Nutcracker syndrome:
Nutcracker syndrome involves compression of the left renal vein between the abdominal aorta and the upper mesenteric artery.[2] .
In cases of retroaortic and circumaortic renal vein,
it is sometimes observed between the aorta and the spine.
The prevalence of nutcracker syndrome is unknown,
and it is estimated that it may be higher in women.
The age range in which it can occur is from children,
to middle-aged people and even cases have been described in the seventh decade of life.
There is high variability in clinical presentation,
some patients present asymptomatic hematuria,
orthostatic proteinuria or more severe forms of presentation such as pelvic congestion.
[1,2]
Doppler ultrasound in patients suspected of this syndrome has a sensitivity of 78% and a specificity of 100%.
[1]
Some of the findings in Doppler ultrasound are:
-
Flow velocity of the left renal vein at clamp level is considered abnormal when it is greater than 100 cm/s.
[3] (Fig.1)
-
Determines the diameter and maximum flow velocity in the proximal and distal portions of the left renal vein.
A ratio >5 is a diagnosis of nutcracker syndrome,
however in cases of long evolution the renal vein may not be distended.
-
Aortomesenteric distance is pathological when it is <8 mm.
(Fig.2)
-
Aortomesenteric angle is considered pathological when it is <25º,
(Fig.3)[3,4].
In some cases the findings can be confirmed by magnetic resonance (Fig.4)
Median arcuate ligament syndrome:
It is produced by extrinsic compression of the medial arcuato ligament,
prominent fibrous bands and periaortic ganglion tissue.
The origin of the compression is due to an abnormally low insertion of the diaphragm or it may be produced because the celiac axis has an excessively high origin in the aorta.
Clinical manifestations are variable,
may be asymptomatic or present symptoms such as abdominal pain during exercise or post-prandial,
nausea,
vomiting and weight loss.
[5]
Ultrasound is the diagnostic method of election at first.
Assessment by Doppler-Colour ultrasound can be used as a screening method,
but the results obtained must be confirmed by other imaging tests.
Some of the findings in Doppler ultrasound are:
-
Blood velocity measurements should be included in the celiac axis at the end of inspiration and at the end of exhalation.
Peak velocities greater than 200 cm/s are considered to be suggestive of significant stenosis.
(Fig.
5).Findings increase in exhalation.
(Fig.
6) .
-
Reverse flow can be found in the common hepatic artery.[5]
AngioMRI and AngioCT provide information on anatomy and allow differential diagnoses to be evaluated.[5] (Fig.7)
Thoracic outlet syndrome:
Set of symptoms produced by the compression of the neurovascular structures at the level of the upper thoracic narrowing.
Depending on the structure involved,
it may be neurological,
venous or arterial [6,7].
Clinical manifestations: discomfort in the forearm,
arm and shoulder.
Severe pain that appears with the activity of the limb,
some patients may have paresthesias.
[8]
Doppler ultrasound has the advantage of allowing evaluation of subclavian flow in supraclavicular fossa during provocative maneuvers such as the modified Adson maneuver (Progressive Abduction-Hyperabduction of the arm with contralateral extension of the neck).
The main advantage of this technique is the direct comparison between the dynamically induced symptoms and the concomitant visualization of the vessels.
Some of the findings in Doppler ultrasound are:
Normal size and adequate flow in basal position.
Anomalous behaviour with venous dilation and total cessation of venous flow in abduction 45º and 90º,
indicative of preocclusion.
(Fig.
8)
Calibre increase with anomalous flat flow in hyperabduction.
Normal calibre and adequate flow in basal position.
Abnormal behavior in abduction 45º and 90º,
with duplicated Vs in abduction and postoclusive arterial wave with decrease of the resistance index.
(Fig.9)
Then the radial flow is explored with the Allen and Adson maneuvers.
However,
it is based on indirect signs of arterial stenosis and does not demonstrate the exact site of arterial compression.
[8,9]
On the other hand,
B-mode ultrasound can allow the detection of anatomical abnormalities such as aneurysmal dilatation and vessel deviation.[7]
Ultrasound findings are confirmed by CT study with arms in hyperabduction.(Fig.
11)
Popliteal artery entrapment syndrome:
It is produced by the compression of the popliteal artery by an anomalous anatomical relationship.
Among its causes may be due to abnormal embryonic development of the popliteal fossa.
Both the muscle and the artery may be responsible for the abnormal anatomy and numerous variations may arise.
Identification of different types does not affect treatment or prognosis.
It is a rare entity,
usually affecting young men,
often athletes.
[9,10]
Doppler ultrasound has a limited role in the diagnosis of this pathology because the findings are not specific.
[9,10]
Some of the findings in Doppler ultrasound are:
-
Arterial compression with decrease or absence of flow,
through maneuvers such as plantar flexion and dorsiflexion of the foot.
-
Other nonspecific findings are occlusion of the popliteal artery or an aneurysm in the popliteal artery.
(Fig.12,13).
Magnetic resonance imaging (MRI) is a very useful diagnostic modality because it provides the necessary information for the diagnosis of entrapment.
[10] (Fig.14).