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

If the same side of your nose consistently feels harder to breathe through, you may wonder whether something is physically blocking the nasal passage. Temporary congestion can occur with a cold, allergies, or the natural nasal cycle. A blockage that remains on the same side for weeks or months may have a different explanation.

A sinus CT can provide detailed images of nasal and sinus structures that cannot always be fully evaluated from symptoms or an office examination alone. Depending on the findings, it may help identify a deviated septum, enlarged turbinates, sinus inflammation, narrowed drainage pathways, or another abnormality affecting airflow.

For patients in Gilbert, Mesa, Tempe, and surrounding communities, Trinity ENT evaluates persistent nasal congestion and uses diagnostic tools such as nasal endoscopy and CT imaging when clinically appropriate.

Direct Answer: What Can a Sinus CT Show?

When congestion primarily affects one side, a sinus CT may show whether that side has structural narrowing, inflamed sinus tissue, trapped fluid, an obstructed drainage pathway, or a soft-tissue abnormality requiring further evaluation.

A CT scan cannot always determine the exact cause of a finding on its own. The images must be considered together with the patient’s symptoms, medical history, nasal examination, and any other necessary testing.

Why Does One Side of the Nose Feel More Blocked?

The nose naturally alternates airflow between the left and right nasal passages. This process, known as the nasal cycle, occurs as tissue inside one side gently swells while tissue on the other side contracts. The pattern generally reverses after several hours.

It is normal for one side to feel somewhat less open and then switch. The pattern is less consistent with the normal nasal cycle when:

• The same side remains blocked
• The obstruction continues for weeks or months
• Symptoms progressively worsen
• Congestion occurs with recurring bleeding
• Facial pressure or drainage consistently affects one side
• The sense of smell decreases
• Breathing problems interfere with sleep or exercise

Possible causes include a deviated septum, enlarged turbinates, chronic inflammation, nasal polyps, dental disease, or another obstruction.

What Is a Sinus CT?

A sinus CT scan is an imaging examination that uses specialized X-ray equipment and computer processing to produce cross-sectional images of the nasal passages and paranasal sinuses.

The images can be reviewed in multiple planes, allowing the provider to evaluate:

• The nasal septum
• The turbinates
• The sinus cavities
• Sinus drainage pathways
• Surrounding bony anatomy
• Areas of fluid or thickened sinus tissue
• Certain soft-tissue abnormalities

Routine sinus CT scans are commonly performed without contrast. Contrast, MRI, or another study may be recommended when more information is needed about a mass, complication, blood vessel, or surrounding soft tissue.

What Might a Sinus CT Show?

Several CT findings may help explain why one side of the nose feels more obstructed.

A deviated septum

The nasal septum is the wall of cartilage and bone separating the nasal passages. If it bends significantly toward one side, it can reduce the space available for airflow.

A CT can show the position and shape of the septum and its relationship to nearby structures. However, many people have some degree of septal deviation without significant symptoms. The provider must determine whether the deviation corresponds with the location and severity of the patient’s obstruction.

When a deviation causes substantial breathing problems that do not improve with appropriate nonsurgical treatment, septoplasty may be considered.

Enlarged turbinates

Turbinates are structures along the sidewalls of the nose that warm, humidify, and filter inhaled air. The soft tissue covering them can swell in response to allergies, irritants, infections, or other inflammation.

A CT may show that a turbinate is enlarged or that the available airway is narrow. Because turbinate swelling can change during the day, an office examination or nasal endoscopy is also important.

Narrowed sinus drainage pathways

Each sinus drains through a relatively small opening. Inflammation, anatomical differences, polyps, or another condition can narrow these pathways and interfere with ventilation and mucus drainage.

CT imaging can map deeper drainage anatomy that cannot be directly seen during a routine examination. This information may be especially useful when one-sided congestion occurs with recurring infections, facial pressure, or persistent drainage.

Sinus inflammation

A CT may show findings associated with sinus inflammation, including:

• Thickening of the sinus lining
• Fluid inside a sinus
• Partial or complete opacification
• Involvement of one or multiple sinus cavities
• Changes around a drainage pathway

An abnormal CT does not automatically mean that a patient has an active bacterial sinus infection. Imaging cannot always determine whether inflammation is viral, bacterial, fungal, dental, allergic, or related to another cause. Mild changes can also appear in people without significant sinus symptoms.

