Tx and Followup:
Patient was initially treated with heparin (anticoagulation) and metoprolol (to retard further dissection by decreasing BP and the arterial pulse wave). Heparin was later switched to warfarin. Abdominal pain subsided. Surgical or endovascular interventions were deferred. Patient was discharged on metoprolol and warfarin in stable condition and pain-free.
Full Diagnosis: Superior mesenteric artery dissection, spontaneous, isolated, idiopathic.
Spontaneous SMA dissections are exceptional events. During a period of 52 years, only 35 cases (including this one) have been reported. Nevertheless, they represent the most frequent type of digestive artery dissection, with those of the hepatic artery, splenic artery, left gastric artery, and celiac artery being even less frequent. Patients with SMA dissections are predominantly male (88%) and have an average age of 55 years (between 45 and 87 years). Whereas atherosclerosis, fibromuscular dysplasia, cystic medial necrosis, and connective tissue disorders (Marfanâ€™s, Elhers-Danlos syndroms) are often mentioned as possible causes, in most cases no cause could be found. Other possible aetiologies of isolated SMA dissection include iatrogenic or blunt trauma and segmental mediolytic arteriopathy (uncommon nonatherosclerotic and nonvasculitic arteriopathy, characterized by lytic degeneration of the arterial media, intramural dissection and thrombosed or ruptured aneurysm; mainly involves the intraabdominal arterial system; however, a few cases of involvement of intracranial arteries have been reported).
Two main clinical symptom patterns are described: (1) acute epigastric or nonspecific abdominal pain syndrome combined with nausea and vomiting and an image of pseudoobstruction on the abdominal plain film results, indicating an acute mesenteric ischemia; and (2) chronic intestinal angina (postprandial pain, vomiting, anorexia, weight loss, epigastric murmur). More exceptionally, cases of hemorrhagic shock have been reported as the result of rupture of the dissecting artery or SMA aneurysm into the peritoneal cavity.
Abdominal ultrasound scan, which is often performed as an emergency procedure for a painful abdominal syndrome, may be helpful for diagnosis when an aneurismal dilatation or the intimal flap is observed. However, flap visualization is inconstant. This examination is more sensitive when associated with a Doppler scan examination. The Doppler scan can be used in the assessment of bowel viability in the operating room to decide as to whether vascular surgery is necessary.
CT angiography allows visualization of the false lumen together with the intimal flap during the arterial phase. CT angiography provides signs of acute ischemic bowel (lack of bowel wall enhancement, mesenteric edema) and gives an estimation of the extent of the lesion. The portal phase gives an indication of the severity of mesenteric ischemia by showing mesenteric or portal venous gas that is often associated with bowel necrosis.
Urgent surgery is recommended when such signs are observed.
However, abdominal plain film, abdominal US, and CT angiography findings are inconstant, and arteriography remains the â€śgold standardâ€ť to confirm the diagnosis.
In most cases, the dissection begins within the first 6 cm from the origin, which remains intact, giving an image either of double lumen and dissection flap or an image of eccentric stenosis.
Treatment options include:
Surgical revascularization via laparotomy (bypass grafting)
Endovascular revascularization with stent (?) or endoprosthesis placement
Medical treatment (mainly anticoagulation and BP/HR control)
Spontaneous dissections of the SMA remain exceptional, but they have been underestimated and are now more frequently reported as the result of the progress of imagery. Surgery is indicated in acute symptomatic forms with suspicion of mesenteric ischemia. In the other cases, a simple follow-up examination may be appropriate.