• Nephrolithiasis accounts for a significant proportion of emergency department visits every year.
• The severity of symptoms, as well as the degree of intervention required is variable.
• Controversy remains regarding the optimal diagnostic imaging modality for the diagnosis of nephrolithiasis in the ED.

• Common presenting symptoms include flank pain, nausea/vomiting, dysuria, urinary urgency and/or frequency, and hematuria.
• Absence of hematuria does not rule out nephrolithiasis.
  • Up to 35% of patients will NOT have hematuria by day 3 of symptoms.
• Potential complications include:
  • Complicated UTI or pyelonephritis.
  • Acute urinary obstruction, potential for renal damage.

• Very broad differential diagnosis to consider.
• Nephrolithiasis is a clinical diagnosis.
• Workup may include:
  • Urinalysis.
  • CBC, electrolytes and renal function.
    • Renal function is rarely significantly impacted and therefore electrolytes/creatinine are often of little value
• STONE tool has been validated and places patient into low, medium or high probability group.
  • Stone Tool (MD Calc).
  • Can be used in conjunction with clinical picture to decide whether to image and/or what modality to use.

• Imaging not required in every case.
• Controversy remains between non-contrast CT and ultrasonography as first choice modality.
• Abdominal x-ray, IV pyelogram and MRI are not recommended.

CT Scan:

• Non-contrast CT remains gold standard – low dose protocols may be used.
• Low dose CT has sensitivity of up to 99% and specificity of 94%.
• Provides information regarding stone size and location, potential complications and ability to make alternate diagnoses.
• Cons include increased health care costs and radiation exposure.

Ultrasonography:

• Stones may be directly visualized as hyperechoic lines with distal shadowing.
  • “Twinkling” sign when color doppler is used.
• Indirectly detects nephrolithiasis based on findings of hydronephrosis or lack of ureteral jetting.
• Sensitivity and specificity vary with practitioner skill and patient body habitus.
  • Pooled literature review found sensitivity of 45% and specificity of 94%.
• 2014 study found that using U/S (either done by the emergency physician or through the radiology department) as first choice modality, did not lead to an increased risk of serious adverse events and avoided radiation exposure in large subset of patients.

Recommendation of Imaging Modality:

• In younger (< 35), healthy patients with high clinical suspicion of nephrolithiasis, imaging is not always required and CT can often be avoided.
• U/S is a good first choice modality and should be used to guide clinical suspicion and need for further imaging.
• U/S is imaging modality of choice in pregnant and pediatric populations.
• Low dose CT is generally recommended in elderly patients and in those whom the clinical suspicion is lower, or alternative diagnoses are equally as likely.

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