ACUTE MESENTERIC ACUTE MESENTERIC ISCHEMIAISCHEMIA

BY DR. M. MAHER KHAWATMIBY DR. M. MAHER KHAWATMI

Blood flow to the intestine is supplied by three vessels: Blood flow to the intestine is supplied by three vessels:

the celiac artery (CA), the superior mesenteric artery the celiac artery (CA), the superior mesenteric artery (SMA), and the inferior mesenteric artery (IMA). These (SMA), and the inferior mesenteric artery (IMA). These are the arteries to the foregut (stomach to second part are the arteries to the foregut (stomach to second part of duodenum), midgut (second part of duodenum to of duodenum), midgut (second part of duodenum to right two thirds of transverse colon), and hind gut right two thirds of transverse colon), and hind gut (distal third of the transverse colon to the rectum), (distal third of the transverse colon to the rectum), respectively.respectively. Anastomoses exist between the CA and the SMA via the Anastomoses exist between the CA and the SMA via the pancreaticoduodenal arcade, and between the SMA and pancreaticoduodenal arcade, and between the SMA and IMA via the marginal artery of Drummond and IMA via the marginal artery of Drummond and the arc the arc of Riolan (meandering mesenteric artery)of Riolan (meandering mesenteric artery). . The marginal artery of Drummond and the arch of The marginal artery of Drummond and the arch of Riolan are discrete branch vessels capable of Riolan are discrete branch vessels capable of significant enlargement in the face of occlusion or significant enlargement in the face of occlusion or stenosis of the proximal splanchnic arteriesstenosis of the proximal splanchnic arteries..

The gastroduodenal artery and pancreaticoduodenal arcades provide The gastroduodenal artery and pancreaticoduodenal arcades provide important collateral flow between the celiac and superior mesenteric important collateral flow between the celiac and superior mesenteric

arteries.arteries.The superior mesenteric artery supplies blood to the duodenum and The superior mesenteric artery supplies blood to the duodenum and

head of the pancreas, jejunum, ileum, ascending colon, and right half of head of the pancreas, jejunum, ileum, ascending colon, and right half of the transverse colonthe transverse colon

The inferior mesenteric artery (IMA) supplies blood to the left half of The inferior mesenteric artery (IMA) supplies blood to the left half of the transverse colon and the entire descending colon, including the the transverse colon and the entire descending colon, including the sigmoid colon and rectum. The IMA serves as an important source of sigmoid colon and rectum. The IMA serves as an important source of collateral blood supply when the proximal two visceral vessels are collateral blood supply when the proximal two visceral vessels are

occludedoccluded..

Lateral aortogram demonstrating normal origins of the CA and the Lateral aortogram demonstrating normal origins of the CA and the SMASMA..

TheThe marginal artery of Drummond and marginal artery of Drummond and the arc of Riolan the arc of Riolan (meandering mesenteric artery)(meandering mesenteric artery) . .

Dilated Arc of Riolan (meandering mesenteric artery) due to celiac and Dilated Arc of Riolan (meandering mesenteric artery) due to celiac and SMA stenoses from Takayasu's arteritisSMA stenoses from Takayasu's arteritis..

Acute Embolic Mesenteric IschemiaAcute Embolic Mesenteric Ischemia SMA embolism is responsible for 50% of acute SMA embolism is responsible for 50% of acute mesenteric ischemia (AMI) events. Among these, 20% mesenteric ischemia (AMI) events. Among these, 20% present with synchronous embolization to other present with synchronous embolization to other arterial beds.arterial beds. Most emboli occur in patients with atrial fibrillation or Most emboli occur in patients with atrial fibrillation or following myocardial infarction. following myocardial infarction. The SMA distribution is highly prone to embolic The SMA distribution is highly prone to embolic occlusion owing to its parallel course/flow vectors to occlusion owing to its parallel course/flow vectors to that of the aorta. that of the aorta. 15% of emboli lodge proximally at the SMA origin, 15% of emboli lodge proximally at the SMA origin, while the remaining 85% lodge 3-10 cm downstream.while the remaining 85% lodge 3-10 cm downstream. Abdominal pain out of proportion is the classic Abdominal pain out of proportion is the classic presentation. Frequently, bowel emptying occurs presentation. Frequently, bowel emptying occurs secondary to intestinal spasm as a consequence of secondary to intestinal spasm as a consequence of

ischemiaischemia..

