Kidney Stones

back pain

Overview

Kidney stones are one of the most common reasons that people seek care from a Urologist. The pain of a kidney stone is often sudden and severe causing a panicked rush to the emergency room. The pain has been described as worse than child-birth and often occur at the most inopportune times. Patients often ask why kidney stones form and how to prevent them. There is a plethora of urban legends and folk treatments for possible causes and treatment of kidney stones. In fact, the cause of kidney stones is different for every person and prevention strategies have to be individualized. At North Austin Urology, we are committed to keeping you stone-free, reducing the down-time from a kidney stone episode and providing surgical treatment when necessary in a way that prevents complications.

About kidney stones

Kidney stones are usually small hard crystals that form inside the kidneys. There are several different types of stones that form with different properties. For small stones, however, there is a common cause of an imbalance between the amount of mineral and the amount of water that is available to dissolve the mineral.

This is why dehydration is one risk factor for development of stones.

The various types of stones have different causes.

Calcium stones are most common type of stone and occur most often in men in their 20’s and 30’s. They are very likely to recur. The cause of these stones is an imbalance in the amount of calcium in the urine (which is independent of calcium in the diet) and the level of oxalate. Hydration status is also a very important factor.

Uric acid stones are the second most common type of stone and occurs frequently in men with an elevated uric acid level in the blood or urine.

•Cystine stones can form in people who have cystinuria, a genetic disorder that runs in families.

• Struvite stones are caused by urinary tract infections and occur more often in women. They can become very large and cause severe damage to the kidneys.

The stone can be analyzed once it has passed.

stone next to pennyOnce a stone forms in the kidney it can stay in place for many years and even grow bigger. Once a stone decides to move (like while you are on vacation or right before your wedding) it must move out of the kidney into the ureter (the tube that joins the kidney to the bladder), pass into the bladder and then out of the urethra (the tube that urine passes through out of the body). The ureter is much smaller than the urethra and the the most common place that stones become lodged and cause pain.

Many kidney stones are small enough to pass through the urinary tract on their own and treatment is not required. Larger stones can cause pain, bleeding, fever or infection.

Diagnosis

Flank pain on one side along with blood in the urine is the most common sign of a kidney stone.  When a stone is suspected, usually some form of radiologic imaging is ordered.

These may include:

• Computerized tomography (CT) scan uses a series of thin X-ray beams to image the inside of the body. CT imaging scans are quick and can reveal tiny kidney stones that may not appear on other types of X-rays.  CT scans also impart a high dose of radiation and its use should be limited.

• CT-IVP is performed by injecting an iodine-containing dye into a vein to better outline the kidneys, ureters and bladder.

• Abdominal X-ray (KUB) is a quick and simple way to obtain images of the urinary system and identify a kidney stone. However, not all stone types show up on an abdominal X-ray and often smaller stones are obscured by other organs or gas.  This type of imaging is necessary to identify stones that can be treated using Extracorporeal Shock Wave Lithotripsy (ESWL).

• Intravenous pyelography (IVP) consists of a series of abdominal x-rays performed over 1-2 hours after injection of a dye into a vein to outline the urinary system. This imaging study can be useful in determining the location of kidney stones, the anatomy of the urinary system and identify whether the kidneys are blocked by a stone.

• Ultrasound uses sound waves to create a picture of a patient's internal organs. An ultrasound is painless, noninvasive and imparts no radiation but is used less frequently because small stones are often missed and pinpointing exact location can be difficult. Ultrasound imaging is often performed in children and pregnant women because of the desire to avoid radiation exposure.

Treatment

The goal of surgical treatment is to relieve symptoms, unblock the kidneys and prevent further symptoms from stones that may still be in the kidney and not causing pain. The goal of medical treatment in some cases is to dissolve stones already in the urinary tract, to prevent more stones from forming or current stones from increasing in size.

