A 58-year-old male with a history of chronic kidney disease (CKD) stage 3 presents to the clinic reporting increased fatigue, swelling in his ankles, and decreased urine output over the past week. His serum creatinine is 3.8 mg/dL (baseline 2.1 mg/dL), BUN is 42 mg/dL, and his glomerular filtration rate (GFR) has dropped from 35 to 18 mL/min/1.73m². The nurse is reviewing his lab results and clinical findings to determine whether this represents a worsening of his CKD or a new acute process. Which finding most strongly suggests that this client is experiencing an acute kidney injury (AKI) superimposed on his chronic kidney disease rather than simply disease progression?
- Presence of bilateral ankle edema and fatigue
- A GFR of 18 mL/min/1.73m² placing him in stage 4 CKD
- A rapid rise in serum creatinine from his documented baseline over days to one week
- BUN of 42 mg/dL indicating azotemia