Radiology glossary

What does "kidney stone" mean on your scan?

Part of: Abdomen findings, explained

Full explainer: Kidney Stone — What It Means on Your Report

A hardened mineral deposit has formed in the kidney or urinary tract — the famously painful condition nicknamed nephrolithiasis. Stones form when urine becomes concentrated enough for minerals (usually calcium salts, sometimes uric acid or others) to crystallize, like scale building up in a kettle. Small stones may sit quietly in the kidney and never be noticed; the trouble starts when a stone moves into the narrow ureter, where it can block urine flow and cause hydronephrosis behind it. The classic symptom is renal colic: severe, wave-like flank pain radiating toward the groin, often with nausea — pain so distinctive that doctors recognize the story immediately. The report typically notes the stone's size in millimeters (the key number — small stones often pass on their own, larger ones less so), its exact location, whether it is blocking flow, and whether there are additional stones. Size and location drive the entire plan, which is why precise measurement matters.

What it means on Ultrasound

Ultrasound can show kidney stones as bright echoes with shadowing, and it excels at showing the consequence — hydronephrosis, the swelling behind a blockage. It is the preferred test in pregnancy and children to avoid radiation, and for monitoring known stones. Its limitations are real: small stones, especially in the mid-ureter, are easily missed, and bowel gas can obscure the view. It answers “is there blockage?” well and “exactly where is the stone?” less well.

What radiologists look at next

For a kidney stone, the radiologist measures its largest diameter in millimeters — the single most management-relevant number — and records its precise location: in which calyx, the renal pelvis, or at what level of the ureter. They assess for obstruction: hydronephrosis above the stone, ureteral dilation, and delayed contrast excretion if contrast was given. Additional stones are cataloged, the stone's density is noted (which hints at composition), and the surrounding tissues are checked for complications. Prior studies are compared to see whether a known stone has moved, grown, or passed.

Where it commonly shows up

• kidney
• ureter
• renal pelvis
• right kidney
• left kidney

Questions to ask your doctor

• How big is the stone, and where exactly is it?
• Is it blocking urine flow?
• Will it pass on its own, or does it need intervention?
• Are there more stones?
• How can I reduce the chance of forming another?

Common questions

What does passing a kidney stone feel like?

Often severe, cramping flank pain that comes in waves and radiates toward the groin, frequently with nausea, restlessness, and sometimes blood in the urine. The pain typically lasts until the stone moves or passes. Severe pain, fever, vomiting, or inability to urinate need prompt medical attention — do not try to endure those at home.

Will my stone pass on its own?

Size is the main predictor: stones under about 5 millimeters usually pass spontaneously, larger ones less often, though shape and location matter too. Your doctor estimates the likelihood from the CT measurements and may suggest watchful waiting with pain management or an intervention. Either way, straining the urine to catch the stone helps confirm passage.

How can I prevent another stone?

The universal advice is generous fluid intake — diluting the urine is the single most effective prevention. Beyond that, prevention depends on the stone's composition: your doctor may analyze a passed stone and check urine and blood to tailor advice on diet, and occasionally prescribe preventive medication. Bring it up at your follow-up.

Related conditions

• Hydronephrosis — What It Means on Your Report
• Renal Cyst — What It Means on Your Report
• Ascites — What It Means on Your Report