Blood Flow and Oxygenation in the Portal Vein in Subjects With Chronic Narrowing of the Blood Vessels to the Gut

Inclusion Criteria: * \- Written informed consent * Male or female persons \> 18 years * Subjects with postprandial abdominal pain considered compatible with mesenteric ischemia, and severe stenosis of the SMA and eventually other mesenteric arteries, diagnosed with CT-angiography or Doppler ultrasound * OR subjects with severe stenosis of the SMA and eventually other mesenteric arteries, diagnosed with CT-angiography or Doppler ultrasound, but not postprandial pain Exclusion Criteria: * \- Serious concurrent illness * BMI \> 30 * Cardiac arrhythmia * Anemia with Hgb \< 7,0 mmol/l * Pregnancy or breastfeeding (urine HCG is performed on all fertile women) * Systolic blood pressure \< 90 or \> 200 mmHg * Claustrophobia * Patients who, in the judgement of the investigator, is incapable of participating * Metallic foreign objects in the body, or pacemakers