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Prevalence of Incidentally Detected Mulgeta Getu K. et al.
47
ORIGINAL ARTICLE
Prevalence of Incidentally Detected Vascular Compressions in
Abdominal Computed Tomography
Mulgeta Getu Kassa1, Ferehiwot Bekele Getaneh2*
OPEN ACCESS
Citation: Mulgeta Getu Kassa, Ferehiwot
Bekele Getaneh. Prevalence of
Incidentally Detected Vascular
Compressions in Abdominal Computed
Tomography. Ethiop J Health Sci.
2022;32(si1):47. doi:
http://dx.doi.org/10.4314/ejhs.v32i1.8S
Received: December 21, 2021
Accepted: August 14, 2022
Published: October 1, 2022
Copyright: © 2022 Mulugeta Getu Kassa
and Ferehiwot Bekele Getaneh. This is an
open acc ess article distributed under the
terms of the Creative Commons
Attribution License, which permits
unrestricted use, distribution, and
reproduction in any medium, provided the
original author and source are credited.
Funding: This work was supported by
Addis Ababa University, College of
Health Sciences, Ethiopia
Competing Interests: The authors declare
that this manuscript was approved by all
authors in its form and that no competing
interest exists.
Affiliation and Correspondence:
1Department of Radiology, A mbo
University Referral Hospital, Ambo,
Ethiopia
2Addis Ababa University, School of
Medicine, College of Health Scienc e,
Department of Radiology
*Email: teguazh@gmail.com
ABSTRACT
BACKGROUND: Abdominopelvic vascular structures are exposed
to be compressed by adjacent organs or might cause compression
of the adjacent hollow viscera. Most of these conditions are
asymptomatic and they are detected on imaging incidentally.
However, when they are symptomatic, they can lead to a variety of
uncommon syndromes in the abdomen and pelvis. Aim of the study
was to assess the prevalence of incidental abdominopelvic vascular
compressions on computed tomography.
METHOD: A retrospective cross-sectional study was conducted.
All the CT was performed using 64 slice machine. All computed
tomography scan of the abdomen between January and April 2019
were evaluated. Data were collected by evaluating abdominal
Computed Tomographic scans from Picture archiving and
communication system (PACS). Statistical analysis was performed
by using SPSS version 25.0 software.
RESULTS: Out of 623 multi detector abdominopelvic computed
tomography (MDCT) performed between January 2019 and April
2019; a total of 513 (N = 513) patients were included in the study.
This study group comprised of 277 (54 %) females and 236 male
(46%) patients. Mean age was 38 ± 20 (mean ± SD). We identified
35(6.8%) participants with imaging features of Superior mesenteric
artery (SMA) compressions and a 34(6.6%) with imaging features
of nutcracker phenomenon. The celiac artery was compressed by
median arcuate ligament (MAL) in 22(4.3%) of them.
CONCLUSION: Incidentally detected intraabdominal vascular
compressions are common to asymptomatic patients. This result
emphasizes that, vascular compression syndromes diagnosis should
not be made on imaging alone.
KEYWORDS: Computed Tomography, median arcuate ligament
compression, nutcracker phenomenon, superior mesenteric artery
compression
INTRODUCTION
Vascular structures in the abdomen or pelvis are liable to be
compressed by structures in their vicinity or may cause a
compression to the hollow viscera organs(1). The clinical
presentations of individuals with these abnormalities may vary from
asymptomatic to a significant degree of morbidity. Vascular
Ethiop J Health Sci. Vol. 32, Special issue No. 1 October 2022
48
compression syndromes like median arcuate
ligament syndrome, nutcracker syndrome, May-
Thurner syndrome, superior mesenteric artery
syndrome, ureteropelvic junction obstruction,
ureteral vascular compression syndromes and
portal biliopathy have characteristic clinical
symptoms and a predisposing anatomic variant of
vascular structures in imaging. Therefore,
diagnosis should be considered carefully in
patients with incidentally detected abnormalities
in imaging (2).
Nevertheless, imaging plays a role in
evaluating the vascular structures and the
hemodynamic changes during compression and
the adjacent anatomic structures. In addition,
imaging directs the surgical approach for patients
who are subject to intervention for this condition
or other causes.
Doppler ultrasound can be used as a first line
imaging, although it is highly an operator
dependent and technically difficult to perform it in
obese individuals (3).
Barium examination can also be utilized as
one of the diagnostic modalities in patients
presented with bowel obstruction symptoms and
SMA syndrome (duodenal obstruction) (4).
In particular, Multidetector CT (MDCT) has
a superior advantage over the others due to its
capability of in producing reconstructed images,
contrast resolution and less invasive nature. The
main drawback of CT is its use of ionizing
radiation(5).
MRI is an alternative diagnostic modality
when radiation exposure is a high concern and in
iodinated contrast allergic patients (6).
Celiac axis compression: Harjola et al. first
described the compression of the celiac axis by the
median arcuate ligament (MAL)(7). The existence
of the syndrome and its mechanism of causing
pain have been controversial issue since this entity
is reported (8).
