Kidney Stones Introduction to the Urinary Tract The urinary tract or system consists of the kidneys, ureters, bladder, prostate in males and urethra. The kidneys are two bean shaped organs protected by the ribs towards the middle of the back. The kidneys remove extra water and wastes from the blood, converting it to urine. They keep a stable balance of salts and other substances in the blood as well as produce hormones that help build strong bones and help form red blood cells. Narrow tubes called the ureters carry urine from the kidneys to the bladder which is a chamber in the lower abdomen. Like a balloon, the bladder’s elastic walls stretch and expand to store urine. They flatten together when urine is emptied through the urethra to outside the body. What is a kidney stone? A kidney stone is a hard mass developed from crystals that separate from the urine and build up on the inner surfaces of the kidney. Normally, urine contains chemicals that prevent these crystals from forming. When the urine is very concentrated these inhibitors do not seem to work for everyone, so some people form stones. If the crystals remain tiny enough, they will travel through the urinary tract and pass out of the body in the urine without being noticed. Kidney stones may contain various combinations of chemical substances. Most are wastes that are being excreted by the kidney. The most common type of stone contains calcium in combination with either oxalate or phosphate. These chemicals are part of a person’s normal diet and make up important parts of the body, such as bones and muscles. Stones composed of uric acid are less common. Another uncommon type of stone is caused by infection in the urinary tract. This type of stone is called a struvite or infection stone. Cystine stones are quite rare. Urolithiasis is the medical tem used to describe stones occurring in the urinary tract. Other frequently used terms are urinary tract stone disease and nephrolithiasis. Doctors also use terms that describe the location of the stone in the urinary tract. For example, a ureteric stone is a kidney stone that has moved down the ureter. To keep things simple, the term ‘kidney stones’ is used here at all times. Gallstones and kidney stones are not related. They form in different areas of the body and have different causes. If you have a gallstone, you are not more likely to develop kidney stones. What causes kidney stones? Doctors do not always know what causes a stone to form. While certain foods may promote stone formation in people who are susceptible, foodstuffs only contribute a small amount to the likelihood of forming stones. A person with a family history of kidney stones is more likely to develop stones. Urinary tract infections, kidney disorders such as cystic kidney diseases, and metabolic disorders such as hyperparathyroidism are also linked to stone formation. More than 70% of people with a rare hereditary disease called renal tubular acidosis develop kidney stones. Cystinuria and hyperoxaluria are two other rare, inherited metabolic disorders that often cause kidney stones. In cystinuria, too much of the amino acid cystine, which does not dissolve in urine, is voided. This can lead to the formation of stones made of cystine. In patients with hyperoxaluria, the body produces too much of the salt oxalate. When there is more oxalate than can be dissolved in the urine, the crystals settle out and form stones. A high concentration of calcium in the urine causes crystals of calcium oxalate or calcium phosphate to form in the kidneys or urinary tract. Other causes of kidney stones are hyperuricosuria (a disorder of uric acid metabolism), excess intake of vitamin D and blockage of the urinary tract. A high concentration of calcium may also lead to the patient developing gout. Calcium oxalate stones may also form in people who have a chronic inflammation of the bowel or who have had an intestinal bypass operation, or ostomy surgery. As mentioned above, struvite stones can form in people who have had a urinary tract infection. People who take the protease inhibitor Indinavir, a drug used to treat HIV infection and AIDS, are at risk of developing kidney stones although this is extremely rare. Who gets kidney stones? For unknown reasons, the number of people with kidney stones has been increasing over the past 20 years. This is approximately 10%of the population. Stones occur more frequently in men. Kidney stones strike most typically between the ages of 20 and 40. Once a person has had one stone, he or she is more prone to developing others. This is a 50% chance over 5 years. What are the symptoms? Usually, the first symptom of a kidney stone is extreme pain. The pain often begins suddently when a stone moves in the urinary tract, causing irritation and blockage. Typically, a person feels a sharp, cramping pain in the back and side area of the kidney, or in the lower abdomen. Sometimes nausea and vomiting occur. Later, pain may spread to groin. If the stone is too large to pass easily, pain continues as the muscles in the wall of the tiny ureter try to squeeze the stone along into the bladder. As a stone grows or moves, blood may appear in the urine. As the stone moves down the ureter closer to the bladder, you may feel the need to urinate more often or feel a burning sensation during urination. If fever or chills accompany any of these symptoms, an infection may be present. In this case, you should contact a doctor immediately. How are kidney stones diagnosed? Sometimes a ‘silent’ stones –those that do not cause symptoms – are found on x-‐rays or Ultrasound taken during a general health exam. Some stones may be present with blood in the urine, and or with no pain. Recurrent urinary tract