Age

18–any

Sex

ALL

Healthy volunteers

Not accepted

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

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.
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

Incidence of Hyponatremia in PEG-SD Compared to PEG-ELS