Diagnosis can be made in CT angiography
when stenosis is detected on the axial images, and
the celiac artery has a hook or J appearance (9).
Compression of the duodenum by superior
mesenteric artery (SMA): The third part of the
duodenum can be disposed to compression by
superior mesenteric artery due to anatomical or
mechanical factors and reduction of the
retroperitoneal fat. Various debilitating conditions
which cause marked weight loss such as, anorexia
nervosa, malabsorption, or hypercatabolic states
such as burns, major surgery, severe injuries or
malignancies cause retroperitoneal fat loss and
acute angulation of SMA (10).
The normal aortomesenteric angle (AMA)
and aortomesenteric distance (AMD) ranges 28°–
65° and 10–34 mm, respectively (11, 12).
Left renal vein compression by SMA
(Nutcracker phenomenon): This phenomenon is
characterized by the compression of the left renal
vein (LRV) between the SMA and aorta (anterior
nutcracker) or the aorta and vertebral body
(posterior nutcracker) (1).
The reasons of nutcracker syndrome has been
suggested to be posterior renal ptosis, abnormally
high course of the LRV and an abnormal SMA
branching from the aorta (13).
Abrupt narrowing of the LRV with a triangular
shape at the aortomesenteric portion, the “beak
sign”, and LRV diameter ratio (hilar-
aortomesenteric) of ≥4.9 are most sensitive and
specific CT parameters to diagnose nutcracker
syndrome(14).
The aim of this study is to assess the
magnitude of incidentally detected vascular
compressions in asymptomatic individuals.
Imaging, particularly CT allows evaluation of the
anatomic position of these structures and
predisposing anatomic and non-anatomical
factors. Diagnosis relies on both clinical and
imaging findings. However, increasing the
awareness of vascular compressions among
Radiologists would be important as the disease
entity has intermittent character and positive
imaging findings should be documented in
patient’s medical history.
MATERIALS AND METHODS
Image analysis: A retrospective analysis of 623
MDCT of the abdomen, in whom 64-detector CT
was taken for various indications, between
January and April was performed. Patients with
large abdominal mass which caused distortion of
vascular anatomy, poor vascular enhancement and
those with suboptimal sagittal reconstruction were
excluded from the study. MAL compression of
celiac artery was defined by 50% luminal
Prevalence of Incidentally Detected Mulgeta Getu K. et al.
49
narrowing and hooked appearance on sagittal
image with or without presence of ancillary
findings. In image with this finding, the vertebral
level at which the MAL crossed the celiac axis
origin, post-stenotic dilatation and presence of
collaterals were also looked for and recorded(9,
15) (Fig. 1).
A B
Figure 1. Abdominopelvic CT of 60-year-old, known cervical ca patient. This mid sagittal image shows the
celiac artery is compressed by median arcuate ligament (arrow) (A) and has hooked appearance and
narrowing (B).
Sagittal images were obtained for assessment of
the branching configuration of the SMA from the
aorta. AMD was measured as the maximum
distance between the anterior margin of the aorta
and the posterior aspect of the superior mesenteric
artery at a level where the duodenum was
crossing. For the angle measurement (AMA), a
line was drawn between the root of SMA and an
imaginary point on the SMA where SMA begins
to descend parallel to the abdominal aorta.
Measurements were obtained by electronic
calipers. The angles were obtained by manual
tracing and the degrees were automatically
calculated. AMA < 22 degree and AMD of < 8
mm was used for definition of compression in this
research(11, 12) (Fig. 2).
Figure 2. Abdominopelvic CT of a 12-year-old,
known acute lymphocytic leukemia patient, on a
Ethiop J Health Sci. Vol. 32, Special issue No. 1 October 2022
50
post contrast mid sagittal image aortomesenteric
angle (AMA) is 14.90
The left renal vein diameter was measured on an
axial image closest to the centerline of the vein as
it crosses between the aorta and the SMA. On this
same axial image, the anteroposterior distance
between the aorta and the SMA was measured.
Between this axis and the left kidney, the maximal
axial diameter of the left renal vein was then
measured. The compression ratio was calculated.
In this study CR of greater than 3 and those with
2.7-3 and beak angle of greater than 32 degrees
were included (14) (Fig. 3). Collateral veins of the
LRV were deemed present when dilated enhanced
left gonadal, lumbar, or adrenal veins were
observed with a normal unenhanced right gonadal
vein on arterial phase CT images.
Figure 3. Abdominopelvic CT of a 30-year-old
male patient presented with left chest pain and for
work up for unknown primary. Post contrast axial
abdominal CT at the level of renal vein shows
compression of left renal vein as it passes between
abdominal aorta and superior mesenteric artery
(SMA).
Statistical analysis: Data were analyzed using
statistical methods with SPSS version 25 software
package. The average values of CT parameters are
expressed as means ± standard deviations (SD).
Categorical variables were reported using
frequencies.
Ethical consideration: Ethical approval to
conduct the study was obtained from ethics review
committee of the department of radiology before
the commencement of the study.
RESULTS
Out of 623 MDCT performed, a total of 513 (N =
513) patients were included in this study. Females
comprised 277 (54 %) and 236(46%) were male.
