**Metabolic Anomaly in Pyloric Stenosis**

**Core Concept**
Pyloric stenosis is characterized by a congenital narrowing of the pyloric channel, leading to gastric outlet obstruction. This condition results in metabolic changes due to prolonged vomiting and gastric decompression.

**Why the Correct Answer is Right**
In pyloric stenosis, the metabolic anomaly is primarily due to the loss of hydrochloric acid (HCl) and electrolytes through persistent vomiting. The body compensates for this loss by increasing the secretion of aldosterone, which leads to hyperkalemia (elevated potassium levels) and metabolic alkalosis (elevated blood pH). The kidneys respond by retaining hydrogen ions, which further exacerbates the alkalosis. This metabolic derangement is a hallmark of pyloric stenosis.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect as it does not accurately describe the metabolic anomaly in pyloric stenosis.
* **Option B:** This option is incorrect as it is more commonly associated with other conditions such as diabetic ketoacidosis or lactic acidosis.
* **Option C:** This option is incorrect as it is more commonly associated with conditions such as renal failure or adrenal insufficiency.

**Clinical Pearl / High-Yield Fact**
Prolonged vomiting in pyloric stenosis can lead to hypochloremic metabolic alkalosis, which is characterized by elevated blood pH, low chloride levels, and low bicarbonate levels. This condition requires prompt medical attention to prevent complications such as hypokalemia and cardiac arrhythmias.

**Correct Answer:** D.