What are Kidney Stones?
Kidney stones occur when minerals filtered from the blood combine to form hard deposits in the ducts that drain the kidney. It is uncommon before age 20 and peaks at around age 50. Those who suffer from kidney stones in the U.S. are more often than not Caucasian men who live in the southeastern region, or those states with warmer temperatures. Men are twice as likely as women to have kidney stones at some point during their lives, and Caucasians more than any other race.
Most kidney stones are made of calcium. Less common are uric acid stones, infection (struvite) stones, and cystine stones. Some people form stones very early in life and may have frequent episodes of pain when they pass the stones. Others may have only one or two stone episodes starting much later in life.
- Causes & Symptoms
- Glossary of Terms
Causes & Symptoms
A kidney stone may remain in the kidney for years and never cause any obstruction to the flow of urine down the ureter (the tube leading from the kidney to the bladder). When the stone does pass into the ureter, it is likely to cause severe flank pain that may also be felt in the lower abdomen on the same side. This pain can be very intense and may also cause nausea and vomiting. People who have passed stones before can usually recognize “ureteral colic” (the pain of a stone passing down the ureter).
Other symptoms may include the observation of blood in the urine (visible to you, possibly only on microscopic analysis of the urine), urinary urgency or frequency, and less commonly, painful urination.
Fever may be a sign that urine is not easily getting past the stone and may be infected. Fever is fortunately uncommon; but when it occurs, it is an important sign that may require medical intervention.
An IVP (intravenous pyelogram) is another test that can diagnose most stones. It is less commonly used nowadays because it does not have the precision of a CAT scan, and it involves the injection of intravenous contrast to “light up” the kidneys. People with poor kidney function cannot have IV contrast. A small percentage of people may have a serious reaction to contrast, so the IVP is less commonly done today.
A renal ultrasound might show a kidney stone and kidney obstruction, but the ultrasound can miss a ureteral stone. A plain X-ray of the abdomen (called a “KUB”, short for kidneys, ureters, and bladder film) can show larger stones, but it will often miss small stones. A KUB is unreliable for diagnosis of uric acid and cystine stones.
The urinalysis may show blood in the urine and occasionally the presence of an infection. Blood work may show impairment of kidney function.
Medical Expulsive therapy – Stones in the lower ureter may pass more quickly if you are prescribed Tamsulosin (Flomax). We call this Medical Expulsive Therapy (MET).
For small stones of any type, we may offer you pain killers (e.g., non steroid anti-inflammatory drugs – e.g., Ibuprofen, Motrin, Naprosyn, Advil). We may give medication to relieve the nausea, and we often give IV fluids. We would give you a strainer to catch any stones that pass. A finely meshed fish net works well also!
Chemodissolution of stones – Calcium stones generally will not dissolve with medication. The less common uric acid and cystine stones may melt away with drugs that increase the urinary pH (alkalinizing the urine). These same stone types may need additional medications to prevent their recurrence.
We are more likely to advise a procedure for the following cases:
- A stone that continues to cause severe pain, or nausea and vomiting despite the measures listed above.
- A large stone that is very unlikely to pass (e.g., >10cm)
- A stone that is associated with infected urine and fever
- A patient at high risk. This might include:
- Patients with stones who have urinary infections
- Patients who may be immunocompromised – HIV positive, on chronic steroid medication, getting chemotherapy or radiation
- Diabetics, especially when blood sugar levels are very high
- People with only one working kidney, or people born with only one kidney
Listed below are procedures we offer to remove stones.
Shock Wave Lithotripsy (SWL)
A fluid filled cylinder is applied to the back. Soundwaves are generated that pass through the body and are focused on the stone. The stone is pulverized to small particles that can more readily pass down the ureter. SWL is non-invasive and works best on smaller stones of the kidney or upper ureter. SWL requires heavy sedation or full anesthesia. Even though it is non-invasive, there are limitations. It may not fully pulverize a large stone, a very dense stone, or a stone in the lower pole of the kidney. When a large stone is treated with SWL, it can occasionally lead to fragments that line up in the ureter and cause obstruction and pain. This is called a “Steinstrasse” or street of stones. If this occurs, a ureterostomy may need to be performed to remove the fragments.
A thin endoscope is passed through the urethra, into the bladder, then up the ureter until the stone is seen. If it is small, a basket can be passed through the ureteroscope to retrieve the stone. If the stone is large, a laser fiber can be passed that will pulverize the stone into smaller pieces that can pass or be retrieved. A ureteral stent is often placed after the procedure (small tube interposed between the kidney and ureter) to ensure proper drainage. The stent is removed after several days.
Percutaneous Nephrostolithotomy (PCNL)
This procedure is reserved for large, often branched stones of the kidney. A nephrostomy tube is placed through the flank into the kidney. While under anesthesia, the nephrostomy track is dilated, exchanging the small nephrosotomy tube for a larger sheath placed from the flank into the kidney. A nephroscope can be passed down the sheath. Various instruments can be passed through the nephroscope to pulverize and retrieve pieces of the stone. The case concludes by placing a drainage tube from the kidney out the small flank incision. This is removed when post-op imaging shows good healing and no residual stones. Some urologists are not using any external tubes, preferring an internal ureteral stent. Consult with your urologist about your individual case to decide whether you need a drainage tube and where it may be placed.
