WHY IS THE ILEUM INVOLVED IN THE MAJORITY OFCASES OF INTERNAL HERNIAS? A BIOMECHANICAL HYPOTHESIS

Background:Ileum is involved in 64–81% of cases of epiploicforamen entrapment and 49–53% of inguinal hernias. To dateno explanation for this occurrence has been proposed.Objectives:To offer a possible explanation of the high rate ofileal involvement in internal herniasMethods: Analysis of the surgical and anatomical features of21 cases of strangulation of the small intestine in internalhernia in horses.Results:In 6/13 cases involving the ileum, the incarceratedsegment presented less severe pathological featuresproceeding proximal to distal. These suggest a different,progressive involvement of the distal bowel along with theduration of the pathology. We hypothesised that the relativemovement between bowel and ingesta may cause this.Once a portion of intestine enters the hernial port, its luminalcontent cannot proceed aborally due to the external luminal occlusion caused by the port itself. At this stage, peristalsis,that cannot push the luminal content aborally, will insteadpull the intestinal segment orally. This can eventually lead tothe exit of the proximal intestine until the luminal content inthe herniated portion will block this progression. Distally, beingthe intestine empty, it is easily and progressively brought intothe hernia. This progression ends only when the ileum isinvolved and traction on the ileocaecal valve prevents thisphenomenon.Conclusions:This hypothesis can explain why the ileum isinvolved in the majority of cases of internal hernias.Eventually, antiperistaltic drugs administered early in thecourse of the disease, may reduce the length of intestineaffected