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Kidney Stones

Reviewed by Ojas Shah, M.D.

Kidney stones are an extremely common condition, estimated to affect 5%–10% of the U.S. population at some point in their lives.

Definition, causes and risk factors

Kidney stones are solid masses made up of tiny crystals. Multiple stones may be present in the kidney or ureter at one time.

The causes of kidney stones are not completely understood, but diet, genetic factors, work environment, and even the geographical region where you live may influence kidney stone formation.

Under normal circumstances, the kidneys filter and clean the blood and produce waste products that are transported out of the body in the urine. Urine passes from the kidney through the ureters to the bladder and then through the urethra and out of the body.

When certain mineral salts or other substances reach too high a concentration in the urine, they can form small crystals that grow to become stones. Stones frequently may consist of calcium salts (in combination with oxalate, phosphate or carbonate), cystine, struvite or uric acid.

Image of a kidney stone
© Nucleus Medical Art

Kidney stones are more common in men than women and are most common between age 20 and 50. The incidence in women increases post-menopause.

Other risk factors for kidney stones may include:

  • Previous occurrence of kidney stones
  • Having a family member who has had kidney stones
  • Gout
  • Recurrent urinary tract infections by specific bacteria
  • Metabolic disorders such as cystinuria or hypercalciuria
  • Renal tubular acidosis
  • Undergoing chemotherapy
  • Taking certain medications such as diuretics
  • Intestinal or bowel disease
  • Bariatric surgery
  • In infants, premature birth

Symptoms

Some stones do not cause any symptoms at all and may pass out of the body unnoticed or may be discovered incidentally on an X-ray during examination for another medical issue. However, some stones may have grown larger by the time they leave the kidney and may become lodged in a narrow part of the ureter, causing pain and possibly blocking the flow of urine. The pain is usually severe and often starts in the flank region, then moves down to the groin.

Symptoms may include

  • Pain in the abdomen, flank region, lower back, groin or testicles
  • Nausea, vomiting or diarrhea
  • Blood in the urine, or abnormal urine color
  • Frequent urge to urinate
  • Painful urination
  • Fever and/or chills

Diagnosis

Your doctor will ask about your symptoms and your medical history and will perform a physical exam. To determine which variety of kidney stone may be present, and to check for blockage in the urinary tract, your doctor may also prescribe one or more of the following tests:

  • Stone analysis (to determine the composition of the stone, if you have already passed one)
  • Urinalysis (to check the chemical composition of your urine)
  • Urine culture (to check your urine for bacterial growth)
  • Blood tests (to analyze your kidney function and signs of infection or inflammation)
  • 24-hour urine collection (to analyze the volume and chemical composition of your urine over the course of one to two days)
  • CT scan
  • Ultrasound
  • Standard X-ray
  • Intravenous pyelogram (a series of X-rays that allow your doctor to view obstruction in your urinary tract after the injection of a high-contrast dye)

Treatment

At NYU Urology, we tailor treatment regimens to each patient’s medical history and specific type of kidney stone. Once we have determined the type of stone, we will offer medical or surgical treatment depending on the consistency, size and location of the stone. Treatments may include:

