Urinary Calculi (Stones)
Urinary calculi (also called "stones") can be found in the kidneys, ureters (the tubes that connect the kidneys to the bladder), or bladder. There are many reasons stones can form, for example infection, metabolic disorder, hormonal disorder, or diet. Stones may be composed of different materials, depending on what caused them to form. For example, an infection causes one type of stone, and a metabolic disorder (i.e., high calcium level) causes a different type of stone.
The most common stones are composed of calcium and oxalate. Small stones that form in the urinary tract may travel downstream (i.e., from the kidneys, through the ureters, into the bladder, and out the urethra), and be excreted in the urine. The passage of the stone through the narrow ureters or urethra may result in excruciating pain, nausea, or vomiting. If the stone becomes stuck en route, intervention may be required.
Signs and symptoms
Some stones do not cause any signs or symptoms, while others make themselves painfully recognized. Some possible symptoms of a stone include:
- Excruciating pain along the sides of the lower back, with or without nausea and vomiting
- Blood in the urine
- Frequent urination
- Sudden urges to urinate
- Pain on urination
In order to diagnosis the presence of a stone, the physician relies on the patient's history, the physical examination, and specific tests. An IVP (intravenous pyelogram) may be requested, which shows how the urinary system fills with contrast. This test can determine how well the kidney functions and the amount of obstruction present. It can also determine the size and location of the stone. In some cases, another test (spiral CT) may be ordered to determine the location of the stone. To diagnose the cause of the stone, the stone can either be removed and analyzed, or chemical analysis can be performed of 24 hour urine output.
Approximately 90 percent of stones that are less than 4mm will pass through the urinary tract on their own, and require no treatment. Additionally, stones that are composed of uric acid can be dissolved by taking medication, and dietary changes may prevent further stone formation.
Treatment for other stones include shock-wave lithotripsy (SWL), percutaneous kidney stone removal and ureteroscopy. Essentially all treatments are minimally invasive with no incision involved.
- SWL directs shock waves at the stone which breaks the stone up into small pieces that can pass through the urinary tract. SWL is usually used to treat stones that are located in the upper part of the kidney or the uretersand that are smaller than 2.5cm. No incision is necessary, but the patient is asleep for the procedure. After SWL small fragments of pulverized stone can usually pass with minimal discomfort.
- Percutaneous kidney stone removal is performed by making a one-inch incision on the patient's side, which allows the surgeon to enter the kidney and remove the stone piece by piece. This procedure is recommended for stones that are located in the lower half of the kidney, or that are larger than 2.5cm. Percutaneous surgery is the surest way to remove all of the stone.
- Ureteroscopy with laser lithotripsy is used for stones located in the ureter. The ureteroscope is inserted in the urethra, passed through the bladder and into the ureter. The stones are visualized, then fragmented with laser energy, and removed through the urethra. A small tube ("stent") will be left in the ureter for a few weeks to allow the ureter to heal. No incisions are made, although the patient is asleep for the procedure.
Stones in the bladder can be fragmented and removed without an incision, except in cases where the stones are exceptionally large. Surgical removal is safest and most efficient for large bladder stones.