Renal calculi: Kidney stones. A common cause of blood in the urine and pain in the abdomen, flank, or groin. Occurs in 1 in 20 people at some time in their life. Development of the stones is related to decreased urine volume or increased excretion of stone-forming components such as calcium, oxalate, urate, cystine, xanthine, and phosphate.
The stones form in the urine collecting area (the pelvis) of the kidney and may range in size from tiny to staghorn stones the size of the renal pelvis itself . The pain is usually of sudden onset, very severe and colicky (intermittent), not improved by changes in position, radiating from the back, down the flank, and into the groin. Nausea and vomiting are common. Predisposing factors may include recent reduction in fluid intake, increased exercise with dehydration, medications that cause hyperuricemia (high uric acid) and a history of gout. Treatment includes relief of pain, hydration and, if there is concurrent urinary infection, antibiotics. The majority of stones pass spontaneously within 48 hours. However, some stones may not. There are several factors which influence the ability to pass a stone. These include the size of the person, prior stone passage, prostate enlargement, pregnancy, and the size of the stone. A 4 mm stone has an 80% chance of passage while a 5 mm stone has a 20% chance. If a stone does not pass, urologic intervention may be needed. The process of stone formation is also called nephrolithiasis or urolithiasis. "Nephrolithiasis" is derived from the Greek nephros- (kidney) + lithos (stone) = kidney stone "Urolithiasis" is from the French word "urine" which, in turn, stems from the Latin "urina" and the Greek "ouron" meaning urine = urine stone.