A brief description of commonly used intestinal cleansers before colonoscopy

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Author: Zeng Xiaoling

Unit: Department of Health Medicine, Haikou People's Hospital

Adequate bowel preparation is a prerequisite for high-quality colonoscopy and is closely related to the diagnostic accuracy and treatment safety of colonoscopy.

So what are the intestinal cleansers? Here is a brief description:

(I) Polyethylene glycol (PEG) electrolyte powder: It is a bulk laxative that is not absorbed or metabolized. It cleanses the intestines by taking a large amount of liquid orally. It has no significant effect on the absorption and secretion function of the intestines and is not likely to cause water and electrolyte disorders. It is currently the most commonly used intestinal cleanser in the Chinese population.

Conventional use of single PEG regimen: Start taking it 4-6 hours before colonoscopy and finish taking it within 2 hours; during medication, you can accelerate intestinal peristalsis and excretion through moderate exercise and abdominal massage. Generally, intestinal motility accelerates 1 hour after starting medication, and bowel movements gradually begin. Before defecation, the examinee may feel bloating, so you can postpone taking it and continue taking it after the symptoms disappear until clear water-like stool is discharged. If the defecation characteristics do not meet the above requirements, you can take PEG solution or water, but the total amount generally does not exceed 4L.

The routine usage of the split-dose PEG regimen is as follows: (1) 3L PEG regimen, taken in split doses, i.e., take 1L 10-12 hours before intestinal examination, and take 2L 4-6 hours before the examination on the day of examination; (2) 4L PEG regimen, taken in split doses, i.e., take 2L 10-12 hours before intestinal examination, and take 2L 4-6 hours before the examination on the day of examination.

(ii) Compound oral sulfate solution (OSS), also known as magnesium sodium potassium sulfate oral concentrated solution, is an osmotic laxative that relies on sulfate ions to provide osmotic pressure while supplementing sodium and potassium ions to reduce the risk of water and electrolyte disorders. It is an effective bowel preparation drug.

Conventional use: OSS is a concentrated solution for oral use. Proper intestinal cleansing requires the use of 2 bottles of solution. In the split-dose regimen, dilute 1 bottle of 176 mL of concentrated solution to 500 mL, drink it within 30-60 minutes, and then add 1000 mL of clear liquid within the next hour, and repeat it again after 10-12 hours, for a total of about 3L of liquid. This product can also be taken in a single-dose regimen, that is, starting with the first dose, and repeating it again after an interval of 2 hours.

(III) Magnesium sulfate. It is a hypertonic solution. As a bowel cleanser, it has the advantages of requiring less water and being inexpensive. However, patients with abnormal renal function and inflammatory bowel disease should avoid using it.

Conventional usage: Dilute 50 g of magnesium sulfate with 100 mL of water and take it all at once, followed by drinking about 2 L of water. If clear watery stools are observed, stop drinking water.

(IV) Mannitol. It is a hypertonic solution with advantages such as low price and convenient use. However, it may cause water and electrolyte imbalance during use and has a greater irritation to the gastrointestinal tract, which may cause nausea, vomiting, abdominal distension, abdominal pain and other discomfort. It should be used with caution before the patient is expected to undergo therapeutic colonoscopy.

Conventional usage: dilute 250 mL of 20% mannitol with 250 mL of clean water and take it all at once. Drink 1500-2000 mL of water 10 minutes later. If clear watery stools are observed, stop drinking water.

Of course, we should also pay attention to the health education of intestinal preparation:

(I) Before intestinal preparation, the subjects should be effectively educated and given detailed guidance in a variety of ways, such as oral, written, or Internet-based education such as WeChat, to improve the subjects' compliance with dietary preparation and oral laxatives.

(II) Low-residue/low-fiber foods can help improve the effectiveness of intestinal preparation. It is recommended to stop consuming high-residue/high-fiber foods 24 hours before colonoscopy. This does not include milk and orange juice. Colored liquids and foods (such as watermelon, dragon fruit, etc.) can affect the results of colonoscopy.