Stage based on CT image
The CT imaging demonstrates 5 stages according to the time of onset and the response of body to the virus, including: Ultra-early stage. This stage usually refers to the stage of patients without clinical manifestation, negative laboratory test but positive throat swab for 2019-nCoV within 1–2 weeks after being exposed to a virus-contaminated environment (history of contact with a patient or patient-related family members, unit, or medical staff in a cluster environment). The main imaging manifestations are single, double or scattered focal ground-glass opacity, nodules located in central lobule surrounded by patchy ground-glass opacities, patchy consolidation and sign of intra-bronchial air-bronchogram, which was dominant in the middle and lower pleura (Fig. 6: 7 cases, 8.4% in a total of 83 cases).
Fig. 6 CT imaging of ultra-early stage. a A 33 years old female with patchy ground-glass opacities after occupational exposure. b A 67 years old male with a history of contact with infected patients, showing large ground-glass opacity. c A 35 years old female exhibiting large consolidated opacity with air-bronchogram inside after occupational exposure
(2) Early stage.This stage refers to the period of 1–3 days after clinical manifestations (fever, cough, dry cough, etc.). The pathological process during this stage is dilatation and congestion of alveolar septal capillary, exudation of fluid in alveolar cavity and interlobular interstitial edema. It showed that single or multiple scattered patchy or agglomerated ground-glass opacities, separated by honeycomb-like or grid-like thickened of interlobular septa (Fig. 7: 45 cases, 54.2% in a total of 83 cases).
Fig. 7 CT imaging of early stage. Male, 38 years old, fever without obvious inducement (39.3 ℃), dry cough and shortness of breath for 3 days. Laboratory test: decreased white blood cells (3.01 × 109/L), decreased lymphocytes (0.81 × 109/ L), increased C-reaction protein (60.8 mg/L), increased procalcitonin (0.16 ng/ml). Imaging examination: a (thin layer CT) and b (high-resolution CT) showed multiple patchy and light consolidation in both lungs and grid-like thickness of interlobular septa
(3) Rapid progression stage. This stage refers to the period about 3–7 days after clinical manifestations started, the pathological features in this stage are the accumulation of a large number of cell-rich exudates in the alveolar cavity, vascular expansion and exudation in the interstitium, both of which lead to further aggravation of alveolar and Interstitial edema. The fibrous exudation connects each alveolus through the inter-alveolar space to form a fusion state. The CT manifested a fused and large-scale light consolidation with air-bronchogram inside (Fig. 8: 17 cases, 20.5% in a total of 83 cases).
Fig. 8 CT imaging of rapid progression stage. A 50 years old female with anorexia, fatigue, muscle soreness, nasal congestion and runny nose for 1 week, sore and itching throat for 2 days. Laboratory test: increased erythrocyte sedimentation rate (25 mm/h), normal white blood cells (4.08 × 109/L), decreased lymphocytes (0.96 × 109/ L), increased C-reaction protein (60.8 mg/L). Imaging examination: a (thin layer CT) and b (high-resolution CT) showed multiplepatchy and light consolidation in both lungs and grid-like thickness of interlobular septa
(4) Consolidation stage. This stage refers to the period around 7–14 days after clinical manifestations appeared. The main pathological features in this stage are the fibrous exudation of the alveolar cavity and the disappearance of capillary congestion in the alveolar wall. CT imaging showed the multiple patchy consolidations in slighter density and smaller range than that of the previous stage. (Fig. 9: 26 cases, 31.2% in a total of 83 cases).
Fig. 9 CT imaging of consolidation stage. A 65 years old male with fever (maximum temperature of 39 ℃). Laboratory test: hypoproteinemia (decreased total protein (62.20 g/L), decreased albumin (35.70 g/L)), abnormal liver function (increased alanine aminotransferase (79 U/L), increased aspartate aminotransferase (72 U/L)), increased procalcitonin (0.10 ng/ml), increased C-reaction protein (53 mg/L), decreased white blood cells (3.72 × 109/L), decreased lymphocytes (0.9 × 109/ L), mildanemia (decreased red blood cells (4.10 × 1012/L), decreased hemoglobin (131.10 g/L), decreased hematocrit (39.0%). Imaging examination: a (thin layer CT) and b (high-resolution CT) showedmultiple patchyand large consolidation in right middle lobe, posterior and basal segment of right lower lobe and outer and basal segment of left lower lobe, with air-bronchogram inside
(5) Dissipation stage. This stage refers to the period roughly between 2 and 3 weeks after the onset of clinical manifestations. The range of lesions was further reduced. CT imaging showed patchy consolidation or strip-like opacity. As time goes on, it showed grid-like thickening of interlobular septum, thickening and strip-like twist of bronchial wall and a few scattered patchy consolidations (Fig. 10: 17 cases, 20.5% in a total of 83 cases).
Fig. 10 CT imaging of dissipation stage. A 79 years old female with intermittent fever. Laboratory test after 3 days of comprehensive treatment: decreased red blood cells (3.73 × 1012/L), hemoglobin (107 g/L), decreased hematocrit (31.8%), decreased lymphocytes percentage (13.9%), decreased lymphocytes (0.62 × 109/ L), decreased eosinophil count percentage (0%), decreased eosinophil count (0 × 109/L), increased alanine aminotransferase (46 U/L), deceased total protein (56.8 g/L), decreased albumin (33.5 g/L), normal C-reaction protein and procalcitonin. Imaging examination: a patchy ground-glass opacity and grid-like thickening of interlobular septa in the tongue-like segment of left upper lobe, and patchy consolidation in the posterior segment of right middle and lower lobe. b 9 days after admission to hospotial, CT scan showed absorption of lesions in the middle lobe, narrowing of lesions in the lower lobe of the right lung, and absorption of lesions in the tongue-like segment of left upper lobe which exhibited a cord-like change