Necrotizing pneumonia due to Klebsiella pneumoniae

Clinical History

A 52-year-old man presented to the emergency department with symptoms of cough, haemoptysis, low-grade fever and general weakness for over one week. The patient was an alcoholic and smoker. Significant laboratory findings included leucocytosis and neutrophilia.

Imaging Findings

An urgent chest X-ray revealed downward bulging of the minor fissure due to massive enlargement of the right upper lobe with inflammatory exudate (Fig. 1).

Transverse computed tomography (CT) shows homogeneous parenchymal consolidation in the right upper lobe (Fig. 2a). The consolidation expands and exerts mass effect on the adjacent interlobar fissure, and hilar and mediastinal lymph node enlargement is present (Fig. 2b, 2c).

The radiological interpretation was pneumonia due to Klebsiella. The patient underwent antibiotic therapy, but showed rapid progression in his respiratory symptoms. Two hours later, intubation and mechanical ventilation were performed because of shock and respiratory failure, and the patient was admitted to the intensive care unit.

Two weeks later control chest radiography and CT showed dense consolidation with necrotizing areas (Fig. 3, 4a), interlobular septal thickening and ground-glass opacities in both sides of the lungs, suggesting necrotizing pneumonia (Fig. 4b). It resolved slowly with residual fibrosis in the upper lobe (Fig. 5).

Discussion

Klebsiella pneumoniae is a Gram-negative bacteria and a well-known cause of community-acquired pneumonia, which accounts for less than 5% of all cases of pneumonia. It is an important type of pneumonia because of its severity, high incidence of complications, and elevated mortality [1]. For this reason, it is important to identify the risk factors and to evaluate the radiological findings as soon as possible to initiating appropriate treatment quickly.

This bacterium affects people with underlying diseases, such as alcoholism, diabetes, chronic pulmonary disease and critically ill patients [2, 3]. The usual presenting symptoms are fever and cough, followed by sputum (currant-jelly sputum in some cases), dyspnoea and chest pain [4]. Alcoholics are at particular risk of bacteraemic and fatal Klebsiella pneumoniae [5].

The most common plain radiographic finding is pneumonic consolidation that produces a large inflammatory exudate, causing increased volume of the affected lobe, expanding and exerting mass effect on the adjacent interlobar fissure (bulging fissure sign) [6]. It may result in abscess formation and pleural effusion in complicated cases; these cases start with consolidation, followed by cavities [7].

CT findings in patients with acute Klebsiella pneumoniae consisted mainly of ground-glass attenuation with consolidation and intralobular reticular opacity, which were often associated with pleural effusion (7, 8, 9). Traction bronchiectasis, enlarged lymph nodes at the paratracheal, tracheobronchial and subcarinal regions are also observed [8, 9].

On the other hand, the CT findings of complicated Klebsiella pneumoniae are necrotizing pneumonia associated with pleural abnormalities; abscesses may progress to destroy a section of the lung, and multiple cavities that coalesce into one large cavity may develop, suggesting pulmonary gangrene [9, 7].

Other organisms are prone to cause necrotizing pneumonia similar to Klebsiella; the most common pathogens responsible for lung abscess are anaerobes of the oral flora (Prevotella, Fusobacterium, Streptococcus milleri group). However, necrotizing changes may be seen in up to around 7% of those with aerobic bacterial pneumonia [7, 10].

Staphylococcus aureus is an emerging cause of necrotizing pneumonia affecting young immunocompetent patients. Streptococcus pneumonia (especially type 3) and Haemophilus influenza have been frequently reported, and because these organisms are such common causes of pneumonia, these pathogens may cause a significant fraction of cavitary pneumonias, even though cavitation is relatively rare with these pathogens [7, 8, 11, 12].

Mycobacterium tuberculosis and Aspergillus are classically associated with cavitary pulmonary disease. Pseudomonas, Nocardia, Actinomyces and Enterobacter are also important for the differential diagnosis [7].

Teaching points:
-The bulging fissure sign is associated with Klebsiella pneumoniae infection.
-A common manifestation of complicated Klebsiella pneumoniae was necrotizing pneumonia associated with pleural abnormalities.

Differential Diagnosis List

Final Diagnosis

Necrotizing pneumonia due to Klebsiella pneumoniae

URL:	https://eurorad.org/case/12729
DOI:	10.1594/EURORAD/CASE.12729
ISSN:	1563-4086