Urology

Kidney Stones

Kidney Stones

Why do kidney stones form? Kidney stones mostly form from minor metabolic problems associated with filtration or absorption of electrolytes. Some of these abnormalities are inherited, and it is common to have patients that have a family history of kidney stones. Most commonly stones form from calcium, but they can also form from a variety of other materials including uric acid from gout.

What are my chances of passing a stone without treatment? Most small stones will pass spontaneously with hydration. This process may take some time, but usually the pain that patients experience comes and goes as the stone makes it way down the ureter (the tube between the kidney and the bladder). Once the stone reaches the bladder, it is passed in the urine very easily as the urethra (the tube running from the bladder out) is very large compared to the ureter. If stones are large, then they will often get stuck within the ureter. There are several narrow spots along the ureter where stones typically get stuck. The narrowest spot is where the ureter meets the bladder. Often when patients are seen in the emergency department and have a larger stone that is stuck but may pass on its own, medications are started to relax the ureter and speed passage of the stone. Tamsulosin (Flomax) is a very common medicine to help with stone passage.

When is surgery needed to get rid of a kidney stone? When large stones become lodged in the ureter and cause recurrent pain or are too large to pass, surgery is indicated to remove them. Often a ureteral stent is placed to relieve the acute pain from a stone and surgery is done at a later date. A ureteral stent is a plastic tube that has a tight curl on either end called a pigtail. This tube is completely internal, and the pigtails keep the stent in place between the bladder and the kidney. Stents usually should stay in place for three months or less. Usually stone surgery is scheduled for just a few weeks after a stent is placed. The stent allows the ureter to dilate or enlarge and makes removal of stones easier; stents may also allow infection to drain and treatment with antibiotics to take effect before more intensive surgery is performed.

Sometimes even if stones are not causing pain, they are treated with surgery. Examples of this are large stones that impair the function of the kidney (staghorn stones) or stones in the kidney that are likely to drop down the ureter and cause episodes of obstruction and pain.

What types of surgeries are done for stones? There are many different surgeries that are preformed to remove stones when they are causing pain, infection or are in the kidney and may cause these problems in the future. The surgery that is needed depends a lot upon the nature and location of the stone, along with patient’s health, among other factors. Some of the common surgeries are described below:

  • External shock wave lithotripsy: In this surgery ultrasound energy is used to break up the stone through the body wall. A broad ultrasound head is brought in to meet the body, and the focus of the ultrasound is put onto the stone, which is targeted with x-rays. Over about 30 minutes the stone is broken into dust by the shock rays produced by the lithotripter. This is outpatient surgery done under anesthesia. Patients are expected to have blood in their urine and some soreness in the side where the lithotripter has touched the skin. Rare complications include bleeding around the kidney. This type of surgery is most appropriate for stones that are in the kidney or high in the ureter (the tube between the kidney and the bladder) near the kidney.
  • Ureteroscopy and laser lithotripsy: This is one of the most common ways of treating stones that will not pass through the ureter. A small scope is passed through the urethra into the bladder and up the ureter to the stone. The stone can be visualized directly and is broken up using a small laser fiber. Stone fragments are then often removed from the ureter or the kidney with a small stone basket that also is placed through the scope. Patients are most often left with a temporary plastic stent that is internal and is removed after about a week in clinic.
  • Percutaneous nephrolithotomy: This is a surgery in which large stones in the kidney are removed. Large stones in the kidney do not respond well to external shock wave lithotripsy or uretersocopy and laser lithotripsy due to limitations of the power delivery to the stone with these surgeries. When stones are greater then 2 cm in size in the kidney they often need to be treated with percutaneous nephrolithotomy. In this surgery a large scope is inserted through the back and into the kidney directly through a small half-inch incision. The stone can then be visualized in the kidney and broken up with ultrasonic energy directed onto the stone through the scope. This is a vey efficient method for destroying large stones and removing them from the kidney. Patients are admitted for one to two days after percutaneous nephrolithotomy.

What can I do to prevent stones? In order to prevent kidney stones in the future, the number one strategy is to increase hydration. Patients should concentrate on drinking between 2–3 liters of fluid per day. If stones recur despite good hydration, than a further work up is often done. Further evaluation for stones involves blood tests and collecting the urine to find out what disorder is leading to stone formation. Urine is collected for 24 hours and sent to a lab where several electrolytes are checked. This test often shows what metabolic disorder is causing stones and whether patients need to restrict foods or calcium in their diet or need to be on certain supplements or medicine to prevent stone formation.

Is there any diet that I can follow to prevent stones? The first thing that can be done to prevent stones is proper hydration, which involves drinking two to three liters of fluid per day. The second bit of good advice for patients that form stones is to eat a heart healthy diet. By minimizing the amount of protein or meat as well as salt, stones are less likely to form. It is a common assumption that patients that form kidney stones need to minimize the amount of calcium in their diet. This is rarely actually true. A metabolic urinary evaluation will show if patients would benefit by restricting calcium or other foods in their diet. Some other foods in certain conditions that can promote stones include spinach, strawberries, chocolate, tea, nuts, rhubarb and cola.

What are the chances of having another kidney stone after the first episode? Unfortunately, patients are very prone to recurrent stones after their first episode. In fact over 50 percent of patients will have another stone episode after their first episode.