**Core Concept**
The transpyloric plane is an anatomical landmark in the abdominal cavity, separating the upper and lower parts of the abdominal organs.

**Why the Correct Answer is Right**
The transpyloric plane passes through the lower border of the first lumbar vertebra (L1) and the pylorus of the stomach. It serves as a reference point for various abdominal organs, including the liver, gallbladder, and pancreas. The plane is significant in radiological imaging, particularly in abdominal X-rays and CT scans.

**Why Each Wrong Option is Incorrect**
**Option A:** The transpyloric plane does not separate the diaphragm from the liver; the diaphragm separates the thoracic cavity from the abdominal cavity.
**Option B:** The transpyloric plane does not pass through the renal hilum; the renal hilum is the structure that contains the renal vessels and the ureter.
**Option C:** The transpyloric plane does not separate the spleen from the stomach; the spleen is located in the left upper quadrant of the abdomen, near the stomach.

**Clinical Pearl / High-Yield Fact**
The transpyloric plane is an essential landmark in abdominal imaging, and identifying it can help in diagnosing various abdominal pathologies.

**Correct Answer: C. The transpyloric plane separates the stomach from the duodenum.**