Bronchial Pattern Analysis in the Differential Diagnosis of Pediatric Mycoplasma pneumoniae and Viral Pneumonia

Purpose To analyze the differences in bronchial patterns on CT images between pediatric Mycoplasma pneumoniae (MP) and viral pneumonia, and to evaluate differential diagnosis value.Methods A total of 759 consecutive hospitalized children from the Pediatric Respiratory Department of Xinhua Hospital with etiologically confirmed infections from January 1, 2024, to December 31, 2024 were included. The population included 393 males and 366 females (median age 6 years; IQR 4-9). Patients were classified into three groups: the MP group (n = 604), the Virus group (n = 138), and a bacterial group (n = 17). All patients underwent low-dose chest CT. CT findings of subgroups were retrospectively analyzed based on the incidence and distribution of bronchial patterns: bronchial wall thickening (tram-track sign), density (consolidation) without typical air bronchogram, and air trapping.Results The incidence of tram-track sign was significantly higher in the MP group (92.4%) than in the viral group (68.8%) (χ² = 58.987, P < 0.001). The MP group (72.8%) showed a higher incidence of consolidation than the viral group (26.8%) (χ²=103.694, P < 0.001). No significant difference was found in the incidence of air trapping between the MP group (12.1%) and the viral group (13.8%) (χ² = 0.293, P = 0.589). The overall incidence of bronchial patterns was significantly higher in the MP group (99.5%) than in the Virus group (71.0%) (χ² = 167.003, P < 0.001). Subgroup analysis of patients with the tram-track sign revealed that unilateral involvement was predominant in the MP group (61.6%), while bilateral involvement was more common in the Viral group (82.1%) (χ² = 62.866, P < 0.001). The combined analysis of the tram-track sign and/or atypical consolidation showed that the MP group was characterized by unilateral 1-2 lobe involvement (54.3%, 328/604), whereas the viral group typically involved all five lobes bilaterally (48.5%, 67/138).Conclusions Bronchial patterns are highly prevalent in both MP and viral pneumonia. MP infection is characterized by unilateral tram-track sign and consolidation without typical air bronchogram, whereas viral infection typically presents with a bilateral tram-track sign and lower frequency of consolidation. These features can assist in differential diagnosis.