AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Background

Superior mesenteric artery (SMA) syndrome is an uncommon but well recognized clinical entity characterized by compression of the third, or transverse, portion of the duodenum against the aorta by the SMA, resulting in chronic, intermittent, or acute complete or partial duodenal obstruction. SMA syndrome was first described in 1861 by Von Rokitansky, who proposed that its cause was obstruction of the third part of the duodenum as a result of arteriomesenteric compression.

Despite the fact that about 400 cases are described in the English language literature, many have doubted the existence of SMA syndrome as a real entity; indeed, some investigators have suggested that SMA syndrome is overdiagnosed because it is confused with other causes of megaduodenum. Nonetheless, the entity (also called cast syndrome) is a well-known complication of scoliosis surgery and often poses a diagnostic dilemma; its diagnosis frequently is one of exclusion.

Pathophysiology

The SMA usually forms an angle of approximately 45° (range, 38-56°) with the abdominal aorta, and the third part of the duodenum crosses caudal to the origin of the SMA, coursing between the SMA and aorta. Any factor that sharply narrows the aortomesenteric angle to approximately 6-25° can cause entrapment and compression of the third part of the duodenum as it passes between the SMA and aorta, resulting in SMA syndrome. In addition, the aortomesenteric distance in SMA syndrome is decreased to 2-8 mm (normal is 10-20 mm). Alternatively, other causes implicated in SMA syndrome include high insertion of the duodenum at the ligament of Treitz, a low origin of the SMA, and compression of the duodenum due to peritoneal adhesions.

Frequency

United States

The precise incidence of this entity is unknown. In a review of the literature, approximately 0.013-0.3% of the findings from upper GI tract barium studies support a diagnosis of SMA syndrome.

Mortality/Morbidity

Delay in the diagnosis of SMA syndrome can result in malnutrition, dehydration, electrolyte abnormalities, and even death.

Race

No racial differences have been identified.

Sex

More females are affected by SMA syndrome. In one large series of 75 patients with SMA syndrome, two thirds of the cases involved women, with an average age of 41 years; one third of cases involved men, with an average age of 38 years.

Age

The SMA syndrome usually occurs in older children and adolescents. In one report by Geer, 75% of the cases occurred in patients aged 10-30 years.

CLINICAL

Section 3 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

History

The patient often presents with chronic upper abdominal symptoms such as epigastric pain, nausea, eructation, voluminous vomiting (bilious or partially digested food), postprandial discomfort, early satiety, and sometimes, subacute small-bowel obstruction. Symptoms of SMA syndrome often develop from 6-12 days after scoliosis surgery.

The symptoms are typically relieved when the patient is in the left lateral decubitus, prone, or knee-to-chest position, and they are often aggravated when the patient is in the supine position.

Physical

An asthenic habitus is noted in about 80% of cases. Abdominal examination may reveal a succussion splash. Peptic ulcer disease has been noted in 25-45% of the patients, and hyperchlorhydria has been noted in 50%. Patients can present with signs of subacute small-bowel obstruction.

Causes

Important etiologic factors that may precipitate narrowing of the aortomesenteric angle and recurrent mechanical obstruction include the following:

• Constitutional factors
• • Thin body build
  • Exaggerated lumbar lordosis
  • Visceroptosis and abdominal wall laxity
  • Depletion of the mesenteric fat caused by rapid severe weight loss due to catabolic states such as cancer, surgery, burns, or psychiatric problems
• Severe injuries, such as head trauma, leading to prolonged bedrest
• Dietary disorders
• • Anorexia nervosa
  • Malabsorption
• Spinal disease, deformity, or trauma
• Use of body cast in the surgical treatment of scoliosis or vertebral fractures. SMA cases after corrective spine surgery is due to the result of spinal elongation, which decreases the superior mesenteric/aortic angle. Postoperative weight loss is an important factor for development of SMA syndrome. Although use of Harrington rods for corrective surgery commonly used in the 1950s and 1960s was an important contributory factor for development of SMA syndrome, newer derotation/translation corrective techniques can also be rarely associated with this disease entity.
• Rapid linear growth without compensatory weight gain, particularly in adolescents
• Anatomic anomalies, rarely
• • Abnormally high and fixed position of the ligament of Treitz with an upward displacement of the duodenum
  • Unusually low origin of the SMA
• Unusual causes
• • Traumatic aneurysm of the SMA after a stab wound
  • Familial SMA syndrome
  • Recurrent SMA syndrome

DIFFERENTIALS

Section 4 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Other Problems to be Considered

The differential diagnosis includes anorexia nervosa and bulimia. In addition, SMA syndrome should be differentiated from other causes of megaduodenum, including diabetes mellitus, collagen vascular conditions, and chronic idiopathic intestinal pseudoobstruction.

