Usually, the stone is composed of elements such as oxalat, calcium phosphate, uric acid, magnesium ammonium phosphate, sistin, xantin in pure form or in various compounds of these (mixed stone).
The most common of these elements in a stone are calcium oxalat and calcium phosphate.
Magnesium ammonium phosphate stones (Struvite stones – Infection stones) are more common in women and children. For formation of these stones, infection is necessary. They are usually in the shape of deer horn (koraliform – staghorn stone) and fill the cavities completely.
The uric acid stones are usually more common in people with high protein diet.
Sistin stones are formed due to metabolical defects and they are hereditary. Depending on the elements contained, the color of the stones can be white, yellow, brown, brick red or a combination of these colours.
Stones can be found anywhere in the kidneys and in the urinary tract.
The stones are generally in the sub-calix group (calix: the place in the kidney where the urine is first formed). The reason for this is that, in these places gravitational drainage of the urine is worse than other parts (for a normally standing person). The upper calix group is second in stone formation.
Stone formation starts in the wide parts of the calices and then stones which pass through the narrow calix neck reach the kidney pelvis with the urine. If the calix neck is very narrow the stone cannot pass to the kidney pelvis and continues to grow in that place. The properly sized stones which pass to the kidney pelvis reach the urinary bladder through the ureters. Big stones can be stuck in the kidney exits and anywhere in the ureter and cause blockage. In such cases there may be severe pain due to expansion and stretch of the kidney because of urine pressure. The stones which reach the urinary bladder can usually be easily expelled out. If there is any structural defect in the urinary tract or a urine blocking prostate (which is common in elder men), stones van cause blockage inside the urinary bladder or in the urethra (the part of the urinary tract which is after the urinary bladder). In these cases there may be symptoms of painful urination and blocking of urination.
The stones are usually round or ellipsoid. Their surfaces can be very smooth or rough or ragged with thorns. There may be different shaped stones in the same kidney. Sometimes the stones completely or partially fill the kidney cavity. Stones in the shape of deer horn are also called choraliform or staghorn stones.
