CT scan findings in the COVID era: Ground Glass Opacities (GGO)


The COVID-19 pandemic filled our vocabularies with more medical terms than most of us would ever hear about, but some were familiar.  It soon became clear that CT scans were a useful tool to check for COVID-19.  One 2022 study showed that COVID-19 shares some features with other viral types of pneumonia, despite some differences. They commonly present as “ground glass opacities” (GGO) along with vascular thickening, air bronchogram and consolidations. Also, they differ by age, disease severity, and outcomes among COVID-19 patients.  GGOs refer to findings CT scans of COVID-19 patients that can help diagnose and monitor the infection. A similar study published early on in the pandemic came up with similar conclusions in regard the presentation on CTs of the chest.  Another study said that while it’s important to note that GGOs aren’t specific to COVID-19, meaning they can show up in other conditions and infections, they are common among those infected with COVID-19.  The inference is that the clinical history of the patient showing GGO during or following a COVID-positive scenario must also be a factor.

What are ground glass opacities?

According to Isabel Oliva Cortopassi, MD, senior associate consultant at Mayo Clinic and former chief of thoracic imaging at Yale Medicine, ground-glass opacities (GGOs, for short) indicate abnormalities in the lungs. “Ground-glass opacities are a pattern that can be seen when the lungs are sick,” said Dr. Cortopassi. Dr. Cortopassi added that, while normal lung CT scans appear black, an abnormal chest CT with GGOs will show lighter-colored or gray patches.  Those lighter patches don’t completely obscure the other structures in the lungs, said Jennifer Possick, MD, a Yale Medicine pulmonologist—that makes them different from lesions associated with lung cancer, which can often appear as solid. With GGOs, “there is haziness seen overlying an area of the lung, but the underlying structures of the lung (airways, blood vessels, lung tissue) can still be identified,” said Dr. Possick. It resembles, well, ground glass, or glass that is still transparent but has a matte finish.

What Else can Ground-Glass Opacities Indicate?

As above, it’s important to keep in mind that GGOs aren’t specific to COVID-19 and can be seen in many different settings, emphasized Dr. Possick. GGOs in chest CT scans can also indicate congestive heart failure, inflammatory interstitial lung diseases, and diffuse alveolar hemorrhage (bleeding into the airspaces of the lungs), among other issues. But one of the most common diagnoses for GGOs is viral pneumonia, most often caused by a respiratory syncytial virus (RSV), cytomegalovirus, herpes simplex virus, and coronavirus (all types).  In terms of COVID-19, Dr. Cortopassi explained that GGOs on a CT scan indicates COVID-19-related pneumonia or lung inflammation caused by the viral infection. It’s important to note, however, that not all patients with COVID-19 will go on to develop pneumonia, stressed Dr. Cortopassi. These terms are important to know, especially if your doctor mentions ground glass opacities while treating you for COVID-19 or another illness. But Dr. Cortopassi reiterated that a COVID-19 diagnosis doesn’t automatically lead to a worsened condition in which these GGOs will show up in a CT scan, nor does an abnormal scan definitively mean a coronavirus infection. “Some people will have completely different radiologic findings, and some people will have no imaging abnormalities at all,” said Dr. Cortopassi.

Another study published in the journal, The Lancet Respiratory Medicine used people who had been hospitalized for COVID-19 and had GGOs on initial lung scans; they rescanned their lungs at three and nine months following hospital discharge. Researchers found that 78% of patients still had residual GGOs at three months post-discharge, and 24% had GGOs still showing up on scans at nine months post-discharge.

My own experience

It was a bit of a shock when my wife and I both tested positive in the middle of 2022, despite surviving unscathed through several waves since the pandemic began in early 2020.   It is an experience I would not like to repeat, and I wrote about it in this article – click here.  I was not symptomatic until 29th June and test positive on 30th June.  I was basically out of action for around 11 days and 7 days after testing negative, I’m still suffering some of the symptoms, mainly coughing and a slight shortage of breath at times.  I felt fit enough to attend a planned NET surveillance appointment on 13th July to receive the results of my surveillance tests including a CT scan on 22nd June. It is then my Oncologist informed me that ground glass opacities had been found on this scan which occurred 7 days prior to me becoming symptomatic and testing positive. He described them as “fluffy objects on my left lung.  My own analysis and opinion is that my chest infection history since childhood has perhaps influenced the severity of the covid infection I experienced.  I’m happy that I had been vaccinated before I caught it.  I will be getting a repeat CT of my chest in 3 months to check the GGO.

I wanted to publish my own experience as I frequently see ground glass opacities discussed in my private group, normally by Lung NET patients.  Clearly, a possible connection to COVID-19 must be assessed in new findings.

Disclaimer: The information in this story is accurate as of the publication date.  After almost 2.5 years of pandemic, clinicians know a lot more but the situation around COVID-19 continues to evolve.  It’s possible that some data have changed since the publication of any studies I referenced.  Please refer to the latest guidance from your own national disease control agencies and organisations.

click to read my covid story

C-19 vaccines are also causing imaging issues on PET scans

click on the picture to read

After a few months of introducing C-19 vaccines, many cases of false-positive lymph nodes were reported on nuclear PET scans, some of which led to unnecessary biopsies and unnecessary worry for the cancer patients concerned.  I covered that here – click here or the picture.


I am not a doctor or any form of medical professional, practitioner or counsellor. None of the information on my website, or linked to my website(s), or conveyed by me on any social media or presentation, should be interpreted as medical advice given or advised by me. 

Neither should any post or comment made by a follower or member of my private group be assumed to be medical advice, even if that person is a healthcare professional.   

Please also note that mention of a clinical service, trial/study or therapy does not constitute an endorsement of that service, trial/study or therapy by Ronny Allan, the information is provided for education and awareness purposes and/or related to Ronny Allan’s own patient experience. This element of the disclaimer includes any complementary medicine, non-prescription over the counter drugs and supplements such as vitamins and minerals.

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3 thoughts on “CT scan findings in the COVID era: Ground Glass Opacities (GGO)

  • Susan H Durjan

    I too have GGO at the base of my left lung. In my case, most likely due to pneumonia 2 years in a row prior to my NET diagnosis in 2018. I was surprised and concerned to see the observation on the report of my first CT. My doctors were good at reassuring me that I shouldn’t worry about it. I recently saw Dr. Strosburg at Moffitt, had the usual labs and CT. The GGO is still visualized.

  • Sandy

    I have GGO areas in multiple places on my lungs. The GGO areas are the end result of a massive pulmonary emboli storm. I will be interested in seeing the next CT scan results because my lungs have gotten healthier. In fact healthy enough to expand down into the empty RLL area. So the next annual cancer recheck will be interesting. So add Pulmonary emboli to the list of things that can cause GGO areas.

    • thanks for commenting, Sandy. I could have written a fairly extensive list but opted for the most common but did add “among other issues”. To be honest, there is little or info online from reputable sources to indicate a link between GGO and PE indicating it’s not a very common occurrence – but I’m sorry it happened in your case. I hope yours clears up soon!

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