WORKUP

Section 5 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Imaging Studies

• The diagnosis of SMA syndrome is difficult. Confirmation usually requires radiographic studies, such as an upper GI series, hypotonic duodenography, and CT scanning.
• Upper GI study with barium reveals characteristic dilatation of the first and second parts of the duodenum, with an abrupt vertical or linear cutoff in the third part with normal mucosal folds.
• Fluoroscopy demonstrates a to-and-fro motion of the barium in the dilated proximal portion of the duodenum. Other findings include delay of 4-6 hours in gastroduodenal transit and relief of the obstruction when the patient is in the left lateral decubitus position.
• A Hayes maneuver (ie, pressure applied below the umbilicus in cephalad and dorsal direction), which elevates the root of small-bowel mesentery, may also relieve the obstruction.
• In equivocal cases, hypotonic duodenography may depict the site of obstruction and dilation of the proximal duodenum, with antiperistaltic waves within the dilated portion.
• CT scanning is useful in the diagnosis of SMA syndrome and can provide diagnostic information, including aorta-SMA distances and duodenal distension. Also, it can be used to assess intra-abdominal and retroperitoneal fat.
• Upper GI endoscopy may be necessary to exclude mechanical causes of duodenal obstruction. However, the diagnosis of SMA syndrome may be missed with this study.
• Abdominal ultrasonography may be helpful in measuring the angle of the SMA and the aortomesenteric distance.
• Manometry may be used to differentiate between the possibility of a myopathic form of chronic intestinal pseudoobstruction syndrome (hollow visceral myopathy) by demonstrating low-amplitude waves throughout the duodenum, and frequently the stomach, versus an irregular or absent phase III and no postprandial motility changes in a neuropathic form of chronic intestinal pseudoobstruction syndrome. The pattern of increased amplitude of propagated contractions and retrograde contractions should hint or suggest the mechanical obstruction in SMA syndrome.

TREATMENT

Section 6 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical Care

Reversing or removing the precipitating factor is usually successful in a patient with acute SMA syndrome. Conservative initial treatment is recommended in all patients with SMA syndrome; this includes adequate nutrition, nasogastric decompression, and proper positioning of the patient after eating (ie, left lateral decubitus, prone, or knee-to-chest position). Enteral feeding using a double lumen nasojejunal tube passed distal to the obstruction under fluoroscopic assistance is an effective adjunct in treatment of patients with rapid severe weight loss and also eliminates the need for intravenous fluids and the risks associated with total parenteral nutrition.

In some instances, both enteral and parenteral nutritional support may be needed to provide optimal calories. The patient's weight should be monitored daily. Subsequently, the patient can be started on oral liquids followed by slow and gradual introduction of small and frequent soft meals as tolerated. Finally, regular solid foods are introduced. Metoclopramide treatment may be beneficial. Review of the orthopedic literature reveals that the success rate is 100% with medical management only in cases with an acute presentation of SMA syndrome.

Surgical Care

Surgical intervention is indicated when conservative measures are ineffective, particularly in patients with a long history of progressive weight loss, pronounced duodenal dilatation with stasis, and complicating peptic ulcer disease. Duodenojejunostomy is the most frequently used procedure, and it is successful in about 90% of cases. The use of laparoscopic surgery that involves lysis of the ligament of Treitz and mobilization of the duodenum has been reported.

Consultations

• Pediatric gastroenterologist
• Nutritionist
• Pediatric surgeon

Diet

Medical therapy usually begins with the initiation of intravenous fluids, with the frequent administration of small amounts of liquids. In some cases, nasogastric tube feedings with a standard liquid diet may be indicated.

MEDICATION

Section 7 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Drug therapy currently is not a component of the standard of care for this syndrome. Metoclopramide may be used to provide a prokinetic effect.

Drug Category: Prokinetic agents

These stimulate motility of the GI tract. GI smooth muscle is regulated by autonomic innervation, local reflexes, and hormones. Peristalsis is induced and causes the gut contents to move, encouraging digestion.

