Renal calculi are small chunks of crystallized material which become trapped in the kidneys, bladder, or urinary tract. A renal calculus can be extremely painful, and the patient may not be able to pass it without assistance. A variety of treatments are available to deal with renal calculi, also known as kidney stones, and analgesics are also available to help people cope with the pain involved.
Around one in 10 people experiences a kidney stone at some point during life. Several things appear to increase the risk of developing renal calculi, including dehydration, diet, and certain medical conditions, like gout, diabetes, high blood pressure, and irritable bowel disease. In all cases, the calculus is formed when minerals which would normally naturally precipitate out conglomerate to form a crystallized mass which can vary in size.
A small renal calculus may pass relatively successfully, sometimes with the patient only becoming aware of the issue as the stone moves down the ureter, into the bladder, and out the urethra. In other instances, such as the large staghorn stones which can get quite big, the kidney stone may cause extreme pain, but it will not move on its own. Big renal calculi need to be removed with medical assistance, whether the assistance take the form of a stent inserted to allow the stone to drop out naturally, or surgery to take the calculus out by hand.
Humans have been dealing with renal calculi for a very long time, and lithotomy, the removal of renal calculi, is one of the oldest known surgical procedures. The pain would have been considerable in eras before anesthesia, and complicated by an imperfect understanding of internal anatomy, but often the pain from the calculus itself was so severe that patients were willing to take the risk. With the 20th century came the development of a number of painless and low-pain techniques, including things like extracorporeal shock wave lithotripsy, in which the stones are broken up with ultrasound so that they will be passed by the body.
People usually know when a renal calculus is present, because it causes a distinctive colicky pain and cramping, especially if it moves out of the kidney and into the urinary tract. Difficulty urinating, blood in the urine, and extreme pain in the lower abdomen are common symptoms. The stone can be diagnosed by a doctor with the assistance of medical imaging, and the doctor can make treatment recommendations based on the size and position of the calculus.