What Are Kidney Stones?
Kidney stones are crystals that precipitate from urine. This happens for a number of reasons including dehydration, dietary excess, and inherited metabolic abnormalities. If the crystals are small enough, they flow out with the urine without causing symptoms. If the crystals grow large enough, or aggregate sufficiently, they may not be able to pass easily and then cause symptoms. Kidney stones can be made of a variety of substances, most commonly including calcium, oxalate, and uric acid. Some stones, particularly in the presence of a chronic urinary tract infection, can grow to be very large and fill the inside of the kidney (staghorn stone below).
Symptoms of Kidney Stones
Kidney stone symptoms are generally due to the obstruction of urine flow once the stone leaves the kidney and starts down the ureter toward the bladder. The kidney continues to make urine despite the obstructed flow, stretching the lining of the inside of the kidney. With the stone acting like a cork, blocking normal urine flow out of the kidney, the result is the severe pain known as "renal colic." Often, hydration and pain meds are all that is necessary to help pass the stone. It is important to know that obstruction with fever is an emergency. Anyone with fever and flank pain must seek medical care immediately. Sometimes a large stone may be lodged in the kidney and cause a chronic dull ache in the flank, or intermittent symptoms for many years.
In patients with stones, urine analysis often demonstrates the presence of microscopic blood. CT scan is the best imaging study to evaluate for the presence, location, and size of kidney stones. Plain X-rays are often used, too, but not all stones show up on these films. In particular, uric acid stones are radiolucent, meaning they will not show up on plain x-rays. IVP (intravenous pyelogram) is an older, but useful, study in which IV contrast is given before a series of plain x-rays. This study can delineate the internal anatomy of the kidney before some types of kidney stone procedures. If one has recurrent kidney stones, a metabolic evaluation can be performed to determine what a person might do to reduce their risk of further stones. This study involves a 24-hour urine collection and analysis, as well as a blood draw for calcium and sometimes parathyroid hormone levels. If a kidney stone is passed or removed, it can be sent for chemical analysis, as this information can assist with recommendations to prevent further episodes.
- Observation - not all stones require treatment. The risks of treatment should be weighed against the benefits. Most stones 5mm or smaller will pass spontaneously.
- Medical Expulsive Therapy - certain medications help stones pass through the ureter. The most commonly used drug for this purpose currently is tamsulosin (Flomax). Other drugs used include calcium channel blockers and steroids, but the benefits are debatable. Drinking plenty of fluid and taking a good pain medication is probably the most important means to help a stone pass with the least possible misery.
- Extracorporeal Shockwave Lithotripsy (ESWL) - focused sound waves are used to break up a stone into pieces that can be passed more easily. This is a non-invasive treatment, but requires general anesthesia. Stones most appropriate for this treatment are in the kidney or upper ureter, visible by plain x-ray, and are less than 1.5cm in greatest dimension.
|Ureteroscopy - Many stones are best-treated endoscopically, meaning with a scope. Long, narrow scopes can be passed up the ureter to the stone. The stone is then fragmented with a laser and the fragments washed out or snared with a basket and retrieved.|
|Laparoscopic Stone Removal - Occasionally, a large stone burden is best approached laparoscopically. This is often the best approach when a patient also has an obstruction of drainage from the kidney into the ureter, known as ureteropelvic junction obstruction. Both the stones and the obstruction can then be treated in one operation|
Ask anyone who has had a stone and you will be convinced that the preferred means of treating a kidney stone is to prevent it from forming in the first place. Kidney stone formation and growth are dependent on the concentration of substances in the urine. The easiest way to reduce the risk of crystal formation is to increase the amount of urine in which to dissolve the same amount of minerals - drink more fluids! Water is a great option, but if water is not particularly palatable, drink lemonade-flavored Crystal Light, which contains citrate, a potent kidney stone inhibitor. To make specific recommendations about how one can reduce their risk of recurrent kidney stones, a metabolic evaluation must be performed. The information is obtained from a blood draw and a 24-hour urine collection. With this information, certain dietary changes can be recommended. Often, a diet with reduced oxalate can help decrease recurrence of the most common types of stones. There are several good books about preventing kidney stones and even a cookbook for those who need a low-oxalate diet. If one has high calcium in the urine, then a medication may be provided to decrease it. If one makes uric acid stones, then allopurinol can be taken to decrease uric acid production and thereby decrease the rate of stone recurrence. Other medications that makes the urine less acidic (Urocit-K) can be both stone treatment and prevention.