**Core Concept**
A ureterovaginal fistula is an abnormal connection between the ureter and the vagina, often resulting from complications of surgery, injury, or infection. The primary goal of treatment is to repair the fistula and restore normal urinary function, preventing further complications like incontinence or recurrent infections.

**Why the Correct Answer is Right**
The most effective treatment for ureterovaginal fistula is surgical repair, specifically a ureteral reimplantation or a transvaginal fistula repair. This procedure involves excising the fistulous tract and reattaching the ureter to the bladder or a new ureteral site. The success of this procedure relies on precise anatomical reconstruction and proper ureteral reimplantation to ensure normal ureteral function and prevent future complications.

**Why Each Wrong Option is Incorrect**
**Option A:** Conservative management with catheterization or pelvic rest is often insufficient for ureterovaginal fistula repair, as it may not address the underlying anatomical defect.

**Option B:** Nephrostomy tube placement may be used as a temporary measure to divert urine and alleviate symptoms, but it does not address the fistula itself and is not a definitive treatment.

**Option C:** Endoscopic repair using a ureteral stent or embolization may be used in some cases, but it is often less effective than open surgical repair, especially for larger fistulas.

**Clinical Pearl / High-Yield Fact**
Remember that ureterovaginal fistulas are often associated with significant morbidity, including chronic urinary incontinence, recurrent infections, and electrolyte imbalances. Prompt diagnosis and surgical repair are crucial to restoring normal urinary function and preventing long-term complications.

**Correct Answer:** C.