Nephrolithiasis affects approximately 8.8% of the U.S. population, with a lifetime prevalence of ~13% in men and ~7% in women, and a 5-year recurrence rate of 35–50% without treatment. [1-2] The following is a comprehensive clinical summary organized for emergency medicine and primary care workflows.
1. History
- Pain characterization: Acute, colicky flank pain radiating to the groin; as the stone descends, pain localizes to the lower abdomen and may radiate to the ipsilateral gonad or urethral tip [3]
- Onset/timing: Sudden onset, often waking patients from sleep; waxing/waning intensity corresponding to ureteral peristalsis
- Duration of pain: Short duration (<6 hours) is more predictive of ureteral stone (STONE score component) [4]
- Associated symptoms: Nausea/vomiting (due to shared splanchnic innervation with GI tract), urinary urgency/frequency/dysuria (especially with distal ureteral stones mimicking cystitis) [3]
- Important negatives: Absence of hematuria does not exclude stones (~10% of confirmed stones have no hematuria); ask about fever, chills, anuria, prior stone history, prior urologic procedures [3]
2. Alarm Features
- Fever + obstructing stone = infected urolithiasis → urologic emergency requiring emergent decompression regardless of pain control [3][5]
- Anuria or oliguria (bilateral obstruction or obstruction of a solitary/transplanted kidney) [3]
- Intractable pain or vomiting unresponsive to IV analgesia [3]
- Signs of sepsis: Tachycardia, hypotension, altered mental status in the setting of obstructing stone
- Acute kidney injury: Rising creatinine with obstructing stone [6]
- Toxic-appearing patient with fever, chills, dysuria, and CVA tenderness — consider infected urolithiasis even if pain is controlled [5]
3. Medications
Acute treatment
- First-line analgesia: NSAIDs (ketorolac 15–30 mg IV) — recommended by EAU and AUA as first-line; combination therapy superior to single agents [3][6-7]
- Second-line: Opioids (morphine, hydromorphone) for refractory pain; IV lidocaine as an alternative [8]
- Medical expulsive therapy (MET): Tamsulosin 0.4 mg daily for distal ureteral stones >5 mm (no demonstrated benefit for smaller stones) [7-8]
- Antiemetics: Ondansetron for associated nausea/vomiting
Prevention (recurrent stones)
- Thiazide diuretics (chlorthalidone 25 mg, hydrochlorothiazide 50 mg, indapamide 2.5 mg) [2][9]
- Potassium citrate for hypocitraturia, uric acid stones, and cystine stones [1]
- Allopurinol for hyperuricosuria with calcium oxalate stones and normocalciuria [1]
Medications to avoid/caution
- Nifedipine and aggressive IV fluids are not recommended to facilitate stone passage [8]
- Avoid nephrotoxic agents; use caution with contrast in AKI
4. Diet
Acute
Long-term prevention
- Fluid intake: Sufficient to produce ≥2–2.5 L urine/day [2][10]
- Normal-to-high calcium diet (1000–1200 mg/day dietary calcium) — paradoxically, low-calcium diets increase stone risk by raising urinary oxalate [9][11]
- Low sodium (<2300 mg/day) — reduces urinary calcium excretion [9][12]
- Limit animal protein (0.8–1.0 g/kg/day) — reduces uric acid, calcium, and oxalate excretion [9-10]
- Reduce dietary oxalate (spinach, rhubarb, nuts, chocolate) [2]
- Increase citrus fruits for natural citrate [10]
- Reduce cola/phosphoric acid–containing soft drinks [2]
- DASH diet pattern is protective [13]
5. Review of Systems
- GU: Hematuria (gross or microscopic), dysuria, urgency, frequency, decreased urine output
- GI: Nausea, vomiting, abdominal pain (shared splanchnic innervation can mimic acute abdomen) [3]
- Constitutional: Fever, chills, rigors (→ infected stone)
- MSK: Flank/back pain — distinguish from musculoskeletal causes
- Endocrine: Symptoms of hyperparathyroidism (fatigue, bone pain, constipation, polyuria)
- GYN (women): Menstrual history, vaginal discharge, pregnancy status
6. Collateral History and Family History
- Family history: 55% of patients with recurrent stones have a family history of urolithiasis; positive family history increases risk 3-fold [3]
- Hereditary conditions: Cystinuria, primary hyperoxaluria, renal tubular acidosis, Dent disease, familial hypercalciuria
- Social context: Occupation (hot environments → dehydration), dietary habits, fluid intake patterns, supplement use (vitamin C, vitamin D, calcium supplements) [10]
7. Risk Factors
- Male sex (though the gender gap is narrowing) [1]
- Obesity/high BMI/large waist circumference — risk may be greater in women (RR up to 2.09 for BMI ≥30) [13-14]
- Metabolic syndrome (OR 1.77), hypertension (OR 1.61), diabetes (OR 1.55), dyslipidemia (OR 1.59) [15]
- Low fluid intake/chronic dehydration [10]
