What Are Urinary Calculi or Kidney Stones?

Dr. Kulendran Sivapragasam, Consultant Urologist at Columbia Asia Hospital, Bukit Rimau, Kota Kemuning, Selangor, MALAYSIA provides an overview on stones formed in our kidney and their potential journey in our urinary system.

Dr Kula

Calculi or stones are hard masses or crystals that form in the urinary system. They can be found anywhere in the urinary system such as the kidney, ureters, urinary bladder or even in the urethra. They are often the most common kind of urological problem that an urologist sees and treats.

What causes stones?

Stones can form due to various reasons. They can form due to infective causes and non-infective causes. Non-infective causes can be due to metabolic disease, hereditary causes, and abnormal anatomical structure of the urinary system or even due to certain types of medicines. They can also form when the urine lacks the normal inhibitors of stone formation. Inadequate fluid intake can also cause stone formation especially in those individuals who are already susceptible to stones due to other reasons.

Risk Factors
• Dehydration (decreased urine flow) increases risk significantly
• Obesity
• Family history
• Past history of kidney stones
• Sex (the incidence in women is increasing)
• High-protein, salt, or glucose diet
• Inflammatory bowel diseases (can cause increase calcium absorption)
• Other medical conditions (hyperparathyroidism can cause increase calcium absorption)

What symptoms can they cause?

The symptoms vary according to the size and location of the stone or stones. These symptoms include pain in the flanks that can be very severe and blood in the urine. The pain can be dull and aching as in the case of kidney stones and it can be excruciating and colicky in the case of stones in the ureter. They can be accompanied with nausea and vomiting. Sometimes when the stone is in the ureter and very close to the bladder it can make a person feel like wanting to urinate all the time. If fever and chills accompany these symptoms, it can indicate an infection. In such cases one has to contact a doctor immediately.

How are they diagnosed?

The doctors will usually do blood and urine tests. This will help diagnose the presence or absence of infection and also assess kidney function among other things. The next will be to get diagnostic imaging done. The best form of which is a non-contrast-enhanced computed tomography (NCCT). Ultrasound, intravenous urography and plain x-rays can also be used but they do not give as much information as NCCT does and NCCT can help diagnose smaller stones that may be missed by the other modalities.

Testing for Kidney Stones:

Complete health history assessment and physical examination
• Blood tests for calcium, phosphorus, uric acid and electrolytes
• Urinalysis to check for crystals, bacteria, blood and white cells
• Blood urea nitrogen (BUN) and creatinine to access kidney function
• Examination of passed stones to determine type
• Abdominal x-rays, ultrasound of the kidney, ureter and bladder or a non contrasted CT to look at the size, site and number of the calculi and to look for signs of obstruction.

How are they treated?

Pain which can be severe will be treated with adequate painkillers. Existing infection if any will be treated with antibiotics. Any obstruction in the urinary system will have to be relieved especially if there is infection. Treatment of the stones depends on the type, location, size and number of the stones. Factor such as urinary system obstruction, presence of infection, existing kidney function and other co-existing medical conditions such as diabetes also need to be taken into account in choosing the treatment of choice. Medication which can help to dissolve certain types of stone in the kidney or help the stone in being expulsed from the ureter can be tried. In kidney stones as well as stones in the ureter, extracorporeal shock wave lithotripsy (ESWL) is a treatment option. Another common treatment option the urologist may use is rigid or flexible endoscopes, such as the ureteroscope. These are introduced into the urinary tract and the stones removed or broken into smaller pieces that can be removed or flushed out with the urine. Surgical removal has now become less common with the advances in endourological procedures.
How can they be prevented?

kidney stone

For most types of stones, fluid intake should be increased to maintain urine output at 2-3 litres per day. Salt intake and the amount of meat and animal protein eaten should be reduced. Dietary restrictions defer depending on the composition of stones. Calcium levels should be maintained. In certain types of stones medication will be prescribed to help prevent recurrence.

Key Points
85% of urinary calculi are calcium, mainly calcium oxalate; 10% are uric acid; 2% are cystine; and most of the remainder is magnesium ammonium phosphate (struvite).
• Larger calculi are more likely to obstruct; however, obstruction can occur even with small ureteral calculi (i.e. 2 to 5 mm).
• Symptoms include hematuria, symptoms of infection, and renal colic.
• Test usually with urinalysis, imaging, and if the calculus can later be retrieved, determination of calculus composition.
• Give analgesics and drugs to facilitate calculus passage (eg, α-receptor blockers) acutely and remove calculi that cause infection or persist endoscopically.
• Decrease the risk of subsequent calculus formation by treating with measures such as thiazide diuretics, K citrate, increases in fluid intake, and decreases in dietary animal protein, depending on calculus composition.
MSD Manual by Glenn M. Preminger, MD

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