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Editors

KarriHelin
JukkaSairanen
HeikkiKoistinen

Urinary Calculi

Essentials

  • The treatment of an acute attack should be started with an intramuscular or intravenous NSAID, a combination of an analgesic and a spasmolytic, or an opioid at the health care facility that the patient first attends.
  • Bacterial culture of urine, chemical screening of urine and plasma creatinine should be done/checked.
  • The diagnosis should be confirmed with ultrasonography, in specialized care with CT scan. The vitality of the kidneys should be verified by follow-up.
  • Attempts should be made to retrieve the stone by straining urine and to analyze the composition of the stone.
  • Careful history taking and basic laboratory tests are indicated after the first attack, already, to lower the risk of recurrence.
  • In the case of recurrent urinary calculi, the aim should be to lower the concentration of lithogenic factors (primarily calcium and oxalate) in urine and to increase the urine citrate concentration (citrate prevents the formation of calculi).
  • Lifestyle modification is indicated in all patients, the most important change being drinking plenty of liquids so as to make the daily urine excretion 2 litres, at least.

Types of stones and their aetiology

Calcium stones

  • Account for about 80% of all urinary calculi
  • Aetiology
    • Various types of hypercalciuria
    • Hypocitraturia
    • Hyperuricosuria
    • Primary hyperparathyroidism Hypercalcaemia and Hyperparathyroidism
    • Hyperoxaluria (diet, inflammatory bowel diseases, after small bowel resection, associated e.g. with bariatric surgery)
    • Rare causes, e.g. renal tubular acidosis

Urate stones

  • Account for about 5-8% of all urinary calculi
  • More common in men
  • Often hereditary
  • Urine pH < 5.5 may rouse suspicion.
  • Gout is the cause in about 20% Gout and Pseudogout.

Stones associated with chronic upper urinary tract infection

  • Account for about 7-8% of all urinary calculi
  • Struvite (magnesium ammonium phosphate) stones
  • More common in women
  • Urinary tract infection caused by urease producing Proteus or Klebsiella
  • Alkaline urine, pH > 7

Cystine stones

Risk factors

  • Low fluid intake
  • Animal protein-rich diet
  • High salt intake
  • Low dietary calcium intake
  • Primary hyperparathyroidism, gout, obesity, malabsorption (e.g. small bowel resection in association with bariatric surgery)
  • Excessive sucrose or fructose intake
  • High-dose vitamin C and D supplementation; certain drugs (e.g. sulfa, topiramate, indinavir)

Symptoms and findings

  • Most common in middle-aged men
  • Intense, colicky pain radiates from the costal arch obliquely to the lower abdomen, groins, and genitals. Pain during urination is common if the stone is in the distal ureter.
  • Nausea and vomiting is common.
  • Microscopic, or rarely macroscopic, haematuria in 90%
  • History showing earlier episodes and cases in the family. Tendency for recurrences is 50% in 10 years.
  • Tenderness of the kidneys on percussion may be observed.
  • The patient has difficulty keeping still (in contrast to e.g. peritonitis where the patient prefers to lie still).
  • Most stones (75-90%) are radio-opaque but urate stones are typically radiolucent and therefore invisible, while cystine stones do not show up well on x-rays.
  • Small stones are poorly visible in plain x-rays.
  • Renal calculus may cause chronic back pain and infections.

Differential diagnosis

First aid for an attack Dipyrone for Acute Renal Colic Pain, Nsaids Versus Opioids and Non-Opioids for Acute Renal Colic, Fluids and Diuretics for Acute Ureteric Colic

