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Renal Failure After Oral Sodium Phosphate for Colonoscopy
This rare complication highlights the need to use this agent appropriately.
In three earlier reports, investigators described seven patients who developed chronic renal insufficiency after receiving oral sodium phosphate solution or sodium phosphate tablets before colonoscopy. Now, investigators from the center at Columbia College of Physicians & Surgeons, who reported 5 of the first 7 cases, describe those 5 patients plus 16 additional patients who developed renal insufficiency after oral sodium phosphate administration.
This patient group comprised 17 women and 4 men (mean age, 64; 17 white). Of 16 with hypertension, 7 were taking angiotensin-converting–enzyme (ACE) inhibitors, 7 were taking angiotensin-receptor blockers, and 4 were taking diuretics. Three patients were taking nonsteroidal anti-inflammatory drugs. Nineteen patients received standard doses of oral sodium phosphate solution (timing of the doses was not reported), 1 received a nonstandard high dose of oral sodium phosphate solution, and 1 received sodium phosphate tablets. Renal biopsies were performed at a mean 3.8 months after colonoscopy; mean serum creatinine level was 3.7 ng/dL (range, 2.2–8.0 ng/dL). Renal biopsies typically showed tubular injury, with tubular atrophy and interstitial fibrosis, and abundant calcium phosphate deposits in distal tubules and collecting ducts. During a mean follow-up of 16.7 months, four patients required renal replacement therapy, including one successful renal transplant; none of the patients completely recovered renal function.
Comment: These findings suggest that chronic renal insufficiency sometimes follows bowel preparation with oral sodium phosphate solution. The exact mechanism and incidence of this injury remain uncertain. The number of sodium phosphate doses administered yearly for colonoscopy in the U.S. is enormous, and this reporting group is at a referral center for renal biopsies. Nevertheless, this complication is almost certainly underreported, because the symptoms of chronic renal insufficiency often are mild and nonspecific.
So, what can we conclude? Certainly, sodium phosphate is a more effective bowel preparation than is polyethylene glycol (PEG), particularly if the doses are split so that one dose is given on the evening before the examination and the second dose is given on the morning of the examination. Splitting doses (by as long as 10–12 hours) also might improve safety by reducing the chances of developing very high serum phosphate levels. The results underscore the importance of using sodium phosphate appropriately. Patients should be selected properly and undergo aggressive hydration, preferably with oral rehydration solution. Regimens involving reduced dosages of sodium phosphate, perhaps by combining sodium phosphate with other laxatives, deserve evaluation.
— Douglas K. Rex, MD
Published in Journal Watch Gastroenterology January 31, 2006
Citation(s):
Markowitz GS et al. Acute phosphate nephropathy following oral sodium phosphate bowel purgative: An underrecognized cause of chronic renal failure. J Am Soc Nephrol 2005 Nov; 16:3389-96.
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