Nephrolithiasis Evaluation and Management Reviewed

February 15, 2011 — Evaluation and management of nephrolithiasis are reviewed in an article reported in the February issue of the Southern Medical Journal.

"New information has become available on the clinical presentation, epidemiologic risk factors, evaluative approach, and outcome of various therapeutic strategies. In this report, we will review the epidemiology and mechanisms of kidney-stone formation and outline management aimed at preventing recurrences," write Zachary Z. Brener, MD, from the Nephrology Division, Department of Medicine, Beth Israel Medical Center in New York, NY, and colleagues. "Improved awareness and education in both the general population and among health-care providers about these modifiable risk factors has the potential to improve general health and decrease morbidity and mortality secondary to renal-stone disease."

Nephrolithiasis is a significant source of urinary tract morbidity, with US prevalence increasing from 3.8% in the 1970s to 5.2% in the 1990s. In 2000, nephrolithiasis prompted nearly 2 million clinician-office visits and was responsible for annual costs estimated at $2 billion.

Evaluation of nephrolithiasis centers on 24-hour urine collection, with 2 consecutive collections needed while the patient follows his or her usual diet. In addition to a thorough history and physical examination, evaluation should include analysis of the stone to determine its composition. Helical computed tomography (CT) without contrast material is the preferred imaging procedure to evaluate suspected nephrolithiasis. Urology referral is needed for patients with renal colic.

"If the stone does not pass rapidly, the patient can be sent home with oral analgesics and instructions to return in instances of fever or uncontrollable pain," the review authors write. "After four weeks, an intervention is indicated, because the risk of complications and kidney deterioration increases. Patients presenting either with UTI [urinary tract infection], stones greater than 6 mm in size, localized obstruction, or intractable pain require urgent intervention."

For smaller stones, lithotripsy is the mostly commonly used noninvasive procedure. Basket extraction or fragmentation is invasive but effective for cystoscopic stone removal. Percutaneous nephrolithotomy is still more invasive, requiring placement of a nephrostomy tube, but it is needed for many or large stones including branched (staghorn) calculi. Open surgeries are seldom necessary.

For the prevention of recurrent stone disease, daily fluid intake should be increased to achieve a 24-hour urine output of more than 2 L. Dietary restriction may help avoid hypercalciuria related to calcium oxalate stones, as well as hyperuricosuria, hyperoxaluria, and excessive purine intake contributing to urate stones. In pharmacotherapy, thiazides may be helpful to avoid calcium oxalate stones, allopurinol for urate stones, and citrate supplements or bicarbonate and urine alkalinization to help correct hypocitraturia.

"The nephrologist or primary-care provider should assume responsibility for the long-term prevention program and refer back to the urologist if further surgical interventions are necessary," the review authors conclude. "The plan should include preventive recommendations based on the evaluation of the metabolic measurements after medical or surgical interventions are started, in order to review the success of the intervention, the modification of any recommendations, and any follow-up radiologic studies."

The review authors have disclosed no relevant financial relationships.

Southern Med J. 2011;104:133-139. Abstract