Workup

First urinary stone attack

  • Gout, hypercalcaemia and urinary tract infection should preferably be excluded at the acute stage, already.
  • If the stone can be retrieved, it should be analyzed (urinary calculus analysis).
  • After the first attack, the following tests are indicated http://www.dynamed.com/condition/nephrolithiasis-in-adults-24#BLOOD_TESTS
    • basic blood count with platelet count
    • CRP
    • albumin-corrected calcium or ionized calcium
    • plasma creatinine
    • urate
    • chemical screening of urine and bacterial culture of urine
    • particle count in urine and blood gas analysis (venous Astrup), if available
  • Ultrasonography http://www.dynamed.com/condition/nephrolithiasis-in-adults-24#BLOOD_TESTS will show any hydronephrosis, for instance, and is the primary investigation in non-hospital care.
    • If the patient does not have hydronephrosis, the creatinine level is normal and there is no urinary tract infection, only follow-up is needed (see below).
    • The patient should be referred to specialized care if ultrasonography is not available, the pain does not stop, the patient has a urinary tract infection with fever, or has only one kidney, is pregnant, or has a recurrence.
  • Plain CT is often done as an emergency investigation in specialized care http://www.dynamed.com/condition/nephrolithiasis-in-adults-24#IMAGING_STUDIES.

Recurrent urinary stone attacks

  • More extensive investigations are usually done in specialized care if the risk of recurrence is high.
  • More extensive investigations are indicated if there are recurrent symptoms, a high stone load and strong family history.
  • Treatment is guided by stone analysis http://www.dynamed.com/condition/nephrolithiasis-in-adults-24#STONE_COMPOSITION_ANALYSIS and results from 24-h urine.
  • The tests are most reliable if done from two separate 24-h urine collections. The collection should be carried out 1-3 months after the stone attack with the patient following his/her normal diet.
  • Tests
    • Primary tests in 24-hour urine http://www.dynamed.com/condition/nephrolithiasis-in-adults-24#URINE_STUDIES
      • creatinine (normal result confirming that the collection was completed)
      • calcium
      • sodium
      • citrate
      • potassium
      • oxalate
      • urate
      • pH
        • Both very acid (pH HASH(0x2fd0288) 5.5) and very alkaline (pH HASH(0x2fcfe80) 6.7) urine predispose to formation of calcium stones.
        • Elevated pH > 5.8 in combination with metabolic acidosis may be a sign of renal tubular acidosis.
        • Urine pH may rise to a high level (> 7-8) for example in an infection caused by Proteus mirabilis.
    • The following tests should also be performed
      • serum ionized calcium, plasma parathyroid hormone and plasma inorganic phosphate
      • plasma sodium, potassium, creatinine
    • In addition, the following tests in 24-h urine should be performed, as necessary
      • magnesium
      • inorganic phosphate

Conservative treatment

  • Fluid intake should be increased to make the daily urine excretion 2 litres or more http://www.dynamed.com/condition/nephrolithiasis-in-adults-24#FLUID_AND_ELECTROLYTES.
    • Water, primarily, should be drunk at regular intervals throughout the day.
  • Animal protein intake should be reduced.
  • Salt intake should be reduced. The 24-h urine Na target is no higher than 80-100 mmol (85 mmol being equivalent to a salt intake of 5 g/day).
  • Sucrose and fructose intake should be reduced.
  • More vegetables and fruit should be eaten.
  • In patients with calcium oxalate stones and/or hyperoxaluria (oxalate >0.5 mmol in 24-h urine), vitamin C supplementation should be avoided, oxalate intake should be restricted and food high in oxalate (such as spinach, potatoes, rhubarb, nuts, almonds) should be avoided.
  • Dietary counselling by a dietitian
  • Dietary calcium intake should be normal, 800-1 200 mg/day.
    • Calcium restriction will increase the absorption of oxalate from the alimentary tract, predisposing the patient to recurrent urinary calculi.
  • For hyperuricaemia, a gout diet should be followed and allopurinol given, as necessary.
  • Any condition causing hypercalciuria (such as primary hyperparathyroidism, sarcoidosis, hypervitaminosis D) should be treated.
  • A thiazide diuretic reducing calcium excretion is often added to the treatment of idiopathic hypercalciuria (important to preserve normokalaemia, as hypokalaemia reduces citrate excretion).
  • In hypocitraturia, urine should be alkalized primarily with 1 080 mg potassium citrate (Acalka® , 1-2 tablets 2-3 times daily with meals) or, secondarily, with sodium bicarbonate (1 500 mg 3 times daily).
  • The aim of the intervention is to correct any abnormalities observed in initial tests (e.g. low urine volume, hypercalciuria, hyperoxaluria and/or hypocitraturia) http://www.dynamed.com/condition/nephrolithiasis-in-adults-24#PREVENTION_OF_STONE_RECURRENCE. Response to the intervention should be assessed in 2-3 months and subsequently according to clinical need, once a year, for example.
  • Urine should not be alkalized if the stone consists primarily of calcium phosphate or struvite, because alkalizing might in that case aggravate the disease.
  • Any urinary tract infection should be treated as indicated by resistance testing. Follow-up examinations are indicated and prophylactic medication Urinary Tract Infections is usually necessary for patients with infection stones.

