Reticulonodular Opacities

Alexander J. Towbin, MD

DIFFERENTIAL DIAGNOSIS

Common

Surfactant Deficient Disease
Bronchiolitis
Mycoplasma
Pulmonary Edema

Less Common

Langerhans Cell Histiocytosis
Aspergillus
Tuberculosis
Pneumocystis jiroveci

Rare but Important

Pulmonary Alveolar Proteinosis
Systemic Lupus Erythematosus
Niemann-Pick Disease
Pulmonary Venoocclusive Disease

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Characterized by interstitial thickening and multiple small nodules
Nonspecific pattern of disease

Helpful Clues for Common Diagnoses

Surfactant Deficient Disease
- a.k.a. respiratory distress syndrome, hyaline membrane disease
- Most common cause of morbidity in premature infants
- Most common in premature infants
  - Lack of mature type 2 pneumocytes
  - Most common in infants born at < 28 weeks fetal gestation
  - More common in males and infants of diabetic mothers
- Radiograph: Decreased lung volume and diffuse reticulonodular opacities
  - Findings worst at 12-24 hours of life
- Complications: Pneumothorax, pneumomediastinum, pulmonary interstitial emphysema
- Treatment: Surfactant via endotracheal tube
- Severe disease → bronchopulmonary dysplasia
Bronchiolitis
- Respiratory syncytial virus (RSV) is most common cause
- Most common cause of hospitalization in infants
  - Usually self-limiting illness
- Radiograph: Hyperinflation, atelectasis, and peribronchial cuffing
- Risks for severe disease: Prematurity, age < 12 weeks, chronic lung disease, congenital heart disease, immunocompromised
Mycoplasma
- Common cause of community-acquired pneumonia
  - Most common cause of pneumonia in children > 5 years old
- More severe presentation in children < 5 years old
- Radiograph: Lobar consolidation, air bronchograms, or reticulonodular opacities
  - Reticulonodular opacities in 52%; more common in lower lobes
Pulmonary Edema
- 2 main causes: Cardiogenic and noncardiogenic
- Cardiogenic pulmonary edema occurs when pulmonary capillary pressure is high
  - Overwhelms lymphatic system’s ability to resorb fluid
  - Associated with congenital heart disease
  - Usually occurs in 1st 6 months of life
- Noncardiogenic causes can be neurogenic, negative pressure, or miscellaneous
- Neurogenic: Associated with head trauma
  - Onset within hours of injury
- Negative pressure: Associated with upper airway obstruction
  - Rapid onset and resolves when obstruction is relieved
- Other causes of noncardiogenic edema: Fluid overload, acute glomerulonephritis, inhalational injury, and allergic reaction

Helpful Clues for Less Common Diagnoses

Langerhans Cell Histiocytosis
- Unknown etiology
- Strong association with cigarette smoking
- Typically affects young adults between ages 20-40
  - Can affect any age
- Can present with spontaneous pneumothorax
- Early findings: Upper and middle lobe nodules that spare lung bases and costophrenic sulcus
- Late findings: Reticulonodular opacity and cystic changes
Aspergillus
- Aspergillus fumigatus: Fungus found in soil, water, and decaying organic material
- Disease can be caused by allergic reaction or invasive disease
- Often colonizes in patients with underlying airway disease
- Aspergillomas grow in pulmonary cavities as with tuberculosis or cystic fibrosis
- Invasive disease is associated with chronic granulomatous disease
Tuberculosis
- Caused by Mycobacterium tuberculosis
- Pulmonary infection is most common manifestation
- Infection in children is usually due to close contact with infected adult
- Children are less resistant to organism and disseminated disease is more common
- Hallmark of primary tuberculosis is large hilar or mediastinal adenopathy
Pneumocystis jiroveci
- a.k.a. Pneumocystis carinii, Pneumocystis pneumonia (PCP)
- Increased incidence with AIDS and other immunocompromised states
- Radiograph: Parahilar granular opacities, extensive consolidation, ground-glass opacity

Helpful Clues for Rare Diagnoses

Pulmonary Alveolar Proteinosis
- Characterized by intraalveolar accumulation of surfactant-like material
- 3 types: Idiopathic, secondary, and congenital
- Congenital type manifests in neonates; accounts for 2% of cases
- Radiograph: Bilateral central and symmetric opacities with sparing of costophrenic angles and apices
  - Opacities can range from ground-glass to reticulonodular to consolidation
- CT: “Crazy-paving” are thick septal lines superimposed on ground-glass opacity
- Treatment: Whole-lung lavage, lung transplant
Systemic Lupus Erythematosus
- Systemic disease
- Most common thoracic manifestation is pleuritis
- Can cause interstitial lung disease
Niemann-Pick Disease
- Autosomal recessive disorder
- Characterized by accumulation of sphingomyelin due to deficiency of sphingomyelinase
- Radiograph: Diffuse reticulonodular pattern
Pulmonary Venoocclusive Disease
- Rare cause of pulmonary arterial hypertension
- Characterized by occlusion of pulmonary venules by fibrous tissue
- Findings: Nodular ground-glass opacity, septal lines, lymph node enlargement

Image Gallery

AP radiograph of the chest shows diffuse granular opacities of both lungs. Surfactant deficiency is the most common cause of morbidity in preterm infants.

AP radiograph of the chest in the same patient 2 days later shows new branching lucencies in the right lower lobe

. Pulmonary interstitial emphysema is a complication of surfactant deficiency.

(Left) AP radiograph of the chest shows diffuse granular opacities in both lungs. Surfactant deficiency is most common in infants born at less than 28 weeks fetal gestation. (Right) AP radiograph of the chest in a different patient shows diffuse granular opacities of the right lung. Surfactant deficiency is caused by a lack of mature type 2 pneumocytes. It is treated with exogenous surfactant given by an endotracheal tube.

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