Urinary stones are gravel- like collections of various substances within the urinary tract. Stones nearly always form in the kidney, where they may remain without symptoms and do not require treatment. A ureteral stone is usually a stone from the kidney that has moved down into the ureter.
The stone begins as a tiny grain of undissolved material located where urine collects in the kidney. Over time, more undissolved material
is deposited and the stone becomes larger. The material deposited is usually a mineral called calcium oxalate. Other less common materials that may also form a stone include calcium phosphate, uric acid, infected or struvite stones and cystine stones.
The stones may cause obstruction or break loose and try to pass with the normal flow of urine via the urinary tract to the outside. Most stones enter the ureter when they are still small enough to move down into the bladder. From there, they pass out of the body with urination. However if the stone is larger than the diameter of the ureter they get stuck in the narrow passage and cause excruciating pain ,called a colic
, and obstruction. If this happens, treatment is required and, for some stones, ureteroscopy
is the best form of treatment.