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Abstract

Superior mesenteric artery (SMA) syndrome is a rare but serious complication following scoliosis surgery. Early diagnosis and management are key factors for successful conservative treatment to avoid the need for emergency laparotomies which causes higher morbidity or even mortality. We report two adolescent idiopathic scoliosis patients with Cobb angle of 49° and 132°, respectively, and low body mass index who presented with SMA syndrome following posterior spinal fusion from T2 to L3 and were treated successfully with conservative management. Abdominal radiographs showed distended gastric shadow. Computed tomography angiography of the abdomen showed decreased aortomesenteric angle and SMA-aorta distance. Both patients were treated successfully with conservative treatment which included three principles: gastric decompression with nasogastric tube, correction of electrolytes imbalance, and nutritional support with low volume, high calorie nutritional supplement. Both patients were started with small but frequent meals. Surgeries were not required in both cases. Early diagnosis and management are the key factors to successful treatment in SMA syndrome. Patients with SMA can be treated successfully with conservative treatment comprising of nasogastric decompression, electrolyte correction, and nutritional support with small but frequent meals.

Keywords

adolescent idiopathic scoliosis (AIS)aortomesenteric angle posterior spinal fusion (PSF)SMA-aorta distance small frequent meals superior mesenteric artery (SMA) syndrome vomiting weight loss

Introduction

Superior mesenteric artery (SMA) syndrome is a rare complication following scoliosis surgery. It is due to vascular compression of the third part of the duodenum between the SMA and the abdominal aorta when the duodenum traverses the aorta in the axilla of SMA.^1

–4 The incidence was reported to be from 0.013% to 4.7%.^5

–9 Early diagnosis and management should be emphasized as emergent laparotomies which would be required if diagnosis is delayed had a mortality rate of 33%.⁶ We aimed to report two cases of SMA syndrome following posterior spinal fusion (PSF) for adolescent idiopathic scoliosis (AIS) who were managed successfully with conservative treatment comprising of nasogastric decompression, nutritional support, and correction of electrolytes.

Case presentation

Case 1

A 15-year-old girl with AIS Lenke 6C (left T2–T8, apex T5, Cobb angle: 45°, side bending (SB) Cobb angle: 29°; right T8–L3, apex T12/L1, Cobb angle: 49°, SB Cobb angle: 7°) underwent PSF from T2–L3 level (Figure 1(a) and (b)). Preoperative height, weight, and body mass index (BMI) were 158 cm (27.4th percentile), 41 kg (5.48th percentile), and 16.4 kg/m² (6th percentile), respectively. The surgery was uneventful. Postoperative Cobb angle was 15° and correction rate (CR) was 69.4% (Figure 1(b)). Postoperative height gain was 2.5 cm. She was discharged well on postoperative day (POD) 3. On POD 12, she developed recurrent vomiting. She had weight loss of 4 kg (41–37 kg). Abdominal radiograph showed a distended gastric shadow (Figure 1(c)). Computed tomography angiography (CTA) confirmed the diagnosis of SMA syndrome (aortomesenteric angle: 10° and SMA-aorta distance: 3.2 mm) (Figure 1(d) and (e)). She was managed conservatively with correction of electrolyte imbalances and nutritional support with small, frequent meals. Low volume but high calorie nutritional supplements were added. She was discharged after 12 days. She had complete resolution of symptoms on POD 35 and regained her preoperative weight (41 kg) at 12 weeks.

Figure 1.

Case 1: (a) Preoperative and (b) postoperative posteroanterior standing radiographs of the spine revealed correction of the Lenke 6C curve of 69.4% with a height gain of 2.5 cm postoperatively. (c) Anteroposterior standing radiograph of the abdomen demonstrated distended gastric shadow (white arrows) and fluid level (black arrow). (d) Sagittal and (e) axial views of CTA of the abdomen revealed an aortomesenteric angle of 10°, SMA-aorta distance of 3.2 mm, and constriction of the third part of the duodenum by the superior mesenteric artery. CTA: computed tomography angiography; SMA: superior mesenteric artery.

Case 2

A 16-year-old girl presented with severe AIS Lenke 2AR (left T2–T6, apex T4, Cobb angle: 83°, SB Cobb angle: 59°; right T6–L2, apex T10, Cobb angle: 132°, SB Cobb angle: 97°; left L2–L5, apex L5, Cobb angle: 57°, SB Cobb angle: 8°) underwent PSF from T2–L3 level (Figure 2(a) and (b)). The preoperative T5–T12 kyphosis and L1–S1 lordosis were 52° and 68°, respectively (Figure 2(c)). Preoperative weight, height, and BMI were 161 cm (40.5th percentile), 42.3 kg (3.75th percentile), and 16.3 kg/m² (2.6th percentile), respectively. The surgery was uneventful. Postoperative Cobb angle was 63° and CR was 52.3% (Figure 2(b)). The postoperative T5–T12 kyphosis and L1–S1 lordosis were 34° and 55°, respectively (Figure 2(d)). Postoperative height gain was 7.5 cm. She was discharged on POD 5. On POD 7, she developed recurrent vomiting and abdominal distension. Her weight was 40.7 kg (1.6 kg loss). Abdominal radiograph showed double bubble sign (Figure 2(e)). CTA showed aortomesenteric angle of 10° and SMA-aorta distance of 2.6 mm (Figure 2(f) and (g)). She was also treated conservatively with similar protocols mentioned above. As her condition was more severe, her treatment regime was slightly different. She was kept nil per oral for 5 days and was given clear fluids once nausea and vomiting resolved. Total parenteral nutrition was then administered. On POD 21, nourishing fluid was started. On POD 26, she resumed normal diet.

Figure 2.

Case 2: (a) Preoperative and (b) postoperative posteroanterior standing radiographs of a 16-year-old girl with a severe scoliosis Lenke 2AR showed preoperative and postoperative Cobb angle of the major curve of 132° and 63°, respectively. (c) The preoperative T5–T12 kyphosis and L1–S1 lordosis were 52° and 68°, respectively. (d) The postoperative T5–T12 kyphosis and L1–S1 lordosis were 34° and 55°, respectively. Posterior spinal fusion T2 to L3 was performed. Correction rate was 52.3%. (e) Erect abdominal radiograph showed double bubble sign (white arrows). (f) Sagittal and (g) axial of CTA of the abdomen revealed an aortomesenteric angle of 10° and SMA-aorta distance of 2.6 mm which confirmed the diagnosis of SMA syndrome (black arrow indicates the constricted third part of the duodenum). CTA: computed tomography angiography; SMA: superior mesenteric artery.

Discussion

Symptoms of SMA syndrome usually occur after 5–7 days following scoliosis surgery. The patients often presented with persistent, recurrent vomiting in addition to abdominal distension and epigastric tenderness. Postoperative paralytic ileus secondary to general anesthesia, analgesia, or electrolyte imbalance often develop earlier in the postoperative period and resolve spontaneously in 3–5 days.¹⁰ In this case report, both patients presented with persistent, recurrent vomiting 1 week after scoliosis surgery (POD 12 in case 1 and POD 7 in case 2). Delayed onset of persistent, recurrent vomiting following scoliosis surgery should raise suspicion of SMA syndrome especially in higher risk patients. In the plain radiographs of the abdomen, a “distended gastric shadow” indicates a dilated stomach filled with air. In this case, it was due to the vascular compression of the third part of the duodenum between SMA and aorta. The “double bubble sign” which is commonly described in newborn is typical for duodenal obstruction. In the plain upright radiographs of the abdomen, the classical sign indicates gas in the distended stomach and in the dilated proximal duodenum with air-fluid levels.¹¹ In scoliosis patients following surgery, the presence of this sign should raise the suspicion of SMA syndrome.

