Clinical and Nutritional Outcomes in Children With Idiopathic Superior Mesenteric Artery Syndrome : Journal of Pediatric Gastroenterology and Nutrition

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Original Articles: Gastroenterology

Clinical and Nutritional Outcomes in Children With Idiopathic Superior Mesenteric Artery Syndrome

Shiu, Jr-Rung*; Chao, Hsun-Chin*; Luo, Chih-Cheng; Lai, Ming-Wei*; Kong, Man-Shan*; Chen, Shih-Yen*; Chen, Chien-Chang*; Wang, Chao-Jan

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Journal of Pediatric Gastroenterology and Nutrition 51(2):p 177-182, August 2010. | DOI: 10.1097/MPG.0b013e3181c7bdda
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Abstract

Superior mesenteric artery syndrome (SMAS) is a rare cause of proximal-duodenal obstruction resulting from the external compression of the third portion of the duodenum by the superior mesenteric artery. Von Rokitansky (1) first described SMAS in 1842 as a syndrome with intermittent emesis resulting from compression of the duodenum between the aorta and superior mesenteric artery. Wilkie (2) published the first large series of 75 cases, which consisted mainly of chronic cases that responded well to surgery.

It is hypothesized that loss of the retroperitoneal fat pad and connective tissue narrows the aortomesenteric angle, creating a mechanical obstruction of the duodenum. The incidence of SMAS in the general population is extremely difficult to measure but is estimated to be 0.1% to 0.3% based on a review of gastrointestinal studies (3). The patients are usually older children and young adults; females are affected more often than males.

The syndrome is frequent in anorexic women, in those with profound weight loss caused by malignancy, in patients with trauma in the intensive care unit, after bariatric surgery, with prolonged confinement in a body cast, and in patients who have undergone spinal surgery or experienced burns (4,5). This report illustrates the clinical presentation, imaging findings, growth status, and outcome of children with idiopathic SMAS.

PATIENTS AND METHODS

In our institution, we have conducted a prospective program to survey for pediatric SMAS since 1999. This includes sonographic measurement of the aortomesenteric angle, treatment, a questionnaire evaluation of clinical symptoms, and regular visits to clinics to review the clinical symptoms and nutritional status. The SMAS subjects in this study were placed on medical treatment for at least 6 months and were followed as outpatients at pediatric gastroenterology clinics monthly for at least 12 months. Consecutive patients younger than 15 years who underwent regular follow-up visits for the treatment of SMAS at Chang Gung Children's Hospital between January 1999 and January 2009 were prospectively studied. The study was approved by the human research committee of the local institute.

Idiopathic SMAS was defined as the presence of abdominal symptoms; features compatible with SMAS in a barium upper gastrointestinal (UGI) series; and no known or possible triggering factors, such as psychogenic anorexia (anorexia nervosa), congenital gastrointestinal anomalies, central nervous system disorders, traumatic injuries, intraabdominal or spinal surgery, or other organic diseases resulting in chronic weight loss. The parameters studied included clinical symptoms, imaging findings, endoscopic features, intervention effects, appetite, and nutritional status. The diagnosis of SMAS was based on the results of a barium UGI series that revealed dilatation of the proximal duodenum, compression of the third portion of the duodenum, antiperistaltic waves of barium proximal to the obstruction, and delayed gastroduodenal transit. Patients with illnesses requiring hospitalization during the study period or with acute illness–related weight loss for more than 1 week during the follow-up period that may have influenced the study results were excluded from the study.

For the evaluation of effect of treatment in clinical symptoms, patients recorded clinical symptoms every day. The clinical symptoms investigated included postprandial abdominal pain (or fullness) and vomiting episodes. Appetite was evaluated using a 3-day dietary record completed by the patient or patient's family. The weight-for-age z score was used to evaluate the nutritional status, and the z score was computed according to the stature percentile on growth charts used by the Department of Health of Taiwan. In the intervention protocol, those patients presenting with intractable obstructive symptoms (progressive abdominal pain and bilious vomiting despite medical treatment and parenteral nutrition for 1 week) or those with persistent anorexia and weight loss were recommended to receive enteral nutrition (via nasojejunal or jejunostomy) tube feeding, or referred to a pediatric surgeon for surgical intervention. In our institution, surgical procedure of duodenojejunostomy was routinely done by a pediatric surgeon for SMAS. The medical treatment consisted of a prokinetic (motilium, a dopaminergic blocking agent, 0.3 mg · kg · dose) and an H2 blocker (cimetidine, a histamine H2 antagonist, 5 mg · kg · dose) 3 times daily; the dosage was tapered to twice or once daily if marked relief of the clinical symptoms (more than 80% symptom relief) was achieved in the 2 weeks before a clinic visit.

