1. Stop…let Me A-”cyst” You
A Case Study about Cystinuria by Amy Albright

2. Patient History 57 year old woman with history of renal problems
Patient hospitalized upon urgent referral from doctor’s office
Urinalysis was performed

3. Urinalysis Results Test Patient Result Reference Range Color Yellow
Clarity Cloudy
Glucose neg (negative)
Bilirubin neg (negative)
Ketones neg (negative)
Sp. Gravity ( )
Blood (negative)
pH ( )
Protein (negative)
Urobilinogen ( )
Nitrite neg (negative)
Leuk. Esterase (negative)
RBC (0-3)
WBC (0-5)
Epithelials (none)
Hyaline cysts (<10)
Bacteria (negative)
Crystals cystine (negative)

4. 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

5. Questions to be Considered:
1.) How does the patient’s 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?

6. 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 don’t usually form stones)

7. Solubility within the Kidney
Normal excretion of amino acids such as cystine into the urine is about 100 mg/day
Heterozygous excrete around mg/day
Homozygous excrete around mg/day
Solubility limit is around 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)

8. 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

9. Positive Nitroprusside Reaction:
Left side: Negative control
Right side: Positive for cystine

10. 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

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

12. 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

13. 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

14. the 2004 MT Class at William Beaumont
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.