Imaging for kidney stones

Kidney Stones (calculi) are hard masses that form in the urinary tract and may cause pain, bleeding, or an infection or block of the flow of urine. Renal calculi are formed when the urine is supersaturated with salt and minerals such as calcium oxalate, struvite (ammonium magnesium phosphate), uric acid and cystine. 60-80% of stones contain calcium. They vary considerably in size from small 'gravel-like' stones to large staghorn calculi. The calculi may stay in the position in which they are formed, or migrate down the urinary tract, producing symptoms along the way. Primary Urinary stones are formed in the kidney, during the course of the migration they may cause symptoms of obstruction ad infection. Bladder stones (calculi) account for around 5% of urinary tract stones and usually occur because of foreign bodies, obstruction or infection. The most common cause of bladder stones is urinary stasis due to failure of emptying the bladder completely on urination, with the majority of cases occurring in men with bladder outflow obstruction. Patients with indwelling Foley catheters are also at high risk for developing bladder stones and there appears to be a significant association between bladder stones and the formation of malignant bladder tumours in these patients.

 

• Incidence of the Urinary stones:
• -Renal stones are common, being present at some time in one in ten of the population, although a significant proportion will remain asymptomatic.
• -The annual incidence is about 1-2 cases of acute renal colic (or ureteric colic) per 1,000 people and the average lifetime risk around 5-10%.
• -Men are more commonly affected than women, with a male:female ratio of 3:1. The difference between the sexes is gradually being eroded. This is thought to be due to lifestyle-associated factors, such as obesity and a Western diet.
• -The peak age for developing stones is between 30 and 50 and recurrence is common.

 

• Cause of Kidney stones:
• Anatomical anomalies in the kidneys and/or urinary tract - eg, horseshoe kidney, ureteral stricture.
• -Family history of renal stones.
• -Hypertension.
• -Gout.
• -Hyperparathyroidism.
• -Immobilisation.
• -Relative dehydration.
• -Metabolic disorders which increase excretion of solutes - eg, chronic metabolic acidosis, hypercalciuria, hyperuricosuria.
• -Deficiency of citrate in the urine.
• -Cystinuria (an autosomal-recessive aminoaciduria).
• -Drugs - eg, diuretics such as triamterene and calcium/vitamin D supplements.
• -More common occurrence in hot climates.
• -Increased risk of stones in higher socio-economic groups.
• -Contamination - as demonstrated by a spate of melamine-contaminated infant milk formula.

 

• Types of kidney stones:
• Stones are made of minerals in the urine that form crystals. Sometimes the crystals grow into stones. About 85% of the stones are composed of calcium, and the remainder are composed of various substances, including uric acid, cystine, or struvite. Struvite stones—a mixture of magnesium, ammonium, and phosphate—are also called infection stones, because they form only in infected urine
• -Calcium stones.
• People with calcium stones may have a condition called hypercalciuria, in which excess calcium is excreted in the urine. For these people, measures that decrease the amount of calcium in the urine can help prevent formation of new stones. One such measure is a diet that is low in sodium and high in potassium. Calcium intake should be about normal—1,000 to 1,500 milligrams daily (about 2 to 3 servings of dairy per day). The risk of a new stone forming is actually higher if the diet contains too little calcium, so people should not try to eliminate calcium from their diet. However, people may need to avoid sources of excess calcium such as antacids that contain calcium. Thiazide diuretics, such as chlorthalidone or indapamide, also reduce the concentration of calcium in the urine in such people. Potassium citrate may be given to increase a low urine level of citrate, a substance that inhibits calcium stone formation. Restricting dietary animal protein may help reduce urinary calcium and the risk of stone formation in many people with calcium stones.A high level of oxalate in the urine, which contributes to calcium stone formation, may result from excess consumption of foods highin oxalate, such as rhubarb, spinach, cocoa, nuts, pepper, and tea, or from certain intestinal disorders (including some kinds of weight loss surgery). Calcium citrate, cholestyramine, and a diet that is low in fat and in oxalate-containing food may help to reduce urinary oxalate levels in some people. Pyridoxine (vitamin B 6 ) decreases the amount of oxalate the body makes. In rare cases, when calcium stones result from hyperparathyroidism, sarcoidosis, vitamin D toxicity, renal tubular acidosis, or cancer, the underlying disorder must be treated.
• -Uric acid stones
• For stones that contain uric acid, a diet low in animal sources of protein (such as meat, poultry, and fish) is recommended, because animal protein increases the level of uric acid in the urine. If a change in diet is not effective,allopurinol may be given to reduce the production of uric acid. Potassium citrate should be given to all people who have uric acid stones to make the urine alkaline, because uric acid stones mainly form when urine acidity increases. Maintaining a large fluid intake is also very important
• -Cystine stones
• For stones made of cystine, urinary cystine levels must be kept low by maintaining a large fluid intake and sometimes taking alpha-mercaptopropionylglycine (tiopronin) or penicillamine.
• -Struvite stones
• People with recurrent struvite stones may need to take antibiotics continually to prevent urinary tract infections. Acetohydroxamic acid may also be helpful in people with struvite stones

