"CRP-first" algorithm to guide imaging in suspected renal colic: a retrospective UK cohort study

Area of Science:

• Radiology
• Emergency Medicine
• Biochemistry

Background:

• Renal colic diagnosis often requires advanced imaging.
• Selecting appropriate imaging modality is crucial for patient management and resource allocation.

Purpose of the Study:

• To determine if admission C-reactive protein (CRP) levels can stratify patients with suspected renal colic.
• To evaluate CRP's utility in guiding the choice between low-dose non-contrast CT KUB and contrast-enhanced CT of the abdomen and pelvis (CTAP).

Main Methods:

• Retrospective diagnostic accuracy study in a UK emergency department.
• Admission CRP levels (cutoff 5 mg/L) were compared against CT findings (normal, simple calculus, complicated calculus, alternative acute diagnosis).
• Sensitivity, specificity, and predictive values were calculated for CRP in identifying complicated calculus or alternative acute diagnosis.

Main Results:

• Of 58 eligible patients, 26 had complicated calculus or alternative acute diagnosis.
• CRP ≥ 5 mg/L showed a sensitivity of 0.73 and specificity of 0.69 for the target condition.
• Likelihood ratios indicated modest shifts in probability for complicated stones or alternative pathology.

Conclusions:

• Admission CRP offers clinically interpretable probability shifts for complicated renal colic or alternative diagnoses.
• A CRP-first approach may aid in selecting initial imaging (CT KUB vs. CTAP).
• Further prospective multicenter validation is necessary.