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Can an 8 mm Kidney Stone Pass Naturally?

Can an 8 mm Kidney Stone Pass Naturally?

📖 8 min read Written/reviewed by Dr. Alhad Naragude, MBBS, MS, DrNB Urology Last updated: June 11, 2026

An 8 mm kidney stone can pass naturally in some patients, but it should not be ignored or managed blindly at home. The chance is better if the stone has moved into the lower ureter, near the urinary bladder, and there is no fever, severe pain, vomiting, infection, kidney swelling or kidney function problem. If the stone is still inside the kidney, stuck in the upper ureter or causing blockage, treatment may be safer. For an 8 mm stone, the decision should be based on CT scan findings, symptoms, urine test and creatinine, not size alone.

Short answer: can an 8 mm kidney stone pass naturally?

Patient situation What it usually means
8 mm stone inside kidney May not pass soon; treatment depends on symptoms, stone position and growth risk
8 mm lower ureter stone May pass in selected stable patients with medicines and follow-up
8 mm upper ureter stone Lower chance of natural passage; treatment is often considered earlier
Fever, chills or repeated vomiting Do not wait at home; urgent medical care is needed
Pain has reduced Does not always mean the stone has passed; follow-up imaging may still be needed

Can an 8 mm kidney stone pass naturally?

Yes, but the chance is borderline.

An 8 mm stone is not tiny. Some 8 mm stones pass with medicines and observation, especially when they are already low down in the ureter. But many 8 mm stones get stuck and need treatment such as ureteroscopy, RIRS or ESWL.

A CT-based study reported that ureter stones measuring 7-9 mm had a spontaneous passage rate of about 48%. The same study found that stones closer to the bladder passed more often than stones near the kidney.

Practical answer:An 8 mm stone may pass naturally, but only selected patients should wait – and they need follow-up.

First decision: is it in the kidney or ureter?

Patients often call every urinary stone a kidney stone. But treatment depends heavily on location.

Stone location What it means Practical meaning
Inside kidney Stone is still in the kidney May stay silent, grow or later move
Upper ureter Stone is stuck near the kidney Lower chance of natural passage
Mid ureter Stone is halfway down Passage is possible but uncertain
Lower ureter Stone is near the bladder Best chance of passing
UVJ stone Stone is at the ureter-bladder junction Often painful, but may pass

The ureter is the narrow tube that carries urine from the kidney to the bladder. Once an 8 mm stone enters the ureter, it may block urine flow and cause severe colicky pain.

Is an 8 mm kidney stone big?

An 8 mm stone is not huge, but it is large enough to get stuck.

Stone size General chance of passing naturally
1-4 mm Often passes naturally
5-6 mm May pass, but needs monitoring
7-9 mm Borderline; many need treatment
10 mm or more Less likely to pass naturally

NIDDK notes that small stones may pass on their own, while larger stones or stones causing blockage, severe pain, vomiting or dehydration may need urgent treatment.

When can you wait for an 8 mm stone to pass?

Waiting may be reasonable only when the situation is stable. A supervised trial of passage may be considered if:

  • Pain is controlled with medicines.
  • There is no fever or chills.
  • You are not vomiting repeatedly.
  • Urine test does not suggest significant infection.
  • Creatinine is normal.
  • Kidney swelling is mild or acceptable.
  • The stone is in the lower ureter.
  • You can come for follow-up.
  • You understand emergency warning signs.

The European Association of Urology supports observation in selected patients when active removal is not required, and recommends alpha-blockers as one option for distal ureteral stones larger than 5 mm, while noting this is off-label.

When should you not wait?

Do not keep waiting at home if there are danger signs. A blocked stone with infection can become serious.

Seek urgent medical care if you have:

  • Fever or chills.
  • Severe pain not settling with medicines.
  • Repeated vomiting.
  • Inability to pass urine.
  • Burning urination with fever.
  • Cloudy or foul-smelling urine.
  • Weakness, dizziness or dehydration.
  • Blood in urine with worsening pain.
  • Known single kidney.
  • Pregnancy.
  • Diabetes with fever.
  • Raised creatinine or known kidney disease.
Do not wait at home:Fever with a blocked stone can be dangerous. It may need urgent drainage before definitive stone treatment.

How long can you wait for an 8 mm kidney stone?

There is no fixed safe waiting period for every patient. Some stable lower ureter stones can be observed for a short period with medicines and repeat imaging. Others need earlier treatment.

Waiting becomes risky if:

  • Pain keeps coming back.
  • The stone is not moving.
  • Kidney swelling is increasing.
  • Fever appears.
  • Urine culture shows infection.
  • Creatinine rises.
  • You need repeated emergency visits.
  • You live far from emergency urology care.
  • You need to travel soon.
  • You prefer definite treatment instead of repeated attacks.

A common mistake is assuming that pain reduced means stone passed. Pain can reduce even when the stone is still stuck. Follow-up imaging is important.

Symptoms of an 8 mm kidney or ureter stone

  • Severe side or back pain.
  • Pain moving to the lower abdomen or groin.
  • Pain going to the testicle in men.
  • Burning urination.
  • Frequent urination.
  • Blood in urine.
  • Nausea or vomiting.
  • Restlessness during pain.
  • Fever if infection is present.

A stone inside the kidney may cause dull pain, repeated urinary infection or blood in urine. Sometimes it is found accidentally on ultrasound.

Tests needed before deciding whether to wait

A urologist usually needs more than the stone size.

CT KUB plain

This is often the most useful test. It shows the exact stone size, location, density, kidney swelling and whether the stone is suitable for ESWL, ureteroscopy or RIRS.

