A renal calculus which does not pose any obstruction is, in layman's terms, a kidney stone. Calculus is the Latin word for pebble, the diminutive form of 'stone', and was used for voting in the agora. Non-obstructing stones produce no symptoms or signs apart from haematuria. Stone passage produces renal colic that turns painful within an hour. If the stone obstructs the junction of the uterus and the pelvis, pain localizes to the side of the body and the stone moves down the ureter tubes. Stones which are less than five millimetres in diameter have a high chance of passage; those between five and seven millimetres have a 50-50 chance of passage, and those greater than seven millimetres almost always require intervention. Stone analysis is performed by infrared spectroscopy or x-ray diffraction. Renal stone burden is best gauged using CT radiographs taken with 5-mm cuts, without infusion of contrast agents. Calcium stones, mainly calcium oxalate, are the most common type of renal calculus, forming when one doesn't drink enough water, allowing calcium that would dissolve to instead precipitate and crystallize. They also form in association with conditions that raise the blood calcium level. Uric acid stones can form with excessive ingestion of purines, which are chemicals which come primarily from meats. In addition, more acidic urine allows uric acid to crystallize more easily. Kidney stones are a fact of life and simple operations can remove them easily after a scan, but proper regulation of calcium and water in your diet can help avoid their build-up.
