Final answer:
Untreated benign prostatic hyperplasia (BPH) may lead to urine reflux and potentially hydronephrosis, but it is not a direct cause of staghorn renal calculi, malignant hypertension, or pyelonephritis.
Step-by-step explanation:
The most accurate answer regarding the potential consequences of untreated benign prostatic hyperplasia (BPH) is that urine reflux and possibly hydronephrosis can result from untreated BPH. This is because the enlarged prostate can lead to obstruction of the urethra, causing urine to back up into the kidneys, potentially causing these conditions. While staghorn renal calculi or small calcium stones can occur due to various reasons, they are not a direct consequence of untreated BPH. Malignant hypertension is also not a result of BPH. Lastly, while untreated BPH can predispose one to urinary tract infections, it does not directly cause pyelonephritis, which is an infection of the kidney itself.