The outcome was evaluated using the clinical symptoms, appetite, and nutritional status (weight-for-age z score) observed monthly for 12 months. The change in the clinical symptoms, appetite, and nutritional status was assessed using 3-day dietary records completed at baseline and at 3, 6, and 12 months. A “good” response to treatment was a symptom reduction >50%, and a “poor” response was a symptom reduction ≤50%. Children with a marked increase in appetite were those in whom there was a ≥20% increase in the daily intake volume of major carbohydrate or protein foods (eg, rice, milk, meat).

Data Collection and Statistical Analysis

The effect of treatment on the clinical symptoms, nutritional status, and appetite was evaluated statistically. Continuous data were expressed as the average ± standard deviation (SD). The data were analyzed using SAS (SAS Institute, Inc, Cary, NC). The Mantel-Haenszel χ2 test was used for analyzing categorical data. The data on clinical symptoms, appetite, and height-for-age and weight-for-age z scores at 3, 6, and 12 months compared with baseline were evaluated using the Student t test, with P < 0.05 considered significant.

RESULTS

Demographic and Clinical Characteristics

In all, 30 subjects diagnosed with idiopathic SMAS were evaluated. Two subjects who experienced acute respiratory illnesses and 1 subject who was hospitalized with severe acute gastroenteritis with decreased appetite and weight loss during the assessment period were excluded. Ultimately, 27 patients (8 boys, 19 girls) were enrolled in the study. Twelve patients experienced admission history due to undetermined vomiting and dehydration, and nasogastric tube placement for bowel decompression was required in 5 patients. The demographic data, clinical characteristics, and growth status of these 27 children are shown in Table 1. Patients' ages ranged from 8.25 to 14.87 years (mean 11.77 ± 2.15) at the initial presentation. Symptoms developed in 4 to 365 days (174.6 ± 137.3). The major presenting symptoms were postprandial pain or fullness (88.9%), vomiting (55.6%), and early satiety (51.9%). Eight patients (29.6%) had weight loss; 3 (37.5%) lost >10% of their body weight. Two (7.4%) had a height status <10th percentile, whereas 15 (55.6%) patients had a weight status <10th percentile.

T1-12
TABLE 1:
Demographic data and clinical features in 27 children with idiopathic SMAS

All of the patients underwent an abdominal ultrasound (US) and a UGI series, revealing the characteristic linear occlusion at the third portion of duodenum on the UGI series (Fig. 1) and small aortomesenteric angles between 10° and 19° on US (Fig. 2). Twelve patients underwent endoscopic examinations. Of these, 10 were initially suspected to have peptic ulcer and 2 had lesions suggesting ulcers on the barium UGI series. Endoscopy of all 12 patients revealed similar results, including gastritis, duodenitis, and a linear compression in the third portion of the duodenum. Three patients underwent computed tomography (CT), which revealed a dilated stomach and duodenum in all of the cases (Fig. 3).

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FIGURE 1:
The SMA-aorta angle on abdominal sonography in the patients varied from 10° to 19°.
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FIGURE 2:
Upper gastrointestinal series shows dilatation of the first and second portion of the duodenum, abrupt vertical compression of the third portion of the duodenum (arrow).
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FIGURE 3:
Axial abdominal CT scan shows severely dilated stomach and duodenum just proximal to a narrowed segment of the third portion of the duodenum compressed between the superior mesenteric artery (arrow) and the aorta (arrowhead).

Clinical Course and Intervention

A total of 6 patients were candidates for enteral nutrition or surgical intervention. These 6 patients underwent surgical intervention because all of their families hesitated to have them treated via long-term enteral nutrition. Among these patients, 3 presented with symptoms of intractable obstruction (progressive abdominal pain and bilious vomiting despite medical treatment and 1 week of parenteral nutrition), and the other 3 had persistent anorexia and weight loss despite 1 month of medical treatment. Of the 6 patients who underwent surgery, 5 had smooth postoperative courses, with marked relief of their abdominal symptoms within 2 weeks. A female patient developed adhesion ileus 3 weeks postoperatively, but her abdominal symptoms resolved gradually during a 10-day treatment of total parenteral nutrition. All 4 surgical patients showed steady improvement in their clinical symptoms, appetite, and weight gain in the following months. Of the 21 patients who received medical treatment only, 14 (66.7%) had attained good resolution of their abdominal symptoms at the first assessment (10–13 weeks) and had continued relief of their abdominal symptoms at the second and third assessments (13–26 and 49–52 weeks).

Follow-up Nutritional and Dietary Status

Table 2 summarizes the nutritional status (weight and height) of the patients at 3, 6, and 12 months. The weight-for-age percentile increased significantly from baseline at 3, 6, and 12 months (P = 0.002, <0.001, and <0.001, respectively, Student t test; Table 2). Significant increments of weight-for age z score were achieved at 6 and 12 months (P = 0.021 and 0.015, respectively, Student t test; Table 2).

