Quick Summary: Up to 21% of reprocessed endoscopes still show contamination. Most failures happen during channel cleaning — not during disinfection. This article covers the 5 steps to clean endoscope channels the right way, based on AAMI ST91 guidelines.
In This Guide
- Why Channel Cleaning Matters More Than You Think
- Step 1: Pre-Clean at Point of Use
- Step 2: Leak Test Before You Brush
- Step 3: Brush Every Channel
- Step 4: Flush and Rinse
- Step 5: Dry for at Least 10 Minutes
- Common Mistakes
- Frequently Asked Questions
Why Channel Cleaning Matters
High-level disinfection (HLD) cannot fix bad cleaning. If organic material stays inside a channel, disinfectants can’t reach the surface underneath. The result: bacteria survive, and the next patient is at risk.
The numbers are clear. A French study checked 90,311 endoscope samples from 490 hospitals. Result: 21.1% had contamination above safe levels (Houssier et al., Journal of Hospital Infection, 2023). A separate review found 5.4% of duodenoscopes still carried dangerous bacteria after full reprocessing.
Most of these failures trace back to the manual cleaning step — especially channel brushing.
Step 1: Pre-Clean at Point of Use
Start cleaning right after the procedure ends. Don’t wait.
AAMI ST91 calls this the “golden hour.” If you wait longer than 60 minutes, bioburden dries inside the channels. Dried material is much harder to remove and can form biofilm.
What to do:
– Wipe the insertion tube with a wet, lint-free cloth soaked in fresh cleaning solution
– Suction cleaning solution through the biopsy channel
– Flush air and water channels with clean water
– Transport the scope in a closed container labeled as biohazard
This step alone removes a large share of organic material before it has time to stick.
Step 2: Leak Test Before You Brush
A damaged channel wall means bacteria can get trapped in places you can’t clean. Always leak test before manual cleaning.
How:
– Connect the leak tester to the scope
– Submerge the scope in water
– Apply air pressure per the manufacturer’s instructions
– Watch for bubbles — any stream of bubbles means a leak
If you find a leak, stop cleaning and send the scope for repair. Cleaning a damaged scope wastes time and won’t fix the contamination risk. A worn biopsy channel or cracked insertion tube needs to be replaced, not just cleaned harder.
Step 3: Brush Every Channel
This is the most important step — and the one most often done wrong.
Brush size matters. The brush bristle diameter should be about 1–3 mm larger than the channel inner diameter. Bristles that are too small won’t touch the walls. Bristles that are too large will fold over and skip spots.
Here are common channel sizes and the brush you need:
| Channel Type | Inner Diameter | Brush Bristle Size |
|---|---|---|
| Standard biopsy/suction | 2.8 mm | 3.0–4.0 mm |
| Large biopsy/suction | 3.2–3.7 mm | 4.0–5.0 mm |
| Air/water channel | 1.0–1.5 mm | 2.0 mm |
| Auxiliary water jet | 1.2–1.5 mm | 2.0 mm |
How to brush:
1. Insert the brush at one end and push until it comes out the other end
2. Pull it back through — that’s one pass
3. Do at least 3 passes per channel
4. Check the brush tip each time. If you see debris, keep brushing until the brush comes out clean
5. Use a new or properly reprocessed brush for each scope
Use disposable brushes when possible. A 2023 AAMI study found that reusable brushes can carry bacteria from one scope to the next if not properly cleaned themselves.
Tip: If you feel resistance when pushing the brush through, stop. Don’t force it. Resistance may mean the channel is blocked or damaged. Forcing the brush can puncture the channel wall. Check with a light guide inspection or send for repair.
Step 4: Flush and Rinse
After brushing, flush every channel with cleaning solution, then rinse with clean water.
Key points:
– Use a syringe or automated flushing device
– Flush until the water runs clear
– Make sure all channels get flushed — including the ones you can’t brush (like elevator wire channels on duodenoscopes)
– Follow your facility’s protocol for cleaning solution concentration and contact time
After this step, run a cleaning verification test before moving to disinfection. AAMI ST91 now requires this for high-risk scopes like duodenoscopes and bronchoscopes. If the test fails, go back and brush again.
Step 5: Dry for at Least 10 Minutes
Wet channels grow bacteria. Drying is not optional.
AAMI ST91 says: dry all channels with filtered, pressure-regulated air for at least 10 minutes. If moisture remains, dry longer.
This applies to both the inside channels and the outside of the scope. Storing a wet scope — even in a proper drying cabinet — creates conditions for bacteria to multiply.
Before storage:
– Confirm all channels feel dry when you blow air through them
– Hang the scope vertically in a ventilated cabinet
– Record the drying time and storage time (required by AAMI ST91)
Common Mistakes
| Mistake | Why It’s a Problem |
|---|---|
| Waiting too long to pre-clean | Bioburden dries and becomes hard to remove |
| Using one brush size for all channels | Wrong-sized brush misses parts of the wall |
| Brushing only once | One pass is not enough — 3 minimum |
| Skipping the leak test | Damaged channels trap bacteria in unreachable areas |
| Short drying time | Wet channels let bacteria grow during storage |
| Reusing damaged brushes | Worn bristles clean poorly; broken tips can scratch channels |
Frequently Asked Questions
Q: How often should I replace endoscope biopsy channels?
Replace the biopsy channel when you see damage during leak testing, when the channel feels rough during brushing, or when cleaning verification repeatedly fails. Most facilities replace channels every 300–500 procedures, but this varies by usage and scope model. Browse biopsy channel options by model.
Q: Can I use the same brush for different scope brands?
Yes, as long as the brush size matches the channel diameter. Brush selection depends on channel size, not scope brand. Check your scope’s manual for channel diameters.
Q: What if my scope fails cleaning verification after brushing?
Brush again and re-test. If it still fails, inspect the channels for damage. A scratched or worn channel surface traps bacteria. You may need to replace the biopsy channel or insertion tube.
Q: Is high-level disinfection enough without manual cleaning?
No. HLD kills bacteria on clean surfaces. But organic material like blood or tissue blocks the disinfectant. Manual cleaning must happen first. There is no shortcut.
Summary
Good channel cleaning comes down to 5 things: pre-clean fast, leak test first, brush with the right size, flush well, and dry long enough. Most contamination problems happen because one of these steps was rushed or skipped.
If your channels are worn or damaged, no amount of cleaning will make them safe. Need parts for your scope model? Send us the model number and we’ll help you find the right replacement.
Sources:
– AAMI ST91:2021 — Flexible and Semi-Rigid Endoscope Processing — AAMI, 2021
– Endoscope reprocessing: Retrospective analysis of 90,311 samples — Journal of Hospital Infection, 2023
– Criteria for the Use, Processing, and Disposal of Flexible Endoscope Cleaning Brushes — AAMI, 2023
– Navigating AAMI ST91: Enhancing Patient Safety — Infection Control Today, 2024