Kidney Stones

By Talsk Research's Physician Group

Overview

Kidney stones are small, hard crystalline particles that form in the kidney or urinary tract (excretory system), which removes extra fluids and waste products from the body in the form of urine. The kidneys are two bean-shaped organs located below the ribs toward the middle of the back, one on each side of the spine. Most stones start forming in the kidney, but can travel along with the urine to other parts of the excretory system like the ureter (the tube leading from the kidney to the bladder) or to the bladder itself, where they can get larger.

Kidney stones also known as renal calculi are made up of various combinations of chemicals. The most common type of stone contains calcium, sometimes in combination with either oxalate or phosphate. Chemicals like uric acid and amino acid cystine can also form stones in the urinary tract. These chemicals are a part of a person’s normal diet and constitute important parts of the body, such as bones and muscles. When these stones are small, they pass through urine unnoticed. However, if they are larger, they can result in sudden severe pain in the back, abdomen, or groin area sometimes associated with nausea and vomiting. Some larger stones can even block the flow of urine. Discoloration of urine or flank blood in urine is also a common symptom. Men are more likely to develop kidney stones than women. Most patients with kidney stones are treated medically while surgical treatment is used to remove larger stones.

Risk Factors

• Family history or personal history of kidney stones

• Adults between 20 to 40 years; the risk is higher as age increases. However, stones can occur at any age

• Men are more likely to develop kidney stones than women

• People with high body mass index, increased waist size and weight gain increase the risk

• Excessive meat, calcium or sodium in the diet

• Chronic diseases such as diabetes and high blood pressure

• Pregnancy can increase the risk of stone formation due to the slow movement of the ureters

• Specific medications and medical conditions discussed below.

Causes

The main cause of stone formation is concentrated urine. The normal urine does contain salts like calcium, uric acid, cystine, or xanthine. However, if there is not enough urine, or if unusually high amounts of crystal-forming salts are present, they no longer dissolve completely, and can form crystals. This may occur due to various reasons like:

• Not drinking enough liquids or dehydration (due to excessive loss of fluids from the body by excessive sweating or vomiting or diarrhea) lowers the urine volume or disorders such as hyperoxaluria, hypercalciuria increase the concentration of the salts in the urine, both of which increase the risk for calcium oxalate stones which compromise 70% of all kidney stones.

• Persistent high levels of uric acid in the blood in patients with conditions like gout, intestinal disorders leading to chronic diarrhea or those with excess animal protein in their diet increase the risk for uric acid stones.

• Medical conditions like hyperparathyroidism (which causes bones to lose calcium in the urine) and renal tubular acidosis increases the risk for calcium phosphate stones

• Urinary tract infections increase the risk for struvite stones

• Cystinuria, a genetic disorder increases the chance of cystine stones.

• Certain medications (e.g. chemotherapy, drugs to treat HIV, excessive vitamin D supplements) also can lead to kidney stones

Symptoms

The symptoms may vary from person to person. However, some of the common symptoms include:

• Sudden, excruciating cramping or colicky pain in the side of abdomen, or low back or groin sometimes so severe that it can be associated with nausea and vomiting

• Flank pain or pain radiating from hip to legs

• Persistent urge to urinate

• Nausea

• Vomiting

• Flank blood in urine

• Discoloration of urine

• Fever and chills (if there is infection)

• Foul smelling or cloudy urine

Diagnosis

Sometimes during a routine medical exam ‘silent’ or surprise stones, which have not caused any symptoms, may be found on the X-ray. If the stones are small, they will often come out of the body unnoticed. After a detailed history, the doctor may examine you to check the specific location of your pain. Collecting the stone passed in the urine will help diagnose the type of stone and the diagnostic tests can be tailored accordingly. The following tests may be employed to help diagnose and treat kidney stones appropriately:

• X-ray of the kidney and urinary tract: to detect the presence and location of the stones

• Urine tests: to measure the levels of chemicals that prevent or promote stone formation in the urine and check for infection

• Microscopic examination: the kidney stones obtained from the urine sample are examined under a microscope to identify the substance forming the stone

• Blood tests: to measure the levels of calcium, phosphate, uric acid, urea, nitrogen, creatinine, and sometimes parathyroid hormone levels

• Lately Helical CT scans are replacing Intravenous pyelograms in which a special dye injected into the vein after which X-rays are taken as the dye enters the kidneys and travels down the urinary tract to check for any abnormalities

• Magnetic resonance imaging: may be preferred for pregnant women, as there is no radiation involved with this procedure

• Ultrasound is usually used in pregnant women to eliminate the risk of radiation exposure to the fetus.

Treatment

The main aim of the treatment is to relieve symptoms and prevent further recurrence of kidney stones. Treatment usually depends on the type of stone and the severity of the symptoms. Medicines that help control the alkaline or acid content of the urine, the key factor in stone formation, may be prescribed by the caregiver. The choice of the medications also depends on the presence of associated medical conditions like heart problems or diabetes. People with severe symptoms might need to be hospitalized for further treatment and follow-up.

Medical Treatment

• If the stone is small, increasing the amount of liquids and managing the diet to change the ph and the chemical composition of the urine may help pass the stone along with the urine without requiring any other treatment. However, some people might need to be given fluids through a vein (intravenous) especially when oral intake is affected by nausea or vomiting.

