Severe acute graft-versus-host disease (GVHD) can occur during allogeneic hematopoietic stem cell transplantation (allo-HSCT), causing considerable morbidity and mortality. Although several biomarkers have been reported for predicting acute GVHD, they are often difficult to measure in routine clinical practice. Recently, three-dimensional computed tomography (3D-CT) has been used to quantify the detailed bronchial structure, which might correlate with acute GVHD. We retrospectively evaluated 55 patients who underwent their first allo-HSCT at our hospital between 2016 and 2020. Using 3D-CT analysis, the airway inner luminal area (Ai), wall area (WA), and wall thickness (WT) were measured at each third- to fifth-generation bronchus. Values were adjusted according to body surface area (BSA). Ratios of values at neutrophil engraftment to those of pre-conditioning were assessed. In the cohort, Ai/BSA narrowed, WA/BSA enlarged, and WT/BSA thickened during neutrophil engraftment compared with pre-conditioning. The cumulative incidence of grade II-IV acute GVHD after allo-HSCT was 24%. The ratio of WA/BSA at neutrophil engraftment to that of pre-conditioning in fourth-generation bronchi (WA4/BSA) was significantly lower in patients with grade II-IV acute GVHD compared with those with grade 0-I (0.99 vs. 1.08, P <
0.01). The ratio of WA4/BSA of <
0.955 was significantly associated with the incidence of grade II-IV acute GVHD (<
0.955
60% vs. ≥ 0.955
16%, P <
0.01). This is the first study to demonstrate that 3D-CT analyses could quantify changes in bronchial structure during neutrophil engraftment after allo-HSCT
these changes might correlate with the incidence of severe acute GVHD.