Dunbar syndrome,
or median arcuate ligament syndrome (MALS),
is a condition caused by an extrinsic compression of the celiac trunk,
and sometimes of the celiac plexus,
by the median arcuate ligament (MAL).
This is a fibrous band at the level of the Th12/L1 vertebral bodies,
across the aortic hiatus,
that connects the right and left diaphragmatic crura.
However,
the location of MAL is very variable.
In fact,
the celiac trunk,
in 33% of cases,
originates at the same level or above the MAL [1].
In case of presence of a more caudal insertion of this ligament,
or an upper cranial origin of the celiac trunk,
these situations could create compression on the vessel.
However this could be considered as an uncompressive anatomical variant [2,
3].
Nevertheless in some individuals,
as observed by Dunbar and other authors [4,
5],
this compression may result in chronic ischemia and subsequent clinical symptoms.From the data available in literature it's possible to find an incidence rate of the aforementioned anatomical variant between 7.3% and 24%; among these patients,
just 1.76 - 4% of patients present MALS; female/male ratio is of 4:1 and age of onset between 30 and 50 years [1,
6,
7].
The etiology of this pathology is still uncertain.
At the base of the most caudal implant of the MAL there would be congenital factors,
as evidenced by some studies on couples of monozygotic twins [7,
8].
There are several theories that try to explain the etiopathogenesis; some authors hypothesize that the symptomatology is a consequence of the compression on the only celiac trunk and that the pain is due to chronic and transitory ischemia towards the abdominal organs [9]; others authors refer that the symptoms are caused by the concomitant compression of the celiac plexus which results in a splanchnic vasoconstriction [10].
The compression by the MAL does not always manifest clinically in relation to the numerous collateral between the mesenteric vessels,
such as the upper and posterior pancreaticoduodenal arch,
the arch of rio branco and the arch of Buhler (last-mentioned is very rare).
The compromised circulation,
due to the stenosis,
becomes hemodynamically significant when at least 2 visceral vessels out of 3 are compromised.
This pathology is characterized by a vague and absolutely non-specific symptomatology: abdominal pain,
especially in postprandial period (94.4%),
nausea and vomiting (55.6%),
weight loss (50%),
abdominal swelling (38.9%),
diarrhea (7.5%),
retrosternal pain (very rare) and presence,
on auscultation of the abdomen,
of a bruit [1-7].
The diagnostic iter should be based on clinical presentation,
typical findings on imaging and the exclusion of other frequent pathologies.
The rarity of this pathology in association with the non-specificity of the symptoms leads to the need to exclude diseases with a similar presentation,
but commoner in general population.
In particular,
it should be performed a differential diagnosis between pathologies of the gallbladder (biliary dyskinesia,
cholecystitis),
gastroparesis,
peptic ulceration,
gastritis,
mesenteric ischemia secondary to atherosclerosis (which may coexist with MALS),
colo-rectal neoplasms,
the appendicitis and hepatitis [11].
The treatment of MALS is basically surgical,
performed with laparoscopic access,
oriented to the MAL section; this treatment leads to a rapid resolution of the symptoms in 85% of cases.
About 7% of these patients undergo recurrence that request endovascular traetment with or without stent implantation [12].
Aneurysms in collateral mesenteric vessels,
above all gastroduodeal artery,
is very important and requests endovascular treatment of embolization with coils.