**Core Concept**
A horseshoe kidney is a congenital anomaly where the two kidneys are fused together at their lower poles, forming a U-shaped structure. This condition arises during embryonic development when the metanephric blastema fails to ascend properly to its normal position in the abdominal cavity.

**Why the Correct Answer is Right**
In a horseshoe kidney, the renal arteries and veins are often anomalous, and the kidneys may be located lower than usual in the abdominal cavity. The lower pole fusion typically occurs at the level of the second lumbar vertebra (L2), which is below the normal position of the kidneys. This lower position can lead to complications such as renal obstruction, hydronephrosis, and increased risk of kidney stones.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not provided.
* **Option B:** This option is not provided.
* **Option C:** This option is not provided.

**Clinical Pearl / High-Yield Fact**
It's essential to note that horseshoe kidneys are more common in individuals with other congenital anomalies, such as urinary tract duplications or ectopic ureters. A high index of suspicion is necessary for early diagnosis and management to prevent long-term complications.

**Correct Answer:** D.