If bowel ischemia is not recognized and treated, the muscle layer of the bowel between the mucosa and serosa starts to die. Soon, the serosa becomes ischemic and starts to die. As this serosa is adjacent (i.e., under the abdominal wall) the patient will now have pain on examination of that location caused by ischemic serosa. It is not until the ischemia progresses through the layers of the bowel and reaches the outer surface that localized pain on examination is found. By that time, the entire loop of bowel involved in the ischemic process is irreversible ischemic.
The amount of time that the ischemic process takes to go completely through a loop of bowel depends on the extent of the SMA thrombosis. If the main trunk of the SMA thromboses acutely, the bowel will have irreversible ischemia of all layers within approximately eight hours. If the thrombosis starts in the branches, the time to irreversible ischemia of the bowel may be longer.
If irreversibly ischemic bowel or necrotic bowel is left in the abdomen, cytokines and bacteria released by the dying or dead gut enter the blood stream and lead to sepsis. This produces a low flow state to the organs which, if not recognized, leads to multiorgan failure. In terms of the ischemic bowel, this low flow state, if not dealt with, leads to decreased perfusion to the already compromised bowel and further ischemia and necrosis.
Bowel Ischemia medical expert witness specialties include vascular surgery, general surgery, gastroenterology, pathology, radiology, and critical care medicine.