Constipation and diarrhoea are the most common signs of large intestinal disease. Dietary, infectious and parasitic diseases are the most common causes of large bowel diarrhoea in dogs. Inflammatory bowel disease caused by lymphocytic-plasmacytic colitis is diagnosed by ruling out other causes of diarrhoea and by performing a histological examination. Colonoscopy using a flexible endoscope has become a common follow-up procedure to survey radiography for imaging the large intestine. Survey radiographs are still important for recognizing situations in which endoscopy may not be feasible, such as obstipation. Strictures may also prevent passage of the endoscope, and contrast radiography may be the only means of diagnosing the extent and nature of disease. Ultrasonography has also replaced much of the use of contrast radiography and should be considered complementary to survey radiography. Artefacts produced by the the contents of the colon can prevent observation of much of the wall using ultrasonography. However, the wall thickness and layering of the colon can be assessed in the near-field of the transducer. The regional lymph nodes and neighbouring organs can also be examined, which can be important for determining the extent of some lesions. The chapter focuses on Normal radiographic anatomy; Contrast radiography; Ultrasonography; Overview of additional imaging modalities; Large bowel diseases; and Perianal diseases.