• For severe pain, narcotic painkillers or non-steroidal anti-inflammatory drugs may be prescribed

• The type of medicines prescribed usually depends on the type of stone. Medications may include:

  • Allopurinol (for uric acid stones)

  • Antibiotics (for struvite stones) to prevent urinary infection

  • Diuretics (to help remove excess fluids in the body)

  • Sodium bicarbonate or sodium citrate (to make the urine more alkaline, which may help in dissolving certain stones)

Surgical Treatment

Surgery may be needed if the renal stone

• is too large

• blocks the flow of urine

• causes recurrent infection in the urinary tract

• has increased in size as noticed on follow-up

• causes constant bleeding

• has started damaging the kidney

• fever and chills indicate an active infection and steps have to be taken not only to relieve the infection but also to remove or bypass the stone for free urine flow and if they are not done promptly the condition can become life threatening with the infection spreading to other parts of the body via blood.

Different types of surgical methods are available and the caregiver may choose any of the following depending on the condition:

• Extracorporeal shock wave lithotripsy (ESWL) is the method used to remove smaller stones by breaking them down using electrical shock waves. Complications may occur with ESWL. Some patients have blood in their urine for a few days after treatment. Redness and minor discomfort in the back or abdomen from the shock waves can occur. To reduce the risk of complications, the doctor may advise to avoid taking medicines that affect clotting of blood for several weeks before treatment. Sometimes, the shattered stone particles cause minor blockage, as they pass through the urinary tract and cause discomfort. In some cases, the doctor may insert a small tube called a stent (a device or mold of a suitable material, used to hold a tube in place) through the bladder into the ureter to help the fragments pass. Larger stones might need more than one of these treatments.

• Percutaneous nephrolithotomy is often the method used to remove larger stones, if the stone is located where effective use of ESWL is not possible

• In this procedure, a tiny slit in the skin and layers underneath creates a tunnel directly into the kidney. And the surgeon locates and removes the stone using an instrument called a nephroscope

• For larger stones, a type of ultrasonic waves may be used to break the stone into smaller pieces which are easier to eliminate

• By this method, the surgeon is able to remove some of the stone fragments directly instead of expectantly waiting for them to be passed naturally in the urine

• There might be a small tube called a nephrostomy tube left after the procedure during the healing process which is removed a few days or weeks after surgery

• Hospital stay might be required until recovery

• Standard open surgery (nephrolithotomy) may be needed if other methods do not work or are not possible

Prevention

• Persons with history of kidney stones are recommended to increase their intake of liquids to enable passing about 2.6 quarts (2.5 liters) of urine a day

• Dietary recommendations for reducing the risk of calcium stone formation include increasing fluid intake, restricting salt and protein intake (choosing non-animal protein sources such as nuts and legumes) and increasing potassium and phosphate intake

• If there is a tendency to form calcium oxalate stones, restricting foods rich in oxalates such as rhubarb, beets, okra, spinach, swiss chard, sweet potatoes, tea, chocolate, and soy products may help

• Continue eating calcium-rich foods, but calcium supplements have to be used cautiously. The calcium in the food does not increase the risk for kidney stones; however, calcium supplements can increase the chance of kidney stone formation.

• Fiber-rich foods may be beneficial, as some of them may contain compounds that help protect against kidney stone formation

• Uric acid stones can be prevented by decreasing the intake of protein while increasing fluid intake

Credits: The copyright to the image used above belongs to LifeART, Wolters Kluwer Health, Inc.- Lippincott Williams & Wilkins. All rights reserved.

References

• US National Library of Medicine

• http://www.nlm.nih.gov/medlineplus/ency/article/000458.htm

• NHS Choices

• http://www.nhs.uk/Conditions/Kidney-stones/Pages/Complications.aspx

• National Kidney & Urologic Diseases Information Clearinghouse (NKUDIC)

• http://kidney.niddk.nih.gov/Kudiseases/pubs/stonesadults/#treatment

• Parkland Medical Center

• http://www.parklandmedicalcenter.com/CustomPage.asp?guidCustomContentID=%7BEDBBE438-458F-441A-8AAD-07BF245F4D15%7D

• Mayo Clinic

• http://www.mayoclinic.com/health/kidney-stones/DS00282/DSECTION=risk- factors

• University of Maryland Medical Center

• http://www.umm.edu/patiented/articles/dietary_factors_lifestyle_measures_used_prevention_of_kidney_stones_000081_8.htm

• http://www.umm.edu/patiented/articles/what_causes_kidney_stones_000081_3.htm

• Cleveland Clinic

• http://my.clevelandclinic.org/disorders/stone_disease/urology_overview.aspx

• Emedicine Health

• http://www.emedicinehealth.com/kidney_stones/page6_em.htm

• Health Central

• http://www.healthcentral.com/encyclopedia/408/137.html

All information provided above is for basic awareness and education purposes only and should not be used for diagnosis or treatment of any medical condition under any circumstance. Please consult a licensed medical professional for these purposes. In case of medical emergency please call 911.

Copyright 2011 Talsk Research Inc. All rights reserved.