**Core Concept**
Unilateral renal agenesis refers to the congenital absence of one kidney, often discovered incidentally during imaging studies. This condition is associated with various morphological and functional changes in the urinary system, including compensatory hypertrophy of the remaining kidney.

**Why the Correct Answer is Right**
The correct answer is related to the concept of compensatory hypertrophy, which occurs due to the increased workload on the remaining kidney. As a result, the solitary kidney undergoes adaptive changes, including increased renal mass and function. This process is mediated by various growth factors and hormones, including erythropoietin, which stimulates erythropoiesis and helps to compensate for the reduced renal mass.

**Why Each Wrong Option is Incorrect**
**Option A:**
This option is incorrect because it does not accurately describe the typical association with unilateral renal agenesis. While there may be some cases of hypertension, it is not a universal finding.

**Option B:**
This option is incorrect because it is not a direct consequence of unilateral renal agenesis. While there may be some cases of proteinuria, it is not a typical association.

**Option C:**
This option is incorrect because it is not a direct consequence of unilateral renal agenesis. While there may be some cases of renal impairment, it is not a universal finding.

**Clinical Pearl / High-Yield Fact**
It is essential to note that patients with unilateral renal agenesis may have a higher risk of developing hypertension and proteinuria due to the compensatory hypertrophy of the remaining kidney. This highlights the importance of regular follow-up and monitoring in these patients.

**Correct Answer:**
A. Hypertension