Although most stones present with pain, many kidney stones have no symptoms. A stone residing in the kidney usually causes no symptoms until it moves. Contrary to popular belief, it is not the movement of the stone which is painful. Kidney stone pain occurs when there is blockage within the urinary system. Thus, the pain usually occurs when the stone moves out of the kidney and into the more narrow ureter. The narrowest point in the urinary system is where the ureter enters the bladder - this is the most common site for stones to obstruct the urinary system.

A stone which enlarges in the kidney but which does not cause any urine obstruction may have no symptoms. These stones still require treatment since they become infected and management becomes more difficult as the stone size enlarges.

• IVP (intravenous pyelogram) - an x-ray study with a dye injection which is used to visualize the kidneys, ureters and bladder
• Ultrasound - a test which studies the kidneys and looks for blockage within the urinary system or stones in the kidneys. Not a good test for studying stones in the ureter or near the bladder
• CT Scan - an x-ray test to study the urinary system and surrounding organs when x-ray dye can not be administered or results of other studies are unclear

Treatment of kidney stones depend upon several factors:

• Size of stone
• Type of stone
• Location of stone
• Ability to see stone on x-ray
• Patients symptoms
• Associated medical problems such as fever, nausea, pain, etc.

Treatment options include:

• Observation - this is still considered the best management for kidney stones when possible. In order for a stone to pass spontaneously, it must be small enough to pass through the ureteral orifice and into the bladder. In general, stones 5mm and under will usually pass spontaneously and warrant conservative treatment unless patients have persistent symptoms. Stones greater than 10mm (1cm) are unlikely to pass spontaneously and will likely be treated more aggressively. Stones between 5mm and 10mm may or may not pass and must be followed closely.

• Lithotripsy (Shock Wave Therapy) - originally developed in the 1980's, shock wave therapy is now a standard method of treating some stones in the kidney and ureter. In general, shock wave therapy is effective for stones up to 1.5 - 2.0 cm in size. Stones larger than 2.0cm are unlikely to be treated effectively with shock wave therapy. Only stones which can be visualized with standard x-rays can be treated with most lithotripters.

  Lithotripsy is performed on an outpatient basis and usually takes about an hour. The patient is placed in the lithotripter and the stone is localized by x-ray guidance. An anesthetic is administered and 3,000 to 4,000 shocks are delivered to the stone depending upon its location. A ureteral stent (tube between the bladder and kidney) may or may not be inserted to help drain the stone fragments. All of our lithotripsy procedures are performed at Keystone Kidney Center located in Willow Grove, PA which has the capability for performing stent insertions and removals on site.

  Stones within the kidney and upper ureter have a high success rate when treated with lithotripsy. Stones in the lower ureter are more difficult to visualize and treat with lithotripsy and may be better treated with ureteroscopy (see below).

• Ureteroscopy - This surgical procedure has replaced open surgery for the majority of kidney stones. For ureteroscopic stone extraction, the urologist looks into the ureter with a small (1/8 inch diameter) telescope to visualize the stone. Once the stone is located, it can either be removed intact via a basket or grasper or it may be broken/fractured and then removed in pieces. This procedure is commonly performed in conjunction with intracoporeal lithotripsy. Several devices can now be used to break up a stone within the ureter to make its removal easier. We prefer to use the Holmium laser since it can fracture all stones and causes minimal tissue damage. This laser is considered state-of-the-art and is the preferable tool for fragmenting kidney stones. Formerly the most common tool, electrohydraulic lithotripsy is only used in certain cases since it may cause more tissue damage. Ureteroscopic surgery and stone extraction is now performed with both rigid ureteroscopes and flexible ureteroscopes which allow stones within the entire urinary system to be treated by endoscopic means.

  After ureteroscopic stone extraction, a double-J stent is commonly placed in the ureter for 1 - 2 weeks. A stent is a small flexible tube which allows urine to drain from the kidney into the bladder. The stent is necessary because manipulation of the ureter from surgery and trauma from the stone itself causes swelling and spasm which may cause the ureter to swell shut.

• PCNL (Percutaneous Nephrolithomy) - PCNL is a procedure used to remove large stones from the kidney. Although these stones previously were treated with open surgery, even large stones can now be extracted through a 1 inch incision. The procedure begins by placing a percutaneous nephrostomy (a small tube) through the flank and directly into the kidney. Once the tube is placed, the urologist will enlarge the opening and look into the kidney with a small telescope (approximately 0.4 inches in diameter). When the large stone is visualized, it can be fragmented with a laser or ultrasound device and removed in pieces.

• Open surgery - Although almost all stones can now be managed by minimally invasive techniques, there still may be certain occasions where open surgical technique is preferred. Most of these cases will involve anatomical abnormalities within the urinary system which predispose the patient to stone formation which can be corrected at the time of stone removal.

Calcium oxalate stones - The most common type of stone (80% of all stones) which can be detected by routine x-ray studies. This type of stone is unlikely to be treated successfully with medical therapy but certain medications may help prevent calcium stones if they have a propensity to recur.

