A team from Munich and Erlangen, Germany, assessed the risk of hyponatremia after gastrointestinal endoscopy.
40 patients (14 women, mean age 57.4 years) underwent elective colonoscopy and were assessed prospectively. 20 gastroscopy patients served as controls.
On the day of the procedure the patients drank 2-3 L of standard bowel-preparation solution containing polyethylene glycol and balanced electrolytes to cleanse the bowel.
Venous blood samples were taken before patients drank the bowel-preparation solution, immediately before and after colonoscopy, and after 1 hour of rest.
In the controls, venous blood samples were taken before, and 20 minutes after, gastroscopy.
Serum sodium and arginine vasopressin concentrations were measured.
27 patients showed no colonoscopic abnormalities, 7 patients had adenomas, 2 adenocarcinomas, 2 distinct colonic diverticulosis, 1 stenosis after resection of the rectum, and 1 ulcerative colitis.
The team found that all patients undergoing colonoscopy had normal serum sodium values at baseline, and immediately before the procedure. After colonoscopy 7.5% of patients had a serum sodium concentration of 130 mmol/L or lower. No gastroscopy patient developed hyponatremia after endoscopy.
Serum concentrations after colonoscopy:|
Sodium 130 mmol/L or lower - 7.5% of patients
Raised arginine vasopressin - 23% of patients
Baseline serum arginine vasopressin concentrations were within the expected range in all patients. However, after bowel cleansing and immediately before colonoscopy, 25% of patients had raised concentrations. 23% also had raised levels at the end of the colonoscopy. By contrast, serum arginine vasopressin concentrations remained about normal in all controls.
Researcher Clemens D Cohen commented on behalf of the group, "Our findings show a high incidence of hyponatremia after colonoscopy, in association with raised serum concentrations of arginine vasopressin.
"Physicians should be aware of this complication, since it may contribute to psychological and neurological symptoms after colonoscopy."