Nephrolithiasis Medical Management

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NephrolithiasisMedical Management

• Common Ambulatory Topics
• Andrea L. Banks, MD
• April 1, 2008

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Roadmap

• Demographics
• Clinical presentation
• Methods of diagnosis
• Evaluation
• Treatment

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Clinical Case

• HPI
• A 34 year-old white man comes to your office
  complaining of severe left flank pain that began
  this morning. The pain comes and goes in waves.
  He also notes nausea and vomiting. He has not
  had any change in his urination. The pain has
  now resolved. He denies any fevers or chills.
• PMHx
• HTN
• Medications
• Atenolol

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Clinical Case (cont.)

• SHx
• Smoker
• Exam
• Afebrile, tachycardic
• Well-appearing, in no obvious pain
• Otherwise normal

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Demographics

• Estimated 5 prevalence in general population
• More prevalent in men
• Risk factors
• Family history
• Gout
• Primary hyperparathyroidism
• Prolonged immobilization
• RTA
• Excess dietary meat
• Excess dietary sodium

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Stone Composition

• Calcium oxalate 70
• Calcium phosphate 5-10
• Uric acid 10
• Struvite 15-20
• Cystine 1

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Clinical Presentation

• Pain
• Paroxysms of severe pain lasting 20-60 minutes
• Originates in flank and radiates to groin
• Location may vary as stone migrates
• Hematuria
• Gross or microscopic
• Nausea/vomiting
• Dysuria and urgency (less common)

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Diagnosis

• Non-contrasted helical CT scan
• Gold standard
• Specificity nearly 100
• Also detects signs of urinary tract obstruction
• Ultrasound
• Misses small stones and ureteral stones
• Test of choice in pregnancy
• KUB
• Misses radiolucent stones (uric acid)
• IVP

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KUB - Calcium Oxalate Stone
Amer Fam Phys, 2006 74(1) 86-94.
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Non-constrast CT scan
Amer Fam Phys, 2006 74(1) 86-94.
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Stone Size

• 90 pass spontaneously
• Alpha-blockers can increase chance of passage
• 10 mm

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Acute Treatment

• Increase fluid intake to goal of 2 L urine output
  per day
• Pain control
• NSAIDs, opioids
• Hospitalization if severe

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Returning to the Clinical Case

• Labs
• CBC normal
• BMP normal, calcium normal
• U/A few RBCs
• Imaging
• Non-constrast CT showed a 4mm non-obstructing
  calculus in the left ureter

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Returning to the Clinical Case

• You send the patient home with PO pain medication
  and instructions to increase fluid intake. You
  tell him the stone should spontaneously pass.
• He calls the office the next week reporting he is
  feeling well.

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Work-up the first episode

• Confirm the diagnosis
• Radiographic evidence of stone
• Comprehensive metabolic evaluation is not cost
  effective after first episode
• Consider straining urine for stone
• Composition analysis
• Consider minimal labs
• Urinalysis, routine electrolytes, calcium (iPTH
  if Ca is elevated)

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Prevention after the first episode

• Increase urine output to 2 L per day
• Reduces urinary saturation of stone-forming salts
• Water is most important orange juice, coffee,
  and alcohol have been proven beneficial
• Dietary modifications
• Calcium
• Should not restrict calcium as it binds oxalate
  in the gut
• Decrease sodium intake
• Enhances calcium reabsorption
• Decrease meat intake
• Protein intake decreases urinary pH and increases
  uric acid

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Back to the case. . .

• Your patient returns one year later with
  complaints that he is passing another kidney
  stone.
• Non-constrast CT confirms the diagnosis.
• The acute episode resolves with conservative
  management.
• He asks what can be done to prevent further
  episodes.

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Work-up recurrent episodes

• Relapse rate of 50 in first 5-10 years after
  first episode
• Strain urine for stone retrieval
• Composition analysis
• Laboratory data
• Calcium, bicarbonate, creatinine, chloride,
  potassium, magnesium, phosphate, uric acid, BUN
• iPTH and vitamin D in hypercalcemic patients

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Work-up recurrent episodes

• 24-hour urine collections for
• Volume
• pH
• Calcium
• Creatinine
• Sodium
• Phosphate
• Citrate
• Uric acid
• Cystine
• Oxalate

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Calcium oxalate stones

• Hypercalciuria
• Primary hyperparathyroidism
• Intestinal hyperabsorption
• Idiopathic
• Treat with thiazide diuretics (increases Ca
  reabsorption in distal tubule)
• Decrease sodium intake
• Hypocitraturia (citrate inhibits calcium salt
  formation)
• RTA
• Idiopathic
• Treat with potassium citrate
• Hyperoxaluria
• Enteric hyperabsorption
• Decrease oxalate intake, increase calcium intake
  (binds enteric oxalate)

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Uric acid stones

• Hyperuricosuria
• Gout
• Low urinary pH
• Malignancy
• Treatment
• Allopurinol for hyperuricemia
• Potassium citrate to raise urinary pH

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Struvite stones

• Consist of magnesium, ammonium, and calcium
  phosphate
• Not associated with metabolic abnormalities
  intrinsic to the patient
• Recurrent UTI with urea-splitting organisms
• Proteus
• Ureaplasma

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Staghorn Calculus
Amer Fam Phys, 2006 74(1) 86-94.
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Cystine stones

• Autosomal recessive disorder leading to decreased
  cystine resorption in the kidney
• Often first presents in childhood
• Hydration, urine alkalinization, cystine binders

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Back to the case. . .

• Stone analysis
• Calcium oxalate
• 24-hour urine
• Hypercalciuria
• Treatment
• Continue increased fluid intake
• Add thiazide diuretic
• Decrease sodium intake

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When to refer to Urology. . .

• Outpatient
• Stone 10 mm
• Failure to pass symptomatic stone after
  conservative management
• Shock wave lithotripsy
• Ureteroscopic lithotripsy
• Percutaneous nephrolithotomy
• Laparascopic stone removal

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When to refer to Urology. . .

• Urgent inpatient
• Bilateral obstructing stones
• Intractable pain
• Urosepsis
• Acute renal failure
• Anuria

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Take home points

• Calcium oxalate stones are the most common type
• Non-contrast CT is test of choice for diagnosis
• Increase fluid intake for acute treatment and
  prevention
• Only limited evaluation necessary after the first
  episode

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References

• Kidney stones pathophysiology and medical
  management. Lancet 2006 367 333-44.
• Medical management of common urinary calculi.
  Amer Fam Phys, 2006 74(1) 86-94.
• Medical management of stone disease. Curr Opin
  Urol, 2003 13 229-233.
• Pathophysiology and management of calcium stones.
  Urol Clin N Am, 2007 34 323-334.
• Management of kidney stones. BMJ 2007 334
  468072.
• The contemporary management of renal and ureteric
  calculi. BJU 2006 98 1283-1288.
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