From the Guidelines
The gold standard for diagnosing renal stones is non-contrast computed tomography (CT) scan of the abdomen and pelvis, as it provides the most accurate detection of kidney stones with a reported sensitivity as high as 97%. This imaging technique allows for rapid acquisition with high spatial resolution and ability for multiplanar reformations, enabling accurate detection of even small stones 1. The use of non-contrast CT also enables visualization of secondary signs of urolithiasis and complications such as periureteral and perinephric inflammation and ureteral dilatation.
Some of the key benefits of non-contrast CT include:
- High sensitivity and specificity for detecting kidney stones
- Ability to visualize the entire urinary tract
- Detection of alternative diagnoses that may mimic renal colic
- Provision of information that helps guide management decisions, such as stone size and location 1
- Low-dose CT protocols that maintain diagnostic accuracy while reducing radiation risk 1
While other imaging modalities like ultrasound and X-ray KUB are sometimes used, they are less sensitive and may miss certain types of stones 1. Ultrasound is often used as an initial screening tool, especially in pregnant patients or children to avoid radiation exposure, but it may miss smaller stones or those in the mid-ureter. Non-contrast CT is currently considered the reference standard for the evaluation of urolithiasis, and its use is recommended for accurate diagnosis and management of renal stones 1.
From the Research
Diagnosis of Renal Stones
- The gold standard for diagnosis of urolithiasis is non-contrast computed tomography (CT) 2, 3, 4, 5
- CT is widely regarded as the most accurate imaging modality for detecting renal calculi, but it is costly, time-consuming, and exposes patients to significant doses of ionizing radiation 2
- Ultrasound is a commonly used alternative to CT, but it has a lower sensitivity (54-78%) and specificity (91%) compared to CT 2, 3
- The sensitivity of ultrasound increases with stone size, with a sensitivity of 90% for stones ≥6 mm 2
- Ultrasound is recommended as the initial imaging modality for suspected renal colic in pregnant women and children 5
Imaging Modalities
- Plain x-ray of the abdomen, ultrasound scan, intravenous urogram, computed tomography (CT), and magnetic resonance imaging are all available imaging modalities for detecting kidney stones 4, 5
- Each modality has its own strengths and weaknesses, and the choice of modality depends on the individual patient and the clinical scenario 4, 5
- CT is the most sensitive and specific imaging modality, but it is not always necessary and may expose patients to unnecessary radiation 6, 5
- Ultrasound is a useful alternative to CT, especially in patients who are pregnant or have a contraindication to CT 6, 5