Macroscopic, histological and ultrastructural assessment of small intestine tissue. (a) Macroscopic picture of the oedematous intestinal wall with multiple submucosal and subserosal cysts. (b) Histological picture of the intestinal mucosa with areactive necrosis. (c) Gram stain of cysts with large rod-shaped bacteria. (d) Electron microscopic picture of a bacterium found in a submucosal cyst.