Colonoscopy Prep: Diet in the Days Before the Exam

Why Pre-Colonoscopy Diet Is Clinically Relevant

The colonic mucosa must be completely free of food and faecal residues for the endoscopist to accurately visualise the entire intestinal wall surface. Solid or semi-liquid residues not eliminated by the laxative preparation may:

• conceal flat or depressed lesions (non-polypoid polyps, Paris classification IIa–IIc) — the most difficult to identify and those carrying the highest risk of malignant progression;
• make polypectomy technically impossible during the same session, requiring a repeat procedure;
• increase procedural time and irrigation water consumption, prolonging patient discomfort.

The Boston Bowel Preparation Scale (BBPS) is the internationally validated tool for quantifying preparation quality: a total score ≥6 (with at least 2 per colonic segment) is considered adequate for a diagnostic and therapeutic colonoscopy. A correct pre-procedural diet is the primary modifiable factor for achieving this target.

Diet in the 3 Days Before Colonoscopy

3 and 2 Days Before: Low-Residue Diet

In the two days preceding the laxative preparation, the patient must follow a low-residue diet, limiting foods rich in insoluble fibre — the main contributors to the formation of faecal residues that are difficult to eliminate with laxative agents.

Permitted foods: White meat (chicken, turkey) and fish, boiled or grilled; eggs; refined pasta and rice (not wholegrain); white bread; low-fat cheeses; yoghurt; strained vegetable broth; pulp-free fruit juices; clear beverages.

Foods to avoid: Raw and cooked vegetables; fresh and dried fruit; legumes; wholegrain cereals; seeds and nuts; red meat and processed meats; large quantities of full-fat dairy products; coloured beverages (red or purple juices, dark tea, coffee with milk).

ESGE guidelines and AIGO recommendations both support the efficacy of a low-residue diet over complete fasting in the preceding days: it delivers comparable preparation quality with a significantly lower impact on patient comfort and nutritional status.

The Day Before: Clear Liquid Diet and Start of Laxative Preparation

The day immediately preceding the colonoscopy involves an exclusively clear liquid diet: strained vegetable broth, unsweetened clear tea, still and sparkling water, herbal infusions, transparent gelatines, and pulp-free apple or pear juice.

Red, orange, and purple-coloured liquids must be strictly avoided, as they may be mistaken endoscopically for blood and interfere with mucosal assessment.

The laxative solution is generally taken the evening before, according to the protocol prescribed by the gastroenterologist. Split-dose protocols — with one evening dose and one morning dose in the 4–6 hours preceding the examination — are currently considered the gold standard for preparation quality, as indicated in the ESGE 2019 Guidelines on bowel preparation for colonoscopy.

On the Morning of the Examination

If the colonoscopy is scheduled for the afternoon, the patient may complete the second laxative dose in the morning, with complete fasting in the final 2 hours before the procedure. If the examination is planned for early morning, the split-dose preparation is completed the preceding evening.

Maintaining adequate hydration throughout the preparation is essential: at least 1.5–2 litres of clear fluids should be consumed during the preparation window to prevent dehydration — particularly relevant in elderly patients and those with cardiac or renal comorbidities.

Medication Management During Colonoscopy Preparation

Colonoscopy preparation also requires careful evaluation of ongoing pharmacological therapy. The main drug categories to manage include:

Anticoagulants and antiplatelet agents. Suspension or bridging of warfarin, direct oral anticoagulants (DOACs), aspirin, and clopidogrel must be planned in advance by the gastroenterologist and the prescribing physician, based on the patient’s thrombotic risk and the type of procedure planned. ESGE guidelines provide specific recommendations for each pharmacological class.

Oral antidiabetic agents and insulin. In diabetic patients, modification of hypoglycaemic therapy during the fasting and preparation period must be agreed upon with the diabetologist or treating physician.

Antihypertensives and other chronic medications. In general, these may be taken regularly with a small sip of water even during fasting periods, unless otherwise instructed by the physician.

Iron supplements. Must be suspended at least 5–7 days before colonoscopy, as they darken stools and may significantly compromise preparation quality.

The Role of Medical Devices in Diagnostic and Therapeutic Colonoscopy

Optimal bowel preparation creates the ideal conditions for the effective use of endoscopic accessories. The single-use colonoscopy accessories distributed by Meditalia S.r.l. — irrigation and washing catheters, polypectomy snares, submucosal injection needles, and haemostatic clips — deliver their highest operational performance in a clean, well-prepared endoscopic field.

The availability of CE-certified devices compliant with EU MDR Regulation 2017/745 ensures traceability, safety, and reproducibility of performance in every procedural scenario, from screening colonoscopy to complex lesion resection. Meditalia supports digestive endoscopy centres with a comprehensive range of accessories compatible with the leading endoscopic systems on the Italian and European markets.