**Core Concept:** Hyperexpansion and hypokalemia are manifestations of certain medical conditions, particularly those affecting the gastrointestinal tract. In this context, CT abdomen is conducted to identify the underlying cause.

**Why the Correct Answer is Right:** The correct answer, **C. Intestinal potassium loss**, is derived from the patient's symptoms and findings. When the gastrointestinal tract undergoes excessive dilation (hyperexpansion), potassium can be lost in the stool, leading to hypokalemia. CT abdomen is a diagnostic tool used to visualize the gastrointestinal tract and identify any abnormalities that may contribute to this loss.

**Why Each Wrong Option is Incorrect:**

A. **Increased renin secretion (Option A)**: This is not directly related to the gastrointestinal tract and does not explain the observed hypokalemia and hyperexpansion.

B. **Hypokalemic periodic paralysis (Option B)**: While hypokalemic periodic paralysis can present with hypokalemia, it typically does not involve hyperexpansion of the gastrointestinal tract.

D. **Intestinal obstruction (Option D)**: While intestinal obstruction can lead to hypokalemia, it is less likely to cause hyperexpansion of the gastrointestinal tract, as obstruction would compress the intestine, not cause dilation.

**Clinical Pearl:** Hypokalemic periodic paralysis is a rare condition characterized by recurrent muscle weakness, typically triggered by hypokalemia. This condition should be distinguished from the provided options, which involve gastrointestinal tract abnormalities leading to hypokalemia.

In conclusion, the correct answer (C) is chosen due to the gastrointestinal tract's involvement in both hypokalemia and hyperexpansion. CT abdomen is a useful diagnostic tool to confirm the clinical suspicion and guide further management.