What Can a Sinus CT Show When Nasal Congestion Is Mostly on One Side?

What Can a Sinus CT Show?

When congestion primarily affects one side of the nose, a sinus CT may show:

• A deviated septum
• Inflamed or thickened sinus tissue
• Fluid or mucus trapped inside a sinus
• Narrowed or obstructed sinus drainage pathways
• Nasal polyps or other soft-tissue changes
• Enlarged turbinates
• Dental-related inflammation near a maxillary sinus
• Anatomical differences between the two sides
• Less common abnormalities that require further evaluation

A CT finding does not establish a diagnosis by itself. Your ENT provider will interpret the images alongside your symptoms, medical history, and examination findings.

Is It Normal for One Nostril to Feel More Blocked?

Your nose naturally goes through a process called the nasal cycle. During this cycle, tissues inside one nasal passage swell slightly while the tissues on the other side shrink. The pattern switches every few hours and is usually subtle enough that you do not notice it.

Persistent one-sided congestion is different. If the same nostril remains obstructed, especially for several weeks or longer, an inflammatory or structural condition may be reducing the space available for airflow.

An ENT evaluation can help determine whether the blockage is related to the nasal cycle, allergies, chronic inflammation, or a physical narrowing inside the nose.

What Is a Sinus CT?

A sinus CT scan, or computed tomography scan, uses X-ray technology to produce detailed cross-sectional images of the nose and paranasal sinuses.

Unlike a traditional X-ray, a CT creates multiple images that can be viewed from different angles. These images show the sinus cavities, bones, nasal septum, soft tissues, and drainage pathways in greater detail.

According to RadiologyInfo.org, sinus CT imaging may be used to evaluate obstruction, fluid-filled sinuses, thickened sinus membranes, inflammatory disease, and certain nasal or sinus abnormalities.

What Happens During a Sinus CT?

During a conventional CT scan, you lie on a padded table that moves through a ring-shaped scanner. The equipment captures multiple images as it moves around your head.

The scan itself is noninvasive and usually completed relatively quickly. Most routine sinus CT scans do not require contrast dye, although the ordering provider may recommend contrast or a different imaging study in certain circumstances.

Because CT imaging uses radiation, it is ordered when the clinical team determines that the expected diagnostic information justifies the exposure. Patients who are or may be pregnant should tell their provider before undergoing imaging.

What May a Sinus CT Reveal About One-Sided Congestion?

A Deviated Septum

The nasal septum is the wall of bone and cartilage separating the right and left nasal passages. When it leans toward one side, it can make that passage narrower and more difficult to breathe through.

A CT can show the position and shape of the septum, as well as how it relates to the surrounding nasal and sinus structures.

Not every deviated septum requires treatment. The important question is whether the deviation corresponds with the patient’s symptoms and meaningfully restricts airflow or sinus drainage.

Chronic Sinus Inflammation

Inflammation can cause the lining of a sinus to become thicker and take up more space. On a CT, this may appear as gray or white areas rather than the darker appearance of a normally air-filled sinus.

Possible findings include:

• Thickening of the sinus lining
• Partially or completely filled sinus cavities
• Fluid or mucus accumulation
• Inflammation affecting one or several sinuses

These findings do not automatically indicate an active bacterial infection. Inflammation may also be associated with allergies, chronic rhinosinusitis, a recent respiratory infection, or other conditions.

One-Sided Sinusitis

Sinus inflammation can sometimes be concentrated on one side. A CT may show that one or more sinuses on that side contain fluid, thickened tissue, or obstructed drainage pathways.

One-sided symptoms do not necessarily mean that only one sinus is involved. The CT helps show which sinus cavities are affected and how extensive the inflammation appears.

Your provider may use this information as part of an evaluation for sinus symptoms, but the images must still be interpreted alongside your symptoms and examination.

Blocked Sinus Drainage Pathways

The sinuses drain through small openings into the nasal passages. Swelling, polyps, or structural narrowing can interfere with this process.

