Urolithiasis, the presence of stones within the urinary tract, can take many forms. Stones in the kidneys can lead to worsening kidney function with time, stones in the ureters can lead to obstruction and pain, and stones in the bladder can cause bleeding, irritation, and are prone to infections, but these are much less common. Each situation can be managed by a urologist, and most, but not all, can be prevented by you, the patient.
Our kidneys are highly efficient filters, keeping in the good and flushing out the bad from our bodies. The nutrients we eat and drink first get absorbed in our intestines and then dissolved in our bloodstream. Human blood is a complex salt solution, and it includes many elements we need to survive mixed in with waste products and excesses from our diet.
The kidney dutifully filters out certain things we may have too much of, such as calcium, potassium, magnesium, sodium, citrate, phosphate, and oxalate, among many others. It attempts to hold on to things we need, such as sugars, fats, proteins, and important minerals. Waste materials are then concentrated in the urine.
This is where stones can form. The creation of a stone can only take place under special conditions in the urine. There must be the right concentration of solutes (dissolved particles) to solution (water) in order to precipitate a small nidus of a stone crystal, which is essentially a salt. Once a salt crystal has formed, most of the time it can never dissolve within the urinary tract, except for certain types of stones under some special circumstances.
Once present, a cycle of salt deposition on the small crystal nucleus can eventually create a large stone. The acidity of the urine can also play a crucial role, but this is highly variable.
If a stone forms in the kidney, there are a few potential outcomes. It may stay there indefinitely and never cause problems. It may grow to a large size in the kidney and lead to kidney dysfunction. It may drop into the ureter, the tube that connects the kidney to the bladder, and cause obstruction or pass through completely.
Some people have a great deal of pain in the back, side, or abdomen caused by a stone in the ureter. This is often associated with nausea, vomiting, blood in the urine, difficulty emptying the bladder or bowels, and generally not feeling well.
A stone in the ureter in the setting of a urinary tract infection is an emergency that requires prompt attention. If a person has a fever or symptoms of infection along with a ureteral stone, they should seek medical care at once.
This obstruction can be relieved with the placement of a stent. This is a small plastic tube that is placed inside the ureter with the aid of a small camera that fits into the urethra. No incisions are necessary. Urine can pass around and through the stent.
Often, stones may pass on their own. Patients with stones of a reasonable size, generally less than 1cm, are encouraged to attempt to pass the stone without surgical intervention. The use of medications, such as anti-inflammatories, bladder numbing agents, alpha blockers, and occasionally opioid narcotics can help patients manage the pain as their body clears the stone for them. It may take up to six weeks for some stones to pass. Once in the bladder, stones generally have no trouble getting out of the urethra.
If a stone does not pass, there are a few options available to urologists to deal with the problem. Open surgery for stones used to be common, but this is rarely done in the modern era. With the advent of minimally invasive technology, including tiny cameras that fit inside the ureter, lasers that can pulverize the stone, and baskets that grasp and remove the fragments, urologists can take care of stones without incisions and with minimal pain and suffering. This is called ureteroscopy.
Another good option for many types of stones is called external shock wave lithotripsy (ESWL), which involves using sound waves to break up a stone and allowing the fragments to pass on their own.
Lastly, percutaneous nephrolithotomy involves making a small incision in the back and placing a camera directly into the kidney to fragment and remove stones. This is generally reserved for large stones.
The most common types of kidney stones are calcium based, including calcium oxalate and calcium phosphate. These make up about 85% of stones in the United States. Uric acid stones are also quite common, and then there are an abundance of less common stones, which are usually the result of other medical problems or medications.
Prevention of stone disease is the best cure, but this can be difficult. As American waistlines have increased, so has our risk for kidney stone formation. Large amounts of sodium, sugar, and oxalates in the diet are all risk factors. Calcium in the diet is actually protective. Citrate, found in most citrus fruits and juices, can also be protective. Avoidance of oxalates is nearly impossible, as they are found in a multitude of foods; however, reduction in intake of large volumes of oxalate containing foods may help.
This list of foods is long, and includes a lot of otherwise healthy staples, such as spinach, strawberries, nuts, chocolate, soy, and many others.
The most important preventative measure for kidney stones is drinking plenty of water. Despite years of research, no specific dietary changes can be applied to all stone forming patients, but data does tell us that making at least 2.5 liters of urine per day can potentially reduce your risk for forming a stone by half.
Considering the prevalence of kidney stones in the population is nearly 10% and the risk of a person who has already formed a stone making another within 5 years is about 50%, a reduction by half in new stone formation would cut back on millions of ER visits and trips to the OR every year.
Not all stones are preventable, but most are treatable, and your urologist can help you decide how to manage your stone disease.