Kidney stones, also known as urolithiasis, are a common affliction of the urinary tract. Depending on the location of the stone in your urinary tract, the stone may be referred to by different names. A stone in your kidney is called a renal calculi or nephrolithiasis. A ureteral calculus or ureterolithiasis is a stone in one of your ureters, the tubes that connect each kidney to your bladder. There are four major types of kidney stones: (1) calcium stones, which are the most common type, are primarily composed of calcium and either phosphate or oxalate, and are primarily due to increased calcium levels in urine; (2) urate or uric acid stones, which are smooth, soft and brown stones that form because of increased uric acid levels in urine; (3) struvite stones, which contain magnesium and ammonia and are typically formed because of infectious bacteria that split a chemical called urea; and (4) cystine stones, which are yellow and are caused by a relatively rare metabolic condition.
When a kidney stone reaches a certain size, usually 2-3 mm, it can cause blockage of the normal flow of urine from the kidneys to the bladder and out of the body. This blockage causes dilation and muscle spasm, causing pain in a patient’s side, lower abdomen or groin. If a kidney stone does not pass spontaneously and is not treated, patients experience a significant amount of pain and eventually damage to the urinary tract.
The number of people who get kidney stones has been increasing over the past several decades, with the probability of getting a kidney stone in your life estimated at around 15% in the United States. The following groups of people are more likely to get kidney stones: men, Caucasians, people between the ages of 40 and 60, people in hot and dry climates, obese individuals and those who have recently gained weight, those who have had multiple kidney or urinary tract infections and patients with a family history of kidney stones. Several other factors increase your general risk for developing a kidney stone, such as: having previously had a kidney stone, not drinking enough fluids, high-protein or low-fiber diet, not maintaining an active lifestyle, and having previously had surgery to remove a kidney or correct small intestine problems.
Stone formation is a complex process. It begins with urine developing a higher concentration of certain salts than is normal. These salts pop out of the liquid urine to form crystals. Crystals can flow out with urine, or become attached at various sites in the kidney. Eventually crystals accumulate at an attachment site to form a stone.
Certain medications may increase your risk of developing kidney stones, such as aspirin, antacids, certain diuretics or “water pills”, calcium and Vitamin D supplements, and anti-retroviral medications such as Indinavir.
Each type of kidney stone has specific factors that increase risk of their formation. The higher than normal levels of calcium in urine that can cause calcium stones could be due to an overactive parathyroid gland (hyperparathyroidism), high levels of Vitamin D, kidney disease, sarcoidosis or some cancers. Uric acid stones can form when your urine is very acidic, which can happen as a result of metabolic imbalances such as gout, chemotherapy, or a high protein diet. Struvite stones, which are more common in women than men, are always associated with urinary tract infections. The bacteria causing these infections release a protein that lowers the acidity of urine, allowing struvite stones to form. Cystine stones are caused by an inherited condition called cystinuria, which affects how much acid is excreted in your urine.
Kidney stones often do not cause any symptoms and are passed painlessly in your urine. These stones are referred to as “silent stones”. However, if a stone is too large to pass without causing blockage, the first symptom is usually severe pain that begins when a stone gets large enough to block your kidney, moves to block the flow or urine, or causes an infection. This pain is typically a cramping, sharp pain in the back or side that can spread to the groin, depending on where the stone is. If a stone is blocking the ureter, it can cause the muscles surrounding the ureter to spasm, causing pain referred to as “renal colic”. Blockage of the flow of urine can also cause symptoms of infection. A list of the common symptoms of kidney stones are shown below:
If the blockage has resulted in an infection, additional symptoms you may experience are:
If you are experiencing fever and/or chills along with pain in your lower back, side or groin, you should contact your doctor immediately.
A patient presenting with pain consistent with a kidney stone, or any of the other symptoms listed above will be imaged to determine if a kidney stone is present, where it is located, and how large it is. Several different diagnostic imaging techniques are available to accomplish these goals:
In addition to imaging, your doctor may order several other tests to check your kidney function and determine the cause of your stone. These include:
Fortunately, about 90% of stones 4 mm or smaller pass spontaneously. A stone that is likely to pass through based on its size is given four weeks in most cases to pass before further intervention is planned. Various measures may be suggested to encourage the passage of a stone including increased hydration, medications to treat infection and reduce any pain, and diuretics to increase urine flow and prevent further stone formation. Waiting for a stone to pass is bypassed in special situations such as if the patient has only one working kidney or an infection is present in a kidney blocked by a stone.
Approximately 99% of stones larger than 6 mm in size need some form of intervention. The most common form of management is for pain, and will depend on your physician. Additionally, a class of drugs called alpha adrenergic blockers, which include Flomax, Terazosin, Doxazosin and Uroxatral, may be prescribed. These drugs reduce the muscular tone of the ureter, and can increase the rate of spontaneous passage of stones significantly. Depending on the type of stone and the underlying situation promoting its formation, you may be prescribed certain medications to correct the conditions that led to the formation of your stone.
Most kidney stones do not require surgery. Reasons to have surgical management for your kidney stone are as follows: the stone has not passed after a reasonable time and is causing constant pain, is too large to pass on its own or is causing significant blockage of urine flow. Other indications for surgery are if there is an infection caused by the stone, damage to kidney tissue or constant bleeding, and if the stone is consistently growing in size.
Over the past two decades, minimally invasive techniques have been developed and improved upon to eliminate kidney stones, greatly reducing the need for open surgery and long recovery times. Several of these techniques are described briefly here, and some have links to more detailed pages.
Each of these procedures has specific indications for use, and carry their own risks and benefits. Your Northwoods urologist will clearly and thoroughly explain all of these before making a recommendation for treatment. Some of the factors that will be discussed and weighed with you are:
Because the risk of having a kidney stone is increased if you have previously had one, prevention is very important. Preventative strategies include dietary modification and some drugs, depending on the cause of your stone. These strategies specifically may include:
Stone location
Number of and sizes of stones
Stone composition
How long the stone has been present and causing symptoms
Pain caused by the stone
Whether or not there is infection
Patient expectation and desire
Patient anatomy
