Pneumonia: diagnosis and examination

Pneumonia is a lung disease characterized by inflammation.


Role of radiology in the diagnosis of pneumonia

In the initial phase and also in
the course of pneumonia can be difficult to diagnose by means of

  • auscultation (to find possible breathing sounds),
  • Percussion.

The chest X-ray is much more accurate.
The main role of radiology in lung infections (in communities, hospital, etc.) is:

  • Identify the presence of a lung infection by means of radiological shading.
  • Determine the location and spread of inflammation. For example, it allows to determine whether a lobe, an entire lung, or a segment (part of a lobe) is affected.
  • Sometimes there are radiological signs that indicate a possible cause of pneumonia to the doctor.
  • It is used to identify the way and the area from which biological material can be taken. In the case of an infection, it may be useful as part of the diagnostic procedure to avoid false-negative findings by bronchoscopy. The pulmonologist performs bronchoscopy and bronchial avage (endoscopic examination of the trachea and bronchi). To do this, he must penetrate the infected segment with the bronchoscope, inject a saline solution there and absorb the secretion from the bronchus that was imaged in the radiography.
  • It is used to monitor development and determine whether the patient is undergoing a healing process or whether the therapy is inadequate. For example, fungal infections have a radiologically similar appearance to bacterial pneumonia.

Radiological diagnosis of pneumonia

One must look at the lobar or segmental spread of inflammation, i.e. determine whether the inflammation affects an entire lobe or only an inner segment.

If pneumonia is lobary, then it is limited by interlobular septa (grooves that divide the lungs into lobes).
The compaction of the lungs means that the lung alveoli are filled with inflammatory fluid.
In radiography, compaction corresponds to shading (whitish area).

Shading has blurred edges because they are numerous and small (they correspond to the alveoli) and are close to each other.
Since lobar pneumonia affects the alveoli and not the bronchi, you can see in the X-ray:

  • Airbronchogram, that is, in the X-ray you can see the darker part near the spine, which corresponds to the bronchi. The air contained in the bronchi gives the X-ray image this color, while the lateral part appears much clearer (opaque) because the alveoli are full of fluid.
  • The air alveologram corresponds to the healing phase from a radiological point of view. Since the alveoli are filled with air again, the shading gradually decreases and in their place X-ray negative images are formed compared to the previous images.

On the right you can see a pulmonary compaction, which is a classic radiological sign that indicates a lobear or alveolar pneumonia.

There is extensive shading and limited septa.

You can notice an air bronchogram, so the cause is probably bacterial.

Between the shadows there is a large radiotransparent area (which absorbs a few X-rays and is therefore black). This is a sign of hollowing out or necrosis melting (decay of organic tissue).

The patient had:

  • pulmonary necrosis (tissue death),
  • as a result, a spontaneous cavitation (structure like a bubble), which becomes larger and larger over time.

This type of radiography suggests that gram-negative bacteria may be responsible, but it is impossible to say with certainty.

In the left image, on the other hand, there is a progressive expansion of the focus of necrosis (small area from which the inflammation originated) in the shaded area.

This situation and the formation of abscesses are typical in drug addicts.

The cause is immunosuppression in HIV and the typical recurrent infections in drug addicts.

Infected embolisms generally originate from this radiological picture.

There may also be:

  • shading in both lungs,
  • Area with a slight increase in lung tissue density.

In this case, you can still see the adjacent lung formations.

In radiology, this is called frosted glass opacity or minimal interstitial opacity and represents a cavity that is radiolucent.

The presence of both signs may indicate fungal pneumonia, very often with immunosuppressants caused by Aspergillus. However, this is always just a guess.

Also in CT, the same person shows more or less extensive shading in the form of nodes, in the vicinity there are:

  • frosted glass-like shaded areas,
  • Small peripheral compaction with cavity.



In patients treated in intensive care with a tumor disease or after a bone marrow transplant, this type of pneumonia can lead to death.
This is not a rare occurrence.

Even if a patient is placed in a sterile room, this pathology can occur without appropriate and prompt therapy and the patient may die from it.

Therefore, radiography is indispensable to detect these diagnostic elements as quickly as possible.