- High sodium, high animal protein, high fructose intake [13]
- Hot climate/occupational heat exposure [10]
- Prior stone history (strongest predictor of recurrence) [16]
- Medications: Topiramate, acetazolamide, calcium supplements (without meals), high-dose vitamin C, indinavir
- Anatomic abnormalities: Medullary sponge kidney, UPJ obstruction, horseshoe kidney
8. Differential Diagnosis
Up to one-third of CT scans performed for flank pain reveal alternative diagnoses: [17]
- Pyelonephritis/UTI — fever, pyuria, bacteriuria; may coexist with stones
- Appendicitis — RLQ pain, peritoneal signs, anorexia
- Diverticulitis — LLQ pain, older patients, fever
- Abdominal aortic aneurysm (AAA) — cannot-miss; pulsatile mass, hypotension, older patient with vascular risk factors [18]
- Renal infarction — consider in patients with atrial fibrillation, age ≥70, elevated LDH ≥500, negative urine RBCs [19]
- Ovarian torsion/ruptured ovarian cyst — most common alternative in women [17]
- Ectopic pregnancy — always check β-hCG in reproductive-age women
- Mesenteric ischemia — older patients, out-of-proportion pain
- Musculoskeletal pain — positional, reproducible on palpation
- Papillary necrosis — sickle cell disease, analgesic nephropathy, diabetes
9. Past Medical History
- Prior stone episodes (number, type, interventions)
- Prior urologic surgery or procedures
- Chronic UTIs (struvite/infection stones)
- Gout (uric acid stones)
- Hyperparathyroidism, RTA, inflammatory bowel disease (calcium oxalate stones from enteric hyperoxaluria)
- Bariatric surgery (increased oxalate absorption)
- Solitary kidney or transplanted kidney (lowers threshold for intervention) [3]
10. Physical Exam
- General: Patient often writhing, unable to find a comfortable position (unlike peritonitis where patients lie still) [3]
- Vitals: Tachycardia (pain-related); fever >37.8°C is a red flag for infected stone; hypotension suggests sepsis [20]
- Abdomen: CVA tenderness; mild ipsilateral abdominal tenderness; peritoneal signs should be absent — if present, consider alternative diagnosis [3]
- GU: Testicular exam in males to exclude torsion; pelvic exam in females if gynecologic pathology suspected
- Vascular: Palpate for pulsatile abdominal mass (AAA)
11. Lab Studies
- Urinalysis: Hematuria (90% sensitivity but not diagnostic alone); pyuria and bacteriuria suggest infection; urine pH (low pH → uric acid stones; high pH → struvite) [8]
- Urine culture: If any concern for infection
- BMP/CMP: Creatinine (assess for AKI, solitary kidney), calcium (screen for hypercalcemia/hyperparathyroidism), potassium, bicarbonate
- CBC: Leukocytosis may indicate infection (though mild WBC elevation can occur with pain alone)
- Uric acid level: If uric acid stone suspected
- β-hCG: All reproductive-age women
- Lactate: If sepsis suspected
- 24-hour urine collection: Not in the acute setting — reserved for metabolic evaluation 3+ weeks after stone passage for recurrent stone formers [1][3]
12. Imaging
- First-line: Non-contrast CT abdomen/pelvis (NCCT) — gold standard with sensitivity >95% and specificity >98%. Low-dose CT (<3 mSv) maintains pooled sensitivity of 97% and specificity of 95% [16]
- Ultrasound: Appropriate as initial study in pregnancy, pediatric patients, and as a radiation-sparing alternative; evaluates for hydronephrosis but less sensitive for stone detection [6-7]
- KUB radiograph: Limited sensitivity; may be useful for follow-up of known radiopaque stones
- Pregnancy: Ultrasound first → non-contrast MRI if inconclusive → CT only as last resort [16]
- When imaging may be unnecessary: Young patients (<35 years) with typical symptoms, hematuria, pain relief with analgesics, and prior stone history may not require CT [21]
The following figure illustrates a suggested imaging algorithm for acute renal colic:
Key imaging findings
- Stone size and location (determines likelihood of spontaneous passage and need for intervention)
- Hydronephrosis/hydroureter
- Perinephric stranding
- Alternative diagnoses (appendicitis, AAA, ovarian pathology)
13. Special Tests
STONE Score (clinical prediction rule for ureteral stone): [4]
- Sex (male = 2 points)
- Timing/duration of pain (<6h = 3, 6–24h = 1, >24h = 0)
- Origin/race (non-Black = 3)
- Nausea/vomiting (nausea alone = 1, vomiting = 2)
- Erythrocytes on UA (present = 3)
- Score 0–5 = low risk (~9–14%), 6–9 = moderate (~50%), 10–13 = high (~75–90%) [4][23]
Additional tools
- Point-of-care ultrasound (POCUS): Assess for hydronephrosis; moderate-to-severe hydronephrosis on POCUS combined with a high STONE score significantly increases specificity for ureteral stone [24]
