Clinical features and outcome of 40 horses with mesodiverticular bands identified during exploratory laparotomy for management of acute colic

BackgroundMesodiverticular bands (MDBs) are an embryonic remnant of the vitelline artery. Information about the clinical significance of equine MDBs is currently limited.ObjectivesTo report the clinical features, surgical findings and outcomes of horses undergoing exploratory laparotomy where a MDB was identified.Study designRetrospective case series.MethodsCase records of horses undergoing exploratory laparotomy for colic over a 14-year period (2009-2022) were reviewed. MDBs identified at laparotomy were classified as the primary or contributory cause of abdominal pain, or as incidental.ResultsMDBs were identified in 40/1943 horses (2.1%) and 15 were primary (32.5%), 10 contributory (25%) and 15 incidental (32.5%). Horses with primary MDBs (median 2 years, IQR 1-12) were significantly younger than horses with incidental MDBs (median 8 years, IQR 6-16; P = 0.01). MDBs were more likely to be incidental if located in the mid-jejunum (5/5) (P < 0.001) or where a mesenteric pocket was absent (11/15) (P = 0.01). Primary MDBs caused extra-mural obstruction due to mesenteric shortening (n = 4), small intestinal entrapment within the MDB pocket (n = 5) or in an adjacent mesenteric rent (n = 4), and volvulus around the MDB (n = 2), with intestinal resection required in 8/15 cases. For horses with primary MDBs, survival to hospital discharge was 60% overall (9/15) and 75% for horses that stood following anaesthesia (9/12) with 88.9% of cases discharged from hospital (8/9) surviving >1 year. Excision of MDB tissue was not associated with complications but 3/4 non-incidental MDBs left in situ required relaparotomy to treat MDB-associated colic.Main limitationsRetrospective single centre data.ConclusionsMost MDBs in horses undergoing surgical treatment of colic in this population were not incidental. MDB-associated colic was most commonly classified as strangulating obstruction, but non-strangulating extra-mural compression was also identified. Excision of MDB tissue should be undertaken where possible, particularly in non-incidental cases.