Kidney stones consisting predominantly of whewellite (calcium oxalate monohydrate, COM) are often found attached to hydroxylapatite (HA) plaques that form in the soft tissue of kidneys, cause lesions and become exposed to urine. Although the processes of stone formation are not entirely known, it is an established view that so-called Randall’s plaques serve as substrates for COM crystal nucleation and growth from correspondingly supersaturated urine. However, the results presented here suggest an additional mineral replacement process is involved. In an experimental approach, HA was reacted in 0.25 mM, 0.5 mM and 1.0 mM oxalate solutions with pH ranging from 4.5 to 7.5, simulating normal to harsh conditions encountered in urine. Extremely acidic solutions induce dissolution of HA crystals coupled with re-precipitation of the released Ca2+ ions as COM on the HA surface. When, instead, bone was used as a substrate, being more similar to the pathological plaque (aggregated HA nanocrystals within an organic matrix), the HA-COM mineral-replacement reaction is induced even under much milder fluid conditions, commonly found in urine. Hence, a process of COM partly replacing and encrusting Randall’s plaque may take place in the urinary tract of idiopathic stone formers, representing a potential starting event for nephrolithiasis.

Several particles of copper accompanied by a few particles of nickel, lead, and a compound composed of selenium containing minor Ni, Si, Cu, and Co were found in human gall, kidney, and bladder stones. The investigated particles occur as tiny grains, <10 µm in size, that are irregularly dispersed in the stones. Therefore, they were studied by scanning electron microscopy and qualitatively analyzed by energy dispersive system. One grain of copper contained a small amount of Ni and Zn, and some grains of nickel proved to contain Cr as trace element. Most of the discovered metals formed a single-phase grain. However, a few grains found in two gallstones were associated with inclusions of calcium and apatite. Based on the results presented in this contribution, we argue that most of the studied metals can be classified as endogenous particles, i.e., directly precipitated from the same fluids that formed their host human stones. This observation suggests that the precipitation and accumulation of metals in some human stones can be considered an efficient way to eliminate them from the human body.

There is a medical myth that ureteral stones larger than 5 mm will not pass spontaneously and require urological intervention for removal. Recent findings indicate that medical expulsive therapy can facilitate spontaneous passage for stones up to 10 mm. For the management of ureteral stones, we recommend administering tamsulosin and a corticosteroid (deflazacort or prednisone) along with the standard therapy of analgesics, antibiotics and hydration.