Kidney stones form when hard minerals and salts inside the kidneys crystallize. Stones can vary greatly in size and shape, and they develop when there is an excess of stone-forming substances in the urine, such as oxalate, calcium, phosphorous and uric acid. Some patients pass stones without much difficulty while others require surgical intervention. Typically, passing a stone can be quite painful.
At Memorial Hermann, your urologist will help you navigate this common condition, so you can get back to a life free from kidney stone pain.
There are several different types of kidney stones, and many different causes for the condition. In general, an excess of stone-forming substances in concentrated urine can lead to stone formation.
The four main types of stones include:
Calcium stones: Calcium-oxalate is the most common kidney stone composition, caused by an excess of dietary oxalate, which is high in certain vegetables, nuts and tea. Calcium-oxalate stones are also caused by excess calcium in the urine. This can be a result of dietary factors (especially excess sodium intake), hyperparathyroidism, high intake of vitamin D, or other disorders affecting the kidney’s handling of calcium.
Calcium phosphate stones are often found in patients with certain metabolic disturbances, such as renal tubular acidosis, or in patients who take certain migraine medications, like topiramate.
For most patients, restricting dietary calcium is not necessary, and may increase kidney stone risk, especially in patients who have undergone gastric bypass procedures.
Uric acid stones: Uric acid stones can be caused by dehydration, due to poor fluid intake or a severe loss of fluid, such as with diarrhea. Other risk factors include a diet high in animal protein and low in fruits and vegetables, being overweight or obese, Type 2 diabetes, gout or certain genetic factors. Uric acid stones are unique in that they are not visible by standard X-rays.
Struvite stones: Struvite stones are related to chronic urinary tract infections (UTIs). Bacteria such as Proteus can cause these stones by splitting the chemical urea, a large component of urine. These stones are often quite large and can fill the entire kidney.
Cystine stones: Cystine stones form in patients with cystinuria, a rare hereditary disorder that causes the kidneys to excrete an abnormally high amount of four amino acids. One of these four amino acids, cystine, undergoes crystallization and results in stones.
In general, factors that increase the risk of developing kidney stones include:
Stones that are within the kidney, in an area called the collecting system, are generally not symptomatic. If a stone exits the kidney, it enters a narrow tube called the ureter. Even small, 1-2mm stones can cause obstruction of the ureter. The resulting pressure on the kidney results in pain and usually detectable kidney swelling or hydronephrosis.
Common symptoms of lodged kidney stones include:
If you’re experiencing symptoms that could indicate kidney stones, your doctor will review your medical history and perform a physical exam. To confirm a kidney stone diagnosis, your doctor will order an imaging study, which may be an ultrasound, an abdominal X-ray or a CT scan of your abdomen/pelvis.
A more in-depth workup may be recommended if you’re experiencing acute stone episodes. This may help your doctor to determine the cause of your stones and how to best prevent them in the future. This workup may include:
If you are diagnosed with kidney stones, several factors may determine the best course of treatment.
Small stones, for example, can be passed, especially with the help of increased fluid intake and medications to relax the ureter open. If this is the recommended treatment, you may be asked to strain your urine in order to collect the stone(s) for later analysis.
If a kidney stone is large enough, is extremely painful or if a month has elapsed since it first began passing, a procedure may be recommended to remove or help facilitate the passing of the stone(s). To determine the most appropriate procedure, your doctor may consider several factors including stone size, composition and location. Many of these procedures may be completed under general anesthesia.
Below is a list of common procedures used to treat Kidney Stones: