Hypocitraturia Despite Potassium Citrate Tablet Supplementation

Chetan Shenoy, MBBS

Disclosures

July 13, 2006

Case Report

A 35-year-old female teacher was referred to the nephrology department of a tertiary care center by her primary care physician for further evaluation of recurrent nephrolithiasis after an episode of renal colic. She had her first episode of nephrolithiasis about 5 years ago and has since had several episodes where she passed noticeably large stones. Her past medical history was also significant for chronic diarrhea diagnosed as irritable bowel syndrome. She had 5 to 6 loose bowel movements a day.

At the time of the referral, the patient was on hydrochlorothiazide 25 mg daily and 60 mEq of potassium citrate in the form of UROCIT-K (Mission Pharmacal Company, San Antonio, Texas) 2 tablets of 1080 mg 3 times a day, both of which she had been taking for more than a year. She was drinking more than 3 L of water daily and had about 2 L of urine output a day. She was compliant with her medications. She mentioned that she had noticed intact pills of UROCIT-K in her feces.

Laboratory investigations showed that her electrolytes and renal function were normal. Analysis of a stone passed by her showed the presence of 80% of calcium oxalate and 20% of calcium phosphate. Her 24-hour urinary volume was 2400 mL. Her 24-hour urinary calcium was normal at 264 mg (normal range 100-300 mg/24 hours). The 24-hour urine citrate was significantly low at 49 mg (normal range 320-1240 mg/24 hours). The 24-hour uric acid, the 24-hour oxalic acid, the 24-hour sodium, and the 24-hour creatinine were normal.

With her history of chronic diarrhea and her hypocitraturia despite the potassium citrate tablet supplementation, she was switched to an equivalent dose of the liquid form of the potassium citrate (Polycitra-K; Alza Pharmaceuticals, Mountain View, California). She was asked to follow-up in a month, and at that visit, the 24-hour urine citrate was 455 mg. She was seen again 6 months later; her 24-hour urine citrate was 410 mg and she reported no episodes of nephrolithiasis after switching to the liquid preparation of the citrate.

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