe acute respiratory syndrome coronavirus two (SARS-CoV-2) infection who were admitted to the Tri-Service General Hospital from 4 February to 26 May 2020 and analyzed their clinical features, radiological findings, and laboratory data. Data collected upon admission and discharge showed a median estimated glomerular filtration rate (eGFR) of 106.7 mL/min/1.732 m² and 112.2 mL/min/1.732 m², respectively, with a p-value of 0.044. A correlation between renal function and the severity of infection was also found and was statistically significant upon admission. Patients with a lower lymphocyte count or higher C-reactive protein, neutrophil count, and neutrophil-to-lymphocyte ratio presented with a decreased eGFR during their early infection phase. The biomarkers (CRP and NLR) may be linked with dynamic changes of renal function in COVID-19 patients who are asymptomatic or have mild symptoms.

Muscle wasting and hyperphosphatemia are becoming increasingly prevalent in patients who exhibit a progressive decline in kidney function. However, the association between serum phosphate (Pi) level and sarcopenia in advanced chronic kidney disease (CKD) patients remains unclear. We compared the serum Pi levels between advanced CKD patients with (n = 51) and those without sarcopenia indicators (n = 83). Low appendicular skeletal muscle mass index (ASMI), low handgrip strength, and low gait speed were defined per the standards of the Asian Working Group for Sarcopenia. Mean serum Pi level was significantly higher in advanced CKD patients with sarcopenia indicators than those without sarcopenia indicators (3.88 ± 0.86 vs. 3.54 ± 0.73 mg/dL; p = 0.016). Univariate analysis indicated that serum Pi was negatively correlated with ASMI, handgrip strength, and gait speed. Multivariable analysis revealed that serum Pi was significantly associated with handgrip strength (standardized β = −0.168; p = 0.022) and this association persisted even after adjustments for potential confounders. The optimal serum Pi cutoff for predicting low handgrip strength was 3.65 mg/dL, with a sensitivity of 82.1% and specificity of 56.6%. In summary, low handgrip strength is common in advanced CKD patients and serum Pi level is negatively associated with handgrip strength.