**Core Concept**
Renal transplantation is a surgical procedure that involves replacing a patient's diseased kidneys with healthy ones from a donor. The decision to perform renal transplantation depends on the underlying cause of the patient's end-stage renal disease (ESRD). Chronic glomerulonephritis is a leading cause of ESRD, making it a common indication for renal transplantation.

**Why the Correct Answer is Right**
Chronic glomerulonephritis is a group of diseases characterized by the gradual destruction of the glomeruli, the filtering units of the kidneys. This leads to a progressive decline in kidney function, ultimately resulting in ESRD. Renal transplantation is the treatment of choice for patients with ESRD due to chronic glomerulonephritis, as it offers a chance for improved quality of life and increased survival. The success of renal transplantation in these patients is due to the fact that the underlying disease process is not directly involved in the transplanted kidney.

**Why Each Wrong Option is Incorrect**
**Option A:** Bilateral staghorn calculus refers to large kidney stones that fill the renal pelvis and calyces, causing obstructive uropathy and potentially leading to ESRD. However, this condition is more amenable to surgical intervention, such as percutaneous nephrolithotomy or open surgery, rather than renal transplantation.
**Option B:** Horseshoe kidney is a congenital anomaly where the two kidneys fuse together at their lower poles, often leading to complications such as hydronephrosis and renal failure. While horseshoe kidney can be an indication for renal transplantation, it is not the most common indication.
**Option C:** Oxalosis, also known as primary hyperoxaluria, is a rare genetic disorder that leads to the accumulation of oxalate crystals in the kidneys, causing ESRD. While renal transplantation may be an option for patients with oxalosis, it is not as common as transplantation for chronic glomerulonephritis.

**Clinical Pearl / High-Yield Fact**
When considering renal transplantation, it is essential to evaluate the underlying cause of the patient's ESRD. Chronic glomerulonephritis is a leading indication for renal transplantation due to its progressive nature and the limited treatment options available.

**✓ Correct Answer: A. Chr. glomerulonephritis**