Nasal polyps or another soft-tissue finding

Nasal polyps are noncancerous growths associated with inflammation of the nasal and sinus lining. Depending on their size and location, they may contribute to congestion, reduced smell, postnasal drip, or impaired sinus drainage.

CT imaging may show soft-tissue changes consistent with polyps and indicate how extensively the sinuses are involved. However, CT cannot always distinguish a polyp from every other soft-tissue abnormality.

A one-sided growth may require closer evaluation with nasal endoscopy. MRI or biopsy may be recommended when a finding is unusual or its identity remains uncertain.

A dental source of sinus inflammation

The roots of the upper teeth are located close to the maxillary sinuses. A dental infection, extraction, implant, or another dental condition may sometimes contribute to inflammation in one maxillary sinus.

A sinus CT may show a pattern that raises concern for a dental source, but it does not replace a dental examination or dedicated dental imaging. The provider may recommend evaluation by a dentist or oral healthcare professional.

Fungal material

Some fungal sinus conditions can primarily affect one sinus and produce recognizable patterns on CT imaging. Imaging may raise suspicion for fungal material, but further clinical evaluation is needed to confirm the diagnosis and determine the appropriate treatment.

An uncommon growth or mass

Most one-sided nasal congestion is not caused by cancer. Nevertheless, persistent unilateral obstruction—particularly when accompanied by recurrent bleeding, facial numbness, swelling, or vision changes—requires careful evaluation.

A CT may show an abnormal soft-tissue area, expansion of a sinus, or changes involving nearby bone. Additional imaging or a biopsy may be necessary to determine exactly what the abnormality represents.

Does One-Sided Congestion Always Require a CT?

No. A CT scan is not automatically needed whenever one nostril feels blocked.

An ENT evaluation generally begins with a discussion of the symptoms and a physical examination. Nasal endoscopy may allow the provider to examine deeper areas of the nasal passages, look for visible inflammation or drainage, and assess potential obstructions.

CT imaging may be considered when:

• The same side remains congested for several weeks
• Symptoms persist despite appropriate treatment
• Chronic or recurrent sinus disease is suspected
• Nasal endoscopy identifies an abnormality
• Congestion occurs with persistent bloody drainage
• The diagnosis remains unclear
• Detailed anatomy is needed for treatment planning

CT imaging uses ionizing radiation. It should be ordered when the expected clinical information is likely to be useful and outweighs the potential risk.

What Happens If the CT Shows an Abnormality?

Treatment depends on what the scan shows, how closely the finding matches the symptoms, and what is identified during the examination.

When inflammation is contributing, treatment may include an appropriate nasal spray, allergy management, saline irrigation, or other medical care. Nasal irrigation must be performed with distilled, sterile, or previously boiled and cooled water.

When a structural condition significantly restricts airflow, an ENT may discuss septoplasty or turbinate reduction. Patients with qualifying chronic sinus disease may be evaluated for balloon sinuplasty or endoscopic sinus surgery.

A CT abnormality does not automatically mean a procedure is necessary. Treatment recommendations should be based on the complete evaluation, the severity of the symptoms, previous treatment, and individual health factors.

When Should Persistent One-Sided Congestion Be Evaluated?

Consider seeing an ENT when:

• The same nostril remains blocked
• Symptoms continue after a cold has resolved
• Congestion interferes with sleep, exercise, or daily comfort
• Facial pressure or drainage repeatedly affects one side
• Your sense of smell has changed
• Sinus infections recur
• Nasal drainage is bloody, foul-smelling, or consistently one-sided
• Appropriate allergy treatment does not improve the obstruction

Seek prompt medical attention for swelling or redness around the eyes, vision changes, facial numbness or weakness, severe headache, confusion, significant facial swelling, neck stiffness, or rapidly worsening symptoms.

Find the Cause of One-Sided Nasal Congestion

A sinus CT may help identify inflammation, narrowed drainage pathways, a deviated septum, enlarged turbinates, polyps, or another finding that could contribute to one-sided congestion. However, imaging is only one part of the evaluation and cannot determine the cause of every abnormality by itself.

Contact Trinity ENT to discuss persistent one-sided nasal congestion and determine whether an office examination, nasal endoscopy, CT imaging, or another approach may be appropriate.