Approximately 5% to 12% of adults will have a kidney stone, and the chance of a recurrent stone is 50% (Parmar, 2004; Teichman, 2004). Whites have the highest risk, particularly men. Family history increases the risk threefold and is present in 55% of recurrent stone formers (Teichman, 2004).
A classic history suggesting renal calculi is the abrupt onset of unilateral flank pain. It often radiates into the groin and may be accompanied by nausea and vomiting. Patients with kidney stones typically have great difficulty finding a comfortable position. On examination, there may be costoverte-bral angle or lower abdominal pain, and hematuria occurs in 90% of patients (Teichman, 2004). Patients may experience UTI symptoms such as dysuria, frequency, and urgency as the stone passes from the ureter into the bladder. However, patients with fever, microscopic signs of infection, or signs of systemic sepsis may have superimposed UTI. Complete obstruction and hydronephrosis can result in renal failure.
Helical non-contrast-enhanced CT is the test of choice for diagnosing renal calculi (Lindbloom and Meadows, 2001). Renal ultrasound and IV urography may be helpful for radiopaque stones and pregnant women (ultrasound only) (Sheafor et al., 2000). Stones larger than 5 mm found in the proximal ureter on more than one imaging study will probably need urology consultation and intervention (Grossfeld et al., 2001b). Stones smaller than 5 mm will likely pass without intervention (Teichman, 2004).
Treatment initially focuses on analgesia and relieving nausea and vomiting. Pain results from ureteral obstruction and renal capsular distention and/or hydronephrosis. Pain can be effectively managed with narcotic analgesics or nonsteroidal anti-inflammatory drugs (NSAIDs; ketorolac, indometh-acin). Ketorolac (Toradol) is more effective than meperidine (Demerol) and probably as effective as narcotics (Larkin et al., 1999; Teichman, 2004). Alpha blockers such as terazosin or tamsulosin appear to increase the likelihood of a stone passing (DasGupta et al., 2009).
Two thirds of stones pass spontaneously. Stones that have not passed within 4 weeks are unlikely to pass (Teichman, 2004). Urine straining is important because a captured stone can be analyzed for content. Repeat imaging is needed when stone passage has not occurred or is uncertain.
It is debatable whether all patients should receive an evaluation for metabolic disorders after a first kidney stone. A reasonable workup includes an electrolyte panel, urinalysis, blood urea nitrogen (BUN), creatinine, calcium, parathyroid hormone (if calcium elevated), and stone analysis, if possible. Calcium oxalate is found in 60% to 80% of stones (Parmar, 2004). Patients with recurrent stones need a more extensive evaluation, including urine culture and a 24-hour urine study to determine calcium, oxalate, uric acid, citrate, phosphate, sodium, and creatinine levels (Teichman, 2004).
Proper hydration is essential in preventing stones. Patients should aim for urine output of 2 to 3 L/day (Parmar, 2004). Cost-effectiveness data suggest that dietary intervention is appropriate for first episodes (Lotan et al., 2004). Patients with recurrent stones need dietary intervention, a metabolic evaluation, and potassium citrate measurement. Hypercal-ciuria is an indication for prophylaxis with thiazide diuretics, which effectively reduce recurrence of calcium oxalate stones. Evidence is less clear for other treatments, such as citrate (Pearle et al., 1999). Men with recurrent stones and idiopathic hypercalciuria will have fewer stones on a low-sodium, low-protein diet than men on a low-calcium diet (NNT = 5.5 for 5 years). Low-calcium diets do not reduce stone formation (Borghi et al., 2002).
Patients with uric acid stones respond to urinary alkalini-zation with potassium citrate (Teichman, 2004).
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