 

General Guidelines

Drink Plenty of Fluids
One of the goals of kidney stone treatment is to keep your urine as dilute as possible. This helps to keep the substances that could potentially form a kidney stone, such as calcium and oxalate, moving quickly through the urinary tract.
Try to drink at least two quarts (12 cups) of fluids a day. Water is best, although juice (other than grapefruit juice) and other beverages can add to the total. Drinking lemonade may also reduce your chances of forming another stone. Limit your intake of caffeine-containing beverages like coffee, tea, and cola to one or two cups a day, since caffeine acts as a diuretic, causing your body to lose fluids too quickly and the urine to become too concentrated. Furthermore, both coffee and tea contain high levels of oxalate, a common component of kidney stones.

A good gauge of whether or not you are drinking enough fluids is urine color. Except for the first thing in the morning—when urine tends to be more concentrated—it should be pale in color. If your urine is dark yellow, that's an indication that you should drink more fluids.
If you are hesitant to drink too much during the day because you have a bladder control problem, discuss this concern with your doctor.
Points to remember:

• Drink at least 12 cups of fluids each day
• Limit your intake of caffeinated beverages
• Your urine should be pale in color

 

 

Watch Your Diet
Whether or not diet can help you avoid another kidney stone depends on what kind of stone you had and what caused it to form in the first place. If your stone was made up of calcium oxalate, calcium phosphate, or uric acid, what you eat or don't eat can help prevent a recurrence.
Note that these are only guidelines. People taking certain kinds of medications will need to avoid certain foods. Always follow the advice of your doctor or registered dietitian in making any diet changes.
Nutrients to consider include:

Calcium
Limiting calcium intake from your diet or dietary supplement does not reduce your risk of getting kidney stones.
Oxalate
Oxalate is a substance found in certain plant foods that binds with calcium and other minerals in the intestine. If your body is not absorbing and using calcium correctly, you could end up with too much oxalate in your urine. You can reduce the level of oxalate in your system by avoiding these foods:

• Spinach
• Rhubarb
• Strawberries
• Chocolate
• Wheat bran
• Nuts
• Beets
• Brewed tea

Protein
A diet high in animal protein—from meat, chicken, and fish—may cause your body to release too much calcium, uric acid, and citrate into your urine. If you consume a lot of these foods, you may be asked to eat meals that include less meat and more of other kinds of foods, such as fruits, vegetables, grains, and beans.
Sodium
Likewise, a diet that is high in salt (sodium) can cause your body to excrete too much calcium into your urine. You may be asked to reduce your intake of salty foods and to not use salt in cooking or at the table. Check with your doctor before using a salt substitute.
Foods high in salt include:

• Lunch meats and cured meats like ham, sausage, and bacon
• Salted snacks
• Prepared salad dressings, mustard, catsup, soy sauce, and barbecue sauce
• Pickled foods and olives
• Canned soup and bouillon


Alkaline Ash Diet
In some cases, the best way to avoid another stone is to manipulate the pH balance of the urine. Uric acid, calcium oxalate, and cystine stones form more readily in acidic urine, so this prevention strategy hinges on keeping the urine slightly alkaline. This is usually done with medication, but your doctor might ask you to make some dietary changes as well.
Ask for a written list of instructions if your doctor wants you to follow this diet. Generally, all fruits (except for cranberries, prunes, and plums) and all vegetables (except for corn and lentils) make the urine more alkaline.
Points to remember:

• You may be asked to make some changes to your diet
• You may need to avoid some foods while taking certain medications
• Follow the advice of your doctor or dietitian in making any diet changes

When to Contact Your Doctor

• If you have questions about your diet or your medication
• If you are experiencing any side effects from your medication
• If you are having difficulty with bladder control as a result of increasing your fluid intake