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Introduction

The first documented urinary tract stones were found among the 7000-year-old remains of the pelvic bones of a teenage boy in El-Amara. Before the Industrial Revolution in Britain, bladder stones were more common than upper urinary tract calculi. Later, around the turn of the nineteenth century, upper tract stone disease began to become more prevalent. In developing countries bladder calculi are still endemic. 4.1 shows the radiographic images of such bladder stones.

4.1

Plain X-ray showing a large bladder stone.

Stone disease in developed countries is more common in males, and in up to 80% of cases there is no obvious precipitating cause.

The presenting symptoms of upper urinary tract stones are loin pain, which may radiate to the groin in a colicky nature, and haematuria (microscopic or macroscopic). If urinary sepsis is present, there may also be symptoms and signs of infection. Stones in the bladder, and sometimes in the lower ureter, may cause lower urinary tract symptoms (frequency urgency and nocturia from their irritative effects, poor stream and hesitancy. Bladder calculi may also cause sudden changes in urinary stream due to the stone acting as a 'ball-valve' over the bladder outlet, and the symptom of 'strangury' where the bladder can contract strongly and painfully in an attempt to evacuate a calculus.

Stone formation

Stone formation occurs when elements normally dissolved in the urine form crystals that then aggregate (4.2). Stone formation may be either homogeneous (where the nucleus of the stone around which crystals aggregate is the same material as that of the crystal) or heterogeneous (where it is different).

4.2

Crystallization theory of stone formation.

Critical to the formation of any crystal is the saturation state of the solution. The saturation state of a solution depends on the pH and ionic strength of the given solution, as well as the presence of any soluble complexes.

When the solution is not saturated with a specific solute, then no crystals will form or grow, and any crystals already present will dissolve.

With increasing concentrations of solute, the solution will become fully saturated with that solute (saturation product KSP). If the concentration of the solute is increased even more, then the formation product (KFP) is reached.

Between the saturation product and the formation product, crystals of the solute cannot form spontaneously, but can aggregate on previously formed crystals (homogeneous crystallization), or aggregate on different formed crystals or foreign bodies (heterogeneous crystallization).

Once the concentration of the solute is greater than the formation product (KFP), the solution becomes unstable and spontaneous crystal formation occurs. Such crystal-lization can be inhibited by other constituents (e.g. ...

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