Kidney stones are hard deposits made of minerals and salts that form inside the kidneys when urine becomes concentrated. Depending on their size and location, kidney stones can pass unnoticed or cause intense pain and complications that may require surgery. This guide breaks down the different sizes of kidney stones, the health risks they pose, and when surgical intervention becomes necessary.
What is a kidney stone?
A kidney stone is a solid mass formed by substances such as calcium, oxalate, urate, cystine, xanthine, or phosphate in the urine. These substances normally dissolve in urine, but when there is not enough liquid or the waste concentration is too high, crystals begin to form. These crystals can then clump together to form a stone.There are four main types of kidney stones:
- Calcium oxalate (most common)
- Uric acid
- Struvite (linked to infections)
- Cystine (rare, genetic cause)
Some stones remain in the kidneys, while others travel through the urinary tract. Small stones often pass without issue, but larger ones can cause painful blockages.
Common symptoms of kidney stones
Kidney stones vary in size, from as small as a grain of sand to as large as a golf ball. While tiny stones may pass without symptoms, larger ones can cause significant discomfort. Common signs include:
- Sharp pain on either side of the lower back or abdomen
- Blood in the urine (haematuria)
- Persistent nausea or vomiting
- Fever and chills (possible sign of infection)
- Urine that looks cloudy or has a foul odour
Pain usually starts when a stone moves or causes blockage, particularly in the ureter (the tube connecting kidney to bladder). While many stones can pass on their own, others may require medical or surgical treatment.
Kidney stone size chart and treatment options
Kidney stone size plays a major role in determining the likelihood of natural passage and the need for intervention. Here’s a general breakdown:
| Stone Size |
Description |
Recommended Management |
| 1–4 mm | Very small stones | Often pass naturally with hydration. Pain relief may be sufficient. |
| 5–7 mm | Medium-sized stones | May pass with fluids and medication, but medical intervention like shock wave lithotripsy may be required if not expelled. |
| 8–10 mm | Larger stones | Less likely to pass on their own. Lithotripsy or ureteroscopy may be needed. |
| 10+ mm | Large stones | Rarely pass naturally. Require surgery, ureteroscopy, or percutaneous nephrolithotomy (PCNL). |
What size of kidney stone requires surgery?
Generally, kidney stones larger than 10 mm are unlikely to pass naturally and often require surgical removal. According to the European Association of Urology (EAU) and NICE (UK) guidelines:
- Stones larger than 10 mm are typically treated with surgery or minimally invasive procedures.
- Stones larger than 5–7 mm may also require intervention if they cause obstruction, pain, or complications.
Factors that influence surgical decisions for kidney stone
While size is a key factor, several other elements determine whether While size is a key factor, several other elements determine whether surgery is necessary:
- Stone Location: Stones in the upper ureter may pass more easily than those closer to the bladder.
- Kidney Anatomy: The shape, size, and drainage ability of the kidney can affect treatment suitability.
- Stone Composition: Some stones, such as uric acid or struvite (infection) stones, are less responsive to certain treatments like shockwave therapy.
- Patient Factors: Age, medical history, pain tolerance, and pre-existing conditions play a role in selecting treatment options.
- History of Recurrence: Individuals with repeated stone formation may benefit from surgical removal and preventive strategies, even for smaller stones.
When to seek medical help
While many kidney stones pass without serious problems, you should consult a doctor if you experience:
- Intense or prolonged pain
- Inability to urinate
- Fever or signs of infection
- Nausea and vomiting that won’t subside
- Blood in the urine
Early medical attention can prevent complications like urinary tract infections, kidney damage, or ongoing pain. Kidney stone size is a critical indicator of how the condition will progress and what treatment is needed. Small stones may pass naturally with fluids and rest, but larger stones, particularly those over 10 mm, often require surgical removal to prevent serious health risks. Understanding your stone type, size, and symptoms can guide timely and effective treatment.Also Read: Is your kidney healthy? Check it yourself with this simple trick; no test needed