EAU Updates Urinary Stone Guidelines
The European Association of Urology (EAU) has updated its urolithiasis guidelines to reflect scientific evidence that has emerged during the last 8 years. The panel of experts who wrote the updated guidelines reviewed them in a European Urology article that addresses which patients are at high risk for stone recurrence, diagnostic and therapeutic algorithms for each stone type, stone prevention, and patient monitoring.
The review, by Andreas Skolarikos, MD, PhD, of the National and Kapodistrian University of Athens and Sismanogleio Hospital in Greece, and colleagues addresses for the first time the risk for kidney function deterioration due to urolithiasis and which patients are risk for chronic kidney disease (CKD) and end-stage kidney disease (ESKD).
“Every patient should undergo baseline metabolic screening, while patients at high risk of recurrence and complications should undergo extensive metabolic screening and receive targeted therapy,” the reviewers concluded. “Patients at high risk of relapse and complications, especially those who do not comply with their medication, should be closely monitored.”
Here are some of the major points:
Stone Evaluation
Stone analysis should be performed for all first-time stone formers. The preferred analytical procedures are infrared spectroscopy and X-ray diffraction.
For diagnostic imaging, clinicians should use ultrasound when the stone composition is known, along with blood analysis for creatinine, calcium, and uric acid, and urinalysis. When stone composition is unknown, clinicians should order helical computed tomography (CT) without contrast enhancement. Urine pH testing after each void, microscopy of urinary sediment in a morning sample, and a cyanide nitroprusside test to rule out cystinuria are also recommended.
Only high-risk stone formers warrant specific metabolic evaluation, according to the reviewers.
For calcium-based stones, clinicians should collect 2 consecutive 24-h urine samples.
Before surgical stone removal, order a CT scan to delineate stone anatomy and characteristics.
Gauging Recurrence Risk
Stone formers at high risk for recurrence have early onset of urolithiasis, a family or personal history of stones, a shorter interval since their last stone episode, or stones containing brushite, uric acid, urate, or infection.
Genetic predisposition to stone formation is apparent among patients with cystinuria, primary hyperoxaluria, renal tubular acidosis type 1, 2,8-dihyroxyadeninuria, xanthinuria, Lesch-Nyhan syndrome, and cystic fibrosis.
Various diseases and medical circumstances are associated with stone formation, including hyperparathyroidism, metabolic syndrome, metabolic bone disorder, high serum vitamin D, nephrocalcinosis, polycystic kidney disease, sarcoidosis, neurogenic bladder, gastrointestinal diseases (eg, Crohn’s disease), gastrointestinal or bariatric surgery, and spinal cord injury.
Drug-induced stone formation can occur with use of allopurinol/oxypurinol, amoxicillin/ampicillin, ceftriaxone, quinolones, ephedrine, indinavir and other HIV-protease inhibitors, magnesium trisilicate, sulfonamides, triamterene, acetazolamide, aluminium magnesium hydroxide, ascorbic acid, calcium, furosemide, laxatives, losartan, methoxyflurane, orlistat, vitamin D, topiramate, or zonisamide.
Stone-Specific Diagnostics
Besides the pointers for diagnostic workout summarized below, see the full review for therapeutic algorithms by stone type.
Calcium oxalate stones: High-risk patients with should have blood testing for creatinine, sodium, potassium, chloride, ionized calcium (or total calcium corrected by the albumin concentration), phosphate, and uric acid, as well as parathyroid hormone (PTH) and vitamin D levels. Urinalysis should additionally include calcium, citrate, oxalate, uric acid, and magnesium levels.
Calcium phosphate stones: High-risk patients should have blood analysis of creatinine, sodium, potassium, chloride, ionized calcium or total corrected calcium, phosphate, and PTH. Urinalysis should include measurement of calcium, phosphate, and citrate.
Uric acid and ammonium urate stones: All uric acid and ammonium urate stone formers are at high risk of recurrence. Blood measurement of creatinine and uric acid levels (with confirmatory repeat testing) is warranted. Urinalysis must include uric acid level. Clinicians should perform urine culture in patients with ammonium urate stones.
Struvite and infection stones: All patients with an infection stone are at high risk of recurrence. Along with routine blood testing for creatinine, urinalysis should include repeat urinary pH measurements and urine cultures. Mixed struvite stones warrant measurement of metabolic abnormalities in 24-hour urine.
Cystine stones: All cystine stone formers, and potentially their siblings, are at high risk of recurrence and CKD. Measurement of serum creatinine is necessary. Urinalysis should include cystine measurement.
Pharmacologic Treatment
Table 7 of the review lists drugs to prescribe to prevent recurrence, including dosage and the type of stones for which they are indicated. The full review also offers specific advice by stone type.
- Thiazide for calciuria (calcium oxalate stones)
- Alkaline citrates for hypocitraturia, calcium oxalate inhibition, or alkalinization (calcium oxalate, uric acid, and cystine stones)
- Sodium bicarbonate for hypocitraturia or alkalinization (calcium oxalate, uric acid, and cystine stones)
- Allopurinol or febuxostat for hyperuricosuria, hyperuricemia (calcium oxalate and uric acid stones)
- Calcium for enteric hyperoxaluria (calcium oxalate stones)
- Magnesium for isolated hypomagnesuria or enteric hyperoxaluria (calcium oxalate stones)
- Pyridoxine for primary hyperoxaluria (calcium oxalate stones)
- Lumasiran for primary hyperoxaluria type I (calcium oxalate stones)
- L-Methionine for acidification (infection stones and ammonium urate and calcium phosphate stones)
- Captopril for cystinuria (cystine stones)
- D-penicillamine for cystinuria (cystine stones)
- Tiopronin for cystinuria (cystine stones)
CKD and ESKD Risk
The highest risk for CKD is found among patients with primary hyperoxaluria or autosomal dominant polycystic disease, the reviewers pointed out. Other patients at high risk include formers of cystine or struvite stones and those with distal renal tubular acidosis, nephrocalcinosis or secondary hyperoxaluria. Anatomic abnormalities of the kidney (eg, horseshoe kidneys) or urinary tract (eg, ureteral stricture) make it easier for stones to form. Patients with a solitary kidney, neurogenic bladder, frequent urinary tract infections, urinary diversion, or obstructions are also at high risk for kidney function decline. Moderate risk of CKD exists for those who form brushite or 2,8 dihydroxyadenine stones or have sarcoidosis, pyeloureteral, or ureteral strictures. CKD possibly develops in patients with xanthine stones, indinavir stones, eating disorders, primary hyperparathyroidism, or medullary sponge kidney.
Stone Prevention
General prevention measures include drinking 2-2.5 liters of fluid daily (preferably water), eating more fiber-rich foods including vegetables and fruits, and limiting salt and protein intake. Physical activity and weight loss are also mainstays.