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:
Calcium 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 Stones: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: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:Cystine stones are rare and occur in an inherited condition called cystinuria. Cystinuria is characterized by high levels of cystine 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.
Diagnosis of urinary stones
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:
Which fluids are preferred to prevent urinary stone?
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.
Which fluids should be avoided by a person with urinary stone? 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-fiber 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
People with calcium oxalate stones should limit foods high in oxalate. Foods rich in oxalate include:
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.
Immediate treatment of kidney stones
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.
Plenty of fluid intake
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 liters 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.
ESWL or extra-corporeal shock wave lithotripsy is the latest, effective and most frequently used treatment for kidney stones. Lithotripsy is ideal for kidney stones less than 1.5 cm in size or upper ureteric stones. In lithotripsy highly concentrated shock waves or ultrasonic waves produced by a lithotriptor machine break up the stones. The stones break down into small particles and are easily passed out through the urinary tract in the urine. After lithotripsy, the patient is advised to drink fluids liberally to flush out stone fragments. When blockage of the ureter is anticipated after lithotripsy of a big stone, a “stent” (special soft plastic tube) is placed in the ureter to avoid blockage.
Lithotripsy is generally safe. Probable complications of lithotripsy are blood in urine, urinary tract infection, incomplete stone removal (may require more sessions), incomplete stone fragmentation (which can lead to urinary tract obstruction), damage to kidney and an elevation in blood pressure.
Advantages of lithotripsy are that it is a safe method that does not require hospitalization, anesthesia and incision or cut. Pain is minimum in this method and it is suitable for patients of all age groups.
Lithotripsy is less effective for large stones and in obese patients. Lithotripsy is not advisable during pregnancy and in patients with severe infection, uncontrolled hypertension, distal obstruction in the urinary tract and bleeding disorders.
After lithotripsy, regular follow up, periodical checkup and strict adherence to preventive measures against recurrence of stone disease, is mandatory.
Percutaneous nephrolithotomy, or PCNL, is an effective method for removing medium-sized or large (bigger than 1.5 cm) kidney or ureteral stones. PCNL is the most frequently used option when other treatment modalities such as ureteroscopy or lithotripsy have failed.
In this procedure, under general anesthesia, the urologist makes a tiny incision in the back and creates a small tract from the skin to the kidney under image intensifier or sonographic control. For the insertion of instruments the tract is dilated. Using an instrument called a nephroscope, the urologist locates and removes the stone (nephrolithotomy). When the stone is big it is broken up using high frequency sound waves and then the stone fragments are removed (nephrolithotripsy).
By and large PCNL is safe, but there are some risks and complications that can arise as with any surgical treatment. Probable complications of PCNL are bleeding, infection, injury to other abdominal organs such as the colon, urinary leak and hydrothorax.
The main advantage of PCNL is that only a small incision (about one centimeter) is required. For all types of stones, PCNL is the most effective modality to make the patient totally stone-free in a single sitting. With PCNL hospital stay is shorter and recovery and healing is faster.
Ureteroscopy is a highly successful modality for treating stones located in the mid and lower ureter. Under anaesthesia, a thin lighted flexible tube (ureteroscope) equipped with a camera is inserted via the urethra into the bladder and up the ureter.
The stone is seen through the ureteroscope and, depending on the size of the stone and the diameter of the ureter, the stone may be fragmented and/or removed. If the ureteric stone is small, it is grasped by the grasper and removed. If a stone is too large to remove in one piece, it can be broken into tiny fragments using pneumatic lithotripsy. These tiny stone pieces pass out on their own in urine. Patients normally go home the same day and can resume normal activity in two to three days.
The advantages of URS are that even hard stones can be broken by this method, and that it does not require incisions. It is safe for pregnant women, obese persons, as well as those with bleeding disorders. URS is generally safe, but, as with any procedure, risks exist. Possible complications of URS are blood in the urine, urinary tract infection, perforation of the ureter, and formation of scar tissue that narrows the diameter of the ureter (ureteral stricture).
Open surgery is the most invasive and painful treatment modality for stone disease requiring five to seven days of hospitalization.
With the availability of new technologies, the need for open surgery has been reduced drastically. At present, open surgery is used only in extremely rare situations for very complicated cases with very large stone burden.
Major benefit of open surgery is complete removal of multiple, very big or staghorn stones in a single sitting. Open surgery is an efficient and cost-effective treatment modality especially for developing countries where resources are limited.
A patient with kidney stone should immediately consult a doctor in case of:
Source: Kidney Education Foundation
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