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TABLE 2:
Growth status at baseline, 3, 6, and 12 months in the 27 patients

The weight-for-age status and appetite increased in all of the patients during follow-up. Those patients who underwent surgical intervention had greater increments in the weight-for-age status and appetite than those who were treated medically. All 6 surgical patients achieved a >10th percentile increment in weight-for age status (12.7th–33.7th percentiles) and >20% increment in appetite (20.2%–40.7%) by 3 months after surgery. Table 3 describes the height- and weight-for-age status at 3, 6, and 12 months in the 6 patients receiving surgical treatment. The weight-for-age percentiles showed marked increment from baseline (16.3rd percentile) to 6 months (38.1st percentile, P = 0.015), and 12 months (42.6th percentile, P = 0.006) (Table 3). The weight-for-age z scores at baseline, 3, 6, and 12 months were −0.99, −0.56, −0.28, and −0.21, respectively (Table 3). The average increment in appetite was 27.4%, 31.8%, and 31.5% at 3, 6, and 12 months, respectively.

T3-12
TABLE 3:
Comparison of growth status at baseline and 12 and 24 weeks in the 6 patients with surgical treatment

Of the patients who received medical treatment only, 11 (52.4%) achieved a >10th percentile increment in weight-for-age status (10.1th–19.7 percentile) and 12 (57.1%) achieved a >20% increment in appetite after 3 months of treatment. Table 4 summarizes the height- and weight-for-age status at 3, 6, and 12 months in the 21 patients receiving medical treatment only. The weight-for-age percentiles increased from baseline to 12 months, the percentile at baseline, 3, 6, and 12 months was 15.8, 24.7, 28.8, and 28.4, respectively, and the weight-for-age z score at baseline, 3, 6, and 12 months was −1.01, −0.70, −0.56, and −0.57, respectively (Table 4). Statistically significant increments in the weight-for-age percentile were achieved after 6 and 12 months of treatment (P = 0.002 and <0.001, respectively; Table 4), whereas the increments in the weight-for-age z score were not significantly achieved after 6 and 12 months of treatment (P = 0.082 and 0.091, respectively; Table 4).

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TABLE 4:
Comparison of growth status at baseline and 12 and 24 weeks in the 21 patients with only medical treatment

The respective average increment in appetite was 17.7%, 22.6%, and 21.8% at 3, 6, and 12 months. Twelve patients had marked increment in appetite at 3, 6, and 12 months. Table 5 presents the correlation between the appetite increment and weight-for-age status after 3 to 12 months of medical treatment. In comparison to the 9 patients who did not have a marked increase in appetite, the height-for-age status and especially the weight-for-age status increased steadily in the 12 patients with a marked increment in appetite after 3 to 12 months of treatment; the increments in the weight-for-age percentile were significantly achieved after 6 and 12 months of treatment (P = 0.047 and 0.045, respectively; Table 5).

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TABLE 5:
Correlation of appetite increment and nutritional status in the 21 patients with only medical treatment

DISCUSSION

This study investigated the clinical and nutritional outcomes of children with idiopathic SMAS during a 12-month period. Our results agree with previous pediatric observations that SMAS usually occurs in older children, and girls are affected more often than boys.

In general, any condition that predisposes the patient to profound weight loss may narrow the aortomesenteric angle. A case series found that 75% of patients developing SMAS were between 10 and 39 years of age, and 80% of these patients were underweight relative to the normal population (6). Other factors causing entrapment and compression of the third part of the duodenum, as it passes between the SMA and aorta, may result in SMAS. In adults, a high insertion of the duodenum at the ligament of Treitz, or peritoneal adhesions related to a low origin of the SMA and compression of the duodenum, can cause a marked drop in the aortomesenteric angle to 8° and shorten the aortomesenteric distance to 6 mm (7). Other explanations for the mechanism of SMAS include visceroptosis, angulation of the gut at the ligament of Treitz, duodenal malrotation (8), and altered intestinal motility (9).

The diagnosis of SMAS is difficult and is usually made by exclusion. SMAS should be considered in the differential diagnosis of upper intestinal obstruction presenting with vomiting, epigastralgia, and anorexia. Compression of the duodenum is most acute in the supine position. Like a previous pediatric study, our patients typically presented with postprandial epigastric pain, early satiety, nausea, and vomiting (10). Some of our patients had weight loss before the diagnosis of SMAS was made, as has been reported in patients with malignancies, eating disorders, malabsorption, head injuries, cerebral palsy, spinal deformities (11), or after spinal surgery (12). Three of our series presented with acute intestinal obstruction, which has been reported as a surgical emergency of SMAS with vomiting and pronounced gastric dilatation (13). Aspiration and pneumonia are life-threatening complications that may occur in association with this acute manifestation. Some of our patients had mentioned choking or coughing symptoms, but none of them had aspiration complications.