Blood test for pneumonia

Blood tests are performed to check if:

  • Inflammatory indicators are increased: PCR, VES and α2-globulins.
  • Neutrophilic leukocytosis exists: white blood cells > 10,000 / mm3, and neutrophils at 80-90%.

The blood test is also carried out to determine the antibodies.

In order to obtain reliable data on antibodies, it is necessary to perform 2 tests 8-10 days apart, obtaining data on:

  • seroconversion,
  • Presence of IgM – one sees a 5-fold increase of specific IgM.

After blood has been taken, laboratory tests are continued.
The test sample is stained and then examined under the microscope:

  • Methylene blue makes it possible to determine the number of leukocytes and squamous cells.
  • The Gram staining allows preliminary information about the responsible bacterium, for example, whether paired bacteria (diplococci) are present, which justifies the suspicion of pneumonia by Streptococcus pneumoniae.

Laboratory tests for pneumonia

It is important to determine the type of sample to be examined.

Depending on the suspected diagnosis, the doctor decides which fluids or secretions to examine.


  1. Sputum
  2. Bronchial aspirate
  3. Bronchial avage
  4. BAL (bronchoalveolar lavage)
  5. Blood

Diagnosis to confirm

  1. Alveolar pneumonia
  2. Interstitial pneumonia
  3. Bronchitis
  4. Pneumonia in immunocompromised patients
  5. Interstitial pneumonia

Sputum examination for pneumonia

Examination of sputum is indispensable for assessing a patient with acute bacterial pneumonia.

Unfortunately, the expectorated material is often contaminated with bacteria that colonize the upper and sometimes the lower respiratory tract. They are therefore not the real cause of the disease.
This contamination reduces the specificity of the sample from the lower respiratory tract.

Studies show that the study identifies the responsible microorganism in patients with bacterial pneumonia in less than 50% of cases.

Sputum can be obtained selectively or spontaneously and is certainly the easiest and least invasive examination to perform, but it is not always sufficient. To be really suitable, it is necessary to take into account some parameters:

  • leukocytes > 25 per microscopic counting chamber (magnification to 100 X),
  • Epithelial scale cells < 10-20 per microscopic counting chamber.

The staining of the sputum by the Gram method is essential to detect whether the responsible microorganism is a

  • gram-positive
  • Gram-negative


Special dyes are very useful, for example:

  • staining according to Ziehl-Neelsen to confirm infection by microbacteria,
  • Giemsa staining for Pneumocystis carinii.

If an infection by Legionella is suspected, the sputum can be grown in special culture media.

The cultivation of the expectorate (secretion from the respiratory tract) is useful, but the result is unreliable because patients are often unable to produce sufficiently deep sputum so that the test sample is inadequate.

The examination becomes reliable if the sample is taken during a bronchospasm crisis (muscular contraction that reduces the width of the bronchi).

Enriched soils are used for cultural testing, as many of these microorganisms are very demanding. For example, blood-enriched soils also allow the evaluation of hemolysis (destruction of red blood cells).

All encapsulated bacteria have a typical appearance in culture, namely they form mucus colonies, which appear as follows:

  • translucent
  • opalescent,
  • slightly frothy.

Blood culture (culture of a blood sample)

During a fever attack you need 2 blood samples, better are 3.

If the culture is positive, it points to the causal diagnosis and indicates how widespread the germ is and whether there is a risk of septicaemia.

Tests for bacterial urinary antigens are used to detect antigens:

  • pneumococci,
  • of pathogenic legionella serotypes,
  • the influenza virus,
  • of respiratory syncytial virus.

The PCR test is performed if TB and Legionella are suspected.

Bronchoscopy and bronchoalveolar lavage in pneumonia

The doctor will order these invasive medical examinations if:

  • To distinguish pneumonia from a tumor is
  • In immunosuppressive patients, the reasons are:
  • Insufficient sputum production
  • “Atypical” clinical signs
  • The X-ray shows diffuse inflammation in a patient that is rapidly worsening
  • Lack of response to therapy
  • Other investigations have not made it possible to understand the cause.


A sample can be taken during bronchoscopy via:

  • Brush removal by protected catheter (PSB),
  • Bronchoalveolar lavage (BAL).

