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\begin{document}

\title{Deadly Aspiration Pneumonia Secondary to Superior Mesenteric Artery
Syndrome}



\author[1]{Rhea Akel}%
\author[2]{Iskandar Daou}%
\author[2]{Dany Jamal}%
\author[2]{Elham Hobeika}%
\author[3]{Rany AOUN}%
\author[2]{Georges Nawfal}%
\affil[1]{Saint Joseph University}%
\affil[2]{Saint Joseph Hospital of the Sisters of the Holy Cross}%
\affil[3]{Hotel-Dieu De France}%


\vspace{-1em}



  
  \date{June 17, 2024}


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\textbf{Deadly Aspiration Pneumonia Secondary to Superior Mesenteric
Artery Syndrome}

Rhea AKEL\textsuperscript{1}, Iskandar DAOU\textsuperscript{1}, Dany
JAMAL\textsuperscript{2}, Elham HOBEIKA\textsuperscript{3}, Rany
AOUN\textsuperscript{4}, Georges NAWFAL\textsuperscript{1}

\textsuperscript{1} Department of Medical Imaging, Saint Joseph
Hospital, Saint Joseph University, Beirut, Lebanon

\textsuperscript{2} Department of Intensive Care Unit, Saint Joseph
Hospital, Beirut, Lebanon

\textsuperscript{3}~Department of Gastroenterology, Saint Joseph
Hospital, Beirut, Lebanon

\textsuperscript{4} Department of Digestive Surgery, Hotel Dieu de
France Hospital, Saint Joseph University, Beirut, Lebanon

\textbf{Corresponding author}

Rhea Akel, akelrhea@gmail.com, Department of Medical Imaging, Saint
Joseph Hospital, University Saint Joseph Medical School, Beirut, Lebanon
+961 70151622.



\textbf{Conflict of interests}

The authors declare that they have no conflicts of interest.

\textbf{Funding}

This study was financed with internal funds. No competing financial
interests exist.

\textbf{Data availability statement}

The data that support the findings of this study are available from the
corresponding author upon reasonable request.

\textbf{Patient consent}

Written informed consent was obtained from the family's patient to
publish this report in accordance with the journal's patient consent
policy.







\emph{Keywords:} Superior mesenteric artery syndrome, aortomesenteric
angle, aortomesenteric distance, aspiration pneumonia, septic shock.



\textbf{Abstract}

Superior mesenteric artery syndrome (SMAS) is a rare and unusual
disease, suspected clinically and confirmed radiologically. It
represents a duodenal obstruction secondary to the impingement of the
third portion of the duodenum between the abdominal aorta (AA) and the
superior mesenteric artery (SMA) due to decreased intra-abdominal fat.
High morbi-mortality rates are linked to missed or late diagnosis that
can lead to complications, such as gastric perforation and gastric
hemorrhage.

We present the case of a 33-year-old-man who was not previously known to
have a SMAS, who presented to the emergency department with signs of
septic shock, complaining of fever and respiratory symptoms for several
days. Investigations showed an aspiration pneumonia secondary to an
upper gastrointestinal obstruction with signs of SMAS on computed
tomography (CT) scanner. Acute and rapid deterioration led to cardiac
arrest and death.

Through this article, we highlight the importance of early and correct
diagnosis of SMAS which can sometimes be challenging, since no number is
strictly diagnostic and radiological images must be interpreted in light
of the clinical history and physical examination.



\textbf{Introduction}

Superior mesenteric artery syndrome (SMAS) is a rare and unusual
disease. It represents a duodenal obstruction secondary to the
impingement of the third portion of the duodenum between the abdominal
aorta (AA) and the superior mesenteric artery (SMA) due to decreased
intra-abdominal fat (1). Clinical symptoms raise suspicion for this
diagnosis that can be confirmed by radiological testing (2). It is known
that a delayed or missed diagnosis is linked to high morbi-mortality
rates secondary to complications, making it a crucial differential to be
considered when there is a duodenal obstruction, especially in the
setting of rapid weight loss (2).

