Well it is a bit more complicated than that. Ischemia frequently causes a secondary edema due to leakage of cell contents, like that found in the brain after stroke. Here is an overview from this source:
http://www.ncbi.nlm.nih.gov/books/NBK6883/
Irrespective of etiology four clinical stages are usually recognized. As mentioned above in arterial embolism the onset of symptoms is often very quick and the progression of symptoms rapid while the process can take several days following venous thrombosis.
The first stage is the hyperactive stage. This is characterized by the intermittent severe pain which starts immediately after occlusion of the vessel. Frequently there is passage of loose stools, sometimes with blood, and vomiting. Usually there is a discrepancy between the often very severe pain and the few findings on physical abdominal examination. Ischemia causes hyperperistalsis reflected in hyperactive bowel sounds on auscultation.
The paralytic stage. The pain is usually diminishing but becomes more continuous and diffuse. During this stage the size of the abdomen increases and it becomes more generally tender and there is no bowel sounds at auscultation.
The stage of disarranged fluid balance. Fluids containing proteins and electrolytes start to leak through the mucosal as well as the serosal side of the gut. When the bowel becomes necrotic peritonitis develops. The fluid loss is usually massive. In this stage the patient does not differ much from other patients suffering from peritonitis of other causes.
The Shock stage. In this stage patients are rapidly deteriorating with severe alterations in the fluid balance and the situation soon goes over into irreversible shock.
