**Core Concept**
Sterile pyuria refers to the presence of white blood cells in the urine in the absence of a bacterial infection. This condition can be caused by various factors, including urinary tract obstruction, kidney stones, or an abnormal immune response.

**Why the Correct Answer is Right**
The correct answer is **Glomerulonephritis**. Glomerulonephritis is a condition characterized by inflammation of the glomeruli, the filtering units of the kidneys. This inflammation can lead to the presence of white blood cells in the urine, even in the absence of a bacterial infection. The inflammation and damage to the glomeruli can disrupt the normal filtration process, resulting in the presence of red blood cells, white blood cells, and protein in the urine.

**Why Each Wrong Option is Incorrect**
**Option A:** **Urinary Tract Infection** - While urinary tract infections (UTIs) can cause pyuria, the presence of white blood cells in the urine is not "sterile" in this case, as it is caused by a bacterial infection.

**Option B:** **Kidney Stones** - Kidney stones can cause hematuria (blood in the urine) but are not typically associated with sterile pyuria.

**Option C:** **Prostatitis** - Prostatitis is an inflammation of the prostate gland and can cause pyuria, but it is usually accompanied by symptoms such as pelvic pain and difficulty urinating.

**Clinical Pearl / High-Yield Fact**
It's essential to differentiate between pyuria caused by a bacterial infection and sterile pyuria, as the latter may require further investigation to determine the underlying cause.

**Correct Answer: D. Glomerulonephritis**