American Board of Internal Medicine (ABIM) Certification Practice Exam

In patients with metabolic alkalosis, what urine chloride level is indicative of saline-responsive metabolic alkalosis?

1. More than 15 mEq/L

2. Less than 5 mEq/L

3. Less than 15 mEq/L

4. Exactly 10 mEq/L

The correct answer is: Less than 15 mEq/L

In the context of metabolic alkalosis, the urine chloride level acts as an important diagnostic tool to determine the underlying cause and whether the condition is responsive to saline administration. When the urine chloride level is less than 15 mEq/L, it typically indicates a saline-responsive form of metabolic alkalosis. This lower level of urine chloride often suggests that the body is compensating for a loss of chloride, which can occur due to external factors such as gastrointestinal losses (e.g., vomiting) or diuretics that deplete fluid and electrolytes. In these cases, administering saline can help correct the alkalosis by providing chloride and restoring a more normal acid-base balance. Conversely, a higher urine chloride level (greater than 15 mEq/L) usually signals that metabolic alkalosis is not primarily due to a chloride deficit, indicating that the condition might not respond to saline administration. Such presentations may be seen in situations where there is an excess of mineralocorticoids or other causes of chloride dysregulation. Understanding these urine chloride levels helps clinicians differentiate between the causes of metabolic alkalosis and guides appropriate treatment strategies.