Most small kidney stones pass on their own, but certain symptoms signal that you need medical attention right away. Pain so severe you can’t sit still, fever with chills, blood in your urine, or an inability to urinate all warrant an immediate visit. Beyond those urgent scenarios, stone size, recurrence history, and pregnancy status all influence when and what kind of doctor you should see.
Symptoms That Need Immediate Care
Kidney stone pain can be intense even when the stone passes without complications. But a few specific warning signs point to something more dangerous, like an infection or a complete blockage of your urinary tract. The Mayo Clinic lists these as reasons to get medical help right away:
- Pain so severe you can’t get comfortable. If you can’t sit, stand, or lie still without significant pain, that level of distress often means the stone is obstructing urine flow or is large enough to need intervention.
- Pain with nausea and vomiting. Vomiting can make it impossible to stay hydrated, which you need to help pass a stone. It can also signal that your body is reacting to a blockage.
- Fever and chills alongside pain. This combination suggests a urinary tract infection behind the stone. An infected, obstructed kidney is a medical emergency that can progress to sepsis within hours.
- Blood in your urine. Some blood is common with kidney stones, but visible blood (pink, red, or brown urine) warrants evaluation to rule out complications.
- Difficulty urinating. If urine flow slows to a trickle or stops entirely, the stone may be blocking your ureter, the tube connecting your kidney to your bladder.
Of these, fever with flank pain is the most time-sensitive. If you have both, go to an emergency room rather than waiting for a primary care appointment.
Stone Size and Your Odds of Passing It
Size is the single biggest factor in whether a stone will pass on its own or need medical help. A large study tracking nearly 400 stones over 20 weeks found a clear relationship between width and passage rates:
- 3 mm or smaller: 98% pass on their own
- 4 mm: about 81% pass on their own
- 5 mm: about 65% pass on their own
- 6 mm: roughly 33% pass on their own
- 6.5 mm or larger: only about 9% pass without intervention
If imaging shows your stone is 5 mm or smaller, your doctor will likely recommend a trial of watchful waiting, with increased fluid intake and pain management at home. Once a stone reaches 6 mm, the odds shift dramatically, and most urologists will discuss procedural options rather than waiting. At 10 mm, spontaneous passage is extremely unlikely.
You won’t know the exact size without imaging. If your pain is manageable and you don’t have any of the red-flag symptoms above, a non-urgent appointment with your primary care doctor to get imaging is a reasonable first step. If you’ve been managing at home for more than a few weeks with no improvement, that’s also a clear signal to be seen.
What Imaging to Expect
A non-contrast CT scan is the gold-standard test for diagnosing kidney stones. It reliably shows the stone’s size, location, and whether it’s causing a blockage, and it can also identify other causes of abdominal pain if the culprit turns out not to be a stone at all.
Ultrasound is less sensitive for detecting stones but plays a role in specific situations. It’s useful for checking whether urine is backing up behind a blockage, and it’s the recommended first-line test during pregnancy to avoid exposing the fetus to radiation. If ultrasound results are unclear in a pregnant patient, MRI without contrast is the next step. CT is generally avoided entirely during pregnancy, particularly between weeks 2 and 15 of gestation when radiation poses the greatest risk to the fetus.
Primary Care vs. Urologist vs. ER
Where you go depends on what’s happening right now and what’s happened before.
The emergency room is the right call when you have fever, can’t keep fluids down, can’t urinate, or have pain that isn’t responding to over-the-counter medication. Emergency physicians can provide IV pain relief, run imaging, and consult a urologist on the spot if the stone needs urgent removal.
Your primary care doctor is a good starting point for a first-time stone with manageable symptoms. They can order imaging, prescribe pain medication, and monitor your progress. If the stone is small enough to pass, they’ll guide you through that process.
A urologist becomes necessary when the stone is too large to pass, when you’ve had stones before, or when there’s a complication like persistent blockage. Patients with recurrent stones, stones that formed in childhood or adolescence, a strong family history, or underlying conditions like inflammatory bowel disease or hyperparathyroidism are typically referred for more specialized evaluation. These higher-risk patients often need detailed lab work and a 24-hour urine collection to identify the metabolic abnormalities driving their stone formation.
Kidney Stones During Pregnancy
Pregnancy complicates kidney stone management in several ways. The common anti-inflammatory painkillers used for stone pain are not safe during pregnancy because they can cause premature closure of a fetal heart structure and other complications. Acetaminophen is considered safe, and low-dose, short-term opioid pain relief can be used carefully when needed.
Any pregnant person experiencing flank pain suspicious for a kidney stone should be evaluated promptly. Beyond the stone workup, doctors will also want to confirm the health of the pregnancy and rule out obstetric causes for the pain. Ultrasound with a full bladder is the first imaging step, and the doctor may specifically look for the presence of urine “jets” entering the bladder to assess whether there’s a blockage.
When to Get Evaluated for Prevention
If this is your first stone and it passes without complications, you may not need anything beyond general dietary advice: drink more water, moderate your sodium intake, and follow any guidance your doctor gives based on the type of stone you passed. Detailed metabolic testing typically isn’t necessary after a single uncomplicated stone.
That changes if stones keep coming back. Recurrent stone formers, and anyone with a high-risk profile, benefit from a comprehensive metabolic workup. This usually involves a 24-hour urine collection, where you save all your urine for a full day so a lab can measure the levels of stone-forming substances and protective compounds your body produces. The results can reveal specific treatable problems, like excess calcium, too much oxalate, or overly acidic urine.
You should also try to save any stone you pass. Urinating through a fine mesh strainer catches fragments that a lab can analyze to determine the stone’s chemical composition. Knowing whether you’re forming calcium oxalate, uric acid, cystine, or another type of stone directly shapes the prevention strategy. Bring any captured stones to your follow-up appointment.
What to Track Before Your Appointment
Whether you’re seeing a primary care doctor or a urologist, arriving with useful information makes the visit more productive. Keep a rough log of how much fluid you drink and how much you urinate over a 24-hour period. Note the timing and severity of pain episodes, any visible changes in your urine color, and whether you’ve noticed gravel or fragments when urinating. If you’ve had prior imaging or stone analysis from a previous episode, bring those results. Your doctor will use all of this to determine the stone’s likely size and type, decide whether to intervene or wait, and build a plan to reduce your chances of going through this again.