Syndrome de l'artère mésentérique supérieure

Superior mesenteric artery (SMA) syndrome is a gastro-vascular disorder in which the third and final portion of the duodenum is compressed between the abdominal aorta (AA) and the overlying superior mesenteric artery. This rare, potentially life-threatening syndrome is typically caused by an angle of 6–25° between the AA and the SMA, in comparison to the normal range of 38–56°, due to a lack of retroperitoneal and visceral fat (mesenteric fat). In addition, the aortomesenteric distance is 2–8 millimeters, as opposed to the typical 10–20. However, a narrow SMA angle alone is not enough to make a diagnosis, because patients with a low BMI, most notably children, have been known to have a narrow SMA angle with no symptoms of SMA syndrome. SMA syndrome is also known as Wilkie's syndrome, cast syndrome, mesenteric root syndrome, chronic duodenal ileus and intermittent arterio-mesenteric occlusion. It is distinct from nutcracker syndrome, which is the entrapment of the left renal vein between the AA and the SMA, although it is possible to be diagnosed with both conditions. Signs and symptoms include early satiety, nausea, vomiting, extreme "stabbing" postprandial abdominal pain (due to both the duodenal compression and the compensatory reversed peristalsis), abdominal distention/distortion, burping, external hypersensitivity or tenderness of the abdominal area, reflux, and heartburn. In infants, feeding difficulties and poor weight gain are also frequent symptoms. In some cases of SMA syndrome, severe malnutrition accompanying spontaneous wasting may occur. This, in turn, increases the duodenal compression, which worsens the underlying cause, creating a cycle of worsening symptoms. Fear of eating is commonly seen among those with the chronic form of SMA syndrome. For many, symptoms are partially relieved when in the left lateral decubitus or knee-to-chest position, or in the prone (face down) position. A Hayes maneuver, which corresponds to applying pressure below the umbilicus in cephalad and dorsal direction, elevates the root of the SMA, also slightly easing the constriction.