Nejm 2010;363:954, 2004;350:684 (acute)
Cause:Calcium oxalate (75%), from hyperparathyroidism (10+%) but probably mostly (>50%) idiopathic (rarely sarcoid) hypercalciuria, which is genetic in most cases with autosomal dominant inheritance; struvite (10-15%), from UTIs w urease-producing organisms; urate (5%); hydroxyapatite or brushite (5%), cystine (1%); not electrolyte-containing beverages (Urolo 2009;182:992)
Pathophys:80% of stones are calcium type, associated with a red blood cell and probable renal tubular oxalate excretion defect (Nejm 1986;314:599) or a deficit of the Ca/Mg pump (Nejm 1988;319:897); another 10% are associated with hyperparathyroidism.
Increased calcium absorption may also play a role, either primary or by bringing out deficits like those above, eg, in sarcoid (Nejm 1984;311:116). Uric acid stones may also precipitate calcium on themselves.
Calcium oxalate stones are increased in colectomy, blind loop syndrome, and intestinal bypass patients due to bacterial breakdown of bile salts leading to absorption of glycolytic acid (Ann IM 1978;89:594)
Struvite stones are caused by ammonia from urea-splitting proteus in patients with chronic UTIs due to indwelling Foley and/or quadraplegia
Roux-en-Y gastric bypass surgery is an independent risk of forming stones (Urolo 2009;181:2573)
Incidence = 100/100 000 men, 36/100 000 women; 3-5% of US population will get sometime in life; incidence higher in SE US
Sx:Pain radiating into groin; hematuria gross and/or microscopic
Acutely, 2/3 pass w/i 4 weeks; if not passed by 8 wk, unlikely to do so later. Recurrence after 1st stone is 15% at 1 yr, 35% at 5 yr, 50% at 10 yr (Ann IM 1989;111:1006)
Pyelonephritis behind the obstruction. Cmplc rate increases to 20% after 4 wk of impaction
r/o renal artery embolism pain (Ann IM 1978;89:477); and rare primary hyperoxaluria w oxalosis as renal failure develops (Nejm 1994;331:1553)
Lab:
Chem:Serum calcium and uric acid w 1st stone
for recurrent stone, 24-h urine
for creatinine clearance, Na, calcium, urate, citrate, oxalate; or spot urine ratios
24-h urine calcium 
300 mg in men, 250 mg in women
Ca/creat ratio 0.2 mg/mg creat
Uric acid >1 gm/24 h; or
urine urate × serum creat/urine creat = >0.7 urine creat
24-h urine oxalate >40 mg (Nejm 1993;328:880)
Path:Stone analysis in all
Urine:Rbc’s (90%), crystals (pictures—Nejm 1992;327:1142)
Xray:Spiral CT w/o contrast (96% sens, 100% specif); or IVP (87% sens, 94% specif); or ultrasound (15% sens, 90% specif), esp in pregnancy
Plain film/KUB to see if stone radio-opaque (80%) so can follow its course
Rx:
Dietary (Nejm 2002;346:77): drink at least 2L of fluid qd, esp coffee and wine but not grapefruit juice! (Ann IM 1998;128:534); reduce salt and protein intake; avoid calcium supplements but further decr in dietary calcium intake is not beneficial because calcium decreases oxalate and urate absorption (Ann IM 1997;126:497, Nejm 1993;328:833, 880); avoid phosphoric acid-containing soft drinks (J Clin Epidem 1992;45:911); flomax (Tamsuolsin) to relax smooth muscle and aid passage of stones.
Thiazides help renal tubular/absorptive type, eg, hydrochlorthiazide 50 mg qd, or amiloride 5 mg po qd (Nejm 1986;314:599; 1984;311:116)
Allopurinol 300 mg po qd decreases calcium oxalate stone recurrence if there is an increased 24-h urine urate (Nejm 1986;315:1386)
Polycitra K 20 mEq po bid-tid, Na bicarb, or citrate in lemon juice as lemonade to alkalinize urine to pH >6.5 and thereby dissolve urate
Na cellulose PO4 5 gm po qd-tid to get 24-h urine calcium <300 mg (Med Let 1983;25:67); blocks gi calcium uptake
Pyridoxine 2 gm po qd for oxalate stones? (Nejm 1985;312:953)
Cholestyramine po for secondary oxalic aciduria (Nejm 1972;286:1371)
Surgical percutaneous dissolution of renal pelvis stones over 1-3 wk (Nejm 1979;300:341); basketing via cystoscope; or surgical excision. Extracorporeal shock wave lithotripsy, $2 million machine, requires anesthesia (Ann IM 1985;103:626) but very effective esp for calcium oxalate stones
of acute stone: NSAIDs (ketorolac iv or diclofenac po) better than narcotics (BMJ 2004;328:1401), narcotics; possibly desmopressin; and moderate iv fluids, but decreased urine flow relieves pain.