Mean age was 38 ± 20 (mean ± SD). Thirty-five
(6.8%) had imaging features of SMA
compression. Thirty-four (6.6%) of the patient
fulfilled imaging criteria of nutcracker
phenomenon and twenty-two (4.3%) of the
patients showed celiac compression by MAL.
Celiac axis compression: The age range was 11-
71years with mean of 47.41 ± 17.67 years. Males
were 13 (59.1%) and females were nine (40.9%).
In 19 out of 22 patients with celiac axis
compression, the origin of the celiac artery was
high (above the first lumbar vertebra). In 18 cases,
MAL was located below the level of L1,
indicating that a low insertion of MAL and normal
in four patients (but low in relation to celiac origin
in all 22 patients). Only three CT showed post
stenotic dilatation of the celiac artery. No
significant collaterals were demonstrated.
Compression of the duodenum by Superior
mesenteric artery (SMA): The imaging sign of
SMA causing duodenal compression was observed
in 27 females and 10 males. The age range was
12-79 years. Mean of AMA and AMD were 16.2
± 2.96 degrees and 5.32 ± 1.18mm respectively.
The degree of compression by AMA, in three
(8.1%) of them was less than 12 degrees, 16
(43.2%) measured 18-220, 18 (48.7%) measured
12-180. Twenty-four (64.9%) of the SMA
compressions had AMD of 4-6mm (table 1).
Table 1. Characteristics of aortomesenteric angle
and aortomesenteric distance of the 37 study
subjects with incidental findings of duodenal
compression by superior mesenteric artery.
Characteristics
Frequency (%)
Aortomesenteric angle (degree)
<12
3 (8.1)
12-15
10 (27.1)
15-18
8 (21.6)
18-22
16 (43.2)
Aortomesenteric distance
< 4mm
6 (16.2)
4-6mm
24(64.9)
6-8mm
7(18.9)
Prevalence of Incidentally Detected Mulgeta Getu K. et al.
51
Left renal vein compression by SMA
(Nutcracker phenomenon): Out of 34 patients
who have CT signs of nutcracker phenomenon,
nine (26.5%) were males and 25(73.5%) were
females. Mean age was 39.26 ± 16.93. The
average AMA, AMD, Compression ratio and beak
angle were 16.2 ± 3 degrees, 5.6 ± 1.2 mm, 4.2 ±
0.82 and 42.9 ± 9.79 degrees respectively.
DISCUSSION
The study was performed in a chronic care setting
and a significant number of abdominopelvic
MDCT were performed in a few months periods.
The capability of sagittal reconstructions has
improved visualization of the vasculatures, the
adjacent structures and performance of
measurements.
In our study the magnitude of celiac artery
compression by median arcuate ligament, as
defined by 50% luminal narrowing and hooked
appearance on sagittal image with or without
presence of ancillary findings was 4.3%. In most
cases high origins of celiac artery and low
insertion of MAL are risk factors for celiac
compression. Our findings are in keeping with
previous studies where they reported the incidence
of celiac axis stenosis in asymptomatic individuals
of 4-24%(16). In other study of with 5.1%
incidence, all the eight subjects with celiac axis
compression, the origin of the celiac artery was
above the first lumbar vertebra. In six of the cases,
MAL was located below the level of L1,
indicating that a low insertion of MAL was
responsible for the compression. Only three
angiograms showed post stenotic dilatation of the
celiac artery, and none showed significant
collaterals(17).
SMA syndrome occurs relatively infrequently, its
exact prevalence in the general population is
extremely difficult to measure, although it has
been estimated to be 0.1%–0.3% on the basis of
gastrointestinal barium studies (12). However, in
patients with scoliosis who undergo corrective
spinal surgery, a prevalence of up to 2.4% has
been reported (18). To the authors knowledge
there are no studies reporting prevalence of
compression of the duodenum by SMA in
asymptomatic individuals. In our study, CT signs
of duodenal compression by SMA was observed
in 35 (6.8%) patients. The relative increment of
the number can be justified by the fact that the
study was performed in a chronic care setting,
where a significant cases of cancers and other
chronic illnesses are treated. These are conditions
known to cause severe weight loss with resulting
in a loss of retroperitoneal fat. The overall
predominant lean body habitus in our population
might have contributed for this number as well.
The occurrence of nutcracker phenomena in this
study is 6.6 %, which is lower than previously
reported (27.3%) (19) and a female preponderance
(73.5%) which is not in line with the mentioned
study.
This study has its own limitation, such as, the fact
that it is a retrospective study, exploration of the
clinical symptoms and follow up of patients was
not possible. Ancillary findings are not included
since it was difficult to assess small vessels in
most of the patients and many of the images were
not CT angiography. Additionally, CT does not
assess the effect of respiration (inspiration vs
expiration) which affects median arcuate ligament
compression of celiac artery.
In conclusion, incidentally detected
intraabdominal vascular compressions is common
to asymptomatic patients. This result emphasizes
that, vascular compression syndromes diagnosis
should not be made on imaging alone.
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