Clinical features of patients with hyperphosphatemia following administration of phosphate-containing laxatives

Background : Oral sodium phosphate (NaP) is currently used for colon preparation prior to colonoscopy or barium enema because of its convenience and efficacy. It can cause transient hyperphosphatemia and should be considered potentially dangerous in the presence of renal impairment. Methods : A retrospective study was done in 48 patients (32 patients with normal renal function and 16 patients with azotemia : serum creatinine 1.4 mg/dL) with hyperphosphatemia (serum phosphate 6 mg/dL or 50% increase in baseline) who were administered NaP solution as bowel preparation at Seoul National University Hospital in the period of January 2000 to June 2003. Results : The patients' mean age was 60 years (range, 25-85 years). The increase of serum phosphate was 5.33.1 mg/dL (7.64.4 mg/dL in azotemia group vs. 4.21.2 mg/dL in normal renal function group). Serum calcium and potassium concentration decreased significantly, while serum sodium level increased significantly. There were no significant differences in serum chloride, total , blood urea nitrogen and creatinine. The product of calcium and phosphate increased from 33.011.3 / to 74.028.7 / (to 93.039.8 / in azotemia group). Only 8 patients ingested the recommended dose of oral NaP with an appropriate time interval. The symptomatic adverse events were numbness in 3 patients and carpopedal spasm in 1 patient. 12 patients underwent or amphojel administration and 1 patient needed hemodialysis as a treatment of hyperphosphatemia. Serum phosphate returned to baseline level at 1.30.6 day (1.80.8 day in azotemia group vs. 1.00.3 day in normal renal function group). Conclusion : NaP is inappropriate for patients who may be at an increased risk for phosphate intoxication, especially patients with impaired renal function. Even to healthy adult without renal disease, NaP should be ingested the recommended dose with an appropriate time interval.