Laboratory Evaluation for Kidney Stones

Initial Laboratory Evaluation

The American Urological Association recommends obtaining serum chemistries, including electrolytes, calcium, creatinine, and uric acid, to evaluate for underlying metabolic abnormalities and kidney function 1
Urinalysis should include complete dipstick and microscopic evaluation to assess for hematuria, urine pH, crystalluria, and signs of infection, with the American College of Radiology suggesting this approach 2
The European Association of Urology recommends assessing for urine pH, as acidic urine pH is associated with uric acid stones 1
Crystalluria can help identify stone type, according to the European Urology guidelines 3
Signs of infection, such as leukocyte esterase, nitrites, and WBCs, should be evaluated, as recommended by the American College of Radiology 1, 4

A 24-hour urine collection is recommended for patients with recurrent stones to identify specific metabolic abnormalities, including volume and creatinine, as suggested by the American College of Radiology and European Urology 1, 2, 3

The American College of Radiology recommends ultrasound of kidneys and bladder as first-line imaging for kidney stones, with sensitivity up to 100% for detecting obstruction 4, 5
Non-contrast CT scan should be considered if diagnosis is uncertain or to assess stone burden, with a sensitivity and specificity of 95% or higher, according to the American Academy of Family Physicians and the American College of Radiology 6, 7

Stone analysis should be performed to determine composition, which will guide preventive measures, as recommended by the American Urological Association and European Urology 1, 3
Pain assessment should be evaluated to determine need for analgesics, preferably NSAIDs as first-line treatment, according to the European Urology guidelines 3
Dermatologic evaluation should include urinalysis to rule out uremia and serum calcium to evaluate for hypercalcemia, as suggested by the American Urological Association and the American College of Radiology 1, 2

Fever with flank pain could indicate pyelonephritis or infected stone, requiring urgent intervention, as recommended by the American Urological Association and the American College of Radiology 1, 4
Lower back pain may not always be due to kidney stones; consider musculoskeletal causes if urinalysis is negative for hematuria, according to the American College of Physicians 8, 9
Limit radiation exposure by using ultrasound as first-line imaging when appropriate, especially in younger patients, as suggested by the American College of Radiology 4, 7

Repeat urinalysis should be performed if initial results are negative but symptoms persist, as recommended by the American Urological Association 1
Metabolic evaluation should be completed within 6 weeks of stone event to guide prevention strategies, according to the American Urological Association and European Urology 1, 3