Kidney Stone

What is the treatment for kidney stones?

Most kidney stones eventually pass through the urinary tract on their own within 48 hours, with ample fluid intake. Pain medications are used for symptom relief. When over-the-counter medications are not sufficient for pain control, narcotics may be prescribed. Intravenous pain medications can be given when nausea and vomiting are present.

There are several factors which influence the ability to pass a stone. These include the size of the person, prior stone passage, prostate enlargement, pregnancy, and the size of the stone. A 4 mm stone has an 80% chance of passage while a 5 mm stone has a 20% chance. Stones larger than 9 mm-10 mm rarely pass without specific treatment.

Some medications have been used to increase the passage rates of kidney stones. These include calcium channel blockers such as nifedipine (Adalat, Procardia, Afeditab, Nifediac) and alpha blockers such as tamsulosin (Flomax). These drugs may be prescribed to some people who have stones that do not rapidly pass through the urinary tract.

For kidney stones that do not pass on their own, a procedure called lithotripsy is often used. In this procedure, shock waves are used to break up a large stone into smaller pieces that can then pass through the urinary system.

Surgical techniques have also been developed to remove kidney stones when other treatment methods are not effective. This may be done through a small incision in the skin (percutaneous nephrolithotomy) or through an instrument known as an ureteroscope passed through the urethra and bladder up into the ureter.

Classification

Kidney stones are typically classified by their location and chemical composition.

Kidney Stone type	Population	Circumstances	Details
Calcium oxalate	80%	when urine is acidic (low pH)	Some of the oxalate in urine is produced by the body. Calcium and oxalate in the diet play a part but are not the only factors that affect the formation of calcium oxalate stones. Dietary oxalate is an organic molecule found in many vegetables, fruits, and nuts. Calcium from bone may also play a role in kidney stone formation.
Calcium phosphate	___%	when urine is alkaline (high pH)
Uric acid	5-10%	when urine is persistently acidic	Diets rich in animal proteins and purines: substances found naturally in all food but especially in organ meats, fish, and shellfish.
Struvite	10-15%	infections in the kidney	Preventing struvite stones depends on staying infection-free. Diet has not been shown to affect struvite stone formation.
Cystine	___%	rare genetic disorder	Cystine, an amino acid (one of the building blocks of protein), leaks through the kidneys and into the urine to form crystals.

Prevention

Dietary measures

Specific therapy should be tailored to the type of stones involved. Diet can have a profound influence on the development of kidney stones. Preventive strategies include some combination of dietary modifications and medications with the goal of reducing the excretory load of calculogenic compounds on the kidneys. Current dietary recommendations to minimize the formation of kidney stones include:

• Increasing fluid intake of citrate-rich foods (especially citrate-rich fluids such as lemonade and orange juice), with the objective of increasing urine output to more than two liters per day
• Attempt to maintain a calcium (Ca) intake of 1000 – 1200 mg per day
• Limiting sodium (Na) intake to less than 2300 mg per day
• Limiting vitamin C intake to less than 1000 mg per day
• Limiting animal protein intake to no more than two meals daily, with less than 170–230 g per day. (A positive association between animal protein consumption and recurrence of kidney stones has been shown in men.
• Limiting consumption of foods containing high amounts of oxalate (such as spinach, strawberries, nuts, rhubarb, wheat germ, dark chocolate, cocoa, brewed tea)

Maintenance of dilute urine by means of vigorous fluid therapy is beneficial in all forms of nephrolithiasis, so increasing urine volume is a key principle for the prevention of kidney stones. Fluid intake should be sufficient to maintain a urine output of at least 2 l (68 US fl oz) per day.A high fluid intake has been associated with a 40% reduction in recurrence risk.
Calcium binds with available oxalate in the gastrointestinal tract, thereby preventing its absorption into the bloodstream, and reducing oxalate absorption decreases kidney stone risk in susceptible people. Because of this, some nephrologists and urologists recommend chewing calcium tablets during meals containing oxalate foods. Calcium citrate supplements can be taken with meals if dietary calcium cannot be increased by other means. The preferred calcium supplement for people at risk of stone formation is calcium citrate because it helps to increase urinary citrate excretion.
Aside from vigorous oral hydration and consumption of more dietary calcium, other prevention strategies include avoidance of large doses of supplemental vitamin C and restriction of oxalate-rich foods such as leaf vegetables, rhubarb, soy products and chocolate. However, no randomized, controlled trial of oxalate restriction has yet been performed to test the hypothesis that oxalate restriction reduces the incidence of stone formation. Some evidence indicates magnesium intake decreases the risk of symptomatic nephrolithiasis.