A CT may show where a drainage pathway is narrowed or obstructed. This can be particularly useful when one-sided congestion occurs with facial pressure, recurring infections, thick drainage, or symptoms that have not responded adequately to treatment.

Nasal Polyps and Other Soft-Tissue Changes

Nasal polyps are soft, noncancerous growths associated with chronic inflammation. Depending on their size and location, they may block nasal airflow, interfere with sinus drainage, or reduce the sense of smell.

CT imaging can help show the extent and location of suspected polyps. However, imaging alone may not determine exactly what every soft-tissue finding represents. Nasal endoscopy, additional imaging, or tissue sampling may occasionally be needed.

Enlarged Turbinates

Turbinates are structures along the sidewalls of the nose that warm, humidify, and filter inhaled air. Their soft-tissue covering naturally swells and shrinks, but allergies or chronic irritation can cause persistent enlargement.

If a turbinate occupies too much space on one side, breathing through that nostril may become more difficult. A CT can provide information about the surrounding anatomy, while an office examination or nasal endoscopy may be particularly useful for evaluating the size and appearance of the nasal tissues directly.

Dental-Related Sinus Inflammation

The roots of the upper teeth sit close to the maxillary sinuses in the cheeks. Occasionally, a dental infection or previous dental procedure may contribute to inflammation in a nearby sinus.

A CT may show one-sided maxillary sinus changes that suggest a possible dental source. If dental involvement is suspected, your ENT provider may recommend evaluation by a dental professional.

Less Common Abnormalities

Most cases of one-sided congestion are not caused by a serious condition. However, persistent symptoms on the same side deserve evaluation because CT imaging may occasionally identify a cyst, unusual bone change, mass, or another abnormality requiring further investigation.

A CT cannot always determine precisely what an abnormal area represents. Depending on the findings, an ENT may recommend nasal endoscopy, MRI, biopsy, or another test.

Can a CT Diagnose the Cause by Itself?

No. A sinus CT is one part of the diagnostic process.

For example, the scan may show mucosal thickening, but that finding does not automatically prove that inflammation is responsible for the patient’s symptoms. Some imaging changes are incidental and may occur in people without significant sinus complaints.

An ENT provider will consider:

• How long the congestion has been present
• Whether the blockage always affects the same side
• Whether symptoms improve with allergy treatment
• Whether facial pressure, drainage, or smell changes are present
• Findings from the nasal examination or endoscopy
• Whether the CT findings match the reported symptoms

This combined evaluation helps prevent treatment based on an image alone.

Is a CT Always Necessary for One-Sided Congestion?

Not necessarily. An evaluation typically begins with a discussion of your symptoms and an examination of the nose.

Nasal endoscopy may allow the provider to inspect the nasal passages, septum, turbinates, visible drainage pathways, and other accessible areas directly. A CT may be recommended when deeper sinus anatomy needs to be evaluated or when symptoms persist despite appropriate treatment.

The purpose of imaging is to answer a specific clinical question—not simply to obtain a scan because one nostril feels blocked.

When Should One-Sided Congestion Be Evaluated?

Consider scheduling an ENT evaluation if:

• The same nostril remains blocked for several weeks
• Congestion does not improve with appropriate allergy treatment
• Nasal obstruction interferes with sleep or exercise
• Symptoms include recurring sinus infections or facial pressure
• Your sense of smell has decreased
• One-sided drainage or nosebleeds keep recurring
• Symptoms are worsening or affecting daily activities

Seek prompt medical evaluation for congestion accompanied by vision changes, swelling around the eyes, severe facial pain, confusion, a severe headache, neck stiffness, or other sudden or concerning symptoms.

Find Out What May Be Blocking One Side of Your Nose

Persistent one-sided nasal congestion can result from inflammation, a deviated septum, enlarged turbinates, nasal polyps, or another condition affecting airflow. A sinus CT may provide important information about the deeper nasal and sinus structures, but its findings should always be interpreted as part of a complete ENT evaluation.

Schedule an appointment with Bethesda ENT & Sinus Center to discuss persistent nasal congestion and determine whether a sinus CT, nasal endoscopy, or another diagnostic approach may be appropriate.