肠系膜上动脉综合征SMA.ppt

Superior mesenteric artery syndrome superior mesenteric artery syndrome is a very rare,life-threatening gastrovascular disorder characterized by a compression of the third portion of the duodenum by the superior mesenteric artery.SMA syndrome was first described in 1861 by Carl Freiherr von Rokitansky in victims at autopsy,but remained pathologically undefined until 1927 when Wilkie published the first comprehensive series of 75 patients.With only about 500 reported cases in the history of English-language medical literature,SMA syndrome is estimated to have a mortality rate of 1 in 3.SMA syndrome is also known as Wilkies syndrome,cast syndrome,mesenteric root syndrome,chronic duodenal ileus It is distinct from Nutcracker syndrome,which is the entrapment of the left renal vein between the AA and the SMA.causes The syndrome is typically caused by an angle of 6-25between the AA and the SMA,in comparison to the normal range of 38-56due to a lack of retroperitoneal and visceral fat.In addition,the aorto-mesenteric distance is 2-8 millimeters,as opposed to the typical 10-20.Retroperitoneal fat and lymphatic tissue normally serve as a cushion for the duodenum,protecting it from compression by the SMA.SMA syndrome is thus triggered by any condition involving an insubstantial cushion and narrow mesenteric angle.SMA Syndrome can present in two forms:chronic/congenital or acute/induced.Risk anatomic factors such as:very thin or lanky body build,an unusually high insertion of the duodenum at the ligament of Treitz,a particularly low origin of the SMA.Predisposition easily aggravated such aspoor motility of the digestive tractretroperitional tumorscachexiaexaggerated lumbar lordosisvisceroptosisabdominal wall laxityperitoneal adhesionsabdominal traumarapid linear adolescent growth spurt,weight lossstarvationcatabolic states(cancer and burns).Symptomsearly satietynauseabilious vomitingextremestabbing postprandial abdominal pain(due to both the duodenal compression and the compensatory reversed peristalsis)severe malnutrition with spontaneous wasting.This,in turn,increases the duodenal compression spurring a vicious cycle.Symptoms are partially relieved when in the left lateral,prone or knee-to-chest position.Symptoms are often aggravated when leaning to the right or taking a supine position.Demographics SMA syndrome is extremely rare,evident in only 0.013-0.3%of uppergastrointestinal-tract barium studies.As the syndrome involves a lack of essential fat,four of every five afflicted are underweight,often to the point of sickliness and emaciation.Females are impacted twice as often as males,with 75%of cases occurring between the ages of 10 and 30.Mortality SMA syndrome is estimated to have a mortality rate of 1 in 3.Delay in the diagnosis of SMA syndrome can result in:fatal malnutrition dehydration oliguria electrolyte abnormalities hypokalemia acute gastric rupture intestinal perforation(from prolonged mesenteric ischemia)gastrectasiaDiagnosis postprandial abdominal painnauseabilious vomitingwastingsymptoms relieved via the left lateral,prone or knee-to-chest positionupper gastrointestinal bariumabdominal and pelvic CT scan with contrast Upper gastrointestinal series showing extreme duodenal dilation(white arrow)abruptly preceding constriction by the SMA Abdominal and pelvic CT scan showing duodenal compression(black arrow)by the abdominal aorta and the superior mesenteric artery.Treatment Conservative treatment should be attempted first,involving the reversal or removal of the precipitating factor with proper nutrition and replacement of fluid and electrolytes.Pro-motility agents such as metoclopramide may also be beneficial.If conservative treatment fails,or if the case is severe or chronic,surgical intervention is required.The most common operation for SMA syndrome,duodenojejunostomy,was first proposed in 1907 by Bloodgood.Less common surgical treatments for SMA syndrome include Roux-en-Y duodeno-jejunostomy,gastro-jejunostomy and lysis of the ligament of Treitz.The worlds first robotically-assisted intestinal bypass for SMA syndrome was performed on July 30,2008 at the London Health Sciences Centre in Ontario,Canada.