Kidney Stones / Nephrolithiasis

The patient rates their flank pain a 10 out of 10, but urinalysis shows no infection and kidney function is normal. The stone itself is the emergency — and how you manage the next 24 hours determines whether it passes or requires intervention.

Nephrolithiasis presents with sudden, severe, colicky flank pain that radiates from the costovertebral angle to the groin — pain intensity waxes and wanes as the ureter spasms around the stone. Hematuria (gross or microscopic) is present in about 85% of cases. Most stones are calcium oxalate (70-80%), followed by struvite (magnesium ammonium phosphate, associated with chronic UTI and alkaline urine), uric acid (radiolucent on X-ray, linked to gout), and cystine (rare, hereditary). Stones ≤5 mm usually pass spontaneously; stones >5 mm increasingly require intervention — tamsulosin (Flomax), an alpha-blocker, is standard medical expulsive therapy for stones 5-10 mm, relaxing ureteral smooth muscle to facilitate passage. Nursing priorities: strain all urine through gauze or a mesh strainer to capture the stone for composition analysis, push oral fluids (intake of at least 2-3 L/day) to promote dilute urine and facilitate stone passage, administer prescribed analgesics (often IV ketorolac or opioids for acute pain), and monitor I&O closely. A non-contrast helical CT is the gold-standard diagnostic. Watch for signs of obstruction — oliguria, rising creatinine, fever with chills (suggesting infected hydronephrosis, a urologic emergency requiring emergent decompression).

Key Distinctions

Don't confuse renal colic (colicky, radiating CVA-to-groin pain with hematuria) with pyelonephritis (steady flank pain with fever and pyuria) — stones cause blood, infections cause pus. Students forget that struvite stones form because of infection, not despite it — chronic urease-producing bacteria (Proteus) alkalinize urine and create the stone. Uric acid stones are radiolucent (invisible on plain KUB X-ray but visible on CT) and are the only common stone type amenable to dissolution via urinary alkalinization. The 5 mm threshold matters: below it, conservative management; above it, anticipate medical expulsive therapy, lithotripsy, or ureteroscopy.

Clinical Pearl

Strain every void, save every fragment. No stone captured means no composition analysis, which means no targeted prevention plan — the stone tells you everything.