New Management Recommendations Issued for Kidney Stones

March 12, 2007 — Researchers offer general practice treatment and evaluation recommendations for kidney stones, based on a literature review reported in the March 3 issue of the BMJ.

"Urolithiasis affects 5-15% of the population worldwide," write Nicole L. Miller and James E. Lingeman, from Indiana University School of Medicine in Indianapolis. "Recurrence rates are close to 50%, and the cost of urolithiasis to individuals and society is high. Acute renal colic is a common presentation in general practice, so a basic understanding of its evaluation and treatment would be useful."

The authors conducted an evidence-based literature review of the management of urolithiasis, including Medline and the Cochrane Library. Although most studies were retrospective, they also cited prospective randomized controlled trials when available.

Based on this review, their summary conclusions were as follows:

For diagnosing urolithiasis, unenhanced helical computed tomography (CT) is the best radiographic technique.

Most ureteral calculi smaller than 5 mm in diameter will pass spontaneously within 4 weeks of symptom onset.

For treating urolithiasis, shock wave lithotripsy, ureteroscopy, and percutaneous nephrolithotomy have replaced open surgery.

Shock wave lithotripsy is effective in approximately 80% to 85% of simple renal calculi.

For complex renal calculi, percutaneous nephrolithotomy is the treatment of choice. Staghorn calculi should be treated, preferably with percutaneous nephrolithotomy in most patients.

For patients who are pregnant, morbidly obese, or have coagulopathy, ureteroscopy is the preferred treatment.
Initial evaluation of urolithiasis should include a complete medical history and physical examination. Systemic illnesses that may increase the risk for kidney stone formation or otherwise affect the clinical course include primary hyperparathyroidism, renal tubular acidosis, cystinuria, gout, diabetes mellitus, inflammatory bowel disease, renal insufficiency, sarcoidosis, and medullary sponge kidney.

Anatomic abnormalities or surgery of the urinary tract that may predispose to or complicate stone formation are presence of horseshoe kidney, previous urinary diversion, obstruction of the ureteropelvic junction, solitary kidney, previous renal or ureteral surgery, previous kidney disease, history of urinary tract infection and/or pyelonephritis, family history of urolithiasis, and previous stone formation.

A complete drug history is crucial because many medications predispose to urolithiasis. These include carbonic anhydrase inhibitors (topirimate), ephedrine, guaifenesin, calcium with vitamin D, triamterene, indinavir, or sulfadiazine.

Evaluation should include physical examination for costovertebral angle or lower abdominal tenderness; urinalysis; and in the acute setting, complete blood count, serum electrolytes, and measurement of renal function.

Indications for urgent intervention include presence of infection with urinary tract obstruction, often indicated by fever, urosepsis, intractable pain and/or vomiting, impending acute renal failure, obstruction in a solitary or transplanted kidney, and bilateral obstructing stones. Acute obstruction must be treated urgently, for once a stone passes into the ureter, obstruction may cause reduced glomerular filtration rate and renal blood flow.

In a randomized controlled trial, ureteral catheters, ureteral stents, and percutaneous nephrostomy tubes were equally effective for urinary tract decompression. Pending bladder and renal pelvic urine culture and sensitivity, broad spectrum antibiotics should be prescribed initially.

Parenteral narcotics have traditionally been prescribed for acute renal colic, but nonsteroidal anti-inflammatory drugs (NSAIDs), such as ketorolac and diclofenac, are also effective. NSAIDs should be avoided in patients with poor renal function or a history of gastrointestinal bleeding.

Detailed metabolic evaluation should be postponed until after the acute stone event has resolved. Factors suggesting a metabolic cause include family history of urolithiasis; bilateral stone disease; presence of inflammatory bowel disease, chronic diarrhea, or malabsorption; history of bariatric surgery; medical conditions associated with urolithiasis, such as primary hyperparathyroidism, gout, or renal tubular acidosis; nephrocalcinosis; osteoporosis or pathologic skeletal fractures; pediatric urolithiasis; and stones formed from cystine, uric acid, or calcium phosphate.

When a comprehensive metabolic evaluation is indicated, it should include analysis of stone composition, cystine screen, and two 24-hour urine collections for volume, pH, calcium, oxalate, citrate, uric acid, phosphate, sodium, potassium, magnesium, ammonium, chloride, sulfate, and creatinine. Blood tests should include serum calcium, bicarbonate, creatinine, chloride, potassium, magnesium, phosphate, uric acid, and blood urea nitrogen. Cystinuric patients should undergo this evaluation plus 24-hour measurement of cystine, and hypercalcemic patients should also have measurement of intact parathyroid hormone and 1,25 dihydroxyvitamin D.

A relatively recent treatment is medical expulsive therapy or use of drugs to facilitate spontaneous passage of ureteral calculi. These may include calcium channel blockers (nifedipine), steroids, and alpha-adrenergic blockers.

"The rationale for using alpha blockers is based on the presence of large numbers of alpha-1 adrenoceptors in the distal ureter," the authors conclude. "These blockers inhibit basal ureteral tone and peristaltic frequency and decrease the intensity of ureteral contractions."

Dr. Lingeman has disclosed having been a consultant and advisor for Lumenis and Olympus, meeting participant and lecturer for Karl Storz, and an investigator and lecturer for Boston Scientific.

BMJ. 2007;334:468-472.

Source: http://www.medscape.com/viewarticle/553460?src=mp