**Core Concept**
Blunt abdominal trauma with splenic rupture involves the sudden and forceful impact to the abdomen, leading to the injury of the spleen, a highly vascular organ located in the upper left region of the abdomen. The spleen's fragility and its location make it susceptible to injury from blunt trauma.

**Why the Correct Answer is Right**
The correct answer involves understanding the pathophysiology and clinical presentation of splenic rupture. Kehr's sign is a clinical finding characterized by left shoulder pain and discoloration around the umbilicus due to the tracking of bleeding from the spleen along the left diaphragmatic crus to the left shoulder. This occurs because the splenic vessels are closely related to the diaphragm. The spleen is indeed the most common organ to be involved in blunt abdominal trauma, due to its location and fragility. Splenectomy, or surgical removal of the spleen, is often considered the treatment of choice for splenic rupture, especially in cases of severe bleeding or hemodynamic instability.

**Why Each Wrong Option is Incorrect**
**Option A:** Discoloration around the umbilicus is not a characteristic of Kehr's sign, which typically presents with left shoulder pain and discoloration around the umbilicus due to the tracking of bleeding from the spleen.
**Option C:** While splenectomy is a treatment option for splenic rupture, it is not the treatment of choice for all cases, especially in hemodynamically stable patients, as non-operative management with splenic salvage is often preferred.

**Clinical Pearl / High-Yield Fact**
In cases of blunt abdominal trauma, the presence of Kehr's sign (left shoulder pain and discoloration around the umbilicus) is highly suggestive of splenic rupture. This clinical correlation is essential for prompt diagnosis and management.

**Correct Answer:** B. The spleen is most common organ to be involved.