Stone disease is a very common urological disease. Kidney stones can cause the most unbearable pain, but sometimes kidney stones can exist silently without any symptom. Stone disease can cause urinary tract infection and can damage the kidney if not treated adequately. Once a stone occurs, its recurrence is common. So understanding, prevention and care of stone disease is essential.
A kidney stone is a hard crystal mass formed within the kidney or urinary tract. Increased concentration of crystals or small particles of calcium, oxalate, urate, or phosphate in urine is responsible for stone formation. Millions of crystals of these substances in urine aggregate, gradually increase in size, and after a long period of time, form a stone.
Normally, urine contains substances that prevent or inhibit the aggregation of crystals. Reduced levels of stone inhibitor substances contribute to the formation of kidney stones. Urolithiasis is the medical term used to describe urinary stones. It is to be noted that the composition of gall stones (found in the gall bladder) and kidney stones is different.
Kidney stones vary in size and shape. They can be smaller than a grain of sand or can be as large as a tennis ball. The shape of the stone may be round or oval with a smooth surface, or they can be irregular or jagged with a rough surface. Stones with a smooth surface cause less pain and their chances of natural removal are high. On the other hand, kidney stones that have an irregular rough surface can cause more pain and are less likely to come out on their own. Stones can occur anywhere in the urinary system but occur more frequently in the kidney and then descend into the ureter, sometimes lodging in the narrow areas of the ureter.
There are four main types of kidney stones:
This is the most common type of kidney stone, which occurs in about 70 - 80% of cases. Calcium stones are usually composed of calcium oxalate and less commonly, of calcium phosphate. Calcium oxalate stones are relatively hard and difficult to dissolve with medical management. Calcium phosphate stones are found in alkaline urine.
Struvite (Magnesium ammonium phosphate) stones are less common (about 10 - 15%) and result from infections in the kidney. A struvite stone is more common in women and grows only in alkaline urine.
Uric acid stones are not very common (about 5 - 10%) and are more likely to form when there is too much uric acid in the urine and urine is persistently acidic. Uric acid stones can form in people with gout, who eat a high animal protein diet, are dehydrated or have undergone chemotherapy. Uric acid stones are radiolucent, so are not detected by an X-ray of the abdomen.
Cystine stones are rare and occur in an inherited condition called cystinuria. Cystinuria is characterized by high levels of cysteine in the urine.
A staghorn calculus is a very large stone, usually struvite, occupying a large part of the kidney and resembling the horns of a stag (deer), thus it is called staghorn. A staghorn stone causes minimal or even no pain, diagnosis is missed in most of the cases and end result is damage to kidney.
Everyone is susceptible to stone formation. Several factors that increase the risk of developing kidney stones are:
The symptoms of urinary stone may vary with size, shape, and location of the urinary stone. Common symptoms of urinary stone are:
Yes. Stones in the kidney or ureter can block or obstruct the flow of urine within the urinary tract. Such obstruction can cause dilatation of the urinary pelvis and calyces in the kidney. Persistent severe dilatation due to blockage can cause kidney damage in the long term in a few patients.
Investigations are performed not only to establish diagnosis of urinary stones and to detect complications but also to identify factors which promote stone formation.
KUB Ultrasound: The KUB ultrasound is an easily available, less expensive and simple test that is used most commonly for the diagnosis of urinary stones and to detect the presence of obstruction.
KUB X-ray : Size, shape and position of the urinary stones can be seen on the X-ray of the kidney-ureter-bladder (KUB). A KUB X- ray is the most useful method to monitor presence and size of stone before and after treatment of calcium containing stones.It cannot be used to identify radiolucent stones such as those containing uric acid.
CT scan: CT scan of the urinary system is an extremely accurate and themost preferred diagnostic method to identify stones of all sizes and to determine the presence of obstruction.
Intravenous urography (IVU): Less frequently used, IVU is very reliable in detecting stones and obstruction. The major benefit of IVU is that it provides information about the function of the kidney. Structure of the kidney and details about ureteric dilatation is better judged by this test. It is not useful and should not be used when the serum creatinine is elevated.
Urine tests: Urine tests to detect infection and to measure pH of the urine; 24 hour urine collection to measure total daily urine volume, calcium, phosphorous, uric acid, magnesium, oxalate, citrate, sodium and creatinine.
Blood tests: Basic tests such as complete blood count, serum creatinine, electrolytes and blood sugar; and special tests to identify certain chemicals which promote stone formation such as calcium, phosphorus, uric acid and level of parathyroid hormone.
Stone analysis: Stones that pass out or are removed by different treatment modalities should be collected for analysis. Chemical analysis of stones can establish their composition, which helps in treatment planning.
“Once a kidney stone former, always a stone former.” Urinary stones recur in about 50 to 70% of persons. On the other hand, with proper precautions and treatment the recurrence rate can be reduced to 10% or less. Thus, all patients who suffer from kidney stones should follow preventive measures.
Diet is an important factor that can promote or inhibit formation of urinary stones. General measures useful to all patients with urinary stones are:
Intake of fluids such as coconut water, barley or rice water and citrate- rich fluids such as lemonade, tomato juice or pineapple fruit juices helps in the prevention of stone. But remember that at least 50% of the total fluid intake should be water.
