**Core Concept**
Recurrent gross hematuria is a symptom characterized by the passage of visible blood in the urine, often indicative of underlying urological or renal pathology. This condition can be caused by various factors, including bladder or kidney stones, tumors, infections, or vascular abnormalities.

**Why the Correct Answer is Right**
The correct answer is associated with the presence of **bladder cancer**, specifically **transitional cell carcinoma** (TCC), also known as urothelial carcinoma. TCC is a type of cancer that arises from the transitional epithelium lining the bladder, ureters, and renal pelvis. Recurrent gross hematuria is a common presenting symptom of bladder cancer, often accompanied by other symptoms such as pain, frequency, or urgency. The exact mechanism of hematuria in bladder cancer involves the invasion of malignant cells into the bladder mucosa, leading to bleeding and the passage of blood in the urine.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because **kidney stones** can cause hematuria, but it is typically microscopic or gross but intermittent, not recurrent.
* **Option B:** This option is incorrect because **pyelonephritis** is an infection of the kidney, which can cause hematuria, but it is typically associated with other symptoms such as fever, flank pain, and costovertebral angle tenderness.
* **Option C:** This option is incorrect because **prostatitis** is an infection of the prostate gland, which can cause hematuria, but it is typically associated with other symptoms such as dysuria, urinary frequency, and pelvic pain.

**Clinical Pearl / High-Yield Fact**
Recurrent gross hematuria in a patient over 50 years old should raise suspicion for **bladder cancer**, and prompt further evaluation with cystoscopy, imaging studies, and biopsy.

**Correct Answer:** C.