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Understanding Kidney Stones

Kidney stones form in the kidney. Urine contains many dissolved minerals and salts, which at high levels can form stones [1]. The kidney stones can start small but can eventually grow larger in size. Most stones stay in the kidney without any problems. However, sometimes the kidney stone can travel down the ureter, the tube between the kidney and the bladder [1]. The stone can be passed out of the body in urine if the stone reaches the bladder. If the stone becomes lodged in the ureter, on the other hand, it blocks the urine flow from that kidney which causes pain [1]. These are known as Ureteral [1].


What are Kidney stones made up of?

  1. Calcium stones (80 percent of stones)- Having too much calcium in the urine, raising the risk of calcium stones [1].

  2. Uric acid stones (5-10 percent of stones)- Uric acid is a waste product that comes from chemical changes in the body. Uric acid crystals do not dissolve well in acidic urine and instead will form a uric acid stone [1].

  3. Struvite/infection stones (10 percent of stones)- These stones are related to chronic urinary tract infections (UTIs). Some bacteria make the urine less acidic and more basic or alkaline [1]. Magnesium ammonium phosphate (struvite) stones form in alkaline urine [1].

  4. Cystine stones (less than 1 percent of stones)- Cystine is an amino acid that is in certain [1]. Cystinuria (too much cystine in the urine) is a rare, inherited metabolic disorder [1]. When high amounts of cystine are in the urine, it causes stones to form [1].

Causes

  • Low Urine Volume- Low urine volume comes from dehydration or loss of body fluids from hard exercise, working or living in a hot place, or not drinking enough fluids [1]. When urine volume is low, urine is concentrated and dark in color. Concentrated urine means there is less fluid to keep salts dissolved. “Adults who form stones should drink enough fluid to make at least 2.5 liters (⅔ gallon) of urine every day. On average, this will take about 3 liters (100 ounces) of fluid intake per day” [1].

  • Diet- One of the more common causes of calcium kidney stones is high levels of calcium in the urine. Reducing urine calcium levels by decreasing your sodium (salt) intake may help. “Too much salt in the diet is a risk factor for calcium stones. This is because too much salt is passing into the urine, keeping calcium from being reabsorbed from the urine and into the blood” [1].

  • Bowel Conditions- E.g. Diarrhoea may result in loss of large amounts of fluid from the body, lowering urine volume [1].

  • Obesity- “Obesity is a risk factor for stones. Obesity may change the acid levels in the urine, leading to stone formation” [1].

  • Other medical conditions- Conditions such as high blood pressure, diabetes, and cystinuria may increase the risk for kidney stones [1].


Symptoms

Common symptoms of kidney stones include sharp, cramping pain in the back and side [1]. This pain moves to the lower abdomen. It can come and go as the body tries to get rid of the stone.

Other signs of a kidney stone include [1]:

  • A feeling of intense need to urinate.

  • Urinating more often or a burning feeling during urination.

  • Urine that is dark or red due to blood. Sometimes urine has only small amounts of red blood cells that can’t be seen with the naked eye.

  • Nausea and vomiting.


Diagnosis of a kidney stone starts with a medical history, physical examination, and imaging tests.

  • Imaging tests: to know the exact shape and size of the stone. This can be done with a high-resolution CT scan [2]

  • Urine testing: to test for levels of stone-forming minerals and stone-preventing substances [2].

  • Blood testing: to test your blood for calcium, phosphorus, and uric acid [2].

  • Stone analysis: The stone will be analysed after it comes out of your body in order to determine the cause and a plan for prevention [2].

Prevention

  • Most importantly by increasing fluid intake for more than 2 liters per day (; eight to 12 cups of fluid per day ) [3][4]

  • Control protein intake; – usually protein is restricted to 60g/day to decrease urinary excretion of calcium and uric acid; [1][4]

  • A sodium intake of three to four g/day is recommended. Table salt and high-sodium foods should be reduced [1][4].

  • Avoid intake of oxalate-containing foods (e.g. spinach, strawberries, tea, peanuts, and wheat bran) [1][4]

  • Avoid activities leading to a sudden increase in environmental temperatures that may cause excessive sweating and dehydration; and

  • Contact your primary health care provider at the first sign of a urinary tract infection [4]

The treatment for a kidney stone depends on the size of the stone, what it is made of, whether it is causing pain and whether it is blocking your urinary tract.

If your test results show that your kidney stone is small, your treatment may include pain medicine and increased fluid intake to help push the stone through your urinary tract [3].


Other medications Include [1]:

  1. Thiazide diuretics- lowers urine calcium

  2. Potassium citrate- makes the urine less acidic

  3. Allopurinol- lowers the levels of uric acid

  4. Acetohydroxamic acid (AHA)- makes the urine unfavorable for struvite stones to form

  5. Cystine-binding thiol drugs- bind to cystine in the urine and reduces the likelihood of crystallization

If your kidney stone is large, or if it is blocking your urinary tract, additional treatment may be necessary. One treatment option is shock wave lithotrips [3]. “This treatment uses shock waves to break up the kidney stones into small pieces. After the treatment, the small pieces of the kidney stone will pass through your urinary tract and out of your body with your urine” [3].


Another treatment option is ureteroscopy. In this treatment, a long tool shaped like a tube is used to find and remove the stone or to find and break the stone into small pieces [3]. In rare cases, a surgery called percutaneous nephrolithotomy is needed to remove a kidney stone where a tube will be inserted directly into your kidney to remove the stone [1][4]

Percutaneous Lithotripsy (PCNL) is the best treatment for large stones in the kidney [1]. This involves making a half-inch incision (cut) in the back or side, just large enough to allow a rigid telescope (nephroscope) to be passed into the hollow center part of the kidney where the stone is located [1]. An instrument passed through the nephroscope breaks up the stone and suctions out the pieces [1]. The ability to suction pieces makes PCNL the best treatment choice for large stones.


Reference


1. Urology Care Foundation. Kidney Stones. What are Kidney Stones?. N.d. Available at: https://www.urologyhealth.org/urology-a-z/k/kidney-stones

2. National Kidney Foundation. Kidney Stones. N.D. Available at: https://www.kidney.org/atoz/content/kidneystones

3. American Kidney Fund. Fighting on all fronts. Kidney Stone Causes, Symptoms, Treatments, & Prevention. Updated 2017. Available at: https://www.kidneyfund.org/kidney-disease/kidney-problems/kidney-stones/

4. The Fiji Times. Frazana Murthey. Kidney Stones. 2021.


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