\textbf{Case presentation}

A 33-year-old man presented to the emergency department (ED),
complaining of worsening fever, dyspnea, vomiting and productive cough
for 5 days, and acute onset desaturation. The patient suffers from
schizophrenia and has been treated for more than 20 years by several
neuroleptic drugs.~ His vital signs were as follows: temperature of
39.6\selectlanguage{ngerman}º, heart rate of 147 beats per minute, blood pressure of 100/50
mmHg, and oxygen saturation 80\% on room air. His body mass index (BMI)
was 14.5 kg/m\textsuperscript{2} Physical examination on admission
showed a conscient, non-cooperant cachectic and dyspneic patient, with
tachycardia but no murmurs. Pulmonary auscultation showed bilateral
wheezing and bronchial congestion. Abdominal examination revealed
epigastric tenderness, and no urinary symptoms were mentioned. Blood
tests showed elevated white blood cells count
(13,300/mm\textsuperscript{3}) and a Protein C level at 26 mg/l.
Alkaline reserve was 12.1 mmol/l. Creatinine, liver function tests,
sodium, potassium and chloride levels were within normal limits. A
computed tomography (CT) of the chest, abdomen and pelvis with
intravenous contrast material was ordered and revealed bilateral
multifocal parenchymal condensations with multiple ground-glass
opacities predominant in the lower lobes, suggestive of aspiration
pneumonia (Figure 1). In addition, there was an extremely important
distension of the esophagus, stomach and proximal duodenum (Figure 2),
upstream of an abrupt transition zone involving a decompressed caliber
in the third part of the duodenum at the level of its crossing in the
mesenteric clamp. The rest of the bowel loops were of normal appearance.
No intra-abdominal collection, parietal pneumatosis or pneumoperitoneum
were noted. The angle between the proximal SMA and the AA, also known as
the aortomesenteric angle, was narrow, at 12.3º (Figure 3) and the
aortomesenteric distance was 3.5 mm (Figure 4), suggestive of a SMAS.
Also, the left renal vein was dilated upstream its passage in the
mesenteric clamp. Initial management included hydration, nasal oxygen,
bronchodilators, nasogastric tube insertion, antipyretics, steroids and
hypercaloric total parenteral nutrition (2500 kilocalories per day).
Empiric intravenous antibiotics (Levofloxacin and
Piperacillin/tazobactam) were started after blood and urine cultures.
Evolution showed severe rapid clinical degradation that resulted in a
cardiac arrest and death.

The diagnosis of a severe septic shock due to aspiration pneumonia
secondary to a SMAS was made.

\textbf{Discussion}

SMAS, also known as Wilkie's syndrome, was first described as a case
report in 1842 by Carl Von Rokitansky and further detailed by Wilkie in
1927 (2,3). Other names for this syndrome include cast syndrome, chronic
duodenal ileus and aorto-mesenteric duodenal compression. It is a rare
entity with an incidence estimated at 0.1\% to 0.3\% (2). This disease
occurs preferentially in young adults and adolescents with an age range
between 10 and 39 years old, but it can occur at any age, and is more
prevalent in females with a ratio of 3 females to 2 males (2). No ethnic
predisposition has been proven, however familial cases have been
reported (4). The pathophysiology of this syndrome is explained by an
important decrease of intra-abdominal fat, causing a decrease of the
intervening mesenteric fat pad between the AA and the SMA, resulting in
narrow aortomesenteric angle and distance (1). The duodenal fat pad
cushion is responsible for holding the SMA off the vertebral column and
protecting it from duodenal compression (2). In healthy individuals, the
aortomesenteric angle ranges from 28° to 65° and the aortomesenteric
distance ranges from 10 to 34 mm (5). In SMAS, when the fat pad cushion
becomes thin, the SMA leaves the AA at an abnormally hyper acute angle,
typically less than 25°, and runs closer to the aorta, typically at a
distance less than 8 mm, depending on the BMI of the patient (1). It is
important to note that no number is strictly diagnostic and radiological
images must be interpreted in light of the clinical history and physical
examination, which makes the diagnosis even more challenging (1). Other
characteristic findings on CT scanner are distention of the stomach and
proximal duodenum with bowel caliber narrowing at the origin of the SMA
from the AA (6). Our patient, in addition to being cachectic due to his
psychiatric condition with a very low BMI of 14,5
kg/m\textsuperscript{2}, had a hyper acute aortomesenteric angle and
short aortomesenteric distance measuring 12.3º and 3.5 mm respectively,
with esophago-gastro-duodenal distension proximal with a transition zone
at the takeoff of the SMA from the AA on the CT scanner. He was also
treated with several neuroleptic drugs. Some of the known side effects
of antipsychotic drugs are bowel hypoperistalsis and constipation (7).

Recent weight loss and symptoms of bowel obstruction should alert
physicians to this condition. Late diagnosis has been linked to severe
morbidity and mortality (2), emanating from electrolyte abnormalities,
dehydration, malnutrition, gastric pneumatosis, portal venous gas,
gastric perforation and hemorrhage (8--10).

Our patient presented to the ED with signs of septic shock, pneumonia
and vomiting. The predominant distribution of the diffuse alveolar
infiltrates, ground glass opacities and condensations in the lower lobes
on the chest CT scan, has allowed to make the diagnosis of aspiration
pneumonia. In aspiration pneumonia, the right lower lobe is most
frequently affected, and if aspiration occurred while in prone position,
both lower lobes might be involved (11).

Once the diagnosis is made, in the acute setting, conservative medical
management is the initial treatment, including hydration, electrolyte
correction, nasogastric tube insertion for gastric decompression and
total parenteral nutrition (2), which were all applied in our case.
Nutritional support through hyperalimentation is added during
conservative therapy in an attempt to increase the duodenal fat pad
cushion, thus increasing the aortomesenteric angle and distance,
decreasing duodenal compression and improving symptoms (2).

Albeit, many patients will fail the conservative measures and will
require undergoing invasive procedures such as total parenteral
nutrition, lysis of ligament of Treitz (Strong procedure),
transabdominal or laparoscopic duodenojejunostomy, percutaneous
jejunostomy tube placement and enteral tube placement (2,6).