Upon presentation, likely embolic sources are reviewed Upon presentation, likely embolic sources are reviewed and heparin is administered to prevent distal and heparin is administered to prevent distal thrombosis or recurrent emboli.thrombosis or recurrent emboli. If the patient is in extremis or demonstrates obvious If the patient is in extremis or demonstrates obvious peritoneal signs, surgical exploration is appropriate. peritoneal signs, surgical exploration is appropriate. Otherwise, preparations should be made for Otherwise, preparations should be made for angiography. angiography. The CA and SMA The CA and SMA origins can be visualized only by can be visualized only by lateral angiographic views, whereas the more distal lateral angiographic views, whereas the more distal SMA distribution is evaluated with anteroposterior SMA distribution is evaluated with anteroposterior projections. projections. A classic "meniscus sign" can often be visualized at the A classic "meniscus sign" can often be visualized at the point of occlusionpoint of occlusion..

Acute Mesenteric IschemiaAcute Mesenteric Ischemia ImagingImaging

1. Plain abdominal radiographs:1. Plain abdominal radiographs:

a. Thumbprinting, indicating intestinal wall edema with a. Thumbprinting, indicating intestinal wall edema with hemorrhage in the setting of acute mesenteric hemorrhage in the setting of acute mesenteric ischemiaischemiab. Pneumatosisb. Pneumatosisc. Portal venous gasc. Portal venous gasd. Pneumoperitoneumd. Pneumoperitoneum

2. Computed Tomography Angiography (CTA):2. Computed Tomography Angiography (CTA):

a. Bowel wall thickening from edema or hemorrhagea. Bowel wall thickening from edema or hemorrhageb. Lack of enhancement indicates infarctionb. Lack of enhancement indicates infarctionc. Pneumatosis, portal venous gas, pneumoperitoneumc. Pneumatosis, portal venous gas, pneumoperitoneumd. Intraluminal thrombus in involved vesseld. Intraluminal thrombus in involved vessel

Mucosal thickening.Mucosal thickening.The haustral folds are very thick (arrowheads), leading to a sign known The haustral folds are very thick (arrowheads), leading to a sign known

as “thumbprinting”. as “thumbprinting”. The distance between loops of bowel is increased (arrows) due to The distance between loops of bowel is increased (arrows) due to

thickening of the bowel wallthickening of the bowel wall  .  .

Top CT image shows gas in portal Top CT image shows gas in portal venous system (blue circle);venous system (blue circle);    

center image shows absence of center image shows absence of contrast in superior mesenteric contrast in superior mesenteric artery due to thrombosis of this artery due to thrombosis of this vessel (blue arrow); lower image vessel (blue arrow); lower image

shows extensive pneumatosis shows extensive pneumatosis intestinalis (red arrows).intestinalis (red arrows).

The patient also has a markedly The patient also has a markedly dilated common duct, not related dilated common duct, not related

to mesenteric ischemiato mesenteric ischemia..

SMA embolus appearing as a meniscus in the artery 5 cm from the origin

Schematic drawing demonstrates usual site for SMA thrombosis Schematic drawing demonstrates usual site for SMA thrombosis versus that for SMA embolusversus that for SMA embolus..

Intraoperative photograph of patient who presented with acute Intraoperative photograph of patient who presented with acute mesenteric ischemia secondary to embolus of SMA shows diffuse mesenteric ischemia secondary to embolus of SMA shows diffuse

bowel ischemia with classic sparing of proximal jejunum (arrow) and bowel ischemia with classic sparing of proximal jejunum (arrow) and transverse colon (arrowhead)transverse colon (arrowhead)..

In the past, acute SMA embolism was not thought to be In the past, acute SMA embolism was not thought to be amenable toamenable to thrombolytic therapy. thrombolytic therapy. Specifically, patients without evidence of bowel Specifically, patients without evidence of bowel necrosis or peritoneal irritation who arrive within 8 necrosis or peritoneal irritation who arrive within 8 hours of the onset of pain are candidates for such hours of the onset of pain are candidates for such therapy.therapy. If there is no evidence of lysis/reperfusion within 4 If there is no evidence of lysis/reperfusion within 4 hours or if peritoneal signs develop, exploration is hours or if peritoneal signs develop, exploration is performed.performed.In most cases, acute SMA embolism is treated via In most cases, acute SMA embolism is treated via operative exploration using a generous midline operative exploration using a generous midline incision. incision. Pulsation and flow are assessed in the main SMA and its arcades using intraoperative Doppler ultrasound. In cases of catastrophic bowel necrosis, consultation In cases of catastrophic bowel necrosis, consultation with the family should be sought and decisions for with the family should be sought and decisions for

treatment or nontreatment weighedtreatment or nontreatment weighed . .