Identifying patients at risk for SMA syndrome is important. Risk factors are staged procedures, lumbar modifier of B and C, height >50% percentile, weight <25% percentile, BMI <25th percentile, sagittal kyphosis, increased thoracic rigidity, and acute spinal lengthening.^7,10,12 Zhu and Qiu reported seven cases of SMA syndrome in their series of 640 scoliosis patients following surgery. Among them, four cases had thoracic hyperkyphosis and two had thoracolumbar kyphosis.¹⁰ Braun et al., in a case–control study comparing 17 patients with SMA syndrome and 34 control subjects, reported a higher percentage of patients with positive thoracic kyphosis (based on Lenke classification) in the group with SMA syndrome (23.5%) than in the control group (14.3%) (p = 0.07).⁷ Patients with increased thoracic curve rigidity (<60% SB flexibility) had an odds ratio of 6.67 of developing SMA syndrome following scoliosis surgery (p = 0.006).⁷

Both patients had risk factors, that is, increased height but low weight for age and low BMI, although BMI of around 16 kg/m² was not particularly low for the Asian population. Case 1 had a long thoracolumbar curve which could probably be a risk factor for SMA syndrome because correction of a long curve may predispose the viscera to more stretching. The second patient had 7.5 cm lengthening after correction. In addition, the patient also had a rigid thoracic curve (SB flexibility of 26.5%) which may also predispose to SMA syndrome after scoliosis surgery.

The literature review on SMA syndrome following scoliosis surgery is illustrated in Table 1. Most patients can be treated conservatively^12

–18 based on three principles, that is, gastric decompression, electrolyte correction, and nutritional support.¹⁹ Tsirikos et al.¹⁵ proposed oral restriction and commencement of nasojejunal feeding. Mandarry et al.²⁰ suggested frequent meals of pureed or blenderized food about 180–240 ml given four hourly. Lam et al.¹³ proposed a treatment algorithm in managing SMA syndrome following AIS surgery. Our patients had low volume but high calorie supplements.

Table 1.

Literature review on superior mesenteric artery syndrome following scoliosis corrective surgery.

