Laxatives for colonoscopy generally do not affect the kidneys, and sodium phosphate oral solution should be used with caution in patients with kidney disease. The occurrence of specific adverse reactions varies from person to person. Clinical laxatives for bowel preparation before colonoscopy generally refer to cotrimoxazole and sodium phosphate oral solution. Copolyethylene glycol electrolytes can produce a diarrheal effect through the osmotic effect in the intestinal tract. Contraindications include patients with abdominal pain without a clear diagnosis, patients with gastric retention, gastrointestinal bleeding, intestinal obstruction, intestinal perforation, inflammatory bowel disease, toxic megacolon toxic enteritis, intestinal torsion. Sodium phosphate oral solution is contraindicated in patients with congenital megacolon, intestinal obstruction, ascites, patients with congestive heart disease or renal failure. During intestinal preparation, if used in large quantities may be nausea, abdominal distension, abdominal cramps, vomiting, anal discomfort adverse reactions, rare urticaria, runny nose, dermatitis and other adverse reactions, patients with renal disease should be cautious to use oral solution of sodium phosphate salts. Specific medication should be under the guidance of a specialist, not unauthorized use of medication.