• Chest infection is the second most common nosocomial infection in intensive care units. It is associated with the greatest mortality among nosocomial infections.
• Atypical pneumonia is applied to the clinical and radiographic appearance of lung infection not behaving or looking like that caused by Streptococcus pneumonia.
• Atypical chest infection usually presents with atypical chest symptoms and the etiologic pathogen could be either a bacterial, viral or fungal infection
• Diagnostic imaging plays an important role in the initial diagnosis of atypical pneumonia. It has an advantage in the assessment of lesions type, and cross-sectional distribution of pneumonia in ICU patients

METHODS
All patients were subjected to the following scheme after admission to intensive care unit department:
• A focused history and physical examination.
• Laboratory studies: BAL/Culture-sensitivity results, viral serology tests or other inflammatory markers such as CRP or pro-calcitonin such as urine analysis and
complete blood count.
Imaging evaluation including: chest X ray ostero-anterior and lateral view whenever indicating and in good quality and High Resolution Computed Tomography (HRCT) without contrast , Contrast administration only when indicated