What laboratory finding is most likely explained by reduced blood flow to the kidneys after surgery in a patient with a ruptured abdominal aortic aneurysm?

Reduced blood flow to the kidneys after surgery, especially in the context of a ruptured abdominal aortic aneurysm, can result in acute kidney injury (AKI), which is often reflected in increased plasma creatinine levels. Creatinine is a waste product produced by muscle metabolism, and when there is impaired renal perfusion due to decreased blood flow, the kidneys are unable to filter this waste effectively.

In this situation, a plasma creatinine level of 2.1 mg/dL indicates that the kidneys are not functioning optimally, likely due to renal hypoperfusion resulting from the surgical context. Elevated creatinine levels are a key marker used to assess renal function and can serve as an indicator of kidney injury, particularly in acute scenarios like renal hypoperfusion.

Other laboratory findings, such as decreased urine output, while relevant, do not provide as direct of a measurement of renal function as creatinine does; urine output can sometimes remain adequate even with renal impairment. High urine sodium levels can also occur in other contexts of renal disease or diuretic use and are not specifically indicative of reduced blood flow. Low blood pressure is a symptom that can contribute to kidney injury but does not directly reflect the state of kidney function itself as creatinine does. Thus,