Kidney stones may cause no symptoms while they remain in the kidney, but pain, blood in the urine, painful urination and changes in urine can occur when a stone moves into the urinary tract or blocks the flow of urine.
Kidney stones, medically known as nephrolithiasis, are hard deposits that form when certain minerals and salts become concentrated in urine and form crystals. They can range from very small stones that pass without noticeable symptoms to larger stones that become lodged in the urinary tract.
Pain is a common warning sign
One of the most recognisable symptoms is sharp pain in the back, side, lower abdomen or groin. The pain can come in waves and may change location as the stone moves through the urinary tract.
A stone that becomes stuck in a ureter, the narrow tube connecting a kidney to the bladder, can obstruct urine flow. This can cause severe pain and swelling in the affected kidney.
Pain or a burning sensation while urinating can also occur. Some people may feel a frequent or persistent need to urinate, or pass only small amounts of urine.
Blood in the urine
Blood in the urine, known medically as hematuria, is another recognised symptom of kidney stones. The urine may appear pink, red or brown, although blood may also be detected only through laboratory testing.
Blood in the urine should not automatically be attributed to kidney stones. Urinary tract infections and other conditions can also cause it, which is why medical assessment may be necessary.
Cloudy or foul-smelling urine can occur with kidney stones, but these changes can also indicate a urinary infection.
Fever can signal an infection
Fever and chills are particularly important when they occur alongside symptoms of a kidney stone.
A stone that blocks the urinary tract can contribute to a kidney infection. Fever, chills, severe pain, vomiting or difficulty passing urine should therefore prompt urgent medical attention rather than being treated as routine symptoms of a stone.
The combination of a possible urinary obstruction and infection can require prompt treatment.
Nausea and vomiting
Kidney stones can also cause nausea and vomiting, particularly when the pain is severe. These symptoms may make it difficult for a person to drink enough fluids and can contribute to dehydration.
Not everyone with a kidney stone develops all of these symptoms. Small stones may pass through the urinary tract without causing noticeable problems.
How kidney stones form
Kidney stones form when certain substances in urine, including calcium, oxalate and phosphorus, become concentrated and form crystals. Different types of stones can develop, with calcium stones being the most common. Other types include uric acid, struvite and cystine stones.
A stone can remain in the kidney without causing symptoms. Problems often begin when it moves into a ureter and becomes lodged or irritates the urinary tract.
The size and location of a stone influence whether it can pass naturally or requires treatment. Small stones can often pass without a procedure, while larger stones or those blocking urine flow may require medical intervention.
How kidney stones are diagnosed
Symptoms alone cannot confirm that a person has a kidney stone. Health professionals may use a physical examination, urine and blood tests and imaging to establish the diagnosis.
Urine testing can detect blood and substances associated with stones and can also help identify bacteria that may indicate a urinary tract infection. Imaging, including CT scans or ultrasound in appropriate cases, can help determine the size and location of a stone and whether it is blocking the urinary tract.
When to seek medical care
People with severe pain, blood in the urine, fever or chills, repeated vomiting, or difficulty passing urine should seek medical attention promptly.
These symptoms can occur with kidney stones but may also point to infection or another condition requiring treatment.
Treatment depends on the stone’s size, location and composition. Some stones pass naturally, while others may need medication or procedures to break up or remove them.
Drinking enough water is an important part of preventing many kidney stones, although people with certain medical conditions may need individual advice about their fluid intake. Diet and other preventive measures can also depend on the type of stone a person has formed.
