When urine can't drain properly from the kidney, it backs up and causes swelling—this is hydronephrosis, a condition where the kidney swells due to urine buildup from a blockage in the urinary tract. Also known as kidney obstruction, it doesn't cause pain at first, but left untreated, it can damage kidney tissue and reduce function over time. This isn't a disease on its own—it's a sign something else is wrong, like a kidney stone, enlarged prostate, pregnancy, or a tumor pressing on the ureter.
People often don’t realize they have hydronephrosis until it’s found on an ultrasound or CT scan. The urinary tract blockage, any obstruction that stops urine from flowing freely from the kidney to the bladder is the core problem. In men, an enlarged prostate is a common cause. In women, pregnancy can put pressure on the ureters. Kids can be born with structural issues that cause urine to back up. Even infections or scar tissue from past surgeries can trigger it. What matters most is not just the swelling, but whether the blockage is partial or complete, and how long it’s been there. A slow buildup might not hurt, but a sudden blockage can lead to severe pain and infection.
Left alone, kidney swelling, the physical expansion of the kidney due to trapped urine can lead to permanent damage. The kidney’s filtering units—nephrons—start to die off when pressure builds up for too long. That’s why early detection matters. Blood tests and imaging can show how well the kidney is working and how bad the swelling is. Treatment doesn’t always mean surgery. Sometimes, a stent placed in the ureter to bypass the blockage is enough. Other times, removing a kidney stone or draining excess fluid with a catheter fixes the issue. But if the cause is cancer or severe scarring, more complex care is needed.
You won’t find a one-size-fits-all fix for hydronephrosis because the cause changes from person to person. That’s why the posts below cover real cases—from how kidney stones trigger swelling, to how pregnancy-related hydronephrosis resolves after birth, to why certain pain meds can worsen urinary flow in older adults. You’ll also find guides on what tests doctors use to track kidney function, how to spot early warning signs before pain hits, and when to push for imaging if you’ve been told it’s "just a UTI." This isn’t about theory. It’s about what actually works when your body’s drainage system fails.
Renal ultrasound is the safest, first-line test for evaluating kidney size and urinary obstruction. It detects hydronephrosis, measures kidney dimensions, and uses resistive index to identify blockages-all without radiation or contrast.