Urine alkalinization

The mainstay for medical management of uric acid stones is alkalinization (increasing the pH) of the urine. Uric acid stones are among the few types amenable to dissolution therapy, referred to as chemolysis. Chemolysis is usually achieved through the use of oral medications, although in some cases, intravenous agents or even instillation of certain irrigating agents directly onto the stone can be performed, using antegrade nephrostomy or retrograde ureteral catheters. Acetazolamide (Diamox) is a medication that alkalinizes the urine. In addition to acetazolamide or as an alternative, certain dietary supplements are available that produce a similar alkalinization of the urine. These include sodium bicarbonate, potassium citrate, magnesium citrate, and Bicitra (a combination of citric acid monohydrate and sodium citrate dihydrate). Aside from alkalinization of the urine, these supplements have the added advantage of increasing the urinary citrate level, which helps to reduce the aggregation of calcium oxalate stones.
Increasing the urine pH to around 6.5 provides optimal conditions for dissolution of uric acid stones. Increasing the urine pH to a value higher than 7.0 increases the risk of calcium phosphate stone formation. Testing the urine periodically with nitrazine paper can help to ensure the urine pH remains in this optimal range. Using this approach, stone dissolution rate can be expected to be around 10 mm (0.39 in) of stone radius per month.

Diuretics

One of the recognized medical therapies for prevention of stones is the thiazide and thiazide-like diuretics, such as chlorthalidone or indapamide. These drugs inhibit the formation of calcium-containing stones by reducing urinary calcium excretion.^[1] Sodium restriction is necessary for clinical effect of thiazides, as sodium excess promotes calcium excretion. Thiazides work best for renal leak hypercalciuria (high urine calcium levels), a condition in which high urinary calcium levels are caused by a primary kidney defect. Thiazides are useful for treating absorptive hypercalciuria, a condition in which high urinary calcium is a result of excess absorption from the gastrointestinal tract.

Allopurinol

For people with hyperuricosuria and calcium stones, allopurinol is one of the few treatments that have been shown to reduce kidney stone recurrences. Allopurinol interferes with the production of uric acid in the liver. The drug is also used in people with gout or hyperuricemia (high serum uric acid levels). Dosage is adjusted to maintain a reduced urinary excretion of uric acid. Serum uric acid level at or below 6 mg/100 ml) is often a therapeutic goal. Hyperuricemia is not necessary for the formation of uric acid stones; hyperuricosuria can occur in the presence of normal or even low serum uric acid. Some practitioners advocate adding allopurinol only in people in whom hyperuricosuria and hyperuricemia persist, despite the use of a urine-alkalinizing agent such as sodium bicarbonate or potassium citrate.

Management

Medical

Stone size influences the rate of spontaneous stone passage. For example, up to 98% of small stones (less than 5 mm (0.20 in) in diameter) may pass spontaneously through urination within four weeks of the onset of symptoms,but for larger stones (5 to 10 mm (0.20 to 0.39 in) in diameter), the rate of spontaneous passage decreases to less than 53%. Initial stone location also influences the likelihood of spontaneous stone passage. Rates increase from 48% for stones located in the proximal ureter to 79% for stones located at the vesicoureteric junction, regardless of stone size. Assuming no high-grade obstruction or associated infection is found in the urinary tract, and symptoms are relatively mild, various nonsurgical measures can be used to encourage the passage of a stone. Repeat stone formers benefit from more intense management, including proper fluid intake and use of certain medications. In addition, careful surveillance clearly is required to maximize the clinical course for people who are stone formers.

Analgesia

Management of pain often requires intravenous administration of NSAIDs or opioids. Orally administered medications are often effective for less severe discomfort.

Expulsion therapy

The use of medications to speed the spontaneous passage of ureteral calculi is referred to as medical expulsive therapy.^[60] Several agents, including alpha adrenergic blockers (such as tamsulosin) and calcium channel blockers (such as nifedipine), have been found to be effective.^[60] A combination of tamsulosin and a corticosteroid may be better than tamsulosin alone.^[60] These treatments also appear to be a useful adjunct to lithotripsy.

Surgical

A lithotriptor machine is seen in an operating room; other equipment is seen in the background, including an anesthesia machine and a mobile fluoroscopic system (or "C-arm").

Most stones under 5 mm (0.20 in) pass spontaneously.^[9][33] Prompt surgery may, nonetheless, be required with persons with only one working kidney, bilateral obstructing stones, a urinary tract infection and thus, it is presumed, an infected kidney, or intractable pain.^[61] Beginning in the mid-1980s, less invasive treatments such as extracorporeal shock wave lithotripsy, ureteroscopy, and percutaneous nephrolithotomy began to replace open surgery as the modalities of choice for the surgical management of urolithiasis. More recently, flexible ureteroscopy has been adapted to facilitate retrograde nephrostomy creation for percutaneous nephrolithotomy. This approach is still under investigation, though early results are favorable.