Bronchoscopy allows imaging of the lower respiratory system.

Samples are collected using a protected double-sheathed brush (PSB) with:

  • BAL
  • Transbronchial biopsy from the shaded lung area.

Bronchoalveolar lavage: a soft and flexible tube with fiber optics is inserted via:

  • the nostrils,
  • the oral cavity.

The purpose of this study is to:

  • examine the respiratory tract,
  • bronchial or bronchopulmonary wash samples.

Usually, the sample is contaminated with the bacterial flora of the upper respiratory tract, and 1 ml of the sterile liquid for culture must be taken by removing the brush from the inner catheter to distinguish contamination (< 1000 cfu/ml) from infection (> or = 1000 CFU/ml).

BAL is usually performed with 150-200 ml of sterile, non-bactericidal saline.

The Gram staining of the sample material from the cytocentrifuged (cellular centrifugation) lavage can be used as a rapid test for antibiotic therapy in anticipation of the result from the culture.

In nosocomial forms, bronchoscopy is used to isolate the microorganisms responsible.

In the case of medically caused pneumonia, it is used:

  • the diagnosis of diagnosis,
  • distinguishing one pathology from other disorders.

As a rule, patients are in the intensive care department, where transbronchial biopsy is also performed, which has a very high specificity to identify the germs responsible.

Examination of pneumonia depending on the type of patient

Patient in the intensive care unit: sputum cultures are prepared and the search for antigens of Legionella pneumococcus is carried out

Leukopenia patient: it is performed:

  • a blood culture,
  • Search for pneumococci.

Patient who has recently traveled: Legionella is being searched for.

Community-acquired pneumonia: It usually starts with an outpatient visit (history and physical examination), followed by chest X-rays, if necessary.

Nursing home: A physical examination is carried out, if necessary followed by a chest X-ray.

Hospital: examinations ordered by the doctor:

  • Blood gas analysis
  • chest X-ray,
  • CT of the thorax.

If the X-ray is not conclusive, one can also advise to:

  • serological examination,
  • microbiological examination (Gram staining, urinary antigens, serology and culture),
  • invasive examination (bronchoscopy with brush removal via protected catheter or BAL).

Diagnosis of interstitial pneumonia

The diagnosis is difficult, because often there is not enough material in the test samples. In addition, the microorganisms responsible are of the intracellular type and are therefore more difficult to detect.

The next step is the following.

Airway material:

  • cultivation (not always possible and difficult),
  • Molecular tests using PCR (molecular diagnostics by gene amplification): they are definitely the most effective,
  • ELISA test or immunofluorescence.

For diagnosis, laboratories always use at least two of these tests, never just one.

Because it is easy to get:

  • False negative results
  • False positives.

The answer to a suspected diagnosis must therefore arise on the basis of several tests.

Acute interstitial pneumonia

Correlation between tissue changes and X-ray findings.

The X-ray does not show:

  • the destruction of mucous cells,
  • whether there is edema (fluid accumulation) or significant cell infiltration in the surrounding tissues of the bronchi.

Peribronchial cuff images (thickening of the bronchial walls) can be seen mainly in CT, but this is more difficult with radiography.

The X-ray image shows when pneumonia is in its final phase, i.e. when the airway endways and alveoli are involved.

The bronchial epithelium (mucous membrane) is thickened, a surrounding inflammation is formed and the bronchus is full of typical necrotic material.

The peribronchial cuff phenomenon is characterized by an interstitial infiltrate (inflammatory cells reach the tissue between the alveoli).

The X-ray shows all the signs of interstitial shading, including the Kerley lines (especially the Kerley B lines).

Any shading of linear or reticulated type indicates inflammation of the interstitium.

The CT shows a much more accurate picture, you can see the cuffs of the peribronchial tissue well.

There is a thickening of the structures:

  • in the middle of the secondary flap,
  • in the periphery.

One sees polygonal shapes with thickened walls, which are not present in a normal subject.

Without therapy, the alveoli gradually fill with fluid.
It can therefore lead to a consolidation of the lungs with a typical bilateral inflammation. In this case, you see linear images or a typical interstitial shading.

In the left picture, the left lung is particularly affected.

We can define three phases:

  1. Initial stage, with the signs of involvement of the interstitium, with lines and lateral mesh in the right lung.
  2. Intermediate phase, spread of shading, with typical compaction of alveolar syndrome in the central areas of the chest, especially on the right.
  3. Final phase in the left lung, with an extensive compaction that occupies the entire lung.

For the diagnosis of Pneumocystis jirovecii pneumonia, no culture examination is carried out, but one continues with the direct examination under the microscope:

  • on a sample of BAL (bronchioalveolar lavage) or
  • lung biopsy with different staining (Giemsa or Groccot-Gomori; this is a special silver staining in mushrooms, in which they are highlighted in a dark color).

Fluorescence microscopy with antibodies labeled with fluorescent substances is the reference test.

Investigations by PCR (by gene amplification) have not become standard.

Diagnosis of infection with Legionella pneumophila

1) The first thing to do when legionellosis is suspected is to search for the antigen in the urine (LPS).

  • This is numerous on the surface of Legionella.
  • A few days after the onset of the disease, urinary excretion begins. This process lasts for several weeks or months.

There are very fast methods to demonstrate the presence or absence of LPS by an immunoenzymatic test for a few drops of urine: direct antibodies against LPS are used together with myeloperoxidase. If the antigen is present, it binds to the antibody.

The result is the activation of the enzyme.

This examination has a high sensitivity (ability to identify sick persons) and is fundamental for diagnosis.

2) On microscopic examination, Legionella is very difficult to see: it is a gram-negative, elongated, very thin and poorly colored bacterium.

3) If the microbial number (amount of bacteria) in the sample taken is increased, small transparent colonies can be seen in the culture, which grow after some time.

4) Search for antibodies in 2 samples 10 days apart by ELISA or direct immunofluorescence.

5) Search for Legionella DNA in cell residues of the expectorate or bronchioalveolar irrigation fluid by PCR.

Diagnosis of lobar pneumonia

Lobär pneumonia is usually caused by Streptococcus pneumoniae or Haemophilus influenzae.

Microscopically speaking, it is a typical pneumonia in which the inflammation leads to clouding in the area of the alveoli.

In the following picture you can see an image with altered tissue on the right, red is the part affected by the disease. It causes:

  • a significant traffic jam,
  • the change in the structure of the lungs.

On the left, on the other hand, a microradiography obtained by X-ray of the part of the lung tissue taken.

Here one notices:

  • the exchange of air inside the alveoli by flammable and necrotizing material,
  • the air bronchogram surrounded by alveolar opacity. The turbidities are:
  • homogeneous
    • with strongly faded edges.

On the right you can see an X-ray of lobar pneumonia, which affects the right tip of the lung.

One notices:

  • the demarcation at the level of the intralobular septa,
  • the classic sign of the air bronchogram.

In the image below, a large affected lung area can be seen in the upper lobe, on the left the limited distribution of the septa between the lobes of the lung is easy to see.

In the picture on the right:

  • The shaded areas are relatively homogeneous.
  • In the middle area (central) you can see the signs of an air bronchogram.

During the development of pneumonia, the characteristics of the shadows are the same, one sees the boundary between the affected and the healthy lung lobe better.

However, the image on the right shows peripheral X-ray transparent (darker) areas indicating partial alveolar marking.

The patient responds to the therapy and the radiological picture slowly returns to normal. This results in:

  • The treatment was correct.
  • The interpretation of shading has been confirmed.

This image could also have indicated a lung tumor.
Of course, pneumonia improves only under therapy with antibiotics.

The doctor recommends repeating the X-ray until the shading of the lungs has completely disappeared.

A common mistake is to compare the patient’s symptoms with previous X-rays. In fact, the X-ray improves much later than the patient.
The delay is a few days, sometimes up to a week. It is therefore useless to take the X-ray two days after the start of therapy with antibiotics, especially if the patient is still young, because he only absorbs X-rays unnecessarily.

One should wait a week before repeating the X-ray.

But there are exceptions: In the case of an intensive care patient and in order to know the short-term course, radiological checks can also be carried out after just a few days.
To radiologically represent the healing process of pneumonia, the doctor orders radiography at least 2-3 weeks after the first examination.

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