Acute treatment

The majority of patients with symptomatic nephrolithiasis can be managed conservatively with adequate analgesia and aggressive oral or IV hydration until the stone passes. Two factors influence spontaneous passage of stones: size and location. Most stones <4 mm in diameter are able to pass spontaneously. For stones >4 mm in diameter, there is a progressive decrease in spontaneous passage. Stones ³10 mm and stones in the proximal ureter are unlikely to pass spontaneously.

Patients who are following a conservative course should be instructed to strain their urine for several days and to submit any stone or gravellike material for analysis.

Although nonsteroidal anti-inflammatory drugs (NSAIDs) are usually recommended for analgesia, caution should be exercised, especially in patients with renal failure, manifested primarily by azotemia or elevated creatinine. Such patients are already at risk for progression of renal failure, and NSAIDs can further this progression through their vasoconstrictive mechanisms. The rare patient may require narcotic analgesics. (Be cautious of the malingerer or manipulative patient.) Oftentimes, if high doses or prolonged courses of narcotic analgesics are required, surgery may be a likely option.


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Time to refer

Urgent urologic consultation is recommended when symptomatology is intractable or there is sepsis. Patients whose stones are less likely to pass spontaneously and those with significant hydronephrosis are also candidates for further urologic evaluation and management.

Stones that don’t pass spontaneously may be treated with shock wave lithotripsy (SWL), ureteroscopic lithotripsy, percutaneous nephrolithotomy, or laparoscopic stone extraction. Traditional open surgical stone extraction is rarely required. In the majority of cases, especially for stones in the renal pelvis or upper ureter, SWL suffices and is well tolerated. Limitations include larger stones (>1.5 cm) or those in the lower-pole calyces or mid to lower ureter; in these, endoscopic stone fragmentation via a percutaneous or ureteroscopic route may be in order.

Monitoring response to treatment

In patients evaluated for nephrolithiasis, response to either dietary therapy or medications is monitored by repeat 24-hour urine collections. The goal is to reverse all metabolic abnormalities and other predispositions to stone formation, e.g., low urine volume, hypercalciuria, hyperuricosuria, etc.

The usual recommendation is to obtain at least one and preferably two 24-hour urine collections at six to eight weeks after treatment is begun. If the desired changes are observed, testing is repeated at six months and then at yearly intervals. Persistent abnormalities will need further therapy.

Dr. Lerma is clinical associate professor of medicine, Section of Nephrology, Department of Medicine, University of Illinois at Chicago College of Medicine/Associates in Nephrology.

References
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3. Soucie JM, Coates RJ, McClellan W, et al. Relationship between geographic variability in kidney stones prevalence and risk factors for stones. Am J Epidemiol. 1996;143:487-495.

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5. Curhan GC, Willett WC, Knight EL, Stampfer MJ. Dietary factors and the risk of incident kidney stones in younger women: Nurses’ Health Study II. Arch Intern Med. 2004;164:885-891.

6. Press SM, Smith AD. Incidence of negative hematuria in patients with acute urinary lithiasis presenting to the emergency room with flank pain. Urology. 1995;45:753-757.

7. Sheafor DH, Hertzberg BS, Freed KS, et al. Nonenhanced helical CT and US in the emergency evaluation of patients with renal colic: prospective comparison. Radiology. 2000;217:792-797.