Oral sodium phosphate, currently used for colon preparation prior to colonoscopy or barium enema, induces hyperphosphatemia, hypocalcemia, and hypokalemia. Elderly patients are at an increased risk for phosphate intoxication due to decreased glomerular filtration rate, medication use, and systemic and gastrointestinal diseases. To investigate these electrolyte disorders and their correlation with creatinine clearance, coexistent diseases, medications, and functional status, Beloosesky et al studied 36 hospitalized patients 65 years or older, who underwent bowel cleansing with the standard sodium phosphate preparation for colonoscopy or barium enema. Venous blood samples for electrolyte determination were obtained at days 1, 2 (the procedure day), and 3, and urine samples were obtained from 10 patients. An increase in serum phosphorus level was correlated with a decreased creatinine clearance (R = −0.52; P = .001). Hypocalcemia and hypokalemia were present in 21 (58%) and 20 (56%) of the patients, respectively. Beloosesky et al conclude that sodium phosphate induces serious electrolyte abnormalities in elderly patients and advise that serum electrolytes, phosphorus, and calcium are assessed prior to sodium phosphate preparation and that in selected patients, postprocedural assessment and correction may be required.