Uric acid stones - These stones are commonly seen in patients with gout or increased levels of uric acid in the urine. The majority of these stones are not detectable by routine x-rays (unless they have a calcium coating) which makes their management somewhat more difficult. Fortunately, uric acid stones may be able to be dissolved by changing the pH (basic vs. acidic) of the urine with medications. There are also medications which may help prevent the formation of uric acid stones.

Struvite Stones - Commonly called "infection stones", these stones are asssociated in conjunction with urinary tract infection. At times these stones can be extremely large and fill the entire collecting system of the kidney. Appropriate management usually includes antibiotics and PCNL (see above).

Cystine Stones - These stones form due to an inherited disorder of amino acid metabolism. This type of stone commonly runs in families and can be very difficult to manage since they have a tendency to recur. With newer medications, prevention (and at least decreasing the rate of new stone formation) is successful in many cases.

Once a person has had a kidney stone, he often wants to know what can be done to avoid forming another stone. A complete metabolic evaluation which consists of a 24-hour urine collection on a routine diet plus a second evaluation with an oral calcium load will not usually be performed with a patient's first stone unless there is a strong family history.

Patients often ask how diet affects urinary stone formation. While lithotripsy or surgery can frequently render a patient stone free, conservative modalities are required to help reduce the risk of recurrent stone formation. Long-term drug therapy and its potential side effects often lead to noncompliance and subsequent failure. Dietary guidelines to help reduce the recurrence rate of urinary stone formation are presented.

Fluids

The association of stone formation with decreased fluid intake is an assumed risk factor for urinary stone patients. Objective supportive evidence is lacking, however. The mean daily intake of water and urine output are similar in renal stone formers and non-stone formers. Chronic dehydration raises urine specific gravity and reduces urinary pH. Hydration may reduce the risk of urolithiasis through multiple mechanisms. A general consensus is that oral fluid intake should produce approximately 2 liters of urine daily. Recent evidence indicates that some fluids may be better than others. Since most stones consist of calcium oxalate, it is best to limit the amount of oxalate in the diet. High levels of oxalate can be found in tea and therefore once should limit the amount of tea (or iced tea) in the diet.

Citrate is a natural inhibitor of urinary stones. Increasing the amount of citrate in the diet may help prevent stone formation. High levels of citrate (citric acid) are found in lemons. In fact, the amount of citrate in lemons is almost 5 times of that found in orange juice. Thus, a diet consisting of a moderate intake of lemons in the form of lemonade may be beneficial in preventing stone recurrence.

Calcium

Traditionally, oral calcium restriction has been the main dietary recommendation for the prevention of calcium nephrolithiasis. The linear relationship between calcium consumption and urinary calcium levels has been interpreted such that increasing calcium consumption heightens the risk of nephrolithiasis and reducing calcium consumption lowers the risk. However, there is now evidence that a global recommendation for dietary calcium restriction may actually increase the risk of stone formation in some stone formers. Calcium restriction may increase stone risk by stimulating calcium release from bone and thereby increasing urinary calcium levels. Men on a high-calcium diet had a 34% reduced incidence of stone occurrence in a 1993 New England Journal of Medicine article. A more recent study in the Annals of Internal Medicine confirmed that a high level of dietary calcium decreased the risk of stone formation. However, patients taking calcium supplements may be at increased risk for stone formation if these supplements are not taken with meals. Women with a history of kidney stones taking supplemental calcium for the prevention of osteoporosis should discuss the benefits and risks of this medication with their physician.

Citrate

Citrate is a naturally occurring urinary stone inhibitor. Citrate binds to calcium in solution to form a highly soluble calcium-citrate complex, which reduces the ionic concentration of calcium and therefore the relative saturation of calcium oxalate and calcium phosphate in urine. Supplemental K-citrate (60 - 80 mEq / day) significantly increases urinary citrate and pH and reduces the incidence of recurrent stone formation. Dietary citrate supplementation through lemonade consumption has been successful. It may increase compliance and is especially useful in patients with moderate hypocitraturia. It may best be used in conjunction with pharmacologic citrate supplementation.

Conclusion

Stone formers should limit their protein intake (maximum, 1 g / kg / day), sodium intake (100 mEq / day), and increase their urine output to approximately 2 L / day (nondairy fluids that contain minimal oxalate). Dietary sources of magnesium and citrate also have a significant impact on urinary stone disease. Pharmacologic supplementation of magnesium and citrate has proved beneficial in patients with documented deficiencies. Patients who are on diets excessively high in oxalate should reduce their intake, and those with absorptive hypercalciuria type II should decrease their oral calcium load. Patients with other types of hypercalciuria need not restrict their calcium intake.

Related links:

• http://www.niddk.nih.gov/health/kidney/pubs/stonadul/stonadul.htm
• http://www.niddk.nih.gov/health/kidney/pubs/whastone/whastone.htm