Infections

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Infections
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Pneumonia

• 6th leading cause of death in the US
• 1st leading cause of death by infection
• Early diagnosis by the clinician is key to
  decreasing morbidity and mortality and expenses
  for treating pneumonia

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Role of Imaging in Pneumonia

• Diagnosis of infection
• Recognition of complications
• Not necessarily pathogen diagnosis
• Organisms may cause more than one radiographic
  pattern
• Most useful when read in setting of clinical
  diagnosis.

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Radiographic patterns

• Lobar- Most common associations S. pneumo and K.
  Pneumo
• Lobular (broncho pneumonia)-Mycoplasma most
  commonly associated
• Interstitial-viruses
• Lobar and bronchopneumonia are alveolar filling
  pneumonias- consolidation
• Interstitial pneumonia will look like too many
  lines

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Associated findings

• air bronchograms
• the silhouette sign
• parapneumonic effusions

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Etiologic agents

• Lobar pneumonia
• S. pneumoinae
• K. pneumoniae
• Also seen with Legionella, Mycoplasma, H.
  Influenza

• Bronchopneumonia
• Gram-s, anaerobes
• Legionella
• Actinomycosis
• Nocardia
• Mycoplasma
• Typical, atypical Tb
• Parasites

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Radiographic patterns

• Lobar pna tends to be homogeneous
• Prominent air bronchograms
• Preserved volume- vs atelectasis

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Radiographic patterns

• Bronchopneumonia
• Tends to be heterogeneous, patchy, coarse and
  irregular
• Can be difficult to differentiate from
  interstitial pna

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Radiographic patterns

• Interstitial pna
• Usually viral pnas
• Influenza A,B,C
• Parainfluenza
• RSV
• Adneoviruses
• Herpes viruses
• SARS
• Too many lines

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Complications of Pneumonias

• Pleural infection-
• Empyema- purulent exudate,WBC gt 25,000 and
  positive organisms

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Complications of Pneumonias

• Cavitation
• Cavitary pneumoina
• Lung abscess
• Pneumatocele
• Gangrene

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Complications of Pneumonias

• Pneumatocele- Ball-valve mechanism
• Most common with S. aureus

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Complications of Pneumonias

• Bronchiectasis-dilatation of bronchi usually due
  to chronically impacted bronchi with mucus
  increasing pressure
• Common with atypical Tb and aspergillus

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Caution!

• Beware of nonresolving consolidation
• There are noninfectious causes of chronic
  consolidation- especially in elderly people
• Ex include
• Bronchoalveolar Carcinoma
• Eosinophilic pna
• Cryptogenic organizing pna
• Consider consult or biopsy!

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Tuberculosis

• Primary tuberculosis- can present without sx and
  normal chest x-ray,
• Can appear with lobar consolidation in any lobe
  with preference for upper lobes, adenopathy,
  atelectasis and pleural effusion
• Adenopathy is usually unilateral, usually on the
  right or paratracheal- more common in children
• Pleural effusion more common in adults
• Cavitation is RARE!
• Usually heals with calcification-granulomas and
  calcified Lymph nodes

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Primary Tb
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Tuberculosis

• Post primary Tb
• Reactivation Tb-Usually in adults is a
  reactivation of a focus acquired in childhood
• Limited to apical and posterior segments of
  upper lobes and superior segments of lower lobes
• Healing occurs with contraction and fibrosis
• Patterns-
• Cavitation is common with thin walled cavity
• Transbronchial spread ex from one upper lobe to
  contralateral lower lobe
• Bronchostenosis-narrowed airways
• Pleural effusion- direct extension to pleural
  cavity
• Direct extension to ribs

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Reactivation Tb
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Miliary Tb

• Hematogenous spread of bacilli during primary Tb
  infection
• Fever, chills, night sweats
• 1mm nodules initially

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Aspergillus

• Ubiquitous fungus
• May result in disease when inhaled in susceptible
  hosts
• Infection usually occurs in immunocompromised
  hosts
• Degree of immunocompromise determines pattern of
  infection

