SMA Syndrome Introduction. Epidemiology. Anatomy. Causes. Clinical Presentation. Physical Examination. Differential Diagnosis. Management. Surgical Management. Follow up.

1. Superior Mesenteric Artery Syndrome
Advanced Laparoscopic in Robotic and Bariatric Surgery
King Saud University Medical City
18th November, 2018
Ibrahim Abunohaiah
R1, Urology

2. Introduction
Superior mesenteric artery syndrome (SMA) is an
unusual cause of proximal intestinal obstruction.
Other names includes:
•Cast syndrome.
•Wilkie syndrome.
•Arteriomesenteric duodenal obstruction.
•Chronic duodenal ileus.

3. Introduction, Cont.
The syndrome is characterized by compression of the
3rd portion of the duodenum due to narrowing of
the space between the superior mesenteric artery
and aorta and is primarily attributed to loss of the
intervening mesenteric fat pad.

4. Epidemiology
In US, the precise incidence of this entity is unknown.
• It is estimated to be 0.1% to 0.3%.1
• Females to males ratio is 3:2.1
1) Superior Mesenteric Artery Syndrome, https://www.ncbi.nlm.nih.gov/books/NBK482209/#article-29707.s3

5. Mortality and Morbidity
Delay in the diagnosis of SMAS can result in:
• Malnutrition, dehydration, electrolyte abnormalities.
• Gastric pneumatosis and portal venous gas,
formation of an obstructing duodenal bezoar.
• Hypovolemia secondary to massive GI hemorrhage,
and even death secondary to gastric perforation.

6. Anatomy
• Normal angle between the SMA
and the aorta is between 38 and
65 degrees.
• This angle correlates with BMI.
• The aortomesenteric distance is
normally 10 to 28 mm.
• In SMA it ca be narrowed to as
low as 6 degrees with the
aortomesenteric distances as
low as 2 mm.
Adapted from UpToDateTM

7. Nutcracker Syndrome
• Left renal vein compression.
• Associated with hematuria and abdominal
pain (classically left flank or pelvic pain).
• Left testicular pain in men or left lower
quadrant pain in women (left gonadal vein
drains via the left renal vein)
• Nausea and vomiting can result due to
compression of the splanchnic veins.
• Unusual manifestation of NCS includes
varicocele formation and varicose veins in
the lower limbs.

8. Causes
Constitutional factors:
• Depletion of the mesenteric fat caused by rapid severe weight loss
due to catabolic states such as cancer, surgery, burns, trauma, or
psychiatric problems.
Dietary disorders:
• Anorexia nervosa
• Malabsorption

9. Causes
Spinal disease, deformity, or trauma:
• Superior mesenteric artery syndrome cases after corrective spine
surgery are due to the result of spinal elongation, which decreases
the superior mesenteric/aortic angle.
Rapid linear growth without compensatory weight gain:
• Adolescents with low body mass index (< 18 kg/m2) may be at
higher risk for developing superior mesenteric artery syndrome after
spinal fusion for scoliosis than patients with a higher body mass
index.

10. Patients at Risk
- Significant weight loss leading to loss of the
mesenteric fat pad (most common).
• as a consequence of medical disorders, psychological disorders or
surgery.
- Anatomic abnormalities (congenital or acquired).

11. Patients at Risk, Congenital Anatomic
Abnormalities
• Congenitally short ligament of Treitz.
• The origin of the superior mesenteric artery may
also be abnormally low.

12. • Following corrective spinal surgery for scoliosis
(cast syndrome).
• Following surgeries that distort normal anatomy
such as esophagectomy.
Patients at Risk, Acquired Anatomic
Abnormalities

13. Clinical Presentation
• Acute or Progressive symptoms.
• Symptoms are consistent with proximal small
bowel obstruction.
• Range from postprandial epigastric pain and early
satiety to severe nausea, bilious emesis and weight
loss.
• Patients may present with symptoms of reflux.

14. Clinical Presentation, cont
Symptoms may be relieved when:
• Patient is lying prone.
• In the left lateral decubitus.
• Knee-chest position.

15. Physical Examination & Labs
• Findings are nonspecific.
• Laboratory examination can be normal or, in
patients with severe vomiting, significant
electrolyte abnormalities may be present.

16. Differential Diagnoses
Includes other causes of bowel obstruction as well as
diseases associated with duodenal dysmotility (and
"megaduodenum") including:
• Diabetes mellitus.
• Collagen vascular diseases.
• Scleroderma.
• Chronic idiopathic intestinal pseudo-obstruction.

17. Diagnosis
High index of suspicion is required since symptoms
can be nonspecific.
• Plain abdominal films.
• Oral contrast studies.

