**Core Concept**
Benign prostatic hyperplasia (BPH) is a condition characterized by the enlargement of the prostate gland, leading to urinary symptoms. Absolute indications for surgery in BPH cases are those that pose a significant risk to the patient's health or quality of life. In this context, recurrent urinary tract infections (UTIs) are a critical concern, as they can lead to complications such as sepsis and kidney damage.

**Why the Correct Answer is Right**
Recurrent UTIs in BPH patients are often due to incomplete bladder emptying, which allows bacteria to colonize the urinary tract. This is exacerbated by the prostatic enlargement, which can cause bladder outlet obstruction. The correct answer, recurrent UTIs, is an absolute indication for surgery because it poses a significant risk to the patient's health. **Option A**, bilateral hydroureteronephrosis, is a complication of BPH but is not an absolute indication for surgery. **Option B**, nocturnal frequency, is a common symptom of BPH but is not an absolute indication for surgery. **Option D**, voiding bladder pressures > 50 cm of water, is a sign of bladder outlet obstruction, but it is not an absolute indication for surgery.

**Why Each Wrong Option is Incorrect**
**Option A:** Bilateral hydroureteronephrosis is a complication of BPH, but it is not an absolute indication for surgery. This condition may be managed with medical therapy or endoscopic procedures before considering surgery.
**Option B:** Nocturnal frequency is a common symptom of BPH, but it is not an absolute indication for surgery. Many patients with BPH experience nocturnal frequency, and it is often managed with medical therapy.
**Option D:** Voiding bladder pressures > 50 cm of water are a sign of bladder outlet obstruction, but they are not an absolute indication for surgery. This condition may be managed with medical therapy or endoscopic procedures before considering surgery.

**Clinical Pearl / High-Yield Fact**
In patients with BPH, recurrent UTIs are a red flag for surgery. It is essential to investigate and manage these infections promptly to prevent complications.

**✓ Correct Answer: C. Recurrent urinary tract infection**