Kidney Stone:A kidney stone, also known as a renal calculus, can be found either in the kidney itself or further down the urinary tract. These stones are a frequent cause of discomfort and abdominal, side, or back pain. At some point in their lives, one in twenty people will experience kidney stones. These stones form due to decreased urine volume or increased excretion of stone-forming substances like calcium, oxalate, uric acid, cystine, phosphate, and others. They develop in the kidney's urine-collecting region (the renal pelvis) and can vary greatly in size, from very small to large staghorn stones that fill the renal pelvis.The cystine stones shown below, compared to the size of a quarter (a U.S. $0.25 coin), were extracted from a young woman's kidney using percutaneous nephrolithotomy (PNL), a method for breaking and removing the dense, persistent stones typical of cystinuria.Kidney stone pain typically begins suddenly, is intense and crampy, does not improve with changes in position, and radiates from the back, through the side, and into the groin. Nausea and vomiting are common accompanying symptoms. Factors that may increase the risk of developing kidney stones include a sudden decrease in fluid intake, increased physical activity leading to dehydration, certain medications that raise calcium levels, and a history of kidney stones.Treatment generally involves pain management, hydration, and antibiotics if a urinary tract infection is present. Most stones pass on their own within 48 hours, although some do not. Several factors can affect the likelihood of passing a stone, including the person’s body size, previous stone passage, pregnancy, and the stone's dimensions.The formation of stones is known as nephrolithiasis or urolithiasis. "Nephrolithiasis" comes from the Greek words "nephros" (kidney) and "lithos" (stone), meaning kidney stone. "Urolithiasis" is derived from the Latin "urina" and the Greek "ouron," meaning urine stone. The stones themselves are referred to as renal calculi, with "calculus" (plural: calculi) being the Latin term for pebble.