**Core Concept**
Splenectomy, or the surgical removal of the spleen, can lead to various immediate complications due to the spleen's vital role in the immune system and blood circulation. The spleen is involved in filtering the blood, storing red blood cells, and serving as a reservoir for platelets and white blood cells.

**Why the Correct Answer is Right**
The most common immediate complication of splenectomy is thrombocytosis, which is an increase in platelet count. This occurs because the spleen is responsible for sequestering platelets, and without it, platelets are released into the bloodstream, leading to an elevated platelet count. This condition can increase the risk of thrombotic events, such as deep vein thrombosis or pulmonary embolism.

**Why Each Wrong Option is Incorrect**
* **Option A:** Hemorrhage - While hemorrhage is a potential complication of splenectomy, it is not the most common immediate complication. The spleen is not a major source of bleeding in the body.
* **Option B:** Infection - Infection is a potential complication of splenectomy, but it is not the most common immediate complication. The spleen plays a role in the immune system, but its removal does not directly increase the risk of infection.
* **Option C:** Hypovolemic shock - Hypovolemic shock is a potential complication of splenectomy, but it is not the most common immediate complication. The spleen is not a major source of blood volume in the body.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that patients who undergo splenectomy are at increased risk of infections, particularly those caused by encapsulated organisms such as Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria meningitidis. This is because the spleen plays a crucial role in filtering out these pathogens from the bloodstream.

**Correct Answer: C. Thrombocytosis**