Study	Year	Patient profile	POD	Type of curve	Surgical procedure	Postoperative Cobb’s angle	Presentation	Investigation	Treatment and outcome
Kennedy et al.²⁴	1983	14/M Thin	40	Thoracic 73°	PSF	54°	Vomiting, circulatory collapse	Diagnosis made at autopsy	Total gastrectomy with esophagojejunal anastomosis
Amy et al.²³	1985	16	16	T4–T11: 54°	PSF T4–L1	N/A	Vomiting, abdominal pain	UGI	Ladd procedure
Moskovich et al.²¹	1986	16.5/F	9	T5–T12: 65°	PSF T4–L3	21°	Bilious vomiting	UGI	Duodenojejunostomy
Tsirikos et al.⁵	2005	14/F 38.5 kg	6	T5–T12: 72° T12–L4: 52°	Two-staged Anterior-posterior fusion T4–L1	Thoracic 22° Lumbar 20°	Nausea, vomiting, abdominal pain	AUS	Nasojejunal tube feeding
		14/F47.9 kg	5	T1–T6: 34°T6–T12: 57°	PSF T2–L1	15°, 22°	Distended abdomen, abdominal pain, vomiting	UGI	Nasogastric decompression, nasojejunal tube feeding
Pan et al.¹⁴	2007	12/F15.6 kg127 cm	3	T4–L1: 83°L1–L5: 61°	Two-staged surgery (ASF T7-T11 and PSF T3-L3)	48°, 15°	Abdominal pain, distended abdomen	NG aspirate (bile-stained)AUSSerum amylase and lipase	Conservative treatment, nasogastric tube decompression
		12/F40 kg155 cm	2	T6–T11: 80°T11–L4: 64°	Three-staged ASF and PSF (anterior T7–T12, anterior L1–L4, posterior T6–L4)	23°, 19°	Distended abdomen, bilious vomiting, abdominal pain,	Serum amylase and lipaseUGI	Nasogastric decompression, metoclopramide gastrojejunostomy on Day 29, TPN
Tsirikos et al.¹⁵	2008	16.8/F56.6 kg164 cmBMI 21.0	45	T10–L2: 50°	ASF T10–L2	7°	Severe nausea and vomiting, dehydrated, LOW distended abdomen	UGI	Nasogastric decompression, nasojejunal tube feeding
Smith et al.¹⁸	2009	13/F39.9 kg155 cmBMI 16.6	7	T3–T10: 42°T10–L4: 60°	PSF	N/A	Vomiting, anorexia	None (clinical diagnosis)	Nasojejunal tube feeding
		19/F50.3 kg168 cm	10	T1–T5: 34°T5–T12: 50°L2–L5: 27°	PSF T3–L1	N/A	Vomiting, anorexia	None (clinical diagnosis)	Nasojejunal tube feeding
		16/M	16	T8–L1: 49°L1–L4: 35°	PSF T4–L3	T8–L1: 7°L1–L4: 10°	Nausea, vomiting	None (clinical diagnosis)	Nasojejunal tube feeding
Lam et al.¹³	2014	12/F42.8 kg165.3 cmBMI 15.1	6	Lenke 2ANT6–T12: 45°T12–L4: 60°	PSF T5–L3	T6–T12: 9°T12–L4: 2°	Bilious vomiting, LOW	UGI	Nasojejunal tube feeding: 1 weekOral liquid diet: 1 weekSoft diet: 1 week
		17/F44.1 kg157.1 cmBMI 17.0	6	Lenke 2CNT7–T12: 69°T12–L4: 21°	PSF T4–L3	T7–T12: 21°T12–L4: 5°	Bilious vomiting, abdominal pain, LOW	UGI	Nasogastric decompression, TPN and continuous nasogastric feeds: 19 daysOral diet: 3 days
		15/M46.5 kg162.1 cmBMI 17.0	27	T5–L3: 65°	PSF	T5–L3: 15°	Bilious vomiting, anorexia, LOW	UGI	Nasogastric decompression, nasojejunal tube feeding: 8 daysContinuous jejunal feeds at homeJejunal feeds converted to clear liquid orally then soft diet
Keskin et al.²²	2014	17/F	5	Lenke 1BThoracic: 50°Lumbar 30°	PSF T3–L3	Complete resolution of spinal curvature	Vomiting, abdominal distension, LOW	Contrast-enhanced CT	Nasogastric decompression, duodenojejunostomy
Oyoun et al.¹⁶	2015	12/F36.2 kg155 cmBMI 15.0	4 years	Lumbar 49°	PSF	N/A	LOW	UGI	Nutritional diet up to 2000–3000 cal/day
Present study	2020	15/F41 kg158 cmBMI 16.4	12	Lenke 6CT8–L3: 49°	PSF T2–L3	T8–L3: 15°	Recurrent vomiting, LOW	CTA	Small, frequent mealsNutritional supplementation—low volume high calorie
		16/F42.3 kg161 cmBMI 16.3	7	Lenke 2ART6-L2: 132°	PSF T2–L3	T6-L2: 63°	Recurrent vomiting, abdominal distension, LOW	CTA	Nasogastric decompressionSmall, frequent mealsNutritional supplementation—low volume high calorie

M: male; F: female; N/A: not applicable; UGI: upper gastrointestinal imaging; AUS: abdominal ultrasound; PSF: posterior spinal fusion; ASF: anterior spinal fusion; NG: nasogastric; TPN: total parenteral nutrition, LOW: loss of weight; BMI: body mass index; CTA: computed tomography angiography.

Failure of conservative treatment might result in life-threatening conditions such as metabolic alkalosis, electrolyte imbalance, and aspiration pneumonia.²⁰ Surgery such as gastrojejunostomy,¹⁴ duodenojejunostomy,^21,22 Ladd procedure,²³ and total gastrectomy with esophagojejunal anastomosis²⁴ may be required. Our patients had responded well to conservative management and no additional surgeries were required. They eventually achieved good weight gain with the treatment regime.

Conclusion

Early diagnosis and management are key factors to successful treatment in SMA syndrome. We report two patients who were treated successfully with conservative treatment comprising of nasogastric decompression, electrolytes correction, and nutritional support with small and frequent meals.

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

ORCID iD

Amir Arif Anuar

Chee Kidd Chiu

Chris Yin Wei Chan

Mun Keong Kwan

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Superior mesenteric artery syndrome: A rare complication of scoliosis corrective surgery