Avoid grapefruit, cranberry and apple juice; strong tea, coffee, chocolate and sugar sweetened soft drinks such as colas. These beverages have been associated with an increased risk of stone formation.
Avoid excessive salt intake in diet. Avoid pickles, chips and salty snacks. Excessive quantities of salt or sodium in the diet can increase the excretion of calcium into the urine and thereby increase the risk of formation of calcium stones. Sodium intake should be restricted to less than 100 mEq or 6 grams table salt per day to prevent stone formation.
Avoid non-vegetarian food such as mutton, chicken, fish and egg. These animal foods contain high uric acid/purines and can increase the risk of uric acid and calcium stones.
Eat a balanced diet with more vegetables and fruits that reduces acid load and tend to make urine less acidic. Eat fruits such as banana, pineapple, blueberries, cherries, and oranges. Eat vegetables such as carrots, bitter gourd (karela-ampalaya), squash and bell peppers. Eat high-fibre containing foods such as barley, beans, oats, and psyllium seed. Avoid or restrict refined foods such as white bread, pastas, and sugar. Kidney stones are associated with high sugar intake.
Restrict intake of vitamin C to less than 1000 mg per day. Avoid large meals late at night. Obesity is an independent risk factor for stone formation.
Diet: It is a wrong concept that calcium should be avoided by patients suffering from kidney stones. Eat a healthy diet with calcium, including dairy products, to prevent stone formation. Dietary calcium binds with oxalate in the gut which limits intestinal oxalate absorption and subsequently reduces stone formation. On the other hand, when dietary calcium is reduced, unbound oxalate in the gut can be easily absorbed from the intestines to promote formation of oxalate stones.
Avoid calcium supplements as well as a diet that is low in calcium, because both increase the risk of stone development. Dietary sources of calcium such as dairy products are preferred over oral calcium supplements for patients at risk for the development of kidney stones. If oral calcium supplements are necessary, they should be taken with meals to reduce the risk.
Medication: Thiazide diuretics are helpful in the prevention of calcium stones because they limit the excretion of calcium in the urine.
People with calcium oxalate stones should limit foods high in oxalate. Foods rich in oxalate include:
Vegetables: spinach, rhubarb, okra, (lady finger), beets and sweet potatoes.
Fruits and dry fruits: strawberries, raspberries, chiku, amla, custard apples, grapes, cashew nuts, peanuts, almonds and dried figs.
Other foods: green pepper, fruit cake, marmalade, dark chocolate, peanut butter, soybean foods and cocoa.
Drinks: grapefruit juice, dark colas, and strong or black tea.
Avoid all alcoholic beverages.
Avoid foods high in animal protein such as organ meat (e.g. as brain, liver, kidney), fish especially those without scales (e.g. anchovies, sardines, herring, trout salmon), pork, chicken, beef and egg.
Restrict pulses, legumes like beans or lentils; vegetables like mushrooms, spinach, asparagus and cauliflower.
Restrict fatty foods such as salad dressings, ice cream, and fried foods.
Medication: Allopurinol to inhibit uric acid synthesis and decrease urinary uric acid excretion. Potassium citrate to maintain urine alkaline, as uric acid precipitates and forms stones in acidic urine.
Other measures: weight reduction. Obese patients are not able to alkalinize urine and this increases the risk for the formation of uric acid stones.
Factors determining the treatment of urinary stones depend on the degree of symptoms; size, position and cause of stone; and presence or absence of urinary infection and obstruction. Two major treatment options are:
Most kidney stones are small (less than 5 mm in diameter) enough to pass on their own within 3 to 6 weeks of the onset of symptoms. The aim of conservative treatment is to relieve symptoms and to help stone removal without surgical operation.
To treat unbearable pain a patient may require intramuscular or intravenous administration of non-steroidal inflammatory drugs (NSAIDs) or opioids. For less severe pain, oral medications are often effective.
In patients with severe pain, fluid intake should be moderate and not excessive because it may aggravate pain. But in pain free periods,drink plenty of fluids, taking as much as 2 to 3 litres of water in a day. Remember though that beer is NOT a therapeutic agent for a patient with kidney stones.
Patients with severe colic and associated nausea, vomiting and fever may require intravenous saline infusion to correct fluid deficit. Patient must save the passed out stone for testing. A simple way to collect stones that have passed out is to urinate through a strainer (sieve).
Maintaining proper urine pH is essential especially for patients with uric acid stone. Drugs like calcium channel blockers and alpha-blockers inhibit spasms of the ureter and dilate the ureters sufficiently to allow the passage of the ureteral stone. This is particularly helpful when the stone is located in the ureter close to the urinary bladder. Treat associated problems such as nausea, vomiting and urinary tract infection. Follow all general and special preventive measures (dietary advice, medication etc.) discussed.
Different surgical treatments are available for kidney stones that cannot be treated with conservative measures. Most frequently used surgical methods are extra-corporeal shock wave lithotripsy (ESWL), percutaneous nephrolithotripsy (PCNL), ureteroscopy and in rare cases open surgery. These techniques are complimentary to each other. These procedures are performed by the urologist who decides which method is the best for a particular patient.
Most patients with small stones can be effectively treated conservatively. But surgery may be needed to remove kidney stones when the stones:
Prompt surgery may be required in patients with kidney failure due to stone obstructing the only functioning kidney or both the kidneys simultaneously.