Objective: To compare the incidence of peri-colonoscopy hyponatremia associated with PEG 3350 + sports drink (PEG-SD) versus PEG 3350-electrolyte solution + sodium sulfate + sodium ascorbate and ascorbic acid (PEG-ELS).

Hypothesis: As compared to PEG-SD, hyponatremia occurs significantly less often with PEG-ELS.

Looking at the Incidence of Hyponatremia With Two Commonly Prescribed Purgatives for Colonoscopy-Polyethylene Glycol 3350 With a Sports Drink (PEG-SD) Compared to Polyethylene Glycol 3350 With Electrolyte Solution (PEG-ELS)

Inclusion Criteria:

• Adults age 18 years or older scheduled for elective outpatient colonoscopy: 8am - noon.

Exclusion Criteria:

• Unable or unwilling to consent

• Pregnant

• Breast feeding

• Significant psychiatric illness

  -> 50% colon resection

• Bowel obstruction

• History of hyponatremia (Serum sodium <135 mmol/L)

• End stage renal disease on dialysis

• History of chronic kidney disease (other than kidney stones)

• Decompensated cirrhosis, including:

  • History of bleeding due to portal hypertension (varices, gastropathy, etc) within 3 months

• Hepatic encephalopathy (not controlled with medications) within 3 months

• Clinical presence of ascites

• Active cardiac disease

• Recent myocardial infarction (<4weeks)

• Unstable angina

• Congestive heart failure NYHA Functional Class Stage III or IV

• Stage III: Marked limitation of activity. Less than ordinary activity (e.g. walking short distances, 20-100 m) causes fatigue, palpitations, dyspnea. Comfortable at rest.

• Stage IV: Severe limitations. Experiences symptoms even while at rest. Mostly bedbound patients.

Exclusion Criteria (post-enrollment), from baseline labs:

• Serum creatinine > 1.5 mg/dL
• Serum potassium < 3.3 or > 5.5 mmol/L
• Serum sodium < 135 mmol/L or >150 mmol/L
• Serum calcium < 8.0 or > 11.0 mg/dL