Labs- CBC, CMP, Lipase, UA, HCG(when applicable), Lactate, Coags.
imaging
from the ED stand point a multiphase contrast CT is the most accurate and timely.(Non-contrast, arterial phase, and venous phase).
oral contrast can help dilineate bowel thickness.
Magnetic resonance venography is another option if testing is non-diagnostic.
from the ED stand point a multiphase contrast CT is the most accurate and timely.(Non-contrast, arterial phase, and venous phase).
oral contrast can help dilineate bowel thickness.
Magnetic resonance venography is another option if testing is non-diagnostic.
meseteric<unk>  filing defect, bowel thickening, bowel hypoattenuation, bowel enhancement, pneumatosis, potential ascites. 
labs, other forms of imaging, and physical exam do not have high enough sensitivity to reliably exclude this diagnosis.
Mesenteric vein thrombosis
Abdominal aortic aneurysm
Splenic infarction
Aortocaval fistula
Superior mesenteric artery syndrome
Acute gastroenteritis
Splenic artery aneurysm
Aortoenteric fisulta