Failing to complete the necessary colonoscopy preparation, often called the “prep,” is a common concern. The preparation involves consuming laxatives and clear liquids designed to completely empty the colon of all solid matter. This step is a fundamental requirement for a successful and diagnostically accurate colonoscopy, as patient compliance is directly linked to the medical outcome of the screening effort.
The Standard: Why Complete Bowel Cleansing is Essential
The goal of the preparation is to create an entirely clear view of the colon’s mucosal lining, where polyps and other abnormalities develop. If residual stool or opaque liquid remains, it obscures the physician’s vision, making a thorough examination impossible. The colonoscope uses a tiny camera to inspect the walls of the large intestine for small, precancerous polyps.
A clean colon allows the gastroenterologist to identify and remove these polyps, preventing them from developing into colorectal cancer. If the bowel is not fully cleansed, the procedure’s primary purpose—cancer prevention—is compromised. Success requires the liquid passing from the body to be clear or a light yellow color, free of any solid material.
Immediate Risks and Medical Consequences of Incomplete Preparation
The consequences of an incomplete preparation range from procedural inconvenience to significant medical risk. If the colon is visibly unclean upon scope insertion, the procedure may be canceled by the physician, necessitating that the patient repeat the entire preparation and book a new appointment. This results in wasted time, unnecessary sedation, and increased healthcare costs, delaying the intended screening.
The most serious consequence is the risk of a false-negative result, which occurs when the procedure proceeds despite inadequate preparation. When preparation is suboptimal, the miss rate for adenomas—precancerous polyps—can be significantly high, sometimes exceeding 40%. Residual material can hide polyps, especially those located in the folds of the colon, defeating the screening’s purpose.
Physicians use standardized tools like the Boston Bowel Preparation Scale (BBPS) to objectively grade the cleanliness of the colon during the procedure. This scale divides the colon into three segments, scoring each from 0 (unprepared with solid stool) to 3 (perfectly clean). A total BBPS score below a certain threshold, often 6 or less, is defined as inadequate, meaning the preparation failed to allow for an accurate examination. When the quality of the prep is poor, guidelines often recommend a repeat colonoscopy within one year.
Action Plan: What to Do If You Cannot Finish the Prep
If you are struggling with or cannot finish the prescribed laxative solution, immediately contact the physician who ordered the procedure or the endoscopy center. Do not attempt to self-adjust the dosage or timing of the preparation without professional guidance. The medical team can provide specific, real-time modifications based on how much of the prep you have consumed and your current physical condition.
When you call, clearly state exactly how much solution you drank and the time you took your last dose. Also report any severe side effects, such as persistent vomiting, which is a common reason for not completing the prep. If time permits, the doctor may recommend switching to an alternative regimen or taking an anti-nausea medication to help you finish the remaining solution.
If you are unable to drink the laxative solution, continue consuming clear liquids, such as water, broth, or sports drinks, to maintain hydration. The medical team will assess the risk of proceeding with a less-than-perfect prep versus the risk of cancellation and rescheduling. Following the instructions of your healthcare provider is the only safe path forward when facing difficulties with the colonoscopy preparation.