USMLE Prep - Medical Reference Library

Nephrolithiasis (Renal Colic) — ED Evaluation & Treatment

System: Urology • Reviewed: Aug 31, 2025 • Step 1Step 2Step 3

Synopsis:

Provide NSAID analgesia and antiemetics; image with noncontrast CT (or ultrasound in pregnancy); start tamsulosin for distal ureteral stones 5–10 mm; urgent urology for obstructed infected stone.

Key Points

  • Stabilize ABCs; begin targeted evaluation without delaying life-saving therapy.
  • Use system-specific risk tools to guide testing and disposition.
  • Order high-yield tests first; escalate imaging when indicated.
  • Start evidence-based initial therapy and reassess frequently.

Algorithm

  1. Primary survey and vitals; IV access and monitors.
  2. Focused history/physical; identify red flags and likely etiologies.
  3. Order system-appropriate labs and imaging (see Investigations).
  4. Initiate guideline-based empiric therapy (see Pharmacology).
  5. Reassess response; arrange consultation and definitive management.

Clinical Synopsis & Reasoning

For Nephrolithiasis Renal Colic Ed, frame the differential by acuity and pathophysiology, then align diagnostics to the leading hypotheses. Prioritize stabilization while obtaining high‑yield studies such as CBC (Baseline hematology), BMP (Electrolytes/renal). Incorporate bedside imaging and targeted labs to define severity and identify complications; synthesize results with clinical trajectory to refine the working diagnosis and disposition needs.


Treatment Strategy & Disposition

Initiate disease‑directed therapy alongside supportive care, titrating to objective response. Pharmacologic options commonly include Analgesia/Antipyretics. Use validated frameworks (e.g., Likelihood of Passage by Size (Approx.)) to guide escalation and site of care. Address precipitating factors, de‑escalate empiric therapies with data, and arrange follow‑up for monitoring and risk‑factor modification; admit patients with instability, high risk of deterioration, or needs for close monitoring.


Epidemiology / Risk Factors

  • Risk factors vary by condition and patient profile

Investigations

TestRole / RationaleTypical FindingsNotes
CBCBaseline hematologyAbnormal counts
BMPElectrolytes/renalDerangements

Likelihood of Passage by Size (Approx.)

Stone sizePassage likelihood
<5 mmHigh (often >68–80%)
5–10 mmModerate; trial of expulsive therapy
>10 mmLow; likely intervention

Pharmacology

MedicationMechanismOnsetRole in TherapyLimitations
NSAID (ketorolac)COX inhibitionMinutesAnalgesia; decreases ureteral spasmRenal/GI risk; ED use
Tamsulosinα1 antagonismDaysFacilitates stone passage (distal)Hypotension; ED use
Ondansetron5-HT3 antagonismMinutesNausea controlQT prolongation; ED use

Prognosis / Complications

  • Prognosis depends on severity, comorbidities, and timeliness of care

Patient Education / Counseling

  • Explain red flags and when to seek emergent care.
  • Reinforce medication adherence and follow-up plan.

Notes

Consider CT radiation exposure, especially in young or recurrent stone formers; low-dose CT protocols can be used. Treat UTI aggressively if present with obstruction.


References

  1. AUA Medical Management of Stones — Link
  2. ACEP Renal Colic Resources — Link