Lobar (croupous) pneumonia. Stages of development. Complications.
Pneumonia can be classified as lobar (croupous) pneumonia, lobular (broncho) pneumonia or interstitial pneumonia. These classifications are based on the anatomical location of the infection. Bronchopneumonia is patchy, and generally involves more than one lobe, while lobar pneumonia affects a single lobe. More commonly however these days, we distinguish pneumonia based on community-acquired or hospital acquired forms.
All pneumonias can be described as an inflammatory condition affecting the alveoli, where exudative fluid fills the alveolar spaces. Symptoms can include productive or dry cough, chest pain, fever, and difficulty breathing. Chest X-ray, blood tests and sputum cultures are the best way of diagnosing patients.
Streptococcus pneumoniae is responsible for more than 90% of lobar pneumonias. Bronchopneumonia occurs more commonly at extremes of age, while lobar pneumonia can occur at any age.
Lobar pneumonia goes through four stages:
- Congestion
- Affected lobe(s) are heavy, red and boggy with vascular congestion, scattered neutrophils and many bacteria in alveoli
- Red hepatization
- The lung starts to display a liver like consistency, as alveolar spaces are filled with neutrophils, RBCs and fibrin
- Gray hepatization
- The lung becomes dry, gray and firm as the RBCs are lysed while fibrinosuppurative exudate persists within the alveoli
- Resolution (/death)
- In uncomplicated cases the alveolar exudate is enzymatically digested to produce granular semifluid debris that is resorbed, coughed up, or organised by fibroblasts
Gross: lobar pneumonia. The lower lobe is diffusely consolidated, airless and liver-like (hepatization), sharply limited by the fissure; the upper lobe is only focally involved.
Image: “Lobar pneumonia (13431416354)” by Yale Rosen from USA, CC BY-SA 2.0, via Wikimedia Commons.
Memory aid: classic timeline in untreated cases: congestion (days 1–2) → red hepatization (days 2–4) → grey hepatization (days 4–8) → resolution (from about day 8). Red = red cells in the exudate; grey = red cells broken down, fibrin and neutrophils remain.
GP NOTEBOOK SAYS:
Investigations:
- Chest X-ray
- Full blood counts
- Urea and electrolytes
- Sputum and blood cultures (look for pneumococcus, M. tuberculosis)
- Further investigations can include serology for atypical organisms
Treatment
- Community acquired:
- Amoxicillin (500mg three times daily)
- Erythromycin (500mg ttd) if allergic
- If atypical pneumonia is expected then add erythromycin or another macrolide, if staph is suspected, add flucloxacillin
- Hospital acquired
- Broad spectrum cephalosporin (e.g. cefotaxime, ceftazidime)
- Metronidazole if anaerobic infection
*Note, this treatment plan is for lobar and lobular pneumonia
Complications:
- Hospital acquired form is most deadly