These are very hard concretions, also called calculi, that can form almost anywhere in the urinary tract from the kidney into the urethra. There are a few different kinds of stones. Calcium stones, the most common kind, occur in 70 to 80% of patients. The other common kinds of stones that patients can present with are uric acid stones and more rarely cystine stones or stones caused by medications.
Many patients who have kidney stones describe some of the worst pain that they have ever had in their lives, but for many others, the stones can be only slightly or minimally symptomatic. They can live with the stones for years and be unaware that they have them, until they are discovered incidentally. It is not uncommon for patients experiencing symptoms to have severe, almost unbearable, flank pain radiating down to the abdomen and occasionally into the vaginal area. These symptoms can be accompanied by nausea and vomiting and malaise and more rarely fevers.
The exact cause of the majority of stones is unknown. Patients may have risk factors such as high calcium or oxalate production in the urine that increase their chances of forming stones. A rarer type, Cystine stones, are caused by a genetic problem.
The best way to diagnose kidney stones is typically with an x-ray, a CT scan, or an ultrasound.
CT scans without contrast are the most accurate way of detecting stones and this method detects all types of stones. The disadvantage of a CT scan, however, is increasing concerns about radiation exposure to patients, particularly for patients who have recurrent kidney stones. With radiation, it is been estimated that every CT scan that a patient has obtained increases the chances of developing a secondary tumor from the radiation by about 1 in 10,000. The advantage to the CT scan is that it will detect stones that are in the kidney as well as in the tube that drains the kidney to the bladder called the ureter and will also detect bladder stones.
An alternative to CT scan is renal and bladder ultrasounds. The advantage of the renal ultrasound is that they do not expose patients to radiation and the costs are typically cheaper than the CT scans are. The renal ultrasounds will often miss smaller stones and stones that are in the tube that drains the kidney to the bladder, the ureter.
A third option for imaging patients who are suspected of having kidney stones is an plain x-ray of the abdomen and pelvis called a KUB. This x-ray can also be a good way of detecting larger stones and typically does not provide as much radiation exposure as does the CT scan. It may be a good option to monitor changes in calcium stones that have already been diagnosed. Unfortunately, the plain x-ray will miss uric acid stones which are not seen on plain x-ray, but can be seen on CT scans and usually on ultrasound.
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