Answer :
Final answer:
Nephrolithiasis can cause ureteral obstruction and unilateral hydronephrosis due to kidney swelling from urine retention.
Explanation:
Renal stones, also known as nephrolithiasis, can cause obstruction of the ureter, leading to severe pain and possible unilateral hydronephrosis, which is kidney swelling due to urine retention. The obstruction typically occurs when the stones grow large enough to block the ureter, preventing urine flow towards the bladder.
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