Kidney Stones

What are kidney stones?

  • Kidney stones are hard stones that can form within the collecting system of the kidney (calyces and renal pelvis).  They may remain within the kidney indefinitely or pass into the ureter (tube connecting the kidney to the bladder).  Usually, it is when the stones pass into the ureter that they cause pain due to obstruction.  The stones may pass from the ureter into the bladder where they are usually passed in the urine.
  • Kidney stones are common in Australia.  The lifetime risk of developing a kidney stone is up to 10%.  The risk is lower in females

Why do kidney stones form?

  • Kidney stones form due to an excess of certain chemical elements in the urine compared to the volume of urine produced.
  • Dehydration, therefore is the most common cause of stones.  When fluids consumed are low, the urine output/volume is subsequently low and stones are more likely to form
  • There are many other metabolic conditions that increase the risk of stones.  Ultimately these result in increased levels of certain elements within the urine. These include:
    • Hypercalciuria – high calcium level in urine
    • Hyperoxaluria – high oxalate level in urine
    • Hyperuricosuria – high uric acid level in urine
  • Conditions that may cause high levels of these elements in the urine include:
    • Excess consumption of oxalate containing foods
    • Gout
    • Sedentary lifestyle/immobilization Obesity
    • Inflammatory bowel disease
    • Renal Tubular Acidosis I
    • Sarcoidosis
    • Hyperparathyroidism
    • Medullary sponge kidney
    • Adult Polycystic Kidney disease
    • Cystinuria – genetic condition resulting in high levels of cysteine in urine
    • Medications that may increase stones include
      • High doses of Vitamin C & D
      • Some HIV medications
      • Frusemide
  • Other conditions that increase the risk of stone formation include:
    • Urinary tract infections
    • Some anatomical abnormalities within the urinary tract

What are the symptoms of kidney stones?

  • Kidney stones usually don’t cause many symptoms when they remain in the kidney, however they may cause intermittent flank pain, blood in the urine (haematuria) or urinary tract infections
  • When the stones pass into the ureter they can cause severe flank pain that can radiate to the groin region or scrotum in males.  This pain is often described as some of the most severe people experience
  • Other symptoms may include:
    • Blood in urine (haematuria)
    • Infection: fever, burning of urine
    • Nausea & vomiting

How are kidney stones diagnosed?

  • A CT scan of the kidneys and ureters (CT KUB) is the best test to detect stones.
  • The scan will provide information on the number of stones, their size and location
  • Stones may also be detected on an ultrasound of the kidneys or a plain Xray, however these are less sensitive than a CT and can easily miss stones
  • In addition to X-rays, a urine test will be required to rule out a urinary tract infection, as well as baseline blood tests including kidney function tests

If a kidney stone is diagnosed, what treatment will be required?

  • There are numerous ways to treat kidney stones, most of which are minimally invasive.
  • Factors which will determine what treatment is required include:
    • Number of stones
    • Size of stones
    • Location of stones
    • Presence of infection
    • Type/composition of stone – if known
    • Patient preference

What are the treatment options for stones located within the kidney (for details on each procedure, see Urological procedures explained):

