[Is the preparation with sodium phosphate purgative for bowel cleansing safe in low-risk patients?]

The development of colonoscopy has increased the oral sodium phosphate (OSP) laxative use. OSP complications like hyperphosphatemia with acute and chronic kidney impairment with nephrocalcinosis have been reported.

To describe and analyze acute and one year after OSP complications in low risk well hydrated patients.

We performed a prospective study in 100 consecutive patients undergoing colonic cleansing with OSP for colonoscopy aged 35-74 year, ASA I-II. Exclusion criteria were congestive heart failure, chronic kidney disease, diabetes, liver cirrhosis, intestinal obstruction, decreased bowel motility, increased bowel permeability, hyperparathyroidism. Arterial pressure, hematocrit, serum osmolality, serum phosphate, ionic calcium, electrolytes (Na+, Cl-, K+), creatinine and urea were measured before and after OSP. The day before colonoscopy all the participants entered a 24 hr-period diet consisting in 4 litres of clear fluids and standard OSP dose (30 g at 17:00 and 30 gr at 22:00). Phosphatemia levels post OSP according to patient's weight (> or =, < or = 70 kg) and one year later kidney function were compared.

Mean age was 58.9 +/- 8.4 years, 66% of patients were women and mean weight was 71 +/- 13 kg. Kidney function showed no significant difference between pre and post OSP, and after one year values. Hyperphosphatemia appeared in 87%. Hyperphosphatemia was higher in patients with low weight (5.8 mg/dl vs 5.3 mg/dl, P < 0.05).

OSP complications were reduced through an adequate patient selection in order to avoid risk factors and an effective hydration. Phosphate overload was tolerated without symptoms. Considering high hyperphosphatemia incidence and its relation with weight, to adjust dose related to weight should be evaluated. There was no acute or a year later renal damage.