BACKGROUND:Lung ultrasound (US) is an available and inexpensive tool for the diagnosis of community-acquired pneumonia (CAP); it which has no hazards of radiation and can be easily used.AIM:To evaluate the efficacy of lung ultrasound in the diagnosis and follow-up of CAP.PATIENTS AND METHODS:100 patients aged from 40 to 63 years with a mean age of 52.3 ± 10 years admitted to the Critical Care Department, Cairo University with pictures of CAP. Lung US was performed for all patients initially, then a plain chest X-ray (CXR) was performed. Another lung ultrasound was performed on the 10th day after admission.RESULTS:Initial chest X-ray was correlated with the initial chest ultrasound examination in CAP diagnosis (R-value = 0.629, P < 0.001). Cohen’s κ was run to determine if there is an agreement between the findings of the initial chest X-ray findings and those of the initial chest ultrasound in CAP diagnosis. A moderate agreement was found where κ = .567 (95% CI, 0.422 to 0.712) and P < 0.001. Upon initial examination, the CXR diagnosed CAP in 48.0% of patients, while lung US diagnosed the disease in 70% of patients. Moreover, lung US was more sensitive than CXR (P-value < 0.001). Compared to the accuracy of computed tomography (CT) chest (100%) which is the gold standard for CAP diagnosis, the accuracy of lung US was 95.0%, while the accuracy of CXR was 81.0%.CONCLUSION:This study proved the effectiveness of lung ultrasound in CAP diagnosis.