Ultrasound KUB

Ultrasound helps check kidney swelling and many kidney stones. It is useful for follow-up, but it can miss some ureter stones.

Urine routine and urine culture

These check for blood, pus cells and infection. Infection with obstruction needs urgent attention.

Serum creatinine

This checks kidney function.

X-ray KUB

This is useful if the stone is visible on X-ray and follow-up is needed.

Can medicines help an 8 mm stone pass?

Medicines may help selected patients, especially when the stone is in the lower ureter.

Treatment may include:

  • Pain-control medicines.
  • Anti-vomiting medicines.
  • Medical expulsive therapy in selected patients.
  • Antibiotics only if infection is suspected or confirmed.

Do not self-medicate with repeated painkillers. Painkillers can be risky if you are dehydrated, vomiting, diabetic, hypertensive or already have kidney disease.

Also, antibiotics are not needed for every stone. Taking antibiotics without urine culture or medical advice can hide infection and delay proper treatment.

Does drinking more water push out an 8 mm stone?

Normal hydration helps, but forcing too much water during severe colic is not a cure.

If the ureter is blocked, excess water may increase pressure and worsen pain. Drink enough to avoid dehydration, but do not overdrink during an acute pain episode.

After the stone passes or is removed, hydration becomes important for prevention. NIDDK advises that drinking enough liquids helps dilute urine and reduce future stone formation.

Treatment options if an 8 mm stone does not pass

The right treatment depends on the stone’s location, hardness, visibility on X-ray, kidney swelling, infection status and patient preference.

Ureteroscopy with laser lithotripsy

This is commonly used for ureter stones. A small telescope is passed through the urinary passage into the ureter. The stone is broken with laser and removed or allowed to pass as tiny fragments. A temporary DJ stent may be placed.

RIRS

RIRS means retrograde intrarenal surgery. It is commonly used for selected kidney stones. A flexible scope is passed through the natural urinary passage into the kidney. The stone is broken with laser.

ESWL

ESWL means extracorporeal shock wave lithotripsy. Shock waves are focused on the stone from outside the body to break it into smaller pieces. It is more suitable for selected stones based on location, density, body habitus and visibility.

EAU guidelines note that shock wave lithotripsy success depends on factors such as stone size, location, composition or hardness, patient habitus and technique.

PCNL

PCNL is usually used for larger or complex kidney stones. It is not commonly needed for a simple 8 mm stone unless there are special circumstances.

Which option is best for an 8 mm stone?

Situation Common practical option
8 mm lower ureter stone, stable patient Trial of passage or ureteroscopy
8 mm upper ureter stone with repeated pain Ureteroscopy or ESWL
8 mm kidney stone with symptoms RIRS or ESWL, depending on CT findings
Fever with blocked stone Urgent drainage first, stone treatment later
Single kidney with obstruction Urgent urologist care
Stone not moving on follow-up Active treatment may be safer

The updated AUA surgical management guideline states that when surgery is indicated for adult distal ureteral stones up to 10 mm, clinicians may offer ureteroscopy or shock wave lithotripsy, with treatment choice guided by patient factors, anatomy, stone characteristics, goals, resources and expertise.

What if the stone passes naturally?

If you pass the stone, collect it in a clean container if possible and show it to your doctor. Stone analysis can help identify the stone type, such as calcium oxalate, uric acid, struvite or cystine.

After stone passage, your urologist may advise:

  • Repeat ultrasound or X-ray.
  • Urine routine.
  • Serum creatinine.
  • Stone analysis.
  • 24-hour urine test in recurrent stone formers.
  • Diet and fluid guidance.
  • Medicines for prevention in selected patients.

Consultation checklist

Please bring:

  • CT KUB report and images, if done.
  • Ultrasound KUB report.
  • X-ray KUB, if done.
  • Urine routine report.
  • Urine culture report.
  • Serum creatinine.
  • Fever records, if any.
  • Current medicines.
  • Previous stone surgery details.
  • DJ stent details, if already placed.
  • Discharge summaries.
  • Diabetes, BP or kidney disease reports.

Related reading

FAQs

1. Can an 8 mm kidney stone pass naturally?

Yes, an 8 mm kidney stone can pass naturally in selected cases, especially if it is in the lower ureter. But many 8 mm stones do not pass and need urologist-guided treatment.

2. Is an 8 mm kidney stone too big to pass?

It is not impossible to pass, but it is big enough to get stuck. Natural passage depends mainly on location, symptoms, kidney swelling and infection status.

3. How long does an 8 mm kidney stone take to pass?

It may take days to a few weeks in selected patients. You should not wait without follow-up imaging and medical advice.

4. Can water dissolve an 8 mm kidney stone?

No. Most kidney stones do not dissolve just by drinking water. Water helps prevent dehydration and future stones, but it may not remove an obstructing 8 mm stone.

5. Can tamsulosin help an 8 mm stone pass?

It may help selected lower ureter stones, but it should be taken only after medical evaluation. It is not useful for every kidney stone.

6. Does every 8 mm stone need surgery?

No. Some can be observed, some may be suitable for ESWL, and some need ureteroscopy or RIRS. The best option depends on CT findings and symptoms.

7. When should I go to hospital immediately?

Go urgently if you have fever, chills, severe pain, repeated vomiting, inability to pass urine, single kidney, pregnancy, diabetes with fever or worsening weakness.

References

Note: This information is for educational purposes only and is not a substitute for medical advice. Please consult your doctor for any symptoms.