infections not responding to antibiotic treatment may also be a sign of stones. More often, kidney stones are found on CT Scan taken in an emergency department on someone who complains of blood in the urine or sudden pain. These diagnostic images give the doctor valuable information about the stone’s size and location. Blood and urine tests help detect any abnormal substance that might promote stone formation. The doctor may also decide to scan the urinary system using a special x-‐ray test called IVP (intravenous pyelogram). A plain abdominal X-‐Ray and ultrasound pick up most stones but are not as accurate as a CT Scan. The best test for you will be decided by your doctor. How are kidney stones treated? Fortunately, surgery is not always necessary. Many kidney stones can pass through the urinary stystem with plenty of water (2 to 3 litres a day) to help move the stone along. The likelihood of passing a stone is dependent on the size and position of the stone. The smaller and lower the urinary tract the more likely to pass. If pain is severe you will be admitted to the hospital and given strong painkillers. Often, you can go home during the process, drinking fluids and taking pain medication as needed. Recently we have begun to use a new drug called flomaxtra, which relaxes the muscle of the ureter and helps stones pass. The doctor usually asks you to save the passed stone(s) for testing. You can catch it in a cup or tea strainer used only for this purpose. The first step – Prevention In e very person who has had a stone, we check the level of calcium in the blood and also perform a urine culture. If a stone has been removed, or if you‘ve passed a stone and saved it, the laboratory can analyse it to determine its composition. If you’ve had a number of kidney stones we usually carry out a more detailed series of tests to try to find other treatable causes. You may be asked to collect you urine for 24 hours after a stone has passed or been removed. The sample is used to measure urine volume and levels of acidity calcium, sodium, uric acid, oxalate, citrate, and creatinine (a product of muscle metabolism). More 24 hour urine collections are sometimes needed to determine whether the prescribed treatment is working. Lifestyle changes By far the most important lifestyle change to prevent stones is to drink more fluids….water is best. If you tend to form stones, you should try to drink enough liquids throughout the day to produce at least two litres of urine every 24 hour period. As stones form only when the urine is concentrated, it is possible to know when you are at high risk – look at your urine – if it is dark then you should be drinking more. Aim for pale clear urine. People who form calcium stones used to be told to avoid dairy products and other foods with high calcium content. But recent studies have shown that foods high in calcium don’t increase the risk of developing stones. Medical Therapy As well as lifestyle changes mentioned above, drugs such as hydrochlorothiazide are also occasionally used to help prevent calcium stones. These drugs decrease the amount of calcium released by the kidneys into the urine. Uric acid stones are the only stones that can be dissolved. This is difficult but is possible by taking medicine to make the urine less acidic (the pH must be over 6.5) and taking a large amount of fluids. Once they are dissolved, fluids alone can prevent more stones. To prevent cystine stones, it is necessary to drink enough water each day to dilute the concentration of cystine that escapes into the urine, which may be difficult. More than four litres of water may be needed every 24 hours, and a third of that must be drunk during the night. Various medicines are used at times also. For struvite stone(s) that have been totally removed, the first line of prevention is to keep the urine free of the bacteria that can caused infection. Your urine will be tested regularly to be sure that no bacteria are present. People with hyperparathyroidism sometimes develop calcium stones. Treatment in these cases is usually surgery to remove the parathyroid glands (located in the neck). In most cases, only one of the glands is enlarged. Removing the glands cures the patient’s problem with hyperparathyroidism and with kidney stones as well. Surgical treatment Surgery is reserved as an option for cases where other approaches have failed or shouldn’t be tried. Surgery may be needed to remove a stone if: Does not pass after a reasonable period of time and causes constant pain. Is too large to pass on its own, or is caught in a difficult place. Blocks the flow of urine. Causes ongoing urinary tract infection. Damages kidney tissue or causes constant bleeding Has grown larger (as seen on follow-‐up x-‐ray studies). Until the last few decades, surgery to remove stones meant an open operation. It involved cutting the skin and was very painful. It also required a lengthy recovery time (4-‐6 weeks). Today, surgical treatment for stones is greatly improved and open surgery is very rarely required. Most treatment options are much easier for the patient and do not require major surgery. Extra-‐Corporeal Shock – Wave Lithotripsy (ESWL) This is a frequently used procedure for the treatment of stones in the kidneys. In ESWL, shock waves that are created outside of the body travel through the skin and body tissues until they hit the dense stones. The stones break down into sand like particles and are e asily passed through the urinary tract in the urine. There are several types of ESWL devices. The one used at North Eastern Urology is a very modern device. It does not require the old-‐fashioned water bath. We usually ask for a light general anaesthetic and you are usually able to go