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  • Nicole Williams

Understanding the Differences Between FEES and MBSS

Updated: Jul 23, 2023

When it comes to evaluating swallowing disorders, two commonly used procedures are the Flexible Endoscopic Evaluation of Swallow (FEES) and the Modified Barium Swallow Study (MBSS). Both tests provide valuable insights into a patient's swallowing function, but they differ in terms of procedure, equipment used, and specific benefits. In this blog post, we will delve into the details of each procedure to help you understand their differences better.

Flexible Endoscopic Evaluation of Swallow (FEES):

The FEES is a procedure that involves passing a flexible endoscope through the nasal passage to visualize the pharynx and larynx during swallowing. This allows for real-time observation of how food or liquid passes through these structures. The endoscope is equipped with a light source and camera that transmits images to a monitor for analysis.


During FEES, patients are typically seated upright while their nose is anesthetized with topical numbing spray or gel. The endoscope is then gently inserted through one nostril until it reaches the back of the throat. As patients swallow various food consistencies mixed with colored dye, clinicians can observe any abnormalities such as aspiration or penetration.


1. Real-time visualization: FEES provides immediate feedback on how well an individual swallows by directly visualizing anatomical structures involved in swallowing.

2. Portability: The equipment used for FEES is portable and can be easily transported to different clinical settings.

3. Repeatability: Since no radiation exposure occurs during FEES, it can be repeated multiple times if necessary without concerns about cumulative radiation effects.

Modified Barium Swallow Study (MBSS):

The MBSS involves fluoroscopy imaging while individuals swallow barium-coated foods or liquids under X-ray guidance. This study allows clinicians to assess both the oral and pharyngeal phases of swallowing, providing detailed information about the timing and coordination of muscle movements.


During an MBSS, patients are positioned in front of a fluoroscopy machine while being given various food consistencies mixed with barium. The radiologist captures X-ray images as the patient swallows, allowing for a dynamic assessment of swallowing function.


1. Detailed imaging: MBSS provides detailed X-ray images that allow clinicians to assess the entire swallowing process, including any abnormalities or dysfunctions.

2. Objective measurements: The use of fluoroscopy enables precise measurements such as timing and duration of specific events during swallowing.

3. Comprehensive evaluation: MBSS can evaluate both oral and pharyngeal phases, making it useful for identifying specific areas where dysfunction may occur.

Key Differences:

1. Procedure: FEES involves direct visualization using an endoscope inserted through the nasal passage, while MBSS utilizes X-ray imaging during swallowing.

2. Portability vs Radiation exposure: FEES is portable but does not involve radiation exposure; in contrast, MBSS requires access to a fluoroscopy machine but exposes patients to low levels of radiation.

3. Real-time vs Dynamic assessment: FEES provides real-time visualization during swallowing, whereas MBSS captures dynamic X-ray images for comprehensive evaluation.


Both Flexible Endoscopic Evaluation of Swallow (FEES) and Modified Barium Swallow Study (MBSS) play crucial roles in diagnosing and managing swallowing disorders. While FEES offers real-time visualization without radiation exposure, MBSS provides detailed imaging that allows for objective measurements throughout the entire swallow process. Understanding these differences will help healthcare professionals determine which procedure is most appropriate based on individual patient needs and clinical settings.

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