What are Kidney Calculi?

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  • Written By: Rebecca Harkin
  • Edited By: Allegra J. Lingo
  • Last Modified Date: 17 February 2020
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Kidney calculi are hard particles which develop in the kidney when substances precipitate out of the urine and bind together. A kidney calculus is usually small enough to pass painlessly through the urinary tract, but sometimes kidney calculi are big enough to cause severe pain as they exit the urinary system. Sometimes a kidney calculus becomes so large it is broken apart, using sound waves or a surgical tool, to make them easier to pass. Kidney calculi can be classified into one of four types based on its composition. Other names for kidney calculi are kidney stones, stones, or renal lithiasis.

Stones form in the kidney when there is imbalance in the urine, causing substances to precipitate, or fall out of the urine. These particles often pass unnoticed through the kidney and the urinary tract, and do not cause any pain. Sometimes, these precipitated substances can become the nucleus around which larger kidney calculi form. When the nucleus collects other precipitated substances and aggregates them together, a larger stone is the result. These bulky kidney calculi are extremely painful to pass.


The four types of these stones that can form in the body are calcium-oxalate stones, struvite stones, uric acid stones and cystine stones. Calcium-oxalate stones, the most common type, are produced when too much calcium or vitamin D is ingested or as a result of some medications, kidney diseases, or can be related to a genetic predisposition. Struvite stones often develop following a kidney infection or are the result of a genetic predisposition. Uric acid stones form from an overabundance of uric acid, and are typically caused by excessive red meat consumption. Cystine stones are caused by an inherited disease called cystinuria.

Development of kidney calculi is most common in Caucasian males over the age of 40 who have had stones before. Large kidney stones cause extreme pain on the lower back and down the front side of the body into the groin area, and also cause bloody, cloudy, or smelly urine, vomiting, fever and chills, and a burning sensation during urination. Most stones are treated with pain-relievers during the painful passage of the kidney calculus through the urinary tract. Large stones are sometimes broken apart into more passable sizes using sound waves, a procedure known as extracorporeal shock wave lithotripsy. If sound wave therapy fails, large stones are sometimes removed through surgery or using a scope passed through the urethra and specially equipped with a tool to break the stone into smaller pieces.



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