Passing a kidney stone can be one of the most painful things a person can experience. Drinking lots of water and taking the medications prescribed are important to help the stones pass.

Trial of Passage

gu system pic of stonesMost stones are small enough to pass without any surgical treatment. These are stones that are about 5 mm or less in size and most people will pass a stone within 2-3 days of symptoms starting. During this time, it is vital to drink plenty of water (as much as 2 to 3 quarts per day), stay physically active and use pain medication as necessary. Some patients may be prescribed a medication such as Flomax to help relax the muscles of the ureter to allow faster passage of the stone. This is a non-FDA approved use of the medication but is generally well tolerated.  It is very important to continuously strain your urine during a trial of passage to catch the stone when it passes. Catching the stone is important to figure out how to prevent ore from forming but also to confirm that the stone has passed. There are many occasions where a stone has not passed but causes no symptoms. These stones can grow and cause silent irreversible kidney damage if not found and treated.

A trial of passage is not appropriate for large stones, if there is evidence of infection or for those who become so nauseous that they cannot hydrate properly.

The size of the stone helps determine if it will pass on its own:

• Smaller than 4 millimeters 80% will pass

• Between 4 and 6 millimeters 59% will pass

• Bigger than 6 millimeters 21% will pass

>Where your stone is at time of diagnosis also matters:

• In the kidney/first part of the ureter: 22% will pass

• Middle part of the ureter: 46% will pass

• End of the ureter: 71% will pass

Surgery

Surgical treatment of kidney stones comes in several forms, all of which are generally well tolerated.  It is rare to have to actually make a large incision to remove a stone in the urinary tract.  Reasons that surgery may be advised include: continued pain, risk of continued damage due to a blocked kidney, bleeding or infection.

stent

• Ureteral Stent Placement: A plastic hollow tube that is placed in the ureter to allow urine to pass from the kidney past the blockage, caused from a stone or swelling, to allow drainage of the kidney. There are times when a stent is placed without another procedure such as when there is an infection or if a patient is in severe pain and other forms of therapy are not available. Ureteral stents are commonly placed during other forms of treatment to prevent post-operative kidney blockage to help in healing of the urinary tract.

eswl

• Extracorporeal shock wave lithotripsy (ESWL): ESWL uses shock waves to break kidney stones into tiny pieces that are then passed in the urine. Physicians often use this procedure to remove stones about 1 centimeter in size or smaller. During ESWL, patients are either lie on a cushioned bed, are placed under a general anesthetic and the kidney stone is located using X-ray. High powered sound waves are then passed through the body and crush the kidney stone. The procedure takes about one hour and may need to be repeated for multiple stones or very large stones. The small fragments of the stone are usually passed as sand-like particles.  Some stones may not be appropriate for ESWL especially if they are: very low in the urinary tract, if you are pregnant, if the stone cannot be seen on X-ray or are too hard.

pcnl

• Percutaneous nephrolithotomy (PCNL): 
PCNL is a procedure that is generally performed for very large stones in the kidney. After these stones are not causing pain but there is a concern for ongoing infection or blockage. In this procedure a tube is placed through the back into the kidney through which a camera can be placed to visualize the stone. A variety of instruments, including lasers, high frequency ultrasound and jackhammer like devices, are then used to break apart the stone and remove them from the body.  This procedure is performed under general anesthesia and patients usually stay in the hospital for one to two days.

urs

• Ureteroscopic stone removal
: One of the most common ways to treat a stone emergently is called ureteroscopy. This procedure involves passing a small rigid or flexible camera into the ureter (the tube that connects the kidney to the bladder) and using a laser to break the stone and/or a basket to extract the fragments. Urologists perform this procedure to remove stones lodged in the ureter or in the kidney. A stent is routinely placed after the procedure to prevent swelling of the tissues from blocking the kidney and causing pain. There are times when the anatomy of a patients urinary system or the location of the stone will not allow a ureteroscopy to be successful.

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