A 60-year-old woman is having symptoms of muscle weakness and fatigue. On examination, her blood pressure is 110/80 mm Hg, pulse 100/min, JVP 1 cm, heart sounds normal, and lungs clear. Her serum potassium level is 2.5 mEq/L, bicarbonate 15 mEq/L, and anion gap is normal. The urine potassium is 10 mEq/L.For the above patient with hypokalemia, select the most likely diagnosis.

**Core Concept**
Hypokalemia, characterized by a serum potassium level below 3.5 mEq/L, is a common electrolyte imbalance that can result from various pathophysiological mechanisms, including excessive potassium loss, inadequate potassium intake, or redistribution of potassium within the body.

**Why the Correct Answer is Right**
The patient's hypokalemia is likely due to excessive potassium loss, as indicated by the high urine potassium level of 10 mEq/L. This suggests that the kidneys are excreting potassium in excess, which can be caused by the renin-angiotensin-aldosterone system (RAAS) activation. The RAAS stimulates the release of aldosterone, which acts on the collecting ducts of the kidneys to increase sodium reabsorption and potassium excretion.

**Why Each Wrong Option is Incorrect**
**Option A:** While renal tubular acidosis (RTA) can cause hypokalemia, the patient's normal anion gap and bicarbonate level make this diagnosis less likely.
**Option B:** The patient's normal JVP and heart sounds suggest that cardiac causes of hypokalemia, such as hypokalemic cardiomyopathy, are unlikely.
**Option C:** The patient's normal blood pressure and lack of symptoms suggestive of adrenal insufficiency make primary adrenal insufficiency an unlikely diagnosis.

**Clinical Pearl / High-Yield Fact**
Remember that the kidneys play a crucial role in potassium balance, and excessive potassium loss can lead to hypokalemia. The urine potassium level can be a useful indicator of the underlying cause of hypokalemia, with high levels suggesting excessive potassium loss.

**Correct Answer:** D.

✓ Correct Answer: A. lower gastrointestinal (GI) losses