It often starts suddenly: intense, cramping pain in your side or back that radiates to your lower abdomen and groin. You may feel nauseous. You cannot find a comfortable position. You may even see blood in your urine.

If this sounds familiar, you likely have a kidney stone — and a CT scan is the fastest way to confirm it.

Why CT Is the Gold Standard

A non-contrast CT scan of the abdomen and pelvis is the preferred imaging study for suspected kidney stones. Here is why:

Sensitivity above 95% based on published diagnostic data — it catches nearly every stone
No contrast needed — the scan is performed without IV dye, making it safer and faster
Shows stone size and location precisely — critical for treatment planning
Detects other causes of pain — appendicitis, ovarian cysts, or other conditions that mimic kidney stone pain
Takes about 5 minutes — fast answers when you are in severe pain

Ultrasound can detect some kidney stones (especially in the kidneys themselves) but misses many stones in the ureters — the tubes connecting kidneys to the bladder — which is where most stones cause pain.

X-rays miss up to 40% of kidney stones, especially smaller ones and those made of uric acid (which are radiolucent).

What the CT Shows Your Doctor

Stone Size - Under 5mm — 80-90% pass on their own within days to weeks - 5-10mm — may pass spontaneously but may need intervention - Over 10mm — usually requires procedural treatment

Stone Location - In the kidney — may be monitored if not causing symptoms - In the ureter — this is where pain happens; location determines treatment approach - At the ureterovesical junction (UVJ) — where the ureter meets the bladder; stones often get stuck here but usually pass

Obstruction CT shows whether the stone is blocking urine flow (hydronephrosis). Complete obstruction with infection is a urological emergency requiring immediate intervention.

Number of Stones Multiple stones may affect treatment planning. CT reveals all of them, even those not yet causing symptoms.

Types of Kidney Stones

Calcium oxalate — most common (80%), often from dietary factors
Calcium phosphate — associated with certain metabolic conditions
Uric acid — associated with gout, high-protein diets, diabetes
Struvite — associated with urinary tract infections
Cystine — rare, genetic condition

CT cannot determine stone composition directly, but stone density (measured in Hounsfield units) provides clues that help urologists plan treatment.

Treatment Based on CT Findings

Conservative Management (Small Stones) - Pain medication (NSAIDs, sometimes opioids) - Alpha-blockers (tamsulosin) to relax the ureter - Hydration - Time (days to weeks)

Shock Wave Lithotripsy (SWL) - External sound waves break the stone into fragments - Best for stones under 2 cm in the kidney or upper ureter - Outpatient procedure

Ureteroscopy - A thin scope passed through the bladder into the ureter - Stone is lasered and fragments removed - Best for ureteral stones

Percutaneous Nephrolithotomy - For large stones (over 2 cm) or staghorn calculi - Small incision in the back; stone removed directly from the kidney - Inpatient procedure

Prevention

Once you have had one kidney stone, you have a 50% chance per NIDDK kidney stone data of having another within 5-10 years. Prevention is key:

Drink 2.5-3 liters of water daily — the single most effective prevention strategy
Limit sodium — high salt intake increases calcium in urine
Moderate animal protein — excess protein increases uric acid
Get enough calcium (from food, not supplements) — counterintuitively, dietary calcium reduces stone risk by binding oxalate in the gut
Limit high-oxalate foods if you form calcium oxalate stones (spinach, nuts, chocolate, beets)
Follow up with your urologist — 24-hour urine testing can identify your specific risk factors

At AMI

We offer same-day CT appointments for urgent kidney stone evaluation. The non-contrast stone protocol is fast (about 5 minutes of scan time), comfortable, and provides your doctor with all the information needed to plan your treatment.

If you are in pain, call (727) 398-5999 for urgent scheduling, or have your doctor fax the order to (727) 231-0772 for immediate processing.

CT Scan for Kidney Stones: The Fastest, Most Accurate Diagnosis