From the Guidelines
Diagnosing nephrolithiasis requires a comprehensive approach combining clinical assessment, laboratory tests, and imaging studies, with non-contrast CT scan being the gold standard imaging modality due to its high sensitivity and specificity of 97% for stone detection, as reported in the most recent study 1. The diagnosis of nephrolithiasis involves a thorough history focusing on pain characteristics, associated symptoms, and risk factors. Physical examination may reveal costovertebral angle tenderness.
- Key aspects of the history include:
- Pain characteristics: sudden, severe flank pain radiating to the groin
- Associated symptoms: nausea, vomiting, hematuria
- Risk factors: family history, dehydration, certain medications
- Laboratory tests should include:
- Urinalysis to detect hematuria
- Urine culture to rule out infection
- Blood tests: complete blood count, renal function tests (creatinine, BUN), and electrolytes
- Imaging studies play a crucial role in diagnosing nephrolithiasis, with the following options:
- Non-contrast CT scan: the gold standard imaging modality with 97% sensitivity and specificity for stone detection, allowing visualization of stone size, location, and density 1
- Ultrasound: an alternative, particularly for pregnant patients or children, though less sensitive than CT, with a sensitivity of 24% to 57% for stone detection 1
- X-ray KUB (kidneys, ureters, bladder): can detect radiopaque stones but misses uric acid stones Once a stone is diagnosed, stone analysis should be performed if retrieved to guide prevention strategies. Metabolic evaluation, including 24-hour urine collection for calcium, oxalate, citrate, and uric acid, is recommended for recurrent stone formers to identify underlying metabolic abnormalities that can be targeted for prevention, as suggested by the American College of Radiology 1.
From the Research
Diagnosis of Nephrolithiasis
The diagnosis of nephrolithiasis, or kidney stone disease, can be made using various imaging techniques. The following are some of the common methods used:
- Non-contrast CT of the kidneys, ureters, and bladder (CT KUB) is considered the gold standard for diagnosing kidney stones, with a sensitivity of >99% 2
- Ultrasound KUB is an alternative imaging modality, especially when CT KUB is contraindicated or not available, although it has limited sensitivity, particularly for ureteric stones 2
- Plain film KUB can be used for follow-up of radiopaque stones 2
- Other imaging techniques, such as MRI, may also be used, although they are not as commonly used due to their high cost and limited ability to visualize stones 3
Imaging Techniques Comparison
Different imaging techniques have their own advantages and disadvantages:
- Non-contrast CT provides the most accurate diagnosis but exposes patients to ionizing radiation 3
- Ultrasonography has a lower sensitivity and specificity than CT but does not require radiation 3
- A study found that non-contrast CT and ultrasonography had equivalent diagnostic accuracy in the emergency department 3
- A novel protocol, including oral hydration and an oral diuretic, can enhance the distention of the renal collecting system, allowing for more accurate preoperative planning for kidney stone treatment 4
Stone Composition Determination
Determining the composition of kidney stones can help in patient management:
- Threshold-based stone segmentation and radiomics can determine the composition of kidney stones from single-energy CT, differentiating between calcium oxalate/phosphate and uric acid stones with an area under the curve (AUC) of 0.78 5
- Automated threshold-based stone segmentation and radiomics can be used to isolate kidney stones and estimate radiomics over the segmented stone volume 5