Superior Mesenteric Artery Syndrome (SMAS) Induced by Tuberculosis-related Cachexia: A Rare Case Study

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 Superior Mesenteric Artery Syndrome (SMAS) Induced by Tuberculosis-related Cachexia: A Rare Case Study

Introduction

Superior Mesenteric Artery Syndrome (SMAS), a rare and potentially life-threatening gastrointestinal disorder, is characterized by the compression of the third portion of the duodenum between the abdominal aorta and the superior mesenteric artery (SMA). While congenital or post-surgical anatomical abnormalities are the usual suspects, extreme weight loss—particularly due to cachexia—can trigger this syndrome. In this case study, we explore an unusual presentation of SMAS in a 26-year-old male suffering from severe pulmonary tuberculosis and associated cachexia.


Clinical Case Overview

A 26-year-old male presented to the emergency department with:

  • Dry cough for 5 months

  • Night sweats

  • Unintentional weight loss of 18 kg

  • Upper abdominal pain and postprandial vomiting

His Body Mass Index (BMI) was calculated at 11, placing him in the category of extreme malnutrition. Physical examination showed significant cachexia, abdominal distension, and mild tenderness on palpation.

Chest X-ray and sputum tests confirmed pulmonary tuberculosis. Despite initiation of intravenous anti-tuberculosis therapy, the patient’s vomiting persisted, especially after meals.

Radiological Diagnosis

An enhanced abdominal CT scan was performed to rule out mechanical obstruction and revealed:

  • Gastric distension [Figure 1]

  • Significant reduction of mesenteric and subcutaneous fat

  • Aortomesenteric distance of 3 mm (normal: 10–20 mm) [Figure 1, arrow]

  • Aortomesenteric angle of 7° (normal: 45–60°) [Figure 2]

These findings confirmed the diagnosis of Superior Mesenteric Artery Syndrome (SMAS).

Figure 1. Axial CT scan showing a markedly dilated stomach (*) and compression of the third portion of the duodenum (arrow) between the SMA and aorta.


Figure 2. Sagittal CT image showing an abnormally narrow aortomesenteric angle (7°), a hallmark of SMAS.


Pathophysiology

SMAS occurs when the angle between the abdominal aorta and the SMA narrows, compressing the duodenum. This angle is normally maintained by a fat cushion, which is lost during severe weight loss.

In this patient, cachexia from tuberculosis led to depletion of retroperitoneal fat, reducing the aortomesenteric angle and distance, culminating in duodenal obstruction.

Treatment and Outcome

Initial management focused on nasogastric decompression and parenteral nutrition to restore weight and reduce duodenal compression. The patient responded to conservative management and was discharged after two weeks. Unfortunately, he was lost to follow-up, and his long-term outcome remains unknown.

Discussion

This case underscores the importance of considering SMAS in patients with:

  • Rapid or extreme weight loss

  • Persistent vomiting post-meals

  • Upper abdominal pain without mechanical obstruction

Although rare, SMAS should not be overlooked, especially in the setting of underlying diseases causing cachexia, such as tuberculosis, cancer, or anorexia nervosa.

Clinical Pearls

  • SMAS is often misdiagnosed due to non-specific gastrointestinal symptoms.

  • CT with contrast is the gold standard for measuring the aortomesenteric angle and distance.

  • Conservative management is effective in many cases, but surgical intervention (e.g., duodenojejunostomy) may be required for refractory cases.

  • Underlying causes of weight loss must be addressed simultaneously.

Quiz

1. What is the minimum normal aortomesenteric angle in a healthy individual?

A. 10°
B. 20°
C. 45°
D. 60°

2. Which of the following is not a common cause of Superior Mesenteric Artery Syndrome?

A. Rapid weight loss
B. Anorexia nervosa
C. Appendicitis
D. Tuberculosis-induced cachexia

3. Which diagnostic modality is most appropriate for evaluating SMAS?

A. Abdominal X-ray
B. Ultrasound
C. MRI
D. Contrast-enhanced CT scan

Answer & Explanation

1. Correct Answer: C. 45°. Explanation: Normal aortomesenteric angles range from 45° to 60°. Angles below this threshold are commonly seen in SMAS.

2. Correct Answer: C. Appendicitis. Explanation: Appendicitis does not typically lead to SMAS, while all the others can cause significant weight loss and mesenteric fat depletion.

3. Correct Answer: D. Contrast-enhanced CT scan. Explanation: A CT scan with contrast offers detailed visualization of vascular anatomy, including the aortomesenteric angle and duodenal compression.

Conclusion

Superior Mesenteric Artery Syndrome is a rare but serious condition that may occur secondary to extreme weight loss and fat depletion, as seen in this tuberculosis-related cachexia case. Prompt recognition, supported by radiological imaging, and appropriate conservative or surgical treatment can significantly improve outcomes. This case serves as a critical reminder of the hidden complications that can arise from seemingly unrelated systemic diseases.

References

  1. T. Welsch, C. Büchler, and J. Kienle, “Replaced right hepatic artery—anatomical considerations and surgical implications,” Surg Radiol Anat, vol. 27, pp. 543–548, 2005.

  2. A. Ahmed, A. Taylor, and A. L. Patterson, “Superior mesenteric artery syndrome: a diagnostic challenge,” Radiol Case Rep, vol. 13, no. 2, pp. 386–389, 2018.

  3. J. D. Lee, S. H. Oh, and C. Y. Park, “SMAS secondary to tuberculosis-induced cachexia,” Korean J Gastroenterol, vol. 73, no. 1, pp. 41–45, 2019.

  4. R. Unal, N. B. Ozcan, and H. Koc, “Superior mesenteric artery syndrome: clinical and imaging findings,” J Clin Imaging Sci, vol. 10, p. 38, 2020.

  5. L. Okugawa, K. Kondo, and M. Endo, “Laparoscopic treatment of SMAS: a case series,” Surg Endosc, vol. 34, no. 6, pp. 2678–2683, 2020.

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