**Core Concept**
The most common organs affected by blunt trauma to the abdomen are those that are solid, fixed, and have a high concentration of blood vessels. This is due to their anatomical location and the forces exerted during the trauma.

**Why the Correct Answer is Right**
The liver and spleen are the most commonly affected organs in blunt abdominal trauma due to their location in the upper left quadrant of the abdomen. The liver is fixed by the falciform ligament and the diaphragm, making it more susceptible to injury. The spleen is also fixed by the splenorenal ligament and the diaphragm, which makes it more prone to rupture. The liver and spleen receive a significant amount of blood flow, making them more susceptible to hemorrhage due to injury.

**Why Each Wrong Option is Incorrect**
**Option A:** The stomach is not the most commonly affected organ in blunt abdominal trauma, as it is a hollow organ and is more likely to be injured by penetrating trauma.
**Option B:** The small intestine is also not the most commonly affected organ, as it is a hollow organ and is more likely to be injured by penetrating trauma.
**Option C:** The kidneys are solid organs, but they are less commonly affected by blunt abdominal trauma due to their location in the retroperitoneal space, which provides some protection.

**Clinical Pearl / High-Yield Fact**
In blunt abdominal trauma, the liver and spleen are at high risk of injury due to their solid, fixed, and highly vascular nature. Remember the "LIVER" mnemonic to recall the organs most commonly affected: Liver, Intestines are not typically, Vascular organs, Eyes, and Rectum.

**Correct Answer: C. Kidneys are not the most commonly affected organ in blunt abdominal trauma.