home same day. Either x-‐rays or ultrasound can be used to pinpoint the stone during treatment. Recovery time is short, and most people can resume normal activities in a few days. Complication may occur with ESWL. Most patients have blood in their urine for a few days after treatment. Bruising and minor discomfort of the back or abdomen from the shock waves are also common. To reduce the risks of complications, we usually ask patients to avoid taking aspirin and other drugs that affect blood clotting for a week before treatment. Another complication may occur if the shattered stone particles cause pain as they pass through the urinary tract. In some cases, we need to insert a small tube, called a stent, through the bladder into the ureter to help the fragments pass. More than one treatment is sometimes required as the stone may not be completely shattered with one treatment. Percutaneous Nephrolithotomy Sometimes a procedure called Percutaneous nephrolithotomy is recommended to remove a stone. We often use this procedure when the stone is quite large or in a location that does not allow effective use of ESWL. The surgeon makes a tiny incision in the back and creates a tunnel directly into the kidney. Using an instrument called nephroscope, the surgeon locates and removes the stone. For large stones, a vibrating probe (like a pneumatic drill) is used to break the stone into small pieces. Generally, you stay in hospital for a few days and may have a small tube called a nephrostomy tube left in the kidney during the healing process. One advantage of percutaneous nephrolithotomy over ESWL is that the surgeon removes the stone fragments instead of relying on their natural passage from the kidney. Ureteroscopic stone removal Ureteroscopy allows more than one stone to be treated at one sitting. A ureteroscope is a very fine telescopic instrument, which is passed through the urethra and bladder into the ureter and sometimes into the kidney itself. Rigid ureteroscopes have been used for several years. These allow your doctor to reach into the lower ureter to grasp or disintegrate stones. We may use an instrument called a basket to grasp the stone. Flexible ureteroscopy More recently, doctors have begun using very fine flexible instruments which reach all the way to the kidney. These instruments are so fine and fragile that the biggest tool that can be passed up them measures 1.2mm across. For practical purposes, this means doctors have to use a laser fibre (little thicker than a human hair) to deliver the energy to disintegrate stones. This is quite slow and delicate surgery but carries very few risk for the patients. Ureteroscopy usually requires a general anaesthetic, but it tends to be quite an easy procedure for the patient. The biggest problem for the patient is usually the stent, if required (see below for more information on stents). Stents Ureteric stents are fine plastic tubes that are inserted into the ureter through the urethra. They run from the kidney to the bladder and have a curl (pigtail) at each end to keep them in a safe place. An anaesthetic is required to put them in, and sometimes to remove them. They are used in a number of different situations: When a patient first comes with severe pain and an impacted stone, it is sometimes not possible to pass a ureteroscope and remove the stone immediately because of severe inflammation at the spot in the ureter where the stone has blocked. Using x-‐ray guidance we can usually place a stent past the stone. This unblocks the kidney and relieves the server pain. ESWL or ureteroscopy is carried out later. If there is a large stone that is to be broken up so that there is a risk that the fragments may block the ureter before passing, a stent is often used to ensue the kidney doesn’t get blocked. Where a ureteroscopic stone removal has been incomplete or difficult, a stent is often used to prevent post-‐operative complications and help the lining of the ureter heal. Stents are used quite frequently in more complex cases, but they have their problems. Although stents don’t worry some patients at all, they can produce quite marked discomfort when you pass urine. They may give a constant urge to void hourly. Symptoms often improve 48-‐72 hours and they often cause More prevention points If you have a family history of stones or have had more than one stone, you are likely to develop more stones. Drink plenty of fluids – water is best. If you are at risk for developing stones, ask your doctor to perform certain blood and urine tests to determine which factors can best be altered to reduce that risk. You may need medicines to prevent stones from forming. If you have chronic urinary tract infections and stones you will often need the stone removed if you doctor determines that the infection results from the stone’s presence. Ensure you receive careful follow up to be sure that the infection has cleared. Food choices for people with kidney stones Dietary recommendations Reduce salty foods in your diet including salted chips/nuts, stock cubes, commercial sauces and spreads and take away foods. Avoid adding salt att he table or in cooking Drink at least three litres of water each day. Try carrying a bottle of water with you or drink one glass of water each hour. Have no more than 600mls of milk (milk substitutes) each day. Reduce meat/fish serves to 150gms each day. Avoid foods high in oxalates: dark green vegetables, rhubarb, beetroot, cocoa, chocolate, milo, ovaltine, strong black tea, berry fruits and nuts. Avoid vitamin c supplements. Weight loss – aim for a body mass index between 20-‐25 as obesity leads to more acidity in the urine which may precipitate stones.
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