American Board of Internal Medicine (ABIM) Certification Practice Exam

In patients with Contrast-Induced Nephropathy (CIN), when is an improvement in serum creatinine typically observed?

1. 24-48 hours

2. 72 hours

3. 3 to 7 days

4. 1 to 2 weeks

The correct answer is: 3 to 7 days

In patients experiencing Contrast-Induced Nephropathy (CIN), an improvement in serum creatinine levels is typically observed within a timeframe of 3 to 7 days post-injury. This period reflects the time needed for the kidneys to recover from the acute injury caused by the contrast agent. The pathophysiology of CIN involves a transient reduction in renal perfusion and direct tubular toxicity caused by the contrast material, which can lead to acute kidney injury. Recovery of renal function often occurs as the effects of the contrast agent diminish, and the kidneys' ability to filter waste products resumes. Monitoring during this phase is crucial, as some patients may continue to show signs of improvement after the first few days. This timeframe aligns with the general understanding of acute kidney injury recovery in many patients, highlighting that a gradual normalization of serum creatinine levels typically occurs over a week. It is important to note that while some improvement can be seen as early as 24 hours, significant recovery is usually expected within the 3 to 7 days range.