  • Observation: for small (usually <3-4mm) asymptomatic stones, observation is an option.  This usually involves a combination of regular x-rays or ultrasound to ensure the stones are not increasing in size as well as implementation of stone prevention techniques (see stone advice info sheet)
  • ESWL – Extra corporeal shock wave lithotripsy
    • This minimally invasive option involves the use of shock/sound waves to target the stone resulting in fragmentation.  The small fragments are then passed
    • The procedure is usually performed under sedation or a “light” general anaesthetic
    • If the stone size is large (>1.5cm) then a ureteric stent may be placed prior to ESWL to ensure the stone fragments pass without obstruction
    • ESWL is less effective for large stones (>2cm), very hard stones (cysteine) or stones located in the lower part of the kidney as fragments in this area are more difficult to pass
  • Ureteropyeloscopy & laser lithotripsy
    • This involves the passage of a small telescope directly into the kidney to visualise the stone. A small laser fibre is then used to fragment the stone into very small fragments/dust.
    • A ureteric stent will usually be left for a week or so after the procedure
    • Although more invasive than ESWL, this technique is more effective at treating larger and multiple stones than ESWL.  It also enables stones in the lower part of he kidney to be relocated with a basket into positions where the stone is more effectively fragmented and passed
  • PCNL – Percutaneous Nephrolithotomy
    • This technique is generally reserved for large stones within the kidney (>2cm)
    • It involves directly accessing the kidney with a telescope via a skin puncture in the back/lumbar region
    • The stone is visualised with the telescope and a combination of ultrasound and a small “jack hammer” type device (Lithoclast) is used to fragment the stone.
  • Open/laparoscopic procedures:
    • Fortunately, open or key hole surgery is rarely required for kidney stones these days
    • Occasionally if the stone is very large or complex may require open surgery
    • If the effected kidney has very poor function, then sometimes a nephrectomy (removal of the whole kidney) is the best option.  This can usually be performed laparoscopically
  • Dissolution therapy
    • This is an option only for some types of stones (uric acid stones)
    • Medication will be prescribed to
      • Reduce the uric acid levels in the blood/urine (Allopurinol)
      • Alter the pH of the urine to help dissolution (Ural, Potassium Citrate)
      • A significant increase in water consumption is also required
      • Dissolution is a reasonable option for smaller asymptomatic stones but is not a good option if the stones are causing symptoms, as dissolution is a slow process.

What are the treatment options for stones within the ureter?

  • These stones usually produce severe pain (renal colic) and more urgent treatment may be required.
  • Pain relief options for renal colic include (usually used in the following order):
    • Paracetamol
    • Anti-inflammatories e.g. Neurofen, Indocid, Voltaren
      • Suppositories are often the most effective
      • Panadeine Forte
      • Endone/ oxycodone
      • Morphine
  • Conservative passage of stone including medical expulsive therapy (MET):
    • This is an option if all of the following exist:
      • Pain is easily controllable with oral medications
      • No signs/symptoms of infection (no fever)
      • Kidney function is normal
      • Size of stone allows reasonable chance of spontaneous passage (usually <6mm)
      • If the above factors exist, then a trial of conservative treatment is possible.  Usually, a medication (Tamsulosin – Flomaxtra) will be prescribed, which increases the chances of spontaneous passage
      • Usually a period of up to 2-3 weeks may be given to determine if the stone passes
      • Follow up x-rays/ CT will be required
      • If conservative treatment is elected, it is imperative to have a follow up Xray to ensure the stone has passed.  A retained stone can result in kidney loss (non functioning kidney) if left untreated
  • Ureteric stent (see Urological Procedures explained)
    • A stent may need to be placed if:
      • There are signs of infection
      • Pain is persisting
      • Stone size is large and unlikely to pass spontaneously
      • The stent will not remove the stone, it bypasses the stone and allows urine to drain around the stone.  This will minimise the chances of infection and recurrent severe pain
      • The stent will allow the ureter to dilate (widen) which allows for easier access in the future to remove the stone
  • Ureteroscopy and laser lithotripsy (see Urological Procedures explained)
    • A small telescope will be passed into the ureter to visualise the stone.  A small laser fibre will be used to fragment the stone. Any large fragments can be removed with a small basket via the telescope

After my stones have all been removed, how can I prevent future stones?

  • If the stones were removed surgically, often a sample will be sent for analysis to determine the type of stone. This may help determine if any preventative/ lifestyle modification can be implemented to prevent future stones
  • In most cases, the best way to prevent future stones is to increase the amount of fluids (water) in your diet.  For details see: Patient resources – Stone prevention advice sheet

If you are a recurrent stone former, or have a large amount of stones, more detailed tests will be ordered. This involves a combination of blood tests as well as a 24hour urine collection to check levels of stone elements in the urine.