Waiting for spontaneous passage of the stone

  • If the stone is less than 5 mm in size, you can wait for its passage through the ureter. This can be accelerated by abundant diuresis and physical activity.
  • If the stone can be treated conservatively, its passage should be checked in one month by ultrasonography.
    • However, a small stone of less than 3 mm need not be followed up if the patient is asymptomatic.
  • The patient should strain his/her urine so that passage of the stone can be confirmed.
  • Follow-up should be continued, as necessary (ultrasonography, creatinine) until the stone is found to have been passed and the patient is asymptomatic.
  • Spontaneous passage of a ureteral stone can be facilitated with alpha-blockers http://app.magicapp.org/#/guideline/2915 Alpha-Blockers for Treatment of Ureteral Stones (tamsulosin or alfuzosin), which have been found to facilitate the passage of stones larger than 5 mm, in particular. The treatment can be used in both male and female patients. Depeding on locally relevant guidelines, the preferred treatment for stones larger than 5 mm may be surgical removal (see below).

Surgical management

Urgent treatment

  • Urgent treatment is indicated if the stone obstructs the ureter http://www.dynamed.com/condition/nephrolithiasis-in-adults-24#DECOMPRESSION_OF_RENAL_COLLECTING_SYSTEM.
  • Emergency treatment is indicated if the obstruction is associated with a urinary tract infection.
    • If the patient has an infection, intravenous antimicrobials (1.5 g cefuroxime three times daily) should be started.
    • Release of infectious obstruction by insertion of a percutaneous pyelostomy tube by a radiologist or by endoscopic insertion of a ureteral catheter
    • If the stone caused by obstruction is in the area of the distal ureter, it can be removed by ureteroscopy even if there is an infection.

Non-urgent treatment

  • Stones exceeding 5 mm
  • Stones below 5 mm not passed during follow-up

ESWL (extracorporeal shock wave lithotripsy)

  • An extracorporeal method where an energy wave from an external source is directed to the stone
    • This is done under fluoroscopy if the stones are x-ray positive or under ultrasound guidance.
  • This is an outpatient procedure requiring analgesics and forced diuresis.
  • It can be used for renal stones below 20 mm in diameter and for x-ray positive stones in the ureter.
  • If the stone obstructs the urinary tract, percutaneous pyelostomy or a ureteral catheter may be needed during ESWL treatment.
  • Obesity reduces the efficacy of ESWL because the distance from the therapy head to the stone affects the results of treatment.

PCNL (percutaneous nephrolithotomy)

Ureteropelveoscopic removal

  • Laser is used to grind the stone into sand.

Endoscopes

  • Removal of ureteral stones by flexible or semirigid endoscopes is effective if the stones are less than 10 mm in size. Stones can be rapidly removed by endoscopy.
  • Stones can also be crushed either by laser or by a mechanical crusher head. The stone fragments can be drawn out by forceps or by an extractor basket/device.

    References

    • Sakhaee K, Maalouf NM, Sinnott B. Clinical review. Kidney stones 2012: pathogenesis, diagnosis, and management. J Clin Endocrinol Metab 2012;97(6):1847-60. [PubMed]
    • European Association of Urology Guidelines for Urolithiasis http://uroweb.org/guideline/urolithiasis/#4_1