A kidney stone is likely stuck if your pain remains constant for several hours without shifting location, you can’t urinate or notice a significant drop in urine output, or you develop a fever alongside flank pain. Stones that are actively passing tend to cause waves of intense pain that move downward from your back toward your groin as the stone travels. When that pattern stalls and the pain camps out in one spot, the stone has probably lodged in a narrow part of your urinary tract.
Knowing the difference between a stone that’s making progress and one that’s stuck matters because a prolonged blockage can swell your kidney, raise your risk of infection, and temporarily reduce kidney function. Here’s how to read your body’s signals.
Where Stones Get Stuck
Your ureter, the thin tube connecting each kidney to your bladder, has two main bottleneck points. The first is right where the kidney meets the ureter at the top. The second is at the very bottom, where the ureter tunnels into the bladder wall. Research tracking stone locations in patients confirms that these two spots account for the vast majority of impacted stones, while the middle section of the ureter is a relatively uncommon place for one to lodge.
Why this matters to you: a stone stuck near the kidney tends to cause deep pain in your flank or back, just below the ribs. A stone stuck at the lower end of the ureter, close to the bladder, is more likely to cause pain that radiates into your groin or inner thigh, along with a strong, frequent urge to urinate even when little comes out. If your pain has stayed in the same general zone for hours without migrating downward, the stone is probably not moving.
Pain Patterns That Signal a Stuck Stone
Kidney stone pain comes in two layers, and understanding both helps you gauge what’s happening. There’s a steady, background ache caused by your kidney swelling as urine backs up behind the blockage. On top of that, you get sharp, cramping waves as the muscles of your ureter squeeze, trying to push the stone along. When the stone is actively moving, those waves of intense pain tend to shift location over time.
A stone that’s firmly stuck produces a different pattern. The background ache becomes the dominant sensation because kidney pressure keeps climbing. Peak pressure from a complete blockage typically builds within two to five hours. After that, the kidney and ureter gradually stretch to accommodate the backed-up urine, and the pain may actually plateau or ease somewhat. This relief can be misleading. It doesn’t necessarily mean the stone passed. It can simply mean your body has adjusted to the obstruction.
Intermittent obstruction, where the stone shifts just enough to partially block and unblock the ureter, often causes more prolonged discomfort than a complete blockage. You might feel surges of pain that come and go over days without ever fully resolving.
Urinary Changes to Watch For
Your urine output and the way it feels to urinate offer important clues. A stone lodged in the ureter blocks urine flow from that kidney. If you have two functioning kidneys, the unaffected one compensates by increasing its output, so you may not notice a dramatic decrease in total urine volume. But you might notice that your urine looks darker, contains visible blood, or smells unusual.
When a stone is near the bottom of the ureter, close to the bladder, it irritates the bladder wall. This creates an urgent, frequent need to urinate, sometimes with burning, even though you’re producing very little urine each time. This is distinct from what happens when a stone actually reaches the bladder. Once inside the bladder, stones can usually pass out of the body through the urethra with relative ease, and the intense flank pain typically stops.
A complete inability to urinate is a red flag that warrants emergency care, especially if paired with severe pain or a distended abdomen.
Signs the Blockage Is Affecting Your Kidney
When a stone blocks the ureter long enough, urine backs up into the kidney and causes it to swell, a condition called hydronephrosis. You can’t feel or see this swelling yourself, but it shows up clearly on imaging. Symptoms that suggest it’s happening include a deep, persistent ache in your flank that doesn’t come in waves, nausea or vomiting, and sometimes a low-grade fever.
The kidney takes a measurable hit during an obstruction. Studies tracking kidney function in stone patients found that a standard blood marker of kidney health rose from 0.84 to 0.97 during an active stone event, reflecting reduced filtering ability. The good news: this change was temporary. After the stone passed or was removed, kidney function returned to baseline. However, each obstructive episode can cause some degree of lasting, microscopic damage to the kidney’s filtering units, which is why prolonged blockages need attention.
When a Stuck Stone Becomes Dangerous
The most serious complication of a stuck stone is infection behind the blockage. Urine pooling in a swollen kidney creates an ideal environment for bacteria. If infection takes hold, it can escalate quickly into a kidney infection or even sepsis. The warning signs are:
- Fever or chills alongside flank pain
- Cloudy, dark, or foul-smelling urine
- Nausea and vomiting that won’t stop
- Pain so severe that you can’t find a comfortable position, sit still, or keep fluids down
Any combination of fever and kidney stone symptoms is a reason to go to the emergency department. An infected, obstructed kidney is a time-sensitive problem that typically requires draining the blockage before antibiotics alone can work.
How Doctors Confirm a Stone Is Stuck
If you suspect a stone isn’t passing, a non-contrast CT scan of your abdomen and pelvis is the gold-standard test. It’s considered the most accurate way to locate a stone, measure its size, and determine whether it’s causing a backup. The scan can show the stone itself, the exact point where it’s lodged, and whether the ureter or kidney above it has started to dilate.
Ultrasound is a radiation-free alternative that works well for detecting hydronephrosis, the kidney swelling that signals a significant blockage. It’s less precise at pinpointing the stone’s exact location, especially in the middle portion of the ureter, but it reliably picks up the downstream effects of an obstruction. It’s often used as a first-line test in pregnant patients, children, or people who’ve had multiple CT scans.
Blood work during an episode may show a temporary rise in creatinine, confirming that the blocked kidney’s function has dipped. Urine tests can flag blood or signs of infection even when they’re not visible to the naked eye.
What Happens if the Stone Won’t Pass
Most small stones (under 5 to 6 millimeters) eventually pass on their own with hydration and pain management, though it can take days to weeks. The concern is when a stone remains lodged without progress. Several signs suggest it’s time to move beyond watchful waiting:
- Pain persists beyond several days without any change in location or character
- Imaging shows worsening hydronephrosis on follow-up
- Infection develops behind the blockage
- The stone is too large to pass based on its measured size
Intervention usually means one of two approaches. For stones in the ureter, a small scope can be passed up through the bladder to grab or break up the stone. For larger stones or those near the kidney, shock waves delivered from outside the body can fragment the stone into pieces small enough to pass. Both are outpatient procedures with relatively short recovery times. In urgent situations involving infection, a temporary stent or drainage tube may be placed first to relieve pressure on the kidney before the stone itself is addressed.
The clearest sign that a stone has finally passed is a sudden, dramatic drop in pain followed by seeing or feeling the stone come out during urination. If that hasn’t happened and your symptoms have simply faded, imaging is the only way to confirm whether the stone cleared or simply settled into a position that your body has temporarily adapted to.