FOLLOW-UP

Section 8 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Further Outpatient Care

• Nasogastric tube feedings with a standard liquid diet may be indicated in some patients.
• These feedings may be continued at home until the obstruction resolves spontaneously.

Complications

• Electrolyte imbalance (eg, hypokalemia)
• Dehydration
• Malnutrition
• Oliguria

Prognosis

• The outcome is excellent if the entity is diagnosed in a timely fashion and if the patient receives appropriate therapy.
• In the past, deaths due to progressive dehydration, hypokalemia, and oliguria have been reported; most of these occurred in patients in whom the diagnosis was delayed or missed.

MISCELLANEOUS

Section 9 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical/Legal Pitfalls

• Failure to diagnose SMA syndrome can lead increased morbidity and even death, resulting in medicolegal pitfalls and potential litigation

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

• Altiok H, Lubicky JP, DeWald CJ, Herman JE. The superior mesenteric artery syndrome in patients with spinal deformity. Spine. Oct 1 2005;30(19):2164-70. [Medline].
• Altman DH, Puranik SR. Superior mesenteric artery syndrome in children. Am J Roentgenol Radium Ther Nucl Med. May 1973;118(1):104-8. [Medline].
• Baltazar U, Dunn J, Floresguerra C. Superior mesenteric artery syndrome: an uncommon cause of intestinal obstruction. South Med J. Jun 2000;93(6):606-8. [Medline].
• Barnes JB, Lee M. Superior mesenteric artery syndrome in an intravenous drug abuser after rapid weight loss. South Med J. Mar 1996;89(3):331-4. [Medline].
• Crowther MAA, Webb PJ, Eyre-Brook IA. Superior mesenteric artery syndrome following surgery for scoliosis. Spine. 2002;27:E528-33.
• Hutchinson DT, Bassett GS. Superior mesenteric artery syndrome in pediatric orthopedic patients. Clin Orthop. Jan 1990;(250):250-7. [Medline].
• Massoud WZ. Laparoscopic management of superior mesenteric artery syndrome. Int Surg. Oct-Dec 1995;80(4):322-7. [Medline].
• Munns SW, Morrissy RT, Golladay ES. Hyperalimentation for superior mesenteric-artery (cast) syndrome following correction of spinal deformity. J Bone Joint Surg Am. Oct 1984;66(8):1175-7. [Medline].
• Ortiz C, Cleveland RH, Blickman JG. Familial superior mesenteric artery syndrome. Pediatr Radiol. 1990;20(8):588-9. [Medline].
• Raissi B, Taylor BM, Taves DH. Recurrent superior mesenteric artery (Wilkie''s) syndrome: a case report. Can J Surg. Oct 1996;39(5):410-6. [Medline].
• Rokitansky C. Handbuch der Pathologischen Anotomie. Vienna: Branmiller and Siedel. 1842.
• Santer R, Young C, Rossi T. Computed tomography in superior mesenteric artery syndrome. Pediatr Radiol. 1991;21(2):154-5. [Medline].
• Shah MA, Albright MB, Vogt MT, Moreland MS. Superior mesenteric artery syndrome in scoliosis surgery: weight percentile for height as an indicator of risk. J Pediatr Orthop. Sep-Oct 2003;23(5):665-8. [Medline].
• Shapiro G, Green DW, Fatica NS, Boachie-Adjei O. Medical complications in scoliosis surgery. Curr Opin Pediatr. Feb 2001;13(1):36-41. [Medline].
• Shetty AK, Schmidt-Sommerfeld E, Haymon ML. Radiological case of the month. Superior mesenteric artery syndrome. Arch Pediatr Adolesc Med. Mar 1999;153(3):303-4. [Medline].
• Vitale MG, Higgs GB, Liebling MS, et al. Superior mesenteric artery syndrome after segmental instrumentation: a biomechanical analysis. Am J Orthop. Aug 1999;28(8):461-7. [Medline].
• Wilkie DPD. Chronic duodenal ileus. Am J Med Sci. 1927;173:643-9.
• Ylinen P, Kinnunen J, Hockerstedt K. Superior mesenteric artery syndrome. A follow-up study of 16 operated patients. J Clin Gastroenterol. Aug 1989;11(4):386-91. [Medline].

Article Last Updated: Jul 16, 2006