Prevalence of an empty colon in patients with acute and chronic small intestinal mechanical obstruction: A retrospective radiographic study in 100 dogs and cats

Small intestinal mechanical obstruction (SIMO) is a common clinical condition, with radiographic studies typically focusing on the small intestine. However, the colon's appearance in SIMO has not been extensively studied. This retrospective study aimed to determine the prevalence of an empty colon on radiographs of dogs and cats with confirmed SIMO. Pre-surgical abdominal radiographs of 100 patients (68 dogs and 32 cats) with surgically confirmed mechanical ileus and a control group of 30 dogs and 20 cats with non-obstructive gastrointestinal (GI) disease and one without GI disease, respectively, were evaluated. The colon was assessed for content (none/collapsed, gas, faeces) and segmental distribution (ascending, transverse, descending colon) and correlated to the duration of clinical signs (acute, chronic). A colon was classified as empty when ≥2/3 was collapsed and/or gas-filled. The overall prevalence of an empty colon in cases of mechanical ileus was 61% (p=0.028), with 49/68 in dogs (72.1%) and 12/32 in cats (37.5%), p=0.001 between dogs and cats. Clinical signs duration did not influence the prevalence 28/61 (45.9%) acute, 33/61 (54.1%) chronic, p=0.522. However, acute cases had more empty colon segments (2/3 segments: 6/28, 21.4%; 3/3 segments: 22/28, 78.6%) than chronic cases (2/3 segments: 23/33, 69.7%; 3/3 segments: 10/33, 30.3%; p≤0.001). In the control groups, the prevalence of an empty colon was 64% (p=0.048) with and 38%, p=0.048) without GI disease, with no statistical difference between dogs and cats. An empty colon can be a supporting radiographic finding in diagnosing patients with GI disease, including SIMO, in addition to other established characteristic features. Dogs are more likely to have an empty colon in the presence of mechanical ileus.