Laparoscopic and Open Surgical Procedures
These are not commonly done unless the other procedures listed are not feasible (e.g., unusual stone location), or there is going to be a reconstructive procedure in addition to the stone removal.
Prevention of kidney stones
Prevention will depend upon the reasons that led your body to make kidney stones. Once removed, your stone is sent to a lab for analysis of content. Blood and urine tests are also ordered to help pinpoint some specific metabolic problems, some of which may require prescription medication to reduce the risk of forming more stones. Less commonly, surgery may be needed (e.g., removal of the parathyroid glands if they are overactive and cause kidney stones).
Dietary adjustments can immensely help to prevent stone development. Anyone who is prone to kidney stones must make sure to stay well hydrated, especially when it’s hot outside. Generally this means drinking enough water to permit a urine output in excess of 2-3 liters daily. A reduction in dietary protein may be necessary. For calcium stone formers, a diet that has reduced salt and oxalate (found in spinach, peanuts, chocolate, and rhubarb) may be beneficial. Citrate is a good inhibitor of stone growth, so adding lemons or lemonade to the diet may be helpful.
Glossary of Terms
A known inhibitor of kidney stones. Lemons are a great source of citrate and may reduce your risk of new stones. If a metabolic evaluation shows very low urinary citrate, the doctor may prescribe pills such as potassium citrate.
A single x-ray of the kidneys, ureters, and bladder; also called a plain film of the abdomen. A KUB may identify stones >3mm if they are dense enough to show up on plain X rays. If the stone is small or less dense, a CAT scan would be a better imaging test to see the stone.
Medical Expulsive Therapy
This refers to the use of an alpha blocker such as Tamsulosin, to help the stone to pass more quickly.
This refers to those tests that the doctor orders to help find out why you are forming stones. There are blood tests and often a 24 urine collection. The results help determine what dietary changes you may need to make. Sometimes the results suggest a need for prescription medication as well.
The medical term for kidney stones.
Often combines with calcium to form stones. People with calcium oxalate stones may need to reduce the oxalate rich foods in their diet – spinach, rhubarb, beet root, chocolate, peanuts.
Percutaneous Nephrosotomy Tube
A small spaghetti sized tube placed through the flank into the kidney. It provides drainage in situations when there is an obstruction to the outflow of urine down the ureter. It is also placed in anticipation of a PCNL procedure (performed to remove an obstructing stone).
Percutaneous Nephrostolithotomy (PCNL)
This is a procedure that is often used for large or branched stones in the kidney. After placing a percutaneous nephrostomy tube, the urologist dilates the track and places a wider sheath from the flank directly into the kidney. A nephroscope can be passed down the sheath. Instruments such as a laser or high frequency ultrasound wand are passed through the nephroscope, and used to break down the stone and retrieve the pieces through the sheath.
Shock Wave Lithotripsy
A treatment for stones that uses sound waves focused on the stone to pulverize the stone in tiny pieces that pass more easily.
German for a “street of stones.” When SWL is used to pulverize a large stone, you may pass many fragments that are lined up in a row in a segment of the ureter. Ureteroscopy may be needed to remove the fragments.
A prescription drug called an alpha blocker – it helps ureteral stones pass more readily.
A narrow telescope that can be passed through the urethra, into the bladder, then up the ureter to retrieve a ureteral or renal stone. Often a laser fiber is passed down the telescope and is used to pulverize the stone if it is large.
Frequently Asked Questions
A KUB may not identify calcium stones that are smaller than 3mm and/or very faint. The KUB will miss the less common uric acid and cystine stones. Only a CAT scan will pick up these smaller stones.
I have been to the ER three times in 3 weeks because of a known stone that is still trying to pass. How long do I have to wait?
If your pain is quite severe, or you cannot hold down fluids from the associated nausea, you might contact us to discuss measures to remove the stone. If you develop a fever or an associated urinary infection, you should contact us about treatment for the infection and stone intervention.
My mother who is 85 years old became confused and had lower abdominal pain. I took her to the ER and she had an obstructing kidney stone. Is that common?
Elderly patients may not have the typical severe flank or abdominal pain when a stone tries to pass. Confusion and vague abdominal pain may be the only symptoms. Unfortunately, confusion may also be a sign of an active urine infection, possibly one that has gotten into the blood system. This patient should go to the ER and may need urgent treatment.
Which is better – shock wave lithotripsy (SWL)or ureteroscopic stone removal?
Both have high success rates. SWL is less invasive, but it may not completely clear the stone as well as ureteroscopy. If you choose SWL and the stone or its fragments does not pass, you would need a ureteroscopy as a backup procedure.
Large stones in the kidney may not be suitable for ESWL. You would have to discuss your individual case with your urologist.
I have a few stones in my kidney that have not passed and cause me no symptoms. Must I have them treated?
Ideally, we would want to remove all of the stones, then work on stone prevention by conducting a metabolic evaluation (see glossary). The newest flexible endoscopes make this much more feasible, although it can sometimes require several procedures to get you “stone free.” This is the preferred goal for younger people with generally good health.
In a very sick or elderly patient, it’s all about risk assessment and likelihood of successful treatment. It’s not always wise to do procedures for non-obstructing stones because of their medical risks and/or their medications (e.g., blood thinners that increase bleeding). Smaller stones that do not cause obstruction may be observed. Larger stones require discussion and shared decision-making whether to treat. Although less common, infection stones, or struvite stones, are best removed to prevent serious urine and blood borne infections.