Abnormal pulmonary interstitial morphology Usual interstitial pneumonia 2018-07-06T12:27:18Z Usual interstitial pneumonia (UIP) is usually identified by a honeycombing pattern in a CT scan; in contrast, diffuse interstitial pneumonia (DIP) is not associated with the honeycombing pattern of fibrotic tissue. DIP tends to stabilize or improve after treatment, UIP often continues to progress (irregular lines or honeycombing). Honeycombing, clustered cysts with well-defined walls involving the subpleural lung, is the key finding for making a definite diagnosis of UIP pattern. UIP is associated with autoimmune diseases such as rheumatoid arthritis (and rheumatoid arthritis-interstitial lung disease, or RA-ILD). Temporal and spatial heterogeneity in lungs based on presence of fibrosis and honeycombing.