**Core Concept:** Management of renal calculi involves determining the size, location, and composition of the stone, as well as the patient's medical history and risk factors. The most common types of renal calculi are calcium oxalate, calcium phosphate, and struvite stones. Struvite stones are composed of magnesium ammonium phosphate and are associated with urinary tract infections (UTIs) due to the presence of magnesium, ammonia, and phosphate from urine precipitates.

**Why the Correct Answer is Right:** The correct answer is "D. Percutaneous nephrolithotomy (PCNL)":

PCNL is considered when the stone size is larger than 2-3 cm. In this case, the stone size is 5 cm, making PCNL the most suitable treatment option. Percutaneous nephrolithotomy allows direct access to the kidney to remove the stone through a small incision, reducing the risk of complications compared to open surgery or extracorporeal shock wave lithotripsy (ESWL) for large stones.

**Why Each Wrong Option is Incorrect:**

A. **Extracorporeal shock wave lithotripsy (ESWL):** ESWL is suitable for stones up to 2-3 cm in size. It is not recommended for stones larger than 2-3 cm as the chances of complete stone fragmentation are low, and the risk of complications increases with stone size.

B. **Ureteroscopy:** Ureteroscopy is suitable for stones in the ureter or urinary bladder. For stones in the kidney, PCNL or shock wave lithotripsy (SWL) are more appropriate.

C. **Urinary tract infection (UTI):** Although UTI is a risk factor for struvite stone formation, the focus of treatment is on removing the stone itself, not treating the UTI.

**Clinical Pearl:** The management of large renal calculi depends on the stone size and location. In cases of a 5 cm renal stone, PCNL is the preferred treatment option, as it provides direct access to the kidney and reduces complications compared to open surgery or ESWL.