18. Plain X-Ray film
Adapted from ”Superior mesenteric artery syndrome: a vicious cycle”, http://casereports.bmj.com/content/2018/bcr-2018-226002.long

19. Upper gastrointestinal contrast study
Adapted from UpToDate.com

20. Upper gastrointestinal contrast study
Adapted from Medscape.com

21. Diagnosis, cont.
• Ultrasound: Can identify and measure the
aortomesenteric angle.

22. Ultrasound in superior mesenteric
artery syndrome
Adapted from UpToDate.com
Sagittal US image
shows SMA-aortic
angle of 12°.
A normal angle
should be
between 38 and
65°.
Inset: Transverse
ultrasonography
image showing
SMA-aorta
distance of 4.4
mm.

23. Diagnosis, cont.
• Arteriography:
Lateral mesenteric arteriography to demonstrate the
narrowing of the aortomesenteric angle.

24. A lateral arteriogram in a patient with
SMA Syndrome
Adapted from UpToDate.com
The angle between the aorta and the SMA is reduced
causing compression of the third portion of the
duodenum.

25. Diagnosis, cont.
• Computed tomographic (CT) and magnetic
resonance (MR) arteriography:
Have largely replaced conventional arteriography
since they are noninvasive and provide additional
anatomic detail such as the amount of intra-
abdominal and retroperitoneal fat.

26. Diagnosis, cont.
CT criteria for the diagnosis of SMAS includes:
• An aortomesenteric angle of less than 22 degrees.
• An aortomesenteric distance of less than 8-10 mm.
• In children, an angle of less than 20° has been
correlated with SMAS.

27. CT scan of the abdomen in a patient
with SMA Syndrome
Adapted from UpToDate.com
There is a distended, contrast-filled stomach (closed
arrowhead) and a dilated, contrast-filled proximal
duodenum (open arrowhead). The duodenum can
be seen narrowing as it approaches the aorta where
it is compressed between the aorta and the SMA.
Computed tomography of the abdomen with intravenous
contrast showing a narrowed angle between the superior
mesenteric artery and the aorta measuring eight degrees.

28. Diagnosis, cont.
Role of Upper GI endoscopy:
It may be necessary to exclude mechanical causes of
duodenal obstruction.

29. Diagnostic imaging criteria
• Duodenal obstruction with an abrupt cutoff in the
third portion and active peristalsis.
• An aortomesenteric artery angle of ≤25° is the
most sensitive measure of diagnosis, particularly if
the aortomesenteric distance is ≤8 mm.
• High fixation of the duodenum by the ligament of
Treitz, abnormally low origin of the SMA.

30. Management
• Conservative Therapy:
• The goal is alleviation of obstructive symptoms and reversal of any
precipitating factors.
• If surgery has altered the anatomy, the likelihood that conservative
therapy will be successful is low.
• Surgical Management.

31. Conservative Therapy
• Gastrointestinal decompression.
• Correction of electrolyte abnormalities.
• Nutritional support:
• Enteral nutrition is preferred (nasojejunal feeding tube
placed distal to the obstruction).
• TPN maybe necessary if enteral feeding is not an option.

32. Conservative Therapy, cont
Conservative management with nutritional support
has good success in:
- Adults who have a brief history of symptoms.
- Children who tend to present acutely.

33. Surgical Management
• Strong's procedure.
• Gastrojejunostomy.
• Duodenojejunostomy with or without division or
resection of the fourth part of the duodenum.

34. Strong’s Procedure
Adapted from UpToDate.com
Strong's procedure mobilizes the
duodenum by dividing the ligament
of Treitz.
Once the duodenal-jejunal junction is
mobilized, the duodenum is
positioned to the right of the superior
mesenteric artery.

35. Gastrojejunostomy
Adapted from UpToDate.com
An end-to-side gastrojejunostomy
can be fashioned to bypass an
obstructed segment of duodenum
using sutures or staples.

36. Duodenojejunostomy
Adapted from UpToDate.com
Duodenojejunostomy is accomplished without (A) or with (B) division of the 4th
portion of the duodenum.

37. Pros and Cons
• Strong's procedure maintains the integrity of the bowel;
however, failure occurs in up to one fourth of patients.
• Gastrojejunostomy decompresses the stomach but the
failure to relieve the duodenal obstruction may result in
recurrent symptoms requiring a second procedure and the
unrelieved obstruction may result in blind loop syndromes
or peptic ulceration.
• Duodenojejunostomy is generally accepted as having
superior results to both Strong's procedure and
gastroenterostomy.
• Duodenojejunostomy with division of the fourth part of the
duodenum establishes bowel continuity and minimizes the
issues associated with a blind loop.

38. Follow Up
• Contrast studies are performed at one to two
weeks postoperatively to demonstrate patency of
the repair and normal emptying of the duodenum.
• Patients are followed for resolution of their
preoperative symptoms and weight gain is
monitored.

39. References
• UpToDate.
• Medscape.
• PubMed.
• BMJ Case Reports.

40. Thank you