INFLAMMATION of the underlying layer of ADIPOSE TISSUE (panniculus) of the PERITONEUM, usually of the MESENTERY or the OMENTUM. There are several forms with various names and are usually characterized by infiltration of LYMPHOCYTES and NEUTROPHILS, fat NECROSIS, and FIBROSIS. The disease is Panniculitis, Peritoneal (Experimental Factor Ontology identifier EFO_1001384).