**Core Concept**
Cisplatinum is a platinum-based chemotherapeutic agent used to treat various cancers, including esophageal carcinoma. Its side effects are primarily related to its mechanism of action, which involves DNA damage and cell death.

**Why the Correct Answer is Right**
The correct answer is nephrotoxicity, which is the most common side effect of cisplatinum. This is due to the drug's ability to cause damage to the renal tubular cells, leading to acute kidney injury. The mechanism involves the formation of platinum-DNA adducts, which disrupts DNA repair and triggers cell death. Cisplatinum also increases the levels of reactive oxygen species (ROS) in the kidneys, further exacerbating renal damage.

**Why Each Wrong Option is Incorrect**
**Option A:** Ototoxicity is a side effect of cisplatinum, but it is less common than nephrotoxicity. Ototoxicity involves damage to the inner ear, leading to hearing loss and tinnitus.
**Option B:** Myelosuppression is a common side effect of many chemotherapeutic agents, but it is not the most common side effect of cisplatinum.
**Option C:** Nausea and vomiting are common side effects of many chemotherapeutic agents, but they are not the most common side effect of cisplatinum.

**Clinical Pearl / High-Yield Fact**
Cisplatinum-induced nephrotoxicity can be reduced by administering the drug with saline hydration and using other protective agents, such as amifostine. It is essential to monitor renal function closely in patients receiving cisplatinum.

**Correct Answer:** C. Nephrotoxicity