Adam Shared "Kidney Stones " - 4 Picmonics
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Kidney Stones
Kidney Stones Ammonium Magnesium Phosphate
- Precipitates with increased pH
- Radiopaque on X ray and CT
- Coffin lid crystal (pictured)
- Also known as struvite
- Account for 15% of stones (second most common)
- Caused by infection with urease ⊕ bugs (eg, Proteus mirabilis, Staphylococcus saprophyticus, Klebsiella) that hydrolyze urea to ammonia causing increased urine alkalinization
- Commonly form staghorn calculi (of calyces, pictured); can act as nidus for UTI
- Treatment: eradication of underlying infection, surgical removal of stone
Kidney Stones Uric Acid
- Precipitates with decreased pH
- RadiolUcent (Urea) on X ray and barely visible on CT; Visible on ultrasound
- Rhomboid (pictured) or rosettes shaped crystals
- About 5% of all stones (third most common)
- Risk factors: decreased urine volume, hot arid climates, acidic pH
- Strong association with hyperuricemia (eg, gout)
- Often seen in diseases with increased cell turnover, such as leukemia and myeloproliferative disorders
- Other causes: Metabolic syndrome and chronic diarrhea
- Treatment: hydration, alkalinization of urine (potassium carbonate), allopurinol (gout patients)
- Usually precipitates in the distal tubules and collecting ducts due to low pH
- U. Chronic diarrhea (or post colectomy) have reduced bicarbonate absorption in the gut, kidney compensate with H+ excretion --> low pH
- Needle-shaped crystals on urinalysis indicate uric acid stones
- Have to be evaluated by CT (non contrast) of the abdomen or intravenous pyelography
- Stones <1 cm may pass spontaneously with hydration and analgesia; otherwise, surgical intervention is needed
- Treatment: hydration, alkalinization (oral potassium citrate) of the urine, and a low-purine diet
- Allopurinol can be added if there are recurrent symptoms despite initial measures , especially if hyperuricosuria or hyperuricemia occurs
Kidney Stones Cystine
- Precipitation with decreased pH
- Radiolucent on X ray; Sometimes visible on CT
- Hexagonal crystals (pictured)
- Associated with cystinuria
- Staghorn calculi
- Treatment: low sodium diet, alkalinization of urine (acetazolamide), chelating agents if refractory
- Cyanide Nitroprusside Test
- Think cystine stones when children present with nephrolithiasis
Kidney Stones Calcium
- Precipitated with calcium oxalate: hypocitraturia; or increased pH with calcium phosphate
- Radiopaque on X ray and CT
- Shaped like envelope (pictured) or dumbbell; (Calcium phosphate shaped like Wedgeshaped prism)
- Calcium stones most common (80%); calcium oxalate more common than calcium phosphate stones
- Hypocitraturia often associated with decreased urine pH
- Can result from ethylene glycol (antifreeze) ingestion, vitamin C abuse, hypocitraturia, malabsorption (eg, Crohn disease), idiopathic hypercalciuria, renal tubular acidosis type 1
- Acute renal failure is the major complication of ethylene glycol intoxidation
- Hyperparathyroidism (calcium oxalate stone)
- Treatment: thiazides (also used for calcium phosphate stones; decreases calcium urine levels), citrate, low-sodium diet
- Crohns cause hyperoxaluria (causing stones)
- High calcium intake reduces calcium oxalate stones by binding oxalate in the gut preventing it from entering circulation
- Surgical resection of bowel and chronic diarrhea
