Urolithiasis--an interdisciplinary diagnostic, therapeutic and secondary preventive challenge

Abstract

Background: The prevalence of urolithiasis in Germany is 4.7%; its incidence has trebled in the last three decades. The risk of recurrence is 50-80%, depending on the type of stone, unless secondary prevention is instituted. Risk-adapted secondary prevention lowers this risk to 10-15%.

Methods: This review is based on publications retrieved by a selective search in PubMed using the key words "urolithiasis," "urinary stones," "epidemiology," "lithogenesis," "biominerals," "risk factors," and "diagnosis, therapy, metaphylaxis." These publications were evaluated with the aid of the urolithiasis guideline of the European Association of Urology.

Results: Acute renal colic can usually be diagnosed without sophisticated equipment. Stones can be dealt with by a variety of techniques depending on their size and location, including extracorporeal shock-wave lithotripsy, ureterorenoscopy, percutaneous nephrolitholapaxy, and open surgery. Most ureteric stones of diameter up to 5 mm pass spontaneously. 75% of patients have no complications. The basic evaluation needed for secondary prevention can be carried out by any physician on an ambulatory basis. In the 25% of patients who have complications, a more extensive interdisciplinary evaluation of metabolic parameters should be performed in a clinical center for urinary stones.

Conclusion: Urolithiasis has many causes and can be treated in many different ways. An extensive metabolic work-up is often necessary for secondary prevention. The various treatment options must be considered for their suitability in each individual patient. Robust data are now available on surgical and interventional methods, but there are as yet no high-quality trials of secondary prevention. Further research should concentrate on the etiology and pathogenesis of urolithiasis.

Figure 1

Starting with pathological processes in the formation of urine, mineralization can occur as high as the renal tubule (a). Crystals just a few micrometers in diameter form further downstream in the urinary tract, preferentially attaching themselves to the urothelium in sheltered niches, where—sometimes with the participation of organic cementing substances—they grow into larger aggregates (b). Under unfavorable conditions, e.g., severe metabolic disease, acute urinary tract infection, or drug-induced alteration of urinary composition, urinary stones several centimeters in diameter can form in a matter of weeks in the kidney (c), the bladder (d), or even the urethra (f). In most cases, however, the concrements (e) are flushed from the kidney into the ureter when they are just a few millimeters in diameter. They cause excruciating colicky pain and if they are too large to pass into the bladder spontaneously they have to be surgically removed.

Figure 2

The so-called stone belt (red) extends all the way around the world and is characterized by urinary stone prevalence of 10 to 15%. In this zone the climatic and social conditions are conducive to stone formation. Some stones are associated with poverty, others with affluence. In Europe and the USA, there has been a sharp, almost exclusively affluence-related rise in the occurrence of calcium oxalate and uric acid stones. Climate simulations for the USA indicate that the stone belt will move northwards in the coming two decades (12).

Figure 3

Dependence of lithogenesis on urinary pH (modified from Laube and Berg (e13).