A young female with history of renal calculi complains of bone pain and abdominal cramps. On investigation, multiple fractures were discovered and serum calcium and PTH was raised. Which of the following will be the best investigation to arrive at a definitive diagnosis?
**Core Concept**
The patient's presentation suggests a systemic disorder involving hypercalcemia (elevated serum calcium) and secondary hyperparathyroidism (elevated parathyroid hormone, PTH). This is likely due to a disorder affecting calcium and phosphate metabolism, leading to bone resorption and renal complications.
**Why the Correct Answer is Right**
The investigation of choice is a bone biopsy with histopathological examination. This is because the patient's presentation of bone pain, multiple fractures, and hypercalcemia with elevated PTH is suggestive of a bone disease characterized by bone resorption and replacement with fibrous tissue, known as osteitis fibrosa cystica. This condition is typically associated with hyperparathyroidism, but in this case, it may be secondary to another underlying disorder. A bone biopsy will provide definitive evidence of the disease process and help identify the underlying cause.
**Why Each Wrong Option is Incorrect**
**Option A:** Serum alkaline phosphatase (ALP) levels may be elevated in various bone disorders, but this is a non-specific finding and does not provide a definitive diagnosis.
**Option B:** 24-hour urine calcium excretion may be elevated in primary hyperparathyroidism, but this test does not provide information about the underlying cause of the hyperparathyroidism or the bone disease.
**Option C:** Whole-body bone scan may show increased uptake in areas of bone resorption, but this test is not specific for osteitis fibrosa cystica and may not provide a definitive diagnosis.
**Clinical Pearl / High-Yield Fact**
Osteitis fibrosa cystica is a classic complication of hyperparathyroidism, particularly in the context of vitamin D deficiency or other disorders affecting calcium and phosphate metabolism. It is essential to consider the patient's overall clinical context and laboratory findings when selecting the best investigation for a definitive diagnosis.
**Correct Answer:** C. Whole-body bone scan may show increased uptake in areas of bone resorption, but this test is not specific for osteitis fibrosa cystica and may not provide a definitive diagnosis.