Stop

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Stoplet Me A-cyst You
A Case Study about Cystinuria by Amy Albright
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Patient History

• 57 year old woman with history of renal problems
• Patient hospitalized upon urgent referral from
  doctors office
• Urinalysis was performed

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Urinalysis Results

• Test Patient Result Reference Range
• Color Yellow
• Clarity Cloudy
• Glucose neg
  (negative)
• Bilirubin neg
  (negative)
• Ketones neg
  (negative)
• Sp. Gravity 1.021
  (1.005-1.030)
• Blood 2
  (negative)
• pH 7.5
  (5.0-8.0)
• Protein 1
  (negative)
• Urobilinogen 1.0 (0.2-1.0)
• Nitrite neg
  (negative)
• Leuk. Esterase 3 (negative)
• RBC 11-24 (0-3)
• WBC 51-100 (0-5)
• Epithelials 57 (none)
• Hyaline cysts 1 (lt10)
• Bacteria 1
  (negative)
• Crystals cystine 1 (negative)
  

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Past Patient History

• Diagnosed with cystinuria as a child
• Left side nephrectomy as a child secondary to
  damage by cystine stones
• Recurrent kidney stones in the remaining right
  kidney
• Nephrostomy tube placed into
• remaining kidney

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Questions to be Considered

• 1.) How does the patients current renal problems
  relate to the cystine crystals found?
• 2.) What laboratory tests are performed to
  confirm the presence of cystine crystals in the
  urine?
• 3.) What are the long term effects of cystine
  crystal formation?
• 4.) Are there treatments available for patients
  with cystinuria?

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Pathogenesis of Cystinuria

• Autosomal recessive disorder
• Involves a defect in the renal transport of
  cystine by the tubules
• Defect results in lack of cystine reabsorbtion of
  the kidney
• Homozygous patients usually the only ones to
  present with problems
• Heterozygotes have a milder form of cystinuria
  (cystine crystals found in urine during analysis
  but dont usually form stones)

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Solubility within the Kidney

• Normal excretion of amino acids such as cystine
  into the urine is about 100 mg/day
• Heterozygous excrete around 100-300 mg/day
• Homozygous excrete around 500-1000 mg/day
• Solubility limit is around 300-400 mg/day
• Stones composed of cystine form when the
  concentration of cystine exceeds the normal
  solubility levels and the excess cannot go into
  solution (cystine crystals favor the existing
  free cystine and will compound it to form the
  stone)

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Cystine Confirmation

• Initially found during a microscopic urinalysis
• crystals are found in neutral to acidic pH and
  are flat hexagonal shapes
• Confirmation test for cystine once crystals are
  found microscopically is a cyanide-nitroprusside
  test
• involves mixing the urine with sodium cyanide and
  then sodium nitroprusside which will chemically
  react to produce a red-purple color indicative of
  presence of cystine crystals in the urine

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Positive Nitroprusside Reaction

• Left side Negative control
• Right side Positive for cystine

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Long Term Effects of Cystinuria

• Recurrent stone formation as seen with this
  patient
• Possible nephrectomy due to renal failure
• Pain associated with stone formation and passage

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Treatments

• Focus is on management
• Relief of symptoms (pain medications)
• Prevention of further stones (drinking large
  amounts of water to dilute the urine)

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Treatments - continued..

• Watching diet ( avoiding methionine rich foods)
• Alkanization of the urine (use of sodium
  bicarbonate or sodium citrate to more readily
  dissolve the cystine)
• Lithotripsy (non-invasive, shock waves to break
  up the stone to where it can be passed)
• Invasive procedures for stone removal

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Summary

• 57 year old women with presence of cystine
  crystals in the urine
• Confirmatory nitroprusside test was positive for
  cystine
• History revealed many renal problems associated
  with cystinuria
• Treatments are unpredictable

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Credits

• This case study was
• prepared by
• Amy Albright, MT(ASCP)
• while she was a
• Medical Technology
• student in
• the 2004 MT Class at William Beaumont
• Hospital, Royal Oak, MI.