Fusion of the caudal portions of the kidneys during embryonic development is most likely to result in which of the following congenital conditions?
**Core Concept**
During embryonic development, the kidneys form from the metanephric blastema and the ureteric bud. The kidneys ascend from the pelvis to their final position in the retroperitoneum. Abnormalities in kidney development can lead to various congenital conditions.
**Why the Correct Answer is Right**
The fusion of the caudal portions of the kidneys during embryonic development results in a horseshoe kidney. This condition occurs when the two kidneys fail to separate and instead fuse together at their lower poles, forming a characteristic "U" shape. The fused kidney then ascends to its final position in the retroperitoneum, often resulting in an abnormal position of the kidneys. The ureters may also be abnormally positioned, which can lead to urinary tract obstruction and other complications.
**Why Each Wrong Option is Incorrect**
**Option A:** Bicornuate uterus is a congenital condition of the female reproductive system, characterized by a heart-shaped uterus with two separate horns. It is not related to kidney development.
**Option B:** Cryptorchidism is a condition where one or both testicles fail to descend into the scrotum. It is not related to kidney development or fusion.
**Option D:** Hypospadias is a congenital condition where the urethral opening is located on the underside of the penis. It is not related to kidney development or fusion.
**Clinical Pearl / High-Yield Fact**
Horseshoe kidney is often associated with an increased risk of urinary tract infections, kidney stones, and hypertension due to the abnormal position of the kidneys and ureters.
**✓ Correct Answer: C. Horseshoe kidney**