CXR Findings in Pulmonary Edema

Sequence of Radiographic Changes (Stage-Based)

Detailed Findings

1. Cardiomegaly

• Cardiothoracic ratio > 0.5 on a PA film.
• The most sensitive individual CXR sign for AHF (74.7% sensitive, negative LR 0.43). - Rosen's Emergency Medicine
• In acute severe cases (e.g., acute mitral regurgitation), the heart may be normal in size despite florid alveolar edema.

2. Vascular Redistribution / Cephalization

• Normally, lower lobe vessels are larger than upper lobe vessels in the erect patient.
• In elevated PCWP, upper lobe veins dilate and become equal to or larger than lower lobe vessels ("upper lobe blood diversion").
• This is an early, subtle finding reflecting early elevation of pulmonary venous pressure.

3. Kerley Lines

• Kerley B lines - Most common. Short (1-2 cm), horizontal, non-branching lines at the lung periphery, particularly the costophrenic angles. They are perpendicular to the pleural surface.
• Kerley A lines - Longer (4-6 cm) linear opacities extending obliquely from the hilum toward the periphery, representing lymphatic engorgement in deeper septa.
• Kerley C lines - Fine reticular pattern at the lung base, representing B-lines seen en face.

A: Cardiomegaly, bilateral effusions, central interstitial thickening. B: Kerley B lines (arrowhead) - peripheral interlobular septal thickening. C: CT showing smooth interlobular septal thickening. - Murray & Nadel's / Roberts & Hedges'

4. Peribronchial Cuffing

• Loss of sharp definition of bronchial walls seen end-on near the hila ("doughnut sign").
• Results from fluid accumulation in the peribronchial and perivascular interstitium.
• Also called perivascular haziness when vessels lose their sharp margins.

5. Perihilar Haze

• Increased opacity radiating from both hila, often bilaterally symmetric.
• Indicates interstitial edema concentrated in the bronchovascular bundles.

6. Bat-Wing / Butterfly Pattern

• Bilateral, confluent, perihilar airspace opacification that spares the periphery, creating the classic "bat-wing" appearance.
• Represents frank alveolar flooding with PCWP typically > 25 mmHg.
• Typical of cardiogenic pulmonary edema; generally absent in high-altitude pulmonary edema (HAPE) and non-cardiogenic causes. - Rosen's Emergency Medicine

A: Classic bat-wing distribution of hydrostatic pulmonary edema on frontal CXR. B: CT showing bilateral perihilar consolidations and small right pleural effusion. - Goldman-Cecil Medicine

7. Air Bronchograms

• Air-filled bronchi made visible against the background of fluid-filled alveoli.
• Seen in severe alveolar edema; also present in pneumonia, atelectasis, and ARDS.

8. Pleural Effusions

• Bilateral (usually right > left or symmetric) transudate.
• Unilateral or markedly asymmetric effusions should prompt further investigation (other diagnoses or additional pathology). - Murray & Nadel's
• Obliterates the costophrenic angle when > 200-300 mL.

Bilateral infiltrates with multiple Kerley A and B lines. The arrows mark peripheral interlobular septal thickening. - Fuster & Hurst's The Heart

9. Alveolar Opacities / Consolidation

• Patchy, irregular, or confluent increases in lung density obscuring vascular markings.
• Represents flooded alveoli; may be asymmetric or change rapidly.

Reticular Pattern (Interstitial Phase)

A: Alveolar edema with bilateral consolidation and air bronchograms. B: Kerley B lines (interlobular septal thickening) in chronic heart failure. - Murray & Nadel's

Diagnostic Performance of CXR Findings (for AHF)

Cardiogenic vs. Non-Cardiogenic Pulmonary Edema on CXR

Summary Mnemonic: "ABC DKPV"

• A - Airspace opacities (alveolar phase)
• B - Bat-wing distribution (perihilar)
• C - Cardiomegaly
• D - Dilation of upper lobe vessels (cephalization)
• K - Kerley lines (A, B, C)
• P - Pleural effusions (bilateral) + Peribronchial cuffing
• V - Vascular haziness (perihilar haze)

Pulmonary Capillary Wedge Pressure (PCWP)

What Is It?

Normal Values

How Is It Measured?

Sequential pressure waveforms as the catheter passes: RA (low, non-pulsatile) → RV (high systolic, low diastolic) → PA (high systolic, elevated diastolic with dicrotic notch) → PCW (low pressure, a/c/v waves). - Barash Clinical Anesthesia

PCWP and Pulmonary Edema (Clinical Thresholds)

The Pressure Cascade: CVP → PCWP → LVEDP

Right atrium (CVP) → Right ventricle → Pulmonary artery
         → [PCWP measured here] ← Pulmonary veins ← Left atrium ← LVEDP

PCWP vs. LVEDP - When They Diverge

• Positive pressure ventilation / PEEP (compresses pulmonary vessels, raises PCWP)
• Catheter tip in West Zone I or II (non-zone III placement - most important technical error)
• COPD / increased pulmonary vascular resistance
• Mitral stenosis or left atrial myxoma
• Increased intrathoracic pressure

• Non-compliant LV (LV hypertrophy, ischemia) - diastolic dysfunction
• Aortic regurgitation (premature mitral valve closure)
• LVEDP > 25 mmHg (the mitral valve closes before full LV filling)
• Miller's Anesthesia, 10th Edition

West Lung Zones - Why This Matters for Accuracy

• In zones I and II, alveolar pressure may exceed venous pressure, collapsing the vessels and interrupting the fluid column - making PCWP reflect alveolar pressure, not LAP.
• Tip position in non-zone III is suspected when: PCWP > PA end-diastolic pressure, or the PCWP tracing is non-phasic. - Barash Clinical Anesthesia; Murray & Nadel's

Key Uses

1. Diagnosing cardiogenic vs. non-cardiogenic pulmonary edema - PCWP > 18 = cardiogenic; PCWP ≤ 15 with hypoxia = ARDS/non-cardiogenic
2. Assessing LV preload and guiding fluid management in critical care
3. Differentiating causes of shock (cardiogenic vs. distributive vs. obstructive)
4. Right heart catheterization for pulmonary hypertension - PCWP > 15 defines post-capillary PH (WHO Group 2)
5. Guiding hemodynamic optimization in perioperative patients

Note: Despite its physiologic elegance, routine PAC use has not been shown to improve outcomes in most ICU populations. Its use is now reserved for specific situations where the hemodynamic question cannot be answered by less invasive means. - Miller's Anesthesia; Barash Clinical Anesthesia