The aim of the present study was to evaluate whether the EGD provides clues on early decision to perform a diagnostic test for SMA syndrome. To the best of our knowledge, no study investigating on the endoscopic features associated with SMA syndrome has yet been conducted. Our study suggests that endoscopic observation up to the third part of the duodenum can give a significant information in determine to perform diagnostic tests of SMA syndrome. The endoscopic features in our study were the three constellations of pulsating vertical or oblique band like luminal narrowing of the third part of the duodenum with luminal expansion no more than one third during air insufflation over 15 seconds, proximal duodenal over distension during air insufflation in the duodenal third part, and bile lakes in the stomach.
SMA syndrome is a disease caused by external compression of the duodenal third part between the aorta itself and the SMA branching from the aorta at the level of the first lumbar vertebra. Although the exact pathogenesis of this syndrome is unknown, it is often associated with rapid linear growth without or small weight gain, rapid weight loss, external cast compression, an abnormally high position of the ligament of Treitz, and unusually a low origin of the SMA [4–8]. Rapid weight loss and certain metabolic states cause depletion of the mesenteric and retroperitoneal fat, subsequently decreasing the aortomesenteric distance (AMD) (1). However, weight loss and low BMI do not necessarily relate with SMA syndrome. Indeed, no substantial difference were observed in the weight and BMI between the SMA syndrome and non-SMA syndrome groups in our study.
SMA syndrome often presents with non-specific upper GI symptoms such as nausea, vomiting, early satiety, anorexia, postprandial discomfort, and abdominal pain [9, 10]. In our study, postprandial discomfort, abdominal pain, and early satiety were the major symptoms. Symptoms can be acute or chronic. Making a diagnosis of SMA syndrome is challenge and diagnosis may commonly be delayed for a period of time after symptoms appear. The median duration of symptoms before diagnosis varies from 5 to 30 days and up to 18 months according to the literature [9, 11, 12]. In our study, the median was 68 days (range: 5 to 760 days) until diagnosis. The reasons for varying duration of diagnostic delays may be due to rarity, nonspecific symptoms, and a lack of high suspicion of clinical index of SMA syndrome. Many clinicians remain unaware of this syndrome. So this syndrome may commonly be diagnosed in the process of excluding other suspected conditions [2, 3]. And many patients may suffer from upper GI symptoms and related comorbidity such as weight loss, malnutrition, and poor quality of life until a diagnosis was made.
A confirm diagnosis of SMA syndrome is made mainly through the conventional upper GI series. CECT scan is also known to assist a diagnosis of SMA syndrome with findings of proximal duodenal dilatation and decreased AMD and aortomesenteric angle (AMA). An AMA of less than 22–25° and an AMD of less than 8 mm correlated well with the development of symptoms of SMA syndrome in adults [13–16]. Sinagra et al.  reported that AMD seems to be more accurate rather than AMA to diagnose SMA syndrome. And these are consequently used as cutoff values for diagnosis of SMA syndrome in adults. However, there is no cutoff value for diagnosis in children and the normal ranges of these are variable in this age. So, interpretation should be performed with caution when using CECT scan for diagnosis of SMA syndrome in children [18, 19]. Ultrasound color Doppler imaging or MRA has recently been proposed as alternative modalities rather than CECT scan for the diagnosis in cases of suspected SMA syndrome .
In the practice, SMA syndrome can be linked to inadequate investigation and ineffective treatment due to its rarity and unawareness by clinicians, which may lead to electrolyte imbalance, dehydration, weight loss, malnutrition, and even death [3, 11]. So, early investigations and detection of SMA syndrome is important to avoid these problems. Most patients with SMA syndrome present nonspecific upper GI symptoms. Thus EGD is usually first performed to differentiate the upper GI diseases such as peptic diseases, functional dyspepsia, and other disease but, it is not possible to make a diagnosis of SMA syndrome with EGD. Lippl et al.  suggested that endoscopic findings such as duodenal dilatation, liquid stasis, and antiperistaltic waves may indicate SMA syndrome. Meanwhile, Sundaram et al.  stated that although the Lippl’s suggested endoscopic findings may indicate duodenal obstruction, a diagnosis of SMA syndrome cannot always be made with certainty with those findings. They recommended using both endoscopic ultrasound and endoscopy for the diagnosis of SMA syndrome. Unlike this, Sinagra et al.  suggested that pulsatile extrinsic compression in the third part of the duodenum by EGD is the most reliable finding to suspect SMA syndrome. Cappell et al.  reported a case with SMA syndrome with an endoscopic photograph showing pulsatile band-like luminal narrowing of the third part of duodenum which was gradually, partially opened by moderate air insufflation. We observed that diagnostic yield of SMA syndrome was significantly higher in patients with endoscopic feature D compared to those without that. The sensitivity and the positive predictive value having SMA syndrome in cases with endoscopic type D were 72.2% and 81.3%, respectively. So we suggest that EGD can be a useful in deciding to investigate SMA syndrome when endoscopic feature D is documented through examination up to the duodenal third part.