ICU Radiology
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Direct answer
Intensive-care radiology is the daily portable chest film plus targeted CT and ultrasound, read in a fixed order — devices first, then lungs, pleura, heart and mediastinum — because in the ICU the commonest acute findings are iatrogenic. The central diagnoses are ARDS by the Berlin definition (bilateral opacities not fully explained by effusion or collapse, within one week of a known insult, with PaO2/FiO2 ≤ 300 at PEEP ≥ 5: mild 201-300, moderate 101-200, severe ≤ 100), ventilator barotrauma tracking from pneumomediastinum to tension pneumothorax, the white-out hemithorax after surgery or aspiration, and the missed complications of lines and drains; bedside ultrasound answers many of these questions before the portable film arrives.
What you must remember
- Berlin ARDS criteria: bilateral opacities, timing within 7 days of insult, not fully explained by heart failure or fluid overload, PaO2/FiO2 ≤ 300 with PEEP ≥ 5; severity bands mild 201-300, moderate 101-200, severe ≤ 100.
- White-out of one hemithorax: work through massive effusion, complete lung collapse (mediastinal shift toward it), pneumonectomy (shift toward with absent lung), consolidation and ARDS — the direction of mediastinal shift is the discriminator.
- Barotrauma sequence: interstitial emphysema first, then pneumomediastinum, subcutaneous emphysema, pneumopericardium and tension pneumothorax; positive-pressure ventilation converts a small leak into a tensioning one fast.
- Deep sulcus and apical lucency are the supine-film signatures of pneumothorax; a lucent stripe along the pericardium suggests pneumomediastinum (continuous diaphragm sign).
- Post-cardiac-surgery films: widening mediastinum raises haemopericardium or mediastinal bleed when width increases beyond baseline, but sternal dehiscence and atelectasis are more common; compare with the earliest post-operative film.
- Bedside ultrasound: B-lines in more than two zones per side suggest interstitial syndrome (pulmonary oedema versus fibrosis), absent lung sliding excludes pneumothorax at that window, and a lung point confirms it.
- Head CT in the ICU: diffuse loss of grey-white differentiation with sulcal effacement indicates severe hypoxic-ischaemic injury — the white cerebellum sign, a preserved bright cerebellum against oedematous hemispheres, is a poor-prognosis marker.
A night in the unit, read systematically
Take a ventilated patient whose oxygenation has fallen overnight. Device review first: endotracheal tube 5 cm above the carina, central line tip at the cavo-atrial junction, nasogastric tube in the stomach — all safe. Lungs next: bilateral patchy opacities that increase over 48 hours following sepsis, no large effusion, no collapse to explain them, and the echocardiogram is normal. That is ARDS by Berlin, moderate if PaO2/FiO2 sits at 150, and the radiology contribution is excluding the alternatives — unilateral effusion, lobar collapse, aspiration — while the intensivist adjusts ventilation.
Two days later the film shows a black stripe along the heart border and air in the neck soft tissues: pneumomediastinum from barotrauma. Nothing needs draining yet, but tension physiology must be watched — tracheal shift, hemidiaphragm depression, deep sulcus — and hypotension that fails fluids means decompression, not another film. This chain — device, lung, pleura, mediastinum, then decide — is the entire subject of ICU radiology compressed into one patient.
How the exam frames it
Two question styles dominate. The first gives a bilateral white-out and asks the next investigation or the diagnosis: name ARDS when the timeline and PEEP are given, and mention effusion versus collapse using mediastinal shift before committing. The second gives a post-operative or vented film and expects device-position errors — the endotracheal tube in the right bronchus with a collapsed left lung is the single most reproduced ICU image in Indian postgraduate papers. A viva favourite is why ARDS is worse posteriorly and basally (dependent atelectasis plus oedema) and why prone positioning works — it recruits those dorsal regions. Quote the Berlin bands rather than the old acute lung injury terminology; examiners now mark the 2012 definition, and mentioning the updated global definition of 2023, which relaxes the PEEP and oxygenation thresholds, reads as current rather than coached.
Frequently asked questions
What are the Berlin criteria for ARDS on imaging and physiology?
Bilateral opacities on imaging within 7 days of a recognised insult, not fully explained by effusion, collapse or heart failure, with PaO2/FiO2 ≤ 300 at PEEP ≥ 5; severity is mild, moderate or severe based on the ratio.
How is a unilateral white-out hemithorax differentiated?
The direction of mediastinal shift separates effusion or large mass (pushed away) from collapse or pneumonectomy (pulled toward); consolidation and ARDS leave the mediastinum central.
Which radiographic signs indicate pneumothorax in a supine ICU patient?
Apical and lateral lucency, the deep sulcus sign, a depressed hemidiaphragm and, on ultrasound, absent lung sliding with a lung point on M-mode.
What is the white cerebellum sign?
Diffuse cerebral hypoxic-ischaemic injury makes the hemispheres low-density while the cerebellum and brainstem keep normal density, so the cerebellum appears relatively bright — a marker of devastating injury after cardiac arrest.
Why must devices be reviewed before lung pathology on ICU films?
Misplaced endotracheal tubes, central lines and drains are common, rapidly lethal and correctable, and they also cause the lung findings (collapse, oedema) that would otherwise be misattributed to primary disease.