The diagnosis of SMAS is difficult. Confirmation usually requires a radiographic study, and the UGI contrast study results are diagnostic (14). Characteristic radiologic findings in SMAS include dilatation of the first and second portions of the duodenum, abrupt vertical or oblique compression of the third portion of the duodenum, antiperistaltic waves of barium proximal to the obstruction, a significant delay in gastroduodenal transit, and relief of the obstruction after postural changes (15,16). The syndrome must be differentiated from other causes of megaduodenum, such as diabetes mellitus, systemic lupus erythematous, and scleroderma (17). Based on the CT results in our patients, we agree with reports that CT is helpful in confirming this diagnosis by demonstrating dilatation of the proximal duodenal loop with a reduced aortomesenteric distance and angle in sagittal plane reconstructions (18–20). Our study also confirms that US can be helpful in making the diagnosis (21,22). Angiography can also be used to measure the aortomesenteric angle at L3 (23).

In the vast majority of cases, conservative therapy for SMAS is successful. Conservative treatment includes frequent small feedings with postprandial assumption of the left lateral decubitus, knee–chest, or prone positions, nasogastric tube decompression as warranted, parenteral nutrition, and placement of a feeding tube distal to the compression (1). The symptoms in the majority of our patients were often relieved by vomiting, prone position, or lateral position. The Hayes maneuver, which involves applying pressure below the umbilicus in a cephalad and dorsal direction, may also provide relief (8,24). Enteral feeding through a tube passed distal to the obstruction or total parenteral nutrition can be an effective adjunct in the treatment of patients with rapid, severe weight loss (11,25). The placement of feeding tube passed distal to the obstruction was not recommended in our patients due to lack of rapid, severe weight loss. Concomitant treatment with H2 antagonists or proton pump inhibitors may also be useful in treating peptic ulcers associated with SMAS (4). Prokinetic agents may help improve motility through the obstructed section of the duodenum. For patients unresponsive to conservative or medical management, surgical options are available, although these are controversial. Our experience confirms that a duodenojejunostomy can relieve the obstruction in pediatric patients with idiopathic SMAS and is generally well tolerated. Transection of the ligament of Treitz (Strong procedure) allows the duodenum to fall away from the vascular angle (6) and has achieved an 89% success rate; furthermore, the procedure allows for future bypass procedures if the patient continues to have symptoms (26). Recently, laparoscopy has been used safely to relieve SMAS, with either enteric bypass or transection of the ligament of Treitz (8,9,27).

Our results indicate that those children with idiopathic SMAS who had a poor medical response remained behind in their growth compared with those with a good response to treatment. In addition, we found that effective medical control of the clinical symptoms of idiopathic SMAS resulted in an increased weight gain. Growth deficits and reduced body weight in children with idiopathic SMAS may be caused by the low energy intake. For highlighting the effective medical control on nutritional status in children with idiopathic SMAS, we further evaluated growth data of 83 non-SMAS healthy children with characteristics (age, height status, weight status, appetite) similar to our patients with SMAS. No marked differences of height status, weight status, and appetite increment were found in these healthy children in a 12-month observation. This result supports effective long-term medical treatment as promoting appetite and nutritional status in children with idiopathic SMAS.

There were no marked differences in terms of aortomesenteric angles, age, initial weight, and height status between the responders and nonresponders (to medical treatment) in our series. Also, we found no clinical parameters (sex, age, duration of symptoms, height status, weight status, and nutritional status) could predict the outcome in patients treated conservatively. A larger series study in evaluating clinical parameters for outcome in pediatric idiopathic SMAS is expected.

Based on the detailed histories of our patients, a majority of the children with poor weight gain were found to have poor or decreased appetite before entering the study. Our results showed that those patients with increased appetite had better increments in weight, suggesting that an increased appetite contributes to better weight gain in children with idiopathic SMAS. Our findings demonstrate that surgical or medical treatment is effective for resolving the clinical symptoms and maintaining an appropriate appetite and nutritional status in children with idiopathic SMAS.

In summary, physicians should consider the diagnosis of SMAS in children with complete or partial gastrointestinal obstruction. An aortomesenteric angle <20° on sonography suggests SMAS in children. In pediatric idiopathic SMAS, long-term medication may aid in the resolution of clinical symptoms and promote weight gain, whereas patients with acute intestinal obstruction or persistent anorexia with significant weight loss may require a duodenojejunostomy to resolve the clinical symptoms and improve their nutritional status.

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Keywords:

aortomesenteric angle; children; idiopathic superior mesenteric artery syndrome; outcome; ultrasound

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