  • Increasing your fluid intake. Your doctor may ask you to drink two to three quarts of water a day in order to help the body excrete small stones in the urine.
  • Dietary manipulation. In general, decreasing your animal protein intake, decreasing salt intake, maintaining an adequate dairy intake, and moderating your intake of foods high in oxalate (such as spinach, rhubarb, beets, okra, berries, black pepper, chocolate, nuts, soy products and tea.)
  • Medications may be prescribed to help return your blood or urine to more normal parameters.
  • Surgery may be necessary to treat larger stones, stones that cause bleeding or infection or stones blocking the flow of urine. At NYU Urology, we aim to remove stones in the least invasive manner possible with the highest chance of success.
    • Ureteroscopy. Ureteroscopy is a minimally invasive, endoscopic approach to treating kidney and ureteral stones. Here, the surgeon inserts a narrow flexible instrument through the urethral opening and passes it up through the bladder into the ureter and/or kidney where the stone is located. The tube typically encloses a fiber optic bundle used to view the stone. Another tiny instrument, most commonly a Holmium laser fiber or basket, is passed through the ureteroscope to break up and/or remove the stone. The advantage of this procedure is that it is performed endoscopically, meaning that an incision through the skin is not needed. It greatly reduces the length of hospitalization, since the majority of procedures are performed on an outpatient basis, and also shortens recuperation time and reduces the cost of treatment.
    • Percutaneous nephrostolithotomy (PNL). PNL is a procedure used to treat large renal or ureteral stones in hard-to-reach locations. In this procedure, a small incision is made in the patient’s back, and a ‘tunnel’ is created directly into the kidney. This allows fragmentation and removal of large or unusual stones using special lithotriptors and stone removal devices. A special tube, called a nephrostomy tube, may be left in the kidney during the healing process. Larger stones may require a staged procedure to remove the entire stone burden. Most patients are able to go home the day after the procedure, and the recuperation period is typically 2 to 4 weeks.
    • Shockwave lithotripsy uses high-energy sound waves and X-rays to localize and break up smaller stones, allowing the smaller stone fragments to be passed naturally through the urinary tract. This is typically performed with intravenous sedation or anesthesia and can be done on an outpatient basis. If the stone is not completely shattered or cannot be successfully passed following the procedure, a ureteral stent or additional procedures may be needed. Recovery time is short, and most people can resume normal activities in a few days.
    • Laparoscopic stone removal is typically used in patients with unusual kidney anatomy, such as a calyceal diverticulum, or in combination with repair of a kidney that may have a congenital or acquired ureteropelvic junction (UPJ) obstruction. Rarely, if a patient has a non-functioning kidney resulting from stone disease, laparoscopic kidney removal (nephrectomy) may be performed.
    • Open stone surgery is rarely required and is usually reserved for the treatment of large stone burdens in kidneys with unusual anatomy that preclude a more minimally invasive approach.

Prevention

At NYU Urology, we take a proactive role in helping patients prevent recurrence of kidney stones.

Genetics, diet, fluid intake, work environment and even geographic location are all factors that may influence the formation of stones. Patients who are involved in stone prevention have fewer visits to emergency rooms and hospitals, fewer treatments and procedures to remove stones, and spend less time away from work. One study demonstrates that stone prevention can save $1,000–$3,000 per year per patient over a five-year period.

If you’ve had more than one kidney stone, you are likely to form another, so prevention is very important. To prevent stones from forming, we first must determine the cause. This is done by stone analysis, blood tests, and 24 hour urine collections. Other causative factors will also be investigated, including medical history, medications, occupation, and dietary habits.

Based on these results, lifestyle changes, dietary changes and possible medical therapy may be recommended for the prevention of future stones.

Further reading

American Urological Association:

Make an appointment with an NYU urologist who treats kidney stones

Related publications by NYU urologists

  • Shah O, Assimos DG. Management of patients with hyperoxaluria, in Urinary Stone Disease: The Practical Guide to Medical and Surgical Management. (Stoller ML, Meng MV, eds.), Humana Press. Totowa, NJ. 2006.
  • Lipkin M, Shah O. Role of alpha blockers in nephrolithiasis. Rev Urol, 8(Suppl 4): S35-42, 2006.
  • Shah O, Assimos DG. Complications of Stone Removal, in Smith’s Textbook of Endourology (2nd edition) (Smith AD, Badlani GH, Bagley DH, Clayman RV, Jordan GH, Kavoussi LR, Lingeman JE, Preminger GM, Segura JW, eds.) Quality Medical Publishing, St. Louis, MO. 2006.
  • Kaufman J, Shah O. Lower pole renal calculi: Choosing the optimal management strategy. Contemporary Urology, 24-37, December 2006.
  • Shah O, Assimos DG, Holmes RP. Genetic and dietary factors in urinary citrate excretion. J Endourol, 19: 171-176, 2005.
  • Matlaga BR, Hodges S, Shah O, Passmore L, Hart LJ, Assimos DG. Percutaneous nephrostolithotomy: Predictors of length of stay. J Urol, 172: 1351-1354, 2004.
  • Shah O, Assimos DG. Quartz stones: spurious vs. iatrogenic? Urology, 64: 808-809, 2004.
  • Matlaga BR, Shah O, Zagoria RJ, Dyer RB, Streem SB, Assimos DG. CT-guided access for percutaneous nephrostolithotomy. J Urol, 170:45-47, 2003.
  • Shah O, Matlaga B, Assimos DG. Selecting treatment for distal ureteral calculi: Shock wave lithotripsy vs. ureteroscopy. Rev Urol, 5(1): 40, 2003
  • Matlaga BR, Shah O, Assimos DG. Drug-induced urinary calculi. Rev Urol, 5(4):227-231, 2003.

    • Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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