Kidney Stones: When to Go to the ER (and When It's Safe to Wait)

It's 2 a.m. and a pain you've never felt before has you pacing the hallway, unable to sit still. It started in your back, under the ribs, and now it's creeping toward your groin. You're wondering if this is a kidney stone, and whether it's bad enough for the hospital.

So, when should you go to the ER for kidney stones? Go now if the pain comes with a fever or chills, if you can't urinate, if you're vomiting too much to keep fluids down, or if medicine won't touch it. Those symptoms can mean a blocked, infected kidney, and that's a true emergency. Without them, many stones can be handled by your doctor, an urgent care clinic or a urologist.

About 11% of men and 6% of women in the US get a kidney stone at some point, and stone disease led to roughly 1.3 million emergency room visits in 2009 alone.

When should you go to the ER for kidney stones?

Any one of these red flags is enough to go to the emergency room, day or night:

• Fever of 100.4°F (38°C) or higher, or shaking chills. This points to infection behind a stuck stone.
• You can't urinate, or only a few drops come out.
• Vomiting that won't stop, so you can't keep water or pills down.
• Severe pain that medications don't touch.
• You have one working kidney, a kidney transplant or chronic kidney disease. A single blockage can threaten your kidney function.
• You're pregnant, or you feel faint, confused or very weak.

If none of these symptoms apply, call your doctor today. That's the middle ground most guides skip: a kidney stone can feel like an emergency without being one.

What kidney stone pain feels like

The classic kidney stone symptom is renal colic. It's sharp and cramping. It comes in waves.

It usually starts in your side or back, just below the ribs, then moves into your lower belly and groin as the stone travels down the ureter (the narrow part of the urinary tract that drains into the bladder).

Other common symptoms, according to the NIDDK, include:

• pink, red or brown blood in the urine
• a constant urge to urinate, or pain when you do
• cloudy or bad-smelling urine
• nausea and vomiting

Blood in urine is a strong clue, showing up in 60% to 90% of stone attacks (Endotext). Its absence doesn't rule a stone out.

Why fever with a kidney stone is an emergency

The stone itself rarely does lasting harm. The trouble starts when it blocks urine flow and that trapped urine gets infected.

A blocked, infected kidney can turn into sepsis, a body-wide reaction to infection that can turn life-threatening quickly. Antibiotics alone can't fix it, because the urine can't drain. A urologist has to relieve the blockage, usually with a small tube called a stent or a drain placed through the back. Clinical guidance calls for this urgently, regardless of stone size.

So if you have stone symptoms plus a fever, get emergency care now. Don't wait to see if it settles.

ER, urgent care or urologist: where to go

Urgent care can be a good first stop for a mild first episode, but many centers can't do a CT scan or give IV medicine.

What the ER will do for a kidney stone

The first goal is pain control.

Pain relief. NSAIDs such as ketorolac are first-line for renal colic, with opioids held back as a second option. You may also get IV fluids for hydration and anti-nausea medicine.

Lab work. Expect a urinalysis to look for blood and bacteria, and blood tests to check kidney function.

Imaging. A non-contrast CT scan is the most accurate test for a stone. Ultrasound avoids radiation, and in the STONE trial of 2,759 ER patients, starting with it led to no more serious complications than starting with CT. If you're pregnant, ultrasound comes first.

A treatment plan. About 80% of ER visits for stones end with a trip home (AHRQ), often with a prescription, sometimes tamsulosin, and a urology follow-up. The rest are admitted, usually for a blockage or pain that won't settle.

Will your kidney stone pass on its own?

Usually, if it's small. Stone size is the biggest factor.

Pooled guideline data show about 68% of stones under 5 mm pass on their own, compared with 47% of stones 5 to 10 mm. Most that pass do so within 4 to 6 weeks.

For stones 5 to 10 mm in the lower ureter, tamsulosin raised passage rates by about 22 percentage points in a meta-analysis summarized in Clinician Reviews. It didn't help smaller stones.

When a stone won't pass, a urologist has treatment options: shock wave lithotripsy, ureteroscopy with a laser, or percutaneous nephrolithotomy (PCNL) for large stones, as NIDDK explains.

Managing a kidney stone at home while it passes

If your doctor has confirmed a small stone and you have no red flags, home care is reasonable. Our approach is simple:

1. Keep up your hydration. Drink enough water that your urine stays pale.
2. Take pain medicine on schedule, as directed. Ask before using over-the-counter NSAIDs if you have kidney disease or ulcers.
3. Catch the stone. Urinate through a strainer so a lab can test it. Knowing whether it's calcium, uric acid or another type shapes how you prevent the next one.
4. Know your trigger to go back. Any red flag from the checklist means the ER, even mid-plan.

Pain that looks like a kidney stone but isn't

Not every bout of flank pain is a stone. Appendicitis, a gallbladder attack, a urinary tract or kidney infection and, in women, an ectopic pregnancy or twisted ovary can all feel similar. In older adults, doctors also rule out an abdominal aortic aneurysm, which can mimic a stone (WikEM).

That's why a first episode deserves a proper exam, not a guess.

Your next step

If you're reading this with pain and any red flag, go to the nearest emergency room or call 911. If your symptoms are milder, book a same-day visit and ask for a urinalysis and imaging.

Once treatment is done, ask how to prevent the next one. After a first stone, 30% to 50% of people get another within 10 years. Calcium stones are the most common type, and here's what many people get wrong: NIDDK advises cutting salt, not calcium, because enough dietary calcium helps block stone formation. Uric acid stones need a different diet plan, which is why the lab test matters.