Management of cystine stone
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cystinuria disease and management of cystinuric patient with stone and cystinuric without stone, with focusing on medical expulsive therapy
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Management of cystine stone
- 1. MANAGEMENT OF CYSTINE STONE Mohammed Taher Aldoukhi,MD
- 2. EVIDENCE AND RECOMMENDATION BY EAU
- 3. CYSTINURIA Cystinuria is an autosomal-recessive defect in reabsorptive transport of cystine and the dibasic amino acids ornithine, arginine, and lysine from the luminal fluid of the renal proximal tubule and small intestine. The only phenotypic manifestation of cystinuria is cystine urolithiasis 1 in 7000 births 1-2% of all stone formers Up to 5% in pediatric stone formers
- 5. PATHOPHYSIOLOGY Renal transport of cystine • Amino acids filtered undergo nearly complete reabsorption by proximal tubular cells. • Only 0.4% of the filtered cystine appears in the urine. • . At least 2 transport systems are responsible for cystine reabsorption, as follows: - High-affinity system: This system is affected in persons with cystinuria. Mediates uptake of 10% of cystine and the dibasic amino acids at the third segment (S3) of the proximal tubule. - Low-affinity system: : This system is present in the (S1-S2) part of the proximal tubule and is responsible for 90% of cystine reabsorption.
- 6. PATHOPHYSIOLOGY (CONT) Intestinal transport of cystine The high-affinity transporter is present in the apical brush-border membrane of the jejunum and is responsible for absorption of cystine and dibasic amino acids.
- 7. PATHOPHYSIOLOGY (CONT) Normally, cystine and the other dibasic amino acids (ie, ornithine, lysine, arginine) are filtered at the glomerulus and reabsorbed in the proximal convoluted tubule . Defects in this channel cause elevated levels of dibasic amino acid secretion in the urine. Whereas ornithine, lysine, and arginine are completely soluble, cystine is relatively insoluble at physiologic urine pH levels of 5-7
- 8. PRESENTATION Presentation is similar to that of other types of renal calculi and includes renal colic, chronic urinary tract infections in a young person with a family history of renal stones, passage of stones or gravel, hematuria, and dysuria.
- 9. DIAGNOSIS Diagnostic confirmation: Positive family history of cystinuria Stone analysis showing cystine Identification of pathognomonic hexagonal cystine crystals on urinalysis A positive cyanide-nitroprusside screen indicates a urinary cystine concentration >75 mg/L Quantitative 24-h urinary cystine excretion more than 30 mg/day are considered abnormal
- 10. :CYSTINE STONE CHARACTERISTICS Poor radiopacity visualized with non-contrast CT SWL-resistant stones Two thirds of persons with cystinuria who form stones make pure cystine calculi One third have a mixture of cystine and calcium oxalate calculi.
- 11. MANAGEMENT
- 12. TREATMENT : The aim of medical therapy is to maintain the cystine concentration in the urine below its solubility level solubility of cystine in urine from 175 to 360 mg/L ≈ about 243 mg/L avoiding cystine crystallisation is to maintain urine pH between 7.5. and 8.5
- 13. TRAETMENT (CONSERVATIVE) High fluid intake Sodium and protein restriction Urinary alkalinization
- 14. RESISTANT TO CONSERVATIVE THERAPY Cystine is formed from the linkage of two cysteine molecules by a disulfide bond sulfhydryl groups that can reduce this disulfide bond, producing mixed disulfides with cysteine that are more soluble than cystine
- 15. PHARMACOLOGICAL SUBSTANCES S/E: fever, rash, abnormal taste, arthritis, leukopenia, aplastic anemia, hepatotoxicity, and pyridoxine deficiency. In addition, proteinuria dose range is 0.5 to 2 g/day, given in three to four divided doses decreases stone size or dissolves stones in up to 75 % forms a penicillamine- cysteine disulfide that is 50 times more soluble than cystine D- penicillamine same but incidence of these side effects is lower than with penicillamine 400 to 1200 mg/day in three divided doses decreases stone size or dissolves stones in up to 70 % forms a tiopronin- cysteine disulfide Tiopronin (thiola) Headache, dry cough, flushing 150 mg/dayto treat patients with cystinuria who are hypertensive. sulfhydryl groups, and form captopril- cysteine Captopril showed a low toxicity available only in Japan and South Korea Bucillamine
- 16. SURGICAL PROCEDURES Indications: Large calculi that are unlikely to dissolve Obstructing or otherwise symptomatic calculi. The ultimate goal of surgery is to make the patient free of stones. While the risk of recurrence is unchanged
- 17. SURGICAL OPTIONS ESWL retrograde endoscopic lithotripsy and extraction, percutaneous nephrolithotomy percutaneous irrigation chemolysis open surgery
- 18. REFERENCES http://emedicine.medscape.com/article/435678-overview#showall http://www.uptodate.com/contents/cystine-stones http://emedicine.medscape.com/article/435678-clinical#showall http://www.uroweb.org/guidelines/online-guidelines/ http://emedicine.medscape.com/article/435678-treatment#showall Mohammed aldoukhi,MD
Editor's Notes
- Cystine is one of the sulfur-containing amino acids; therefore, the urine may have the characteristic odor of rotten eggs. ……………. Cyanide converts cystine to cysteine. Nitroprusside then binds, causing a purple hue in 2-10 minutes. ……………. False-positive test results occur in some individuals with homocystinuria or acetonuria and in people taking sulfa drugs, ampicillin, or N-acetylcysteine
- Knowledge of the rate of cystine excretion can be used to estimate the optimal urine output to achieve a urine cystine concentration of less than 243 mg/L (1 mmol/L). If, for example, cystine excretion is 750 mg/day (3.1 mmol/day), then a urine output of at least 3 L/day will be needed to keep the urine cystine supersaturation less than 1 at a urine pH above 7. A higher volume is advisable to keep supersaturation low throughout the day. ….. Lowering sodium intake to 50 meq/day can markedly reduce cystine excretion [], but adherence to such a diet is difficult. Since there is a linear relationship between sodium and cystine excretion [], a dietary sodium intake of 100 meq/day is better than 200 meq/day. Thus, patients are advised to moderately restrict sodium to 100 meq/day. We also suggest a moderate protein intake (0.8 to 1 g/kg per day), as this provides adequate nutrition and should be tolerated by most patients. ...... Cystine solubility increases by up to threefold in an alkaline urine, but only if the urine pH is greater than 7 []. This degree of urinary alkalinization may require up to 3 to 4 meq/kg per day of potassium citrate or potassium bicarbonate, taken in three to four divided doses. We begin with doses of 20 meq three times daily, and adjust based upon the urine pH. To maintain an alkaline urine pH overnight, the last dose of potassium citrate or potassium bicarbonate should be taken at bedtime. In selected cases, acetazolamide may also be used
- effective for stones smaller than 1.5 cm in diameter ……………………… was successful in treating a limited number of patients in the late 1970s and early 1980s. The 2 most commonly used agents were -acetylcysteine (Mucomyst) A solution containing 60 mL of a 20% solution of N-acetylcysteine and 300 mEq of sodium bicarbonate per liter of saline is recommended. -tromethamine-E (THAM-E). an organic amine buffer with a pH level of 10.2. Treatment times range from weeks to months. relatively low success rates, rarely used today.