- Stone analysis: All passed or retrieved stones should be sent for composition analysis
- Urine strainer: Provide to all discharged patients for stone capture
14. ECG
- Not routinely indicated for uncomplicated nephrolithiasis
- Obtain ECG if:
- Considering alternative diagnoses (e.g., abdominal aortic pathology)
- Hyperkalemia suspected (obstructive AKI) — look for peaked T waves, widened QRS, sine wave pattern [25]
- Older patients or those with cardiac risk factors presenting with atypical pain
- Hemodynamic instability or sepsis
- Pearl: Renal colic can cause a vagal response with bradycardia; severe pain may cause tachycardia and ST changes mimicking ACS
15. Assessment
Spontaneous passage rates by stone size
- <5 mm: ~68–98% pass spontaneously
- 5–10 mm: ~25–53% pass spontaneously; more proximal stones have lower passage rates [3][16]
- >10 mm: Unlikely to pass; typically require intervention [26]
Typical presentation: Young-to-middle-aged adult with acute colicky flank pain, hematuria, nausea/vomiting, writhing in distress, no peritoneal signs [3]
Atypical presentations to recognize
- Distal ureteral stones mimicking cystitis (urgency, frequency, dysuria)
- Elderly patients with vague abdominal pain
- Absence of hematuria (~10% of cases)
- Bilateral obstruction presenting as AKI/anuria
Complications: Obstructive uropathy, infected urolithiasis/urosepsis, AKI, ureteral stricture, chronic kidney disease from recurrent obstruction
16. Treatment Plan
Initial stabilization
- IV access, cardiac monitor if hemodynamically unstable
- Analgesia: Ketorolac 15–30 mg IV (first-line) ± opioids for refractory pain [3][27]
- Antiemetics as needed
- IV fluids for hydration/resuscitation (not to "flush" the stone)
Infected urolithiasis
- Emergent urologic consultation for decompression (ureteral stent or percutaneous nephrostomy) [3][5]
- Broad-spectrum antibiotics: IV ampicillin + gentamicin, or fluoroquinolone; adjust based on cultures [3]
- Fluid resuscitation per sepsis protocols
Uncomplicated stones ≤10 mm — conservative management
- NSAIDs (ibuprofen 600 mg TID or ketorolac) for outpatient pain control
- MET with tamsulosin 0.4 mg daily for distal ureteral stones 5–10 mm [7-8]
- Urine strainer for stone capture
- Follow-up imaging within 14 days to assess stone position and hydronephrosis [26]
- Trial of passage for 4–6 weeks [28]
Stones >10 mm or failed conservative management
- Ureteroscopy (URS): Higher stone-free rate, preferred for distal ureteral stones [28]
- Shock wave lithotripsy (SWL): Lower morbidity, option for proximal ureteral and renal stones <20 mm [28]
- Percutaneous nephrolithotomy (PCNL): For large renal stones (>20 mm) or staghorn calculi [7]
Recurrence prevention
- Increase fluid intake to achieve ≥2 L urine output/day [2]
- Dietary modifications (normal calcium, low sodium, low animal protein) [9]
- Pharmacotherapy if dietary measures fail: thiazides, potassium citrate, or allopurinol based on stone type and metabolic evaluation [1-2]
17. Disposition
Admit if
- Infected obstructing stone / urosepsis [3][5]
- Intractable pain or vomiting despite IV analgesia [3]
- AKI or anuria [6]
- Obstruction of a solitary or transplanted kidney [3]
- Bilateral ureteral obstruction
- Significant comorbidities precluding safe discharge
Observation
Discharge if
- Pain controlled with oral medications
- Tolerating PO intake
- No signs of infection or AKI
- Stone ≤10 mm with plan for outpatient follow-up
- Reliable follow-up arranged
Consult urology
- All infected obstructing stones (emergent)
- Stones >10 mm or unlikely to pass
- High-grade obstruction
- Solitary kidney with obstruction
- Failed conservative management
- Recurrent stone formers for metabolic evaluation [3]
18. Follow Up / Return Precautions
Follow-up timing
- Repeat imaging (CT or ultrasound) within 14 days if stone has not passed [26]
- If stone passes, urology follow-up within 4–6 weeks for metabolic evaluation in recurrent stone formers [3]
- 24-hour urine collection 3+ weeks after stone passage or removal for metabolic workup [3]
Return precautions — instruct patients to return immediately for:
- Fever or chills (infected stone)
- Inability to keep fluids or medications down
- Worsening or uncontrolled pain
- Decreased urine output or inability to urinate
- Blood in urine that worsens significantly
Patient counseling
- Strain all urine and save any passed stone for analysis
- Maintain high fluid intake (goal: clear/light yellow urine)
- Take prescribed medications (NSAIDs, tamsulosin) as directed
- Expected recovery: most small stones pass within 1–4 weeks; pain may be intermittent during passage
References
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