Our patient also received large broad-spectrum antibiotics based on a
combination of Levofloxacin and Piperacillin/Tazocin to treat the septic
shock secondary to aspiration pneumonia.

The most common cause of death in SMAS is gastric perforation and
hemorrhage (8--10). Mortality due to an aspiration pneumonia secondary
to SMAS has not been described yet. Jung et al, reported a case of a
patient with SMAS, who presented with an aspiration pneumonia secondary
to induction of general anesthesia, and had a favorable outcome (12).

In our case, the patient received appropriate initial management for
septic shock, duodenal obstruction and SMAS, the rapid clinical
deterioration resulted in cardiac arrest and death.

\textbf{Conclusion}

SMAS is an unusual and challenging diagnosis that is made based on
clinical suspicion and characteristic findings. Early and accurate
diagnosis is a must to avoid serious complications that can lead to high
morbidity and mortality rates. Gastric perforation and hemorrhage are
considered the most common causes of death in SMAS. However, it is
important to note that aspiration pneumonia in the setting of SMAS can
be life-threatening when diagnosis is delayed.



\textbf{References}

1. England J, Li N. Superior mesenteric artery syndrome: A review of the
literature. J Am Coll Emerg Physicians Open. 2021 Jun 18;2(3):e12454.

2. Van Horne N, Jackson JP. Superior Mesenteric Artery Syndrome. In:
StatPearls {[}Internet{]}. Treasure Island (FL): StatPearls Publishing;
2023 {[}cited 2023 Aug 12{]}. Available from:
http://www.ncbi.nlm.nih.gov/books/NBK482209/

3. Ehlers TO, Tsamalaidze L, Pereira L, Stauffer J. Laparoscopic
Duodenojejunostomy for the SMA Syndrome. Zentralbl Chir. 2018
Oct;143(5):461--3.

4. Hillyard J, Solomon S, Kaspar M, Chow E, Smallfield G.
Gastrointestinal: Reversal of superior mesenteric artery syndrome
following pregnancy. J Gastroenterol Hepatol. 2019 Mar;34(3):486.

5. Inal M, Unal Daphan B, Karadeniz Bilgili MY. Superior mesenteric
artery syndrome accompanying with nutcracker syndrome: a case report.
Iran Red Crescent Med J. 2014 Oct;16(10):e14755.

6. Warncke ES, Gursahaney DL, Mascolo M, Dee E. Superior mesenteric
artery syndrome: a radiographic review. Abdom Radiol (NY). 2019
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7. Stroup TS, Gray N. Management of common adverse effects of
antipsychotic medications. World Psychiatry. 2018 Oct;17(3):341--56.

8. Ganss A, Rampado S, Savarino E, Bardini R. Superior Mesenteric Artery
Syndrome: a Prospective Study in a Single Institution. J Gastrointest
Surg. 2019 May;23(5):997--1005.

9. Silva G, Moreira-Silva H, Tavares M. Iatrogenic superior mesenteric
artery syndrome. Rev Esp Enferm Dig. 2018 Nov;110(11):742--3.

10. Young A, Kinnear N, Hennessey D, Kanhere H, Trochsler M.
Intermittent superior mesenteric artery syndrome in a patient with
multiple sclerosis. Radiol Case Rep. 2018 Dec;13(6):1108--11.

11. Sanivarapu RR, Gibson J. Aspiration Pneumonia. In: StatPearls
{[}Internet{]}. Treasure Island (FL): StatPearls Publishing; 2023
{[}cited 2023 Aug 12{]}. Available from:
http://www.ncbi.nlm.nih.gov/books/NBK470459/

12. Jung YH, Koo GH. Aspiration Pneumonia during Induction of General
Anesthesia in Superior Mesenteric Artery Syndrome Patient: A case
report. Korean Journal of Anesthesiology. 51(4):512--5.

\textbf{Figures}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image1/image1}

\end{center}
\end{figure}

Figure 1: Axial CT scan of the chest with maximal intensity projection
(MIP) reconstruction showing bilateral multifocal parenchymal
condensations with multiple ground-glass opacities predominant in the
lower lobes, suggestive of aspiration pneumonia. It also shows important
distension of the esophagus (E).\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image2/image2}

\end{center}
\end{figure}

Figure 2: Multiplanar reconstruction (MPR) in the coronal plane shows
important distension of the stomach (S), measuring 28 cm. The rest of
the bowel loops shown are not distended.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image3/image3}

\end{center}
\end{figure}

Figure 3: MPR in the sagittal plane shows an aortomesenteric angle of
12.3\selectlanguage{ngerman}º, an extremely distended esophagus (E) and stomach (S).\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image4/image4}

\end{center}
\end{figure}

Figure 4: Axial CT scan showing an aortomesenteric distance of 3.5 mm,
an extremely distended stomach (S) and duodenum (D) and a dilated left
renal vein (white arow) before the mesenteric clamp.\selectlanguage{english}
\begin{figure}[H]
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