Objectives: Superior mesenteric artery syndrome (SMAS), Wilkie syndrome or cast syndrome is a rare condition that usually presents with symptoms of mid to upper gastrointestinal obstruction due to the compression of the duodenum between the abdominal aorta, posteriorly, and the superior mesenteric artery, anteriorly. The aim of this study was to analyze the clinical characteristics, means of diagnosis and management of SMAS in a pediatric population.
Methods: Retrospective chart review of all patients at the Children's Hospital of Wisconsin with SMAS from 1985 to 2005.
Results: Twenty-two cases of SMAS where diagnosed at Children's Hospital of Wisconsin between 1985 and 2005 [14, (64%) female]. Symptoms developed 1 to 393 days (median 5 days) before diagnosis. Presenting symptoms included abdominal pain (59%), vomiting (50%), nausea (40%), early satiety (32%) and anorexia (18%). Diagnosis was made by upper-gastrointestinal radiography in 18 (82%), by computed tomography in 2 (9%) and at laparotomy in 2 (9%). One patient was treated surgically after medical management failed. Mean length of treatment was 65 days (range 13-169), with a mean length of hospitalization of 21 days (range 0-68 days).
Conclusion: SMAS usually presents more acutely than chronically with symptoms of small bowel obstruction. Weight loss is not necessary for SMAS development. Prior neurological injury may be a risk factor for development of SMAS. Upper gastrointestinal radiography remains the primary means of diagnosis. SMAS is typically successfully managed medically. Surgical intervention should be reserved for patients' refractory to medical therapy. The expected outcome of SMAS is excellent.
Superior mesenteric artery syndrome (SMAS) also known as Wilkie syndrome, arteriomesenteric duodenal compression, chronic duodenal ileus or cast syndrome is an unusual form of gastrointestinal obstruction resulting from compression of the duodenum between the abdominal aorta, posteriorly, and the superior mesenteric artery, anteriorly, thought to be related to the loss of the duodenal fat pad.(1) First described by von Rokitansky in 1842, SMAS was associated with orthopedic casting by Willet in 1878. Wilkie in 1927 formally characterized SMAS in a series of 75 patients.(2,3) Classically, patients present after orthopedic surgical casting or acute weight loss, such as due to hyperthyroidism, anorexia nervosa or gastroenteritis. Symptoms typically consist of chronic intermittent abdominal pain, vomiting (occasionally bilious), nausea, early satiety and anorexia(4,5). The diagnosis of SMAS is commonly confirmed by upper gastrointestinal radiography (Fig. 1), but the diagnosis may be made by computerized tomography or laparotomy(6,7).
There have been no large pediatric reviews of SMAS that have focused on modern management in children. The aims of our study were to analyze the clinical characteristics, means of diagnosis and outcomes of SMAS and to determine the impact advances in nutritional supplementation have had on the management of SMAS.
MATERIALS AND METHODS
We reviewed the charts of all patients with SMAS seen at the Children's Hospital of Wisconsin between 1985 and 2005. The data extracted included demographics, presenting symptoms, past medical and surgical records, examination findings, duration of symptoms, means of diagnosis, treatment and outcome. All information was entered into a Microsoft Excel spreadsheet for statistical analysis.
This study was approved by the Children's Hospital of Wisconsin Institutional Review Board.
There were 22 cases of SMAS at Children's Hospital of Wisconsin between 1985 and 2005 [14, (64%) female]. The age range was from 3 to 23 years (median 13 years). The weight range was from 12.2 to 66 kg (median 38.8 kg). The mean body mass index (BMI) was 21.3 kg/m2 or 39th percentile (range 13.3-30.4 kg/m2 or from the less than 3rd percentile to greater than the 97th percentile). The mean weight loss before diagnosis was 3.8 kg (range 0-20 kg). Of the patients that lost weight, 65% lost more than 10% of their body weight. In addition, no weight loss was found in 50% of the patients.
Symptoms developed 1 to 393 days (median 5 days) before diagnosis. Presenting symptoms included abdominal pain, vomiting, nausea, early satiety and anorexia (Table 1). Many individuals (64%) presented with more than 1 symptom. The most frequent constellation of symptoms was abdominal pain, vomiting and nausea occurring in 23% of patients.
Nine patients (41%) had previously undergone Nissen fundoplication. Other premorbid conditions included: cerebral palsy, traumatic brain injury from either motor vehicle accident or hypoxia, and posterior spinal fusion (Table 2). All the patients who underwent Nissen fundoplication had prior neurological impairment.
The diagnosis was made by upper gastrointestinal radiography in 18 (82%), by computerized tomography in 2 (9%) and at laparotomy in 2 (9%). Nonoperative treatment was successful in 19 patients (86%). Transpyloric jejunal feeding past the point of obstruction (via gastrojejunostomy tube or nasojejunal tube) was implemented in 14 patients, parenteral nutrition in 8 patients, and 2 patients were successfully treated with high caloric diets and positional changes. One patient was treated as an outpatient. Nasogastric tube placement for bowel decompression was required in 4 patients. Two patients were diagnosed and treated surgically at time of presentation, and 1 patient was treated surgically after failing medical management. The mean length of treatment was 65 days (range 13-169) and the mean length of hospitalization was 21 days (range 0-68 days). All but 1 patient had complete recovery. This patient developed symptoms consistent with pseudo-obstruction, therefore suggesting that SMAS may not have been the primary cause of her obstructive symptoms.
SMAS is a rare form of upper gastrointestinal obstruction with a reported incidence of 0.013% to 0.3%.(4,8,9)With 22 cases of documented SMAS, our study is the largest single institution case series since Burrington and Wayne in 1974, with just over a case a year for 20 years(10).
SMAS is found more commonly in females than males and typically affects individuals of slender built after acute weight loss. Symptoms of SMAS are similar to those of small bowel obstruction and include vomiting, nausea, early satiety, anorexia and abdominal pain(4,5). Our study supports previous findings that females are more commonly affected than males and that abdominal pain, vomiting, early satiety and nausea are the most frequent presenting symptoms. Most patients presented with a constellation of symptoms, typically including abdominal pain, vomiting and early satiety. Nearly half of those individuals who presented with abdominal pain described their pain as epigastric.
In contrast to previous publications, the range of BMI's found in our sample suggests that a low BMI is not necessary for the development of SMAS. Furthermore, only 50% of our patients had weight loss before diagnosis, suggesting that weight loss is not a requirement for the development of SMAS. Also, although both acute and chronic forms have been documented, previous reports suggest that SMAS more commonly presents more chronic in nature.(11,12) In our series, the median length of time from onset of symptoms to diagnosis was only 5 days, and only 3 individuals were symptomatic for more than 25 days before diagnosis. These findings suggest that SMAS is more likely to present acutely.
Most patients with SMAS present after either acute weight loss, such as due to hyperthyroidism, anorexia nervosa or gastroenteritis, or after orthopedic or spinal surgery.(13-17) Among the numerous documented etiologies of SMAS including fungal abscess, gastric bezoar and aneurysms of the superior mesenteric artery, we found that neurological injury, either acute or chronic, should also be considered as a risk factor for the development of SMAS. Laffont et al reported the occurrence of SMAS in paraplegic patients 3 months after injury(18). They hypothesized that, in the acute setting, an imbalance in the autonomic nervous system results in unchecked parasympathetic activity and may correspond to the development of SMAS. Furthermore, they suggest that patients with neurological injury may in general be prone to developing SMAS due to hyperextension of the spine with increased lumbar lordosis, prolonged supine positioning or from increased flaccidity of abdominal wall musculature. In our study, 11 of the 22 patients (50%) had prior neurological injury resulting in spasticity or associated cerebral palsy. The average weight loss in these patients with neurological injury was only 2 kg, whereas the average weight loss in those patients where SMAS was attributed solely to weight loss was 7.4 kg. These findings suggest that individuals with neurological injury may be at greater risk for developing SMAS, and therefore, that neurological injury should be considered as a risk factor.
Similar to previous literature, we found that 80% of our patients were diagnosed by upper gastrointestinal radiography with only 4 patients being diagnosed via abdominal CT or at laparotomy. The 2 patients who were diagnosed by abdominal CT were being investigated for a possible abdominal mass and an abdominal abscess, respectively, when they were found to have SMAS.
Two patients were diagnosed at surgery, 1 patient for malfunction of a recently placed gastrostomy and the other after an abdominal CT which suggested malrotation with volvulus. Both patients were treated by decompression of the stomach and dissection of the Ligament of Treitz. The latter patient had a surgically placed jejunostomy for nutritional support.
Treatment of SMAS is usually conservative. Acute management is focused on bowel decompression, maintenance of the fluid and electrolyte balance and nutritional support or rehabilitation. Removal of the body cast is required when SMAS is associated with cast syndrome(19). Once stabilized, small frequent high caloric oral feeds may be effective. Changes in feeding position, either knees to chest or right lateral decubidous position, may also be useful in bypassing the obstruction. If symptoms persist, a nasojejunal tube placed past the obstruction to allow for continuous enteral feeding (19,20) may be required. Parenteral nutrition is useful when enteral feedings are not tolerated. Advances in both enteral and parenteral nutrition have dramatically impacted the medical management of SMAS. However, when medical treatment fails, surgical intervention may be necessary, particularly when there is profound dilatation and stasis of the proximal small bowel(19,20). Successful surgical therapies have included duodenojejunostomy, gastrojejunostomy, or resection of the Ligament of Treitz. When comparing our study to Burrington's, we found that the studies are similar in that both are retrospective chart reviews of approximately 20 patients. However, more than 70% of Burrington's patients were treated surgically as opposed to 14% (or 3 patients), and only 1 of those 3 patients required surgery after medical therapy. The 1 patient who failed medial management underwent duodenojejunostomy with only moderate improvement. She has continued to have intermittent symptoms of obstruction suggestive of a diagnosis of pseudo-obstruction.
Our experience that more than 80% of patients responded to medical therapy versus Burrington's investigation where more than 70% of patients required surgical intervention is a dramatic illustration of the benefit advances in both enteral and parenteral nutrition have made in the last 30 years. Furthermore, although jejunal feeding was the most frequent intervention, 2 patients were successfully treated with high caloric oral diet and positioning alone, and 1 patient was treated as an outpatient. Accordingly, surgical intervention is currently only indicated when conservative management fails or when laparotomy is required at the time of presentation.
Reported complications of SMAS include dehydration, metabolic imbalance, and rarely, death. For instance, Dorph in 1950 reported a case of an 18-year-old female who died shortly after presentation with acute metabolic alkalosis and dehydration resulting from profuse vomiting after the application of a hip-spica cast(21). We found that once stabilized, all but 1 patient diagnosed with SMAS had a complete recovery.
SMAS is a condition that usually presents more acutely than chronically with symptoms of small bowel obstruction. Weight loss is commonly associated with the development of SMAS, but is not a necessity. Prior neurological injury may place an individual at risk for the development of SMAS, and therefore, SMAS should be considered in any individual with prior neurological injury who presents with abdominal pain or vomiting. Upper gastrointestinal radiography remains the primary means of diagnosis, but abdominal CT may also be useful. Most importantly, due to the advances in nutritional management over the last 30 years, SMAS is typically successfully managed medically. Surgical intervention should be reserved for those individuals refractory to medical therapy or when laparotomy is required at the time of presentation. The expected outcome of SMAS is excellent.
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