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Aspergillus

• Main patterns of infection
• Decreased immunity
• Invasive aspergillosis angioinvasive, airway
  invasive
• Chronic necrotizing
• Normal Immunity
• Aspergilloma
• Hyperimmunity
• Allergic bronchopulmonary aspergillosis (ABPA)
• Hypersensitivity pneumonitis

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Angioinvasive

• Severe immunocompromise- BMT, AIDS, high dose
  steroids, hematogenous malignancy
• Maximal Risk WBC lt 500 cells/mm3
• Patchy consolidation and nodules that have ground
  glass halo, which then cavitate when neutropenia
  improves ( air cresecent sign

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Angioinvasive
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Aspergilloma

• Occur in pre-existing cavity in upper lobes-
  COPD, Bronchiectasis, Sarcoid
• Cavity with internal opacity- opacity is mobile
  and demonstrates air crescent sign

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ABPA

• Occurs with systemic hypersensitivity
• Occurs usually in asthmatics
• Eosinophilia documented
• Components
• Bronchiectasis- mid and upper lungs, centrally
• Mucoid impaction- transient and recurrent-
  gloved finger

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ABPA
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Mediastinum

• The key to the mediastinum is knowing the anatomy
  and what resides in each compartment
• Pathology includes a range of tumors as well as
  infections, congenital abnormalities, vascular
  malformations, cardiac pathology and esophageal
  pathology

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Mediastinal Compartments

• Anteriorsuperior (retrosternal space)- includes
  the thymus, the extrapericardial aorta and its
  branches, the great veins, and lymphatic tissue
• Middle-includes the heart, intrapericardial great
  vessels, pericardium, and trachea
• Posterior- includes the esophagus, vagus nerves,
  thoracic duct, sympathetic chain, and azygous
  venous system, and extends to the posterior
  aspect of the vertebral bodies and posterior
  ribs.

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Mediastinum
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Anterior mediastinum

• Masses- differential diagnosis
• The 4 Ts- not all inclusive- but includes
  majority
• Thymus tumors- Thymoma, thymolipoma
• Teratoma- and other Germ Cell tumors (e.g.
  seminoma)
• Thyroid goiter
• Terrible Lymphoma

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Anterior mediastinum

• Radiology
• Terrible Lymphoma big bulky LAD, absence of
  calcification is a discriminating feature
• Thymomas- Age over 40, 20-25 contain calcium,
  solid and well defined, unilateral, can be cystic
  . Associated with Myasthenia Gravis
• Teratomas (Germ Cell tumors)predominately
  cystic, age lt 40.  Often calcification or fat 
• Thyroid goiter/CA is continuous with thyroid in
  neck, high attenuation (iodine) usually
  superior mediastinum

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Where is the mass?
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Anterior mediastinal mass

• Anterior- crosses midline- germ cell tumor or
  lymphoma

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Substernal Goiter
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Thymoma- gt age 40, typically solid, can have
peripheral thin calcifications, can be cystic,
usually to one side of midline
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• Morgagni Hernia

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Middle medisatinum

• Tumors of the middle mediastinum include
  pericardial cysts, bronchogenic cysts and
  lymphomas. A middle mediastinal mass may also
  represent lymphadenopathy as a result of
  infectious, malignant (metastatic), and
  idiopathic (eg sarcoidosis) etiologies.
• Mediastinitis from prior granulomatous disease

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Middle mediastinal masses

• Pericardial cyst Bronchogenic cyst

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Fibrosing mediastinitis

• Notice soft tissue thickening surrounding trachea
  and narrowing it after histoplasmosis infection.
  Esophagus may be obliterated.

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Posterior mediastinal mass
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Posterior Mediastinum

• Neurogenic tumor  Schwannoma, neurofibroma,
  ganglioneuroma, neuroblastoma
• Enteric/neurenteric cyst
• Lateral thoracic meningocele
• Osteocartilaginous tumor
• Pulmonary mass or consolidation abutting
  mediastinum
• Extramedullary hematopoesis
• Paraspinal abscess, hematoma

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Posterior mediastinal mass

• Paraspinal ganglioneuroma- notice intimacy with
  spinal canal and mass effect on trachea

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Aortic Aneurysm

• Anuerysm can occur in any part of the mediastinum
  depending on where the aneurysm occurs, so
  consider it in all your differentials

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• Nodules and Masses

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Definitions

• Nodule any pulmonary lesion represented in a
  radiograph by a sharply defined, discrete, nearly
  circular opacity ranging from 2-30 mm
• Mass nodule gt 3 cm
• Not all masses or nodules are malignant, but
  frequency of malignancy is higher in masses

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Solitary Pulmonary Nodule

• What should you do next?

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Diagnostic Dilemma

• Solitary Pulmonary Nodule- What do you do with
  it?
• Options- compare with old films, get follow up
  films, CT scan, PET scan, biopsy or lung
  resection
• Multiple guidelines have been issued and are
  confusing
• Clinicians must consider age of the patient and
  risk factors such as smoking for possibility of
  cancer
• Certain radiologic characteristics can help
  suggest that a nodule or mass is benign or
  malignant
• Calcification pattern- central, popcorn or
  lamellated are benign
• Fat within lesion- suggests hamartoma, benign
• Spiculated margins and distortion of vessels
  suggests malignancy
• Cavitation can occur in either- but malignant
  tumors have thicker walled cavities
• Stability in size for 2 years
• Double in volume equals increase in diameter by
  25- suggests malignant

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Diagnostic Considerations

• Neoplasm
• - Primary malignancy- Small Cell, Squamous Large
  Cell, Adenocarcinoma
• - Metastasis
• - Benign hamartoma
• Infection fungus, prasites, abscess
• Congenital sequestration, CCAM
• Non- infectious inflammatory- Wegeners
  Granulomatosis
• Non- parenchymal lesions

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Solitary Pulmonary Nodule

• Nodule has central fat suggesting hamartoma.
• No more work up necessary.
• Also can see popcorn calcifications which is also
  characteristic

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Malignant Primary neoplasms of lungs

• Adenocarcinoma- (50) most common, usually
  peripheral, low association with smoking, slow
  growth and early metastasis
• Large Cell- (5)Peripheral mass, nonspecific
  appearance, least
• Squamous Cell (25)Central, endobronchial,
  Pancoast Tumor, most likely to cavitate, high
  association with smoking
• Small Cell (20)- Central, perihilar, SVC
  syndrome, Paraneoplastic sydromes, Fast growing
  and early mets

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Pancoast Tumor
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Metastasis

• Suggested by multiple nodules of different sizes
  in a random distribution
• Lower lobes greater than upper lobes due to
  increased blood flow to lower lobes

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Metastasis
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Inhalational Disease

• Asbestos related disorders
• Silicosis

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Asbestos related Chest disease

• Pleural effusions- most common early complication
  of exposure
• Pleural plaques- these are calcified and indicate
  exposure
• Round atelectasis- related to pleural abnormality
• Mesothelioma
• Asbestosis- Fibrosis occurring in lower lobes
• Lung Cancer

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Pleural plaques
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Round atelectasis
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Mesothelioma
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Asbestosis
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Silicosis

• Smaller particles than asbestos and tend to get
  trapped in upper lobes
• Causes small miliary nodules in upper lobes
  first- can be calcified
• Adenopathy with rim calcifications- eggshell
  pattern
• Leads to progressive massive fibrosis-
  conglomerate of lesions with volume loss

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Silicosis
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Pulmonary Embolus

• 5 million episodes of DVTeach year
• 300,000 embolic events
• 50,000 deaths
• Largely undiagnosed!!!

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Goal of Imaging

• View the Clot!
• Diagnostic options
• Chest x-ray- 84 had an abnormality in one study
• Ventilation/Perfusion scanning- Unless totally
  normal or abnormal it leaves you in limbo- High,
  low or intermediate probability
• CT pulmonary angiogram- Study of choice with thin
  slices of 1.25mm. Visualize 75 of subsegmental
  emboli and 90 segmental emboli
• Conventionial angiography- invasive

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Pulmonary embolus

• Ventilation Perfusion scan-
• High Probability Treat
• Intermediate/Low Probability-Ultrasound or angio
  and treat if
• Normal- PE excluded
• Problem- 8 mortality in low prob readings.
  25-30 disagreement between expert readers in
  interpreting intermediate and low probability
• A potentially lethal reading.

