Sudden, squeezing pain in the side that spreads to the lower abdomen may not be a simple muscle ache. It is a hallmark symptom of urinary stones, a condition severe enough to send patients to the emergency room. More than 330,000 people in South Korea were treated for the condition last year, and male patients outnumbered female patients by about two to one.
Men Account for Twice as Many Cases; Severe Flank Pain Warrants Attention
According to the medical community and the Health Insurance Review and Assessment Service on the 16th, 335,807 people received treatment for urinary stones in 2025. Men accounted for 223,092 cases, roughly double the 112,715 cases among women.
Urinary stones are hard, stone-like deposits that form in the passage through which urine is produced and expelled. They are classified by location as kidney stones, ureteral stones or bladder stones.
They form when substances in urine such as calcium, oxalate and uric acid become concentrated and clump together. Genetic factors, diet and urinary tract infections also play a role.
The most common symptom is sudden flank pain. When a stone descends from the kidney and blocks the ureter, urine flow is obstructed and severe pain follows.
The pain can spread to the lower abdomen or groin and may be accompanied by blood in the urine, nausea and vomiting. Stones in the bladder or urethra can cause painful urination or a feeling of incomplete emptying.
Flank pain accompanied by fever or chills may signal a urinary tract infection and requires prompt medical attention. In some cases, however, stones cause no noticeable symptoms at all.
Drinking More Water Helps, but 2 Liters a Day Is Not a Universal Rule
The most basic way to prevent urinary stones is adequate fluid intake.
When the body lacks water, urine volume falls and becomes more concentrated, making it easier for stone-forming substances to clump together. Drinking enough water dilutes urine and lowers the risk of stone formation.
Not everyone needs to drink more than 2 liters a day, however. The appropriate amount varies with body size, activity level and temperature.
"If you have been sweating heavily because of hot weather or exercise, you need to increase your fluid intake above your usual level," said Choi Hoon, a professor of urology at Korea University Ansan Hospital. "If you have to limit fluid intake because of heart or kidney disease, you should consult your medical team."
A high-salt diet is also best avoided. Because urinary stones can recur even after treatment, consistent long-term management matters.
Does a Stone Always Mean Surgery? It Depends on Size and Location
Finding a urinary stone does not automatically mean surgery. If the stone is small and likely to pass on its own, doctors can manage the pain and watch for it to pass in the urine. Medication to help passage is sometimes used.
If a stone is unlikely to pass naturally, treatment is chosen based on its size and location. The best-known option is extracorporeal shock wave lithotripsy, which breaks the stone into small fragments using shock waves delivered from outside the body. The fragments then pass out in the urine.
Ureteroscopic stone removal involves inserting an endoscope through the urethra and then breaking up or removing the stone with a laser or other tools. Flexible endoscopes can be used for stones located deep inside the kidney.
For large kidney stones more than 2 centimeters across, doctors consider percutaneous nephrolithotomy, which removes the stone through a small channel created in the side of the body.
Robot-assisted flexible endoscopy incorporating artificial intelligence has also come into use recently. By helping doctors manipulate the endoscope with greater precision, it can be advantageous for treating multiple stones or stones in hard-to-reach locations.
"Treatment should be decided by looking not only at the size and location of the stone but also at whether the urinary tract is obstructed and whether an infection is present," Choi said.
The professor added that patients should identify their individual risk factors and manage them consistently, since stones can recur even after treatment.
