Nephrolithiasis
Urology
Illness script · Urology
Nephrolithiasis
Crystalline stone formation in the urinary tract causing obstruction, colicky flank pain, and hematuria.
This illness script for Nephrolithiasis covers predisposing factors, classic presentation, mechanism, workup, management, and the clinical pivots that separate it from look-alikes—written for USMLE Step 1 and clerkship reasoning.
01
Predisposing factors
- Most common: calcium oxalate stones (~80%); struvite, uric acid, cystine less common
- Male > female; peak age 20–50s; recurrence ~50% at 10 years
- Low urine volume (dehydration) is the #1 modifiable risk factor
- Hypercalciuria, hyperoxaluria, hypocitraturia increase calcium stone risk
- Recurrent UTIs with urease-producing bacteria (Proteus) → struvite/staghorn stones
- Gout, metabolic syndrome → uric acid stones; cystinuria (autosomal recessive) → cystine stones
02
Presentation
- Sudden-onset severe colicky flank pain radiating to ipsilateral groin ('loin to groin')
- Pain is constant or waxing/waning; patient cannot find comfortable position (writhes)
- Gross or microscopic hematuria in ~90% (absence does NOT rule out stone)
- Nausea/vomiting common; dysuria and urgency when stone near UVJ
- CVA tenderness on exam; fever suggests concurrent obstruction + infection (urologic emergency)
- Passage of stone or sudden pain relief after colicky episode is classic
03
Pathophysiology
- Supersaturation of urine with stone-forming solutes → crystal nucleation and aggregation
- Stones lodge at 3 anatomic narrowings: UPJ, pelvic brim, UVJ (most common)
- Obstruction → ureteral spasm + collecting system dilation → intense colicky pain
- Struvite stones form only in infected alkaline urine (urease splits urea → NH3 + CO2)
04
Diagnostics
- CT abdomen/pelvis without contrast: gold standard, >95% sensitivity, identifies all stone types
- Urinalysis: hematuria ± pyuria; uric acid stones in persistently acidic urine (pH <5.5)
- Plain KUB: calcium/struvite/cystine radiopaque; uric acid stones are radiolucent
- Renal ultrasound: first-line in pregnancy (avoids radiation); shows hydronephrosis
- 24-hour urine collection for recurrent stones: identifies metabolic abnormalities
05
Management
- Pain control: IV ketorolac (NSAID) first-line; opioids if refractory
- Medical expulsive therapy: tamsulosin (alpha-blocker) facilitates passage of stones ≤10 mm
- Stones ≤5 mm: ~90% pass spontaneously with hydration + analgesia
- Stones >10 mm or failed passage: ureteroscopy with laser lithotripsy or ESWL
- Fever + obstructed stone = urologic emergency → emergent ureteral stent or nephrostomy + antibiotics
- Stone prevention: high fluid intake (urine output >2 L/day); dietary sodium reduction for calcium stones
06
Clinical pivots
How to separate this script from the look-alikes that show up on exams and on the wards.
Pyelonephritis
Pyelonephritis: fever + costovertebral tenderness WITHOUT severe colicky pain; no stone on CT
Aortic Dissection / Ruptured AAA
AAA: tearing pain radiating to back in older male with pulsatile mass; no hematuria; hemodynamically unstable
Ectopic Pregnancy
Ectopic: reproductive-age female with positive β-hCG and adnexal tenderness — always check pregnancy test first
Appendicitis
Appendicitis: RLQ pain is steady (not colicky), fever, elevated WBC, rebound tenderness; stone unlikely on CT
Keep reading
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- Nephrotic SyndromeGlomerular disease causing massive proteinuria (>3.5 g/day) with hypoalbuminemia, edema, and hyperlipidemia/lipiduria.
Educational use only. This illness script is a study framework, not medical advice. Confirm decisions with current guidelines and your clinical supervisors.