**Core Concept**
Chronic urethral obstruction due to benign prostatic hyperplasia (BPH) can lead to increased intravesical pressure, which in turn causes a decrease in renal perfusion. This results in ischemia and ultimately affects the kidney parenchyma.

**Why the Correct Answer is Right**
The kidney parenchyma is composed of nephrons, which are responsible for filtering waste and excess fluids from the blood. Chronic obstruction of the urethra leads to increased pressure within the renal pelvis and calyces, causing a decrease in blood flow to the kidneys. This ischemia results in the atrophy of the renal parenchyma, including the loss of renal tubules and glomeruli. The atrophy is a result of the prolonged ischemia and decreased perfusion, leading to a decrease in renal function.

**Why Each Wrong Option is Incorrect**
**Option A:** Hyperplasia is an increase in the number of cells, which is not a result of chronic urethral obstruction due to BPH. Hyperplasia is more commonly associated with conditions such as polycystic kidney disease.

**Option B:** Hypertrophy is an increase in the size of cells, which is not a direct result of chronic urethral obstruction due to BPH. While there may be some hypertrophy of the renal tubules in response to increased workload, it is not the primary change in the kidney parenchyma due to chronic obstruction.

**Option D:** Dysplasia is an abnormal development of tissue, which is not a result of chronic urethral obstruction due to BPH. Dysplasia is more commonly associated with congenital anomalies or developmental disorders.

**Clinical Pearl / High-Yield Fact**
Chronic urethral obstruction due to BPH can lead to a decrease in renal function, which can be irreversible if left untreated. It is essential to diagnose and treat BPH promptly to prevent long-term kidney damage.

✓ Correct Answer: C. Atrophy