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Pulmonary Embolus

• CT Pulmonary Aniography
• Accurate, readily available, cost effective,
  widely accepted
• Provides alternate diagnoses
• Not safe if Cr/Cl is too high or there is iodine
  allergy
• Indeterminate 8-10

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Pulmonary embolus
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Sarcoidosis

• Multisystem granulomatous disorder
• Young and middle-aged adults lt40 usually
• Maybe asymtpomatic or have constitutional
  symptoms, dyspnea, cough, chest pain, palpable
  lymph nodes, cutaneous or ocular involvement
• Mortality 5-10
• Transbronchial or endobronchial bx necessary for
  diagnosis

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Sarcoidosis

• Lung involvement occurs 100 of the time
• 4 Stages
• 0. Normal Chest x ray (10)
• 1. Hilar and mediastinal lymphadenopathy (50)
• 2. Adenopathy andparenchymal abnormalities (30)
• 3. Parenchymal abnormalities alone (10)
• 4. Fibrosis
• Worse prognosis with higher stages

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Radiographic patterns

• Lymphadenopathy usually bilateral hilar and right
  paratracheal. Adenopathy is symmetric.

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Radiographic patterns

• Stage 3- Lymphadenopathy and parenchymal
  abnormalities which includes nodules in a central
  peribronchovascular distribution

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Radiographic patterns

• Stage 4- Parenchymal abnormalities include
  nodules and fibrosis

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Random cases
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Case 1
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DDX diffuse tracheal narrowing

• tracheobronchopathia osteochondroplastica
• amyloidosis
• Wegeners
• Intubation injury / tracheobronchomalacia
• relapsing polychondritis
• papillomatosis (when extensive / severe)

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Case 2
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Dilated esophagus
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DDX Dilated Esophagus

• Gastroesophageal Reflux
• Scleroderma
• Achalasia
• Stricture by obstructing tumor in distal
  esophagus
• Systemic diseases (diabetes, amyloid, myxedema,
  thyrotoxicosis)
• Medications (atropine and other anticholinergics)
  
• Surgery (gastric pull-up)

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Case 3
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Differential Diagnosis - Pneumomediastinum

• Asthma ruptured bleb
• Sudden increase in intrathoracic pressure- cough,
  vomiting
• Iatrogenic
• Post-surgical
• Overinflation / excess PEEP (intubated)
• Dissection of retroperitoneal gas
• Pneumopericardium / pneumothorax
• Esophageal or tracheal/bronchial perforation
• Trauma (incl. blunt trauma, stab wound, etc)
• Infection Pneumomediastinum from gas-forming
  organisms is very rare- mediastinitis.

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Case 4
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DDX-micronodular (milliary) pattern

• Infection-Tuberculosis, histoplasmosis,
  coccidioidomycosis, Varicella
• Metastases-thyroid, renal, melanoma
• Sarcoidosis
• Pneumoconiosis
• Langerhans cell histiocytosis
• Hypersensitivity pneumonitis(Ground glass
  nodules)

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Millary pattern 1-2mm nodules, random/diffuse
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Case 5
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Little change from 3 months ago
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DDx Chronic consolidation

• Fungal infection / granulomatous infection (TB)
• Lymphoma
• Bronchioloalveolar carcinoma (BAC)
• Round atelectasis
• Lipoid pneumonia
• Sarcoid (alveolar form)

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Round atelectasis- whorling pattern
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Case 6
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DDX- opacified hemithorax

• Atelectasis
• Effusion
• Pneumonia
• Pneumonectomy

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Atelectasis-shift toward opacified lung
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Pneumonia- air bronchograms, no shift
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Pneumonectomy-5th rib absent or partially resected
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PCP pneumonia
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PCP pneumonia
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PCP pneumonia-ground glass and cysts
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Pulmonary hemorrhage-hint rapidly clears, trauma
or vasculitis
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Case 7
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DDX-hemidiaphragm elevation

• Diaphragm rupture
• Diaphragmatic hernia/eventration
• Phrenic nerve paralysis
• Abdominal mass/organomegaly
• Atelectasis, lung hypoplasia
• Subpulmonic effusion

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Trauma-diaphragm rupture