The optimal dose of potassium citrate in the treatment of children with distal renal tubular acidosis.

BACKGROUND: Distal renal tubular acidosis (RTA) is a common cause of intractable calcium nephrolithiasis. In adults, the use of potassium citrate (PC) in distal RTA effectively decreases metabolic acidosis and the risk of calcium oxalate stone but it cannot decrease the risk of calcium phosphate stone. However, there is no report for the optimal dose of PC and the risk of calcium stone in distal RTA in children. OBJECTIVE: To evaluate the optimal dose of PC that minimizes the risk of calcium nephrolithiasis in children with distal RTA. METHOD: Prospective study PATIENTS: Children who have distal RTA and were followed-up for 4 months. Patients were studied in a control phase, 1 month of PC 2 mEq/kg/day, 2 months of PC 3 mEq/kg/day and 1 month of PC 4 mEq/kg/day. The urine specimens of 41 normal children were measured for the reference value of the parameters determining the risk of calcium stone. RESULTS: Eight children (mean age of 10 +/- 3.7 years, female : male = 6: 2) with distal RTA were studied during the control phase and after receiving PC 2 mEq/kg/day for I month. Treatment with PC 2 mEq/kg/day was not able to normalize serum bicarbonate and caused no significant change in the urine citrate/creatinine ratio, and activity production of calcium phosphate stone but it caused a significant decrease in the urine calcium/citrate ratio. Although PC 3 mEq/kg/day for I month normalized plasma bicarbonate, only this dose given for 2 months caused a significant increase in the urine citrate/creatinine ratio and urine calcium/ citrate ratio to values that were not different from normal children, while the activity production of calcium phosphate stone did not decrease to normal level. The effect of PC 4 mEq/kg/day was similar to that of 3 mEq/kg/day. CONCLUSION: Potassium citrate 3 mEq/kg/day for 2 months effectively normalized serum bicarbonate and decreased the risk of calcium oxalate stone but this treatment was theoretically unable to reduce the risk of calcium phosphate stone in children with distal RTA.

Antineutrophilic cytoplasmic antibody-positive systemic vasculitis associated with propylthiouracil therapy: report of 2 children with Graves' disease.

Systemic vasculitis is a rare complication of therapy with antithyroid medication. Antineutrophilic cytoplasmic antibody (ANCA)-associated vasculitis has been described in patients treated with propylthiouracil (PTU) and methimazole (MMI). The majority of cases have underlying Graves' disease. The authors report 2 children who developed ANCA-associated systemic vasculitis during PTU therapy of Graves' disease. One patient, after PTU treatment for 3 years, developed severe systemic vasculitis. After 3 weeks of arthritis, she abruptly presented with hematuria, proteinuria and edema concomitant with anemia. Her serum creatinine was elevated, to 6 mg/dl. Renal biopsy revealed crescentic glomerulonephritis. After admission, she developed intracerebral hemorrhage and pulmonary hemorrhage. She had positive perinuclear-ANCA (p-ANCA) with a titer of 1:160. Despite intensive therapy with immunosuppressive agents and plasmapheresis, as well as discontinuation of PTU, she died of the complications of severe systemic vasculitis. The other patient developed fever, arthralgia and leukocytoclastic vasculitis of the skin during treatment with PTU for about 2 years. Her symptoms and skin lesions disappeared after discontinuation of PTU. However, she has had a persistently high titer of p-ANCA 1:320 through 17 months follow-up time. Thus, patients who are treated with PTU can develop ANCA-positive vasculitis in a mild or severe form. Therefore, they should be carefully followed and monitored, not only for their thyroid status but also the serious complications of PTU.

Cystinuria: cause of recurrent renal stones in a 4-year-old girl.

This paper presents the case report of a 4-year and 6-month old girl with cystinuria. She clinically presented with recurrent radiopaque renal stones since the age of 3 years. She received 2 subsequent operations of pyelolithotomy combined with ureterolithotomy at the age of 3 years 6 months, and pyelolithotomy alone at the age of 5 years. She was initially diagnosed as having cystinuria by the presence of hexagonal plate crystals in her acidified urine and positive for the urinary cyanide-nitroprusside test. The diagnosis was confirmed by urinary amino acid analysis using quantitative ion-exchange chromatography which revealed increased amounts of cystine and dibasic amino acids of lysine and ornithine. In spite of maintaining a high fluid intake and alkalinizing urine by giving potassium citrate after the first operation, recurrent renal stones were found. Therefore, after the second operation, D-penicillamine was additionally introduced. During the 18-month follow-up, although there were recurrent renal stones, the rate of stone formation was slower. To the authors' knowledge, this is the first case report in Thailand.