01Purpose and principlesWhat the assessment is for and the core concepts behind it.
Atelectatic collapse occurs when a lobe or segment loses air and becomes smaller. Resorptive collapse follows bronchial obstruction; compression follows pleural air or fluid; passive collapse occurs with reduced ventilation; and scarring can pull structures chronically. Direct signs are displaced fissures and crowded vessels. Indirect signs include hilar or mediastinal shift toward the affected side, elevated hemidiaphragm and compensatory hyperinflation elsewhere.
Consolidation replaces alveolar gas with inflammatory fluid, pus, blood, protein or cells. The radiographic result is air-space opacity, often with air bronchograms because bronchi remain gas filled. Distribution may be lobar, segmental, patchy or diffuse. The pattern supports a differential rather than proving bacterial pneumonia; pulmonary oedema, aspiration, haemorrhage and organising inflammatory disease can look similar.
Interpretation should integrate the clinical tempo. Fever, cough and focal chest signs favour infection, but an obstructing lesion can cause both collapse and post-obstructive consolidation. After treatment, symptoms often improve before the film clears. Failure to recover, recurrence in the same place or suspicious morphology requires a defined further-imaging and responsibility plan.
Key points
- Collapse means loss of aerated lung volume; seek fissural displacement, hilar movement, rib crowding, diaphragmatic elevation and compensatory overinflation.
- Consolidation fills alveoli and usually creates air-space opacity with air bronchograms but little early volume loss; radiography alone rarely defines the organism.
- A negative or equivocal film cannot overrule severe physiology or persistent cancer concern: treat urgent illness and escalate to CT, bronchoscopy or targeted follow-up according to the unresolved question.
- Use the silhouette sign to localise disease: loss of the right heart border suggests middle-lobe contact, while loss of a hemidiaphragm suggests lower-lobe involvement.
- Collapse and consolidation may coexist when an obstructed bronchus leads to distal infection; do not force the image into a single label.
- Current NICE guidance targets a six-week follow-up film to people with persistent or worsening symptoms or risk factors for underlying disease rather than ordering it routinely for everyone.
02Indications, selection and cautionsWhen it is useful, when urgency changes and important limitations.
Fissural, hilar, mediastinal or diaphragmatic displacement toward opacity supports collapse. Air bronchograms with preserved lobe volume support consolidation, although both patterns can coexist.
Look for superior fissural movement, elevated hilum and a triangular or veil-like opacity; central fullness or bronchial cutoff raises an obstructing lesion.
Right heart border loss localises right middle-lobe contact; left heart border loss can reflect lingular disease. The lateral view may reveal a wedge-shaped opacity.
Lower-lobe opacity may hide behind the heart, obscure a hemidiaphragm or create a posterior basal density. Check the spine sign on a lateral image.
Cavitation, loculated pleural fluid, gas-fluid levels, bulging fissures or progressive destruction should prompt CT and urgent specialist assessment.
Persistent lobar collapse, abrupt bronchial cutoff, hilar mass or recurrent same-site infection needs CT and often bronchoscopy to define the obstructing cause.
03Method and interpretationA systematic approach to the test and its findings.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
Chest radiographyFirst step - Why
- Identify air-space opacity, volume loss, pleural complication and an alternative diagnosis.
- Interpretation and limitations
- Projection and inspiration affect appearances; a normal film does not fully exclude early pneumonia and cannot characterise every obstructing lesion.
- 02
Contrast-enhanced chest CT - Why
- Define bronchial obstruction, mass, necrosis, abscess, pleural infection or an alternative cause.
- Interpretation and limitations
- CT separates collapsed enhancing lung from tumour more clearly and maps complications, but tissue diagnosis may still be required.
- 03
Thoracic ultrasound - Why
- Detect and characterise pleural fluid adjacent to consolidation and guide safe sampling or drainage.
- Interpretation and limitations
- Septations and echogenic material support complex fluid but do not replace pleural biochemistry, microbiology and the whole clinical picture.
- 04
Bronchoscopy - Why
- Inspect and sample a suspected central obstruction or remove selected mucus plugs or foreign material.
- Interpretation and limitations
- A patent central airway does not exclude peripheral tumour; urgency depends on respiratory compromise, suspected foreign body and cancer risk.
- 05
Microbiology and inflammatory assessment - Why
- Support pathogen-directed treatment and assess severity when infection is suspected.
- Interpretation and limitations
- Imaging cannot identify the organism reliably; cultures, viral testing and clinical response refine therapy while treatment proceeds.
04Clinical next stepsHow the result changes management or prompts escalation.
01Worked case: persistent opacityRight upper-lobe opacity after treatmentFirst stepAn older smoker has improved fever but persistent right upper-lobe opacity and volume loss six weeks after pneumonia.+
- 1Compare current and original radiographs, confirm the volume-loss pattern and review symptoms, smoking history, haemoptysis, weight change and prior imaging.
- 2Recognise that targeted follow-up has identified unresolved same-site disease and arrange contrast-enhanced chest CT rather than another empirical antibiotic course alone.
- 3Discuss the CT result through the lung-cancer or respiratory pathway and obtain bronchoscopy or tissue sampling when a central lesion remains plausible.
- 4DefinitiveVerify that the patient and responsible team receive the result and that follow-up continues until resolution or a definitive diagnosis is documented.
02Acute collapseSudden lobar loss after surgeryA postoperative patient develops hypoxaemia with new lobar volume loss on a portable radiograph.+
- 1Assess respiratory effort, oxygenation, pain, secretions and airway-device position and seek urgent senior review if deterioration is severe.
- 2Treat reversible contributors with appropriate airway clearance, analgesia and ventilation while considering mucus plugging or aspiration.
- 3EscalationEscalate to CT or bronchoscopy when collapse is extensive, persistent or associated with suspected central obstruction.
03Consolidation pathwayImage supports pneumoniaA patient has compatible symptoms and a new focal air-space opacity without major volume loss.+
- 1Assess severity and sepsis, obtain indicated microbiology and begin guideline-concordant treatment without waiting for radiographic clearing.
- 2Look for pleural fluid, cavitation, multilobar disease or another feature that changes treatment location or prompts CT and ultrasound.
- 3At discharge, arrange clinical review and consider a six-week film only when symptoms persist or underlying disease risk warrants it.
05Risks, monitoring and follow-upComplications, safety checks and further assessment.
- Trend oxygen need, respiratory rate, temperature, haemodynamics and functional recovery rather than using radiographic opacity alone as a severity marker.
- Re-image earlier if the patient deteriorates, fails to respond as expected or develops signs of pleural infection, abscess or airway obstruction.
- Consider a six-week follow-up chest radiograph after discharge when symptoms persist or worsen, or when lung-cancer or other underlying respiratory-disease risk is present; record who orders, checks and acts on it.
- Persistent same-lobe disease requires continued diagnostic ownership until malignancy, foreign body and other obstruction have been addressed.
- After treatment of collapse, confirm clinical improvement and appropriate re-expansion when this will change further airway or procedural management.
06Special situationsVariants, exceptions and circumstances that change the usual approach.
Displacement reveals collapse
Opacity becomes diagnostically different when a fissure, hilum or mediastinum moves toward it; that movement is evidence of lost volume.
Air bronchograms have limits
Air-filled bronchi within opaque lung support an alveolar process but are not specific for infection and may disappear with airway obstruction.
Obstruction can cause infection
A tumour or foreign body may produce distal collapse and post-obstructive consolidation, so dual patterns deserve deliberate airway assessment.
Clearing is clinically paced
Radiographic resolution can lag symptoms, but ongoing or recurrent focal change needs investigation rather than indefinite observation.
The lateral film can localise
A lateral view separates anterior middle-lobe or lingular opacity from posterior lower-lobe disease when a frontal projection is ambiguous.
07Common pitfallsFrequent interpretation and management errors.
- 01
Calling every focal opacity pneumonia without checking for fissural displacement, obstruction, infarction, haemorrhage or mass.
- 02
Repeating antibiotics for recurrent same-site consolidation without arranging CT and airway assessment.
- 03
Ordering universal routine follow-up instead of targeting patients with symptoms or underlying-disease risk and owning the result.
- 04
Waiting for radiographic confirmation before treating severe sepsis or respiratory failure in a compatible clinical syndrome.
- 05
Assuming improvement in fever proves that an underlying obstructing lesion has resolved.