The omentum and transverse colon are lifted cephalad.

All small bowel is retracted to the right, and the sigmoid colon packed to the left. The ligament of Treitz and the superior attachments of the duodenum are sharply divided, with the goal of mobilizing the last portion of the duodenum to the right. Then, with four fingers behind the small bowel mesentery and with the thumb anteriorly, the SMA should be palpable near the base of the transverse colon mesentery. Alternatively, the SMA can also be identified by Alternatively, the SMA can also be identified by following the middle colic artery until it enters the SMA following the middle colic artery until it enters the SMA at the root of the mesenteryat the root of the mesentery..

The SMA has a larger caliber proximal to the middle colic origin, making for technically easier arteriotomy.An approximately 3-4 cm length of artery is exposed and vessel loops placed for proximal and distal control.

If the SMASMA is soft and free of atherosclerotic changes, a transverse arteriotom may be used. Patch angioplasty is used if the artery is small or a longitudinal incision has been made. Conversely, if a bypass to a severely atherosclerotic a severely atherosclerotic SMASMA may be necessary, the arteriotomy is made longitudinally and used for distal anastomosisfor distal anastomosis of thethe bypass.

Fogarty Fogarty balloon catheter embolectomy is performed catheter embolectomy is performed both proximally and distally. Good back-bleeding and both proximally and distally. Good back-bleeding and inflow suggest that the entire embolus has been suggest that the entire embolus has been removed.removed.The arteriotomy is then closed with interrupted The arteriotomy is then closed with interrupted sutures.sutures. Bowel resection is performed as appropriate. Bowel resection is performed as appropriate. A second-look exploration, 24-48 hours following A second-look exploration, 24-48 hours following embolectomy, should be considered in many patients. embolectomy, should be considered in many patients. If nonviable intestine is evident in the second-look If nonviable intestine is evident in the second-look procedure, additional bowel resections should be procedure, additional bowel resections should be

performedperformed..

SMA embolectomy. Exposure of infrarenal aorta, proximal right common SMA embolectomy. Exposure of infrarenal aorta, proximal right common iliac artery, and proximal SMA is achieved by intestinal retraction and iliac artery, and proximal SMA is achieved by intestinal retraction and division of posterior peritoneum, ligament of Treitz, and base of small division of posterior peritoneum, ligament of Treitz, and base of small

bowel mesenterybowel mesentery..

SMA embolectomy.SMA embolectomy. (a). Location of embolus within SMA is identified. (a). Location of embolus within SMA is identified.

(b). Transverse or longitudinal arteriotomy is performed, and embolus is (b). Transverse or longitudinal arteriotomy is performed, and embolus is extracted with balloon catheter.extracted with balloon catheter.

(c). Arteriotomy is closed. Primary closure suffices for transverse (c). Arteriotomy is closed. Primary closure suffices for transverse arteriotomy, but vein patch is usually required for closure of arteriotomy, but vein patch is usually required for closure of

longitudinal arteriotomylongitudinal arteriotomy . .

Exposure of the SMA for embolectomyExposure of the SMA for embolectomy..

Technique of SMA embolectomy using Fogarty balloon catheterTechnique of SMA embolectomy using Fogarty balloon catheter..

Chronic Mesenteric IschemiaChronic Mesenteric Ischemia

70% of patients with chronic mesenteric ischemia have 70% of patients with chronic mesenteric ischemia have a history of abdominal angina. In these patients, the a history of abdominal angina. In these patients, the chronicity of mesenteric atherosclerosis is important, chronicity of mesenteric atherosclerosis is important, as it permits collateral vessel formation. as it permits collateral vessel formation. Multiple mesenteric arteries are typically involved in Multiple mesenteric arteries are typically involved in chronic mesenteric ischemia, and both the CA and SMA chronic mesenteric ischemia, and both the CA and SMA should be revascularized whenever possible; a should be revascularized whenever possible; a collateral called the arc of Riolan may fill the distal collateral called the arc of Riolan may fill the distal SMA from the IMA. SMA from the IMA. Transaortic endarterectomy is indicated for ostial Transaortic endarterectomy is indicated for ostial lesions of patent CA and SMA.lesions of patent CA and SMA.For occlusive lesions located 1-2 cm distal to the For occlusive lesions located 1-2 cm distal to the mesenteric origin, bypass to the SMA should be mesenteric origin, bypass to the SMA should be

performedperformed . .

Chronic mesenteric ischemiaChronic mesenteric ischemia . .Stenoses are evident at the origin of both the CAStenoses are evident at the origin of both the CA and the SMAand the SMA..

Acute Thrombotic Mesenteric IschemiaAcute Thrombotic Mesenteric Ischemia Thrombosis of the SMA is responsible for 20-25% of Thrombosis of the SMA is responsible for 20-25% of AMI events. Concomitant occlusion or stenosis of the AMI events. Concomitant occlusion or stenosis of the CA is almost always present.CA is almost always present. Symptoms of thrombotic mesenteric ischemia may Symptoms of thrombotic mesenteric ischemia may initially be more insidious than those of embolic initially be more insidious than those of embolic mesenteric ischemia.mesenteric ischemia. Unlike embolic occlusions, Unlike embolic occlusions, thrombosis of the SMA commonly occurs in the most thrombosis of the SMA commonly occurs in the most proximal arterial segment, flush with the aortic origin proximal arterial segment, flush with the aortic origin of the vessel.of the vessel. In embolic mesenteric ischemia, the SMA itself is In embolic mesenteric ischemia, the SMA itself is otherwise normal, and embolectomy will usually suffice otherwise normal, and embolectomy will usually suffice to restore mesenteric circulation. to restore mesenteric circulation. Thrombotic mesenteric ischemia usually involves a Thrombotic mesenteric ischemia usually involves a severely atherosclerotic vessel.severely atherosclerotic vessel. Therefore, these Therefore, these patients require a reconstructive procedure to the patients require a reconstructive procedure to the

distal SMA to bypass the proximal occlusive lesiondistal SMA to bypass the proximal occlusive lesion..

Angiography is essential in the diagnosis of SMA Angiography is essential in the diagnosis of SMA thrombosis. thrombosis. The proximal location of thrombosis necessitates The proximal location of thrombosis necessitates lateral views of the aorta and mesenteric vasculature.lateral views of the aorta and mesenteric vasculature. Thrombolysis with subsequent angioplasty has been Thrombolysis with subsequent angioplasty has been used in selected circumstances. In the majority of used in selected circumstances. In the majority of cases, acute SMA thrombosis is treated via operative cases, acute SMA thrombosis is treated via operative exploration and bypass. exploration and bypass. A longitudinal arteriotomy is made in the A longitudinal arteriotomy is made in the SMA and a and a Fogarty balloon catheter passed proximally to dislodge passed proximally to dislodge any thrombus. any thrombus. If thrombectomy is successful, an If thrombectomy is successful, an intraarterial shunt is placed for bowel reperfusion.intraarterial shunt is placed for bowel reperfusion. Next, exposure is obtained for either antegrade or Next, exposure is obtained for either antegrade or retrograde bypass to the SMA using the longitudinal retrograde bypass to the SMA using the longitudinal

arteriotomy for distal anastomosisarteriotomy for distal anastomosis..

Exposure for antegrade bypass is performed by (1) Exposure for antegrade bypass is performed by (1) dividing the left triangular ligament of the liver, (2) dividing the left triangular ligament of the liver, (2) dividing the gastrohepatic ligament, (3) retracting the dividing the gastrohepatic ligament, (3) retracting the esophagus to the left, and (4) the right crusesophagus to the left, and (4) the right crus of diaphragm is spread sharply with scissors and dissected bluntly to surround the aorta.. A nasogastric tube is critical for identification of the A nasogastric tube is critical for identification of the esophagus and decompression of the stomach.esophagus and decompression of the stomach. These maneuvers allow isolation and exposure of an These maneuvers allow isolation and exposure of an 8-10 cm segment of the aorta for supraceliac clamping 8-10 cm segment of the aorta for supraceliac clamping and proximal anastomosis. Circumferential control of and proximal anastomosis. Circumferential control of the aorta at this level is not necessary and, when the aorta at this level is not necessary and, when performed, risks injury to posterolateral intercostal performed, risks injury to posterolateral intercostal branches. Careful finger dissection beneath the branches. Careful finger dissection beneath the pancreas on the left side of the aorta is used to pancreas on the left side of the aorta is used to develop a tunnel for the bypassdevelop a tunnel for the bypass..

SMASMA bypass: antegrade. Shown is bypass from supraceliac aorta to SMA alone (a)

or to hepatic artery and SMA (b).

((AA ) )The gastrohepatic ligament has been divided, and the right crus has been The gastrohepatic ligament has been divided, and the right crus has been exposed. )B( Division of the right crus with retraction of the esophagus to the left exposed. )B( Division of the right crus with retraction of the esophagus to the left

exposes the distal thoracic aortaexposes the distal thoracic aorta..

((AA ) )An end-to-side aorto-common hepatic artery anastomosis is constructed. An end-to-side aorto-common hepatic artery anastomosis is constructed. The aorta-superior mesenteric artery (SMA) limb is commonly passed The aorta-superior mesenteric artery (SMA) limb is commonly passed behind the common hepatic artery. This is then tunneled behind the behind the common hepatic artery. This is then tunneled behind the

pancreas. pancreas. )B()B( Alternatively, the aorta-SMA bypass limb can be passed in front of Alternatively, the aorta-SMA bypass limb can be passed in front of

the common hepatic arterythe common hepatic artery..

Retrograde bypass is performed by first identifying a Retrograde bypass is performed by first identifying a softsoft portion of the distal aorta or common iliac artery. portion of the distal aorta or common iliac artery. After completion of the distal SMA anastomosis, the After completion of the distal SMA anastomosis, the conduit is stretched to lie taut along the left side of the conduit is stretched to lie taut along the left side of the aorta and proximal anastomosis is performed. The aorta and proximal anastomosis is performed. The graft should lie with a fair amount of tension to avoid graft should lie with a fair amount of tension to avoid laxity and kinking.laxity and kinking. Though retrograde bypass is thought to be less durable Though retrograde bypass is thought to be less durable than antegrade bypass, the limited dissection and than antegrade bypass, the limited dissection and avoidance of supraceliac aortic occlusion make this avoidance of supraceliac aortic occlusion make this option attractiveoption attractive..

SMA bypass: retrograde. SMA bypass: retrograde. Shown is bypass from iliac artery to SMAShown is bypass from iliac artery to SMA..

SMA bypass: retrograde. SMA bypass: retrograde. (a). Iliac artery-SMA bypass with prosthetic graft is suitable for cases in (a). Iliac artery-SMA bypass with prosthetic graft is suitable for cases in

which SMA thrombosis produces ischemic but salvageable bowel.which SMA thrombosis produces ischemic but salvageable bowel.(b). Iliac artery-SMA bypass with saphenous vein is suitable for cases in (b). Iliac artery-SMA bypass with saphenous vein is suitable for cases in which some segments of necrotic or perforated bowel must be resectedwhich some segments of necrotic or perforated bowel must be resected..

Although synthetic graft material has been used with Although synthetic graft material has been used with great success for treatment of chronic mesenteric great success for treatment of chronic mesenteric ischemia, questions of bowel viability and bacteremia ischemia, questions of bowel viability and bacteremia argue against its use in the setting of AMI. Many favor argue against its use in the setting of AMI. Many favor an autologous conduit, usually greater saphenous vein.an autologous conduit, usually greater saphenous vein.

Having completed the bypass, attention is turned to Having completed the bypass, attention is turned to assessment of distal perfusion and intestinal ischemia. assessment of distal perfusion and intestinal ischemia. Bowel resection is performed as appropriate, and Bowel resection is performed as appropriate, and

consideration is given to a second-look explorationconsideration is given to a second-look exploration..

NONOCCLUSIVE MESENTERIC ISCHEMIA (NOMI) NONOCCLUSIVE MESENTERIC ISCHEMIA (NOMI)

Up to 30% of AMI episodes are caused by NOMIUp to 30% of AMI episodes are caused by NOMI..Low flow states (e.g., cardiac shock, burns, septic Low flow states (e.g., cardiac shock, burns, septic shock, hypovolemic shock) cause the vasoconstriction, shock, hypovolemic shock) cause the vasoconstriction, intestinal hypoxia, and ischemia/reperfusion injury intestinal hypoxia, and ischemia/reperfusion injury thought to be responsible for NOMI. thought to be responsible for NOMI. Digitalis preparations and Digitalis preparations and α-α-adrenergic agonists are adrenergic agonists are also thought to predispose to NOMI. also thought to predispose to NOMI. Definitive diagnosis and successful treatment of NOMI Definitive diagnosis and successful treatment of NOMI require a high degree of clinical suspicion for early require a high degree of clinical suspicion for early recognition, as well angiography. Angiographic findings recognition, as well angiography. Angiographic findings include spasm of the mesenteric arcades and absent include spasm of the mesenteric arcades and absent

filling of intramural vesselsfilling of intramural vessels..

Nonocclusive mesenteric ischemia causes profound vasoconstriction withinNonocclusive mesenteric ischemia causes profound vasoconstriction within the mesenteric arcadesthe mesenteric arcades..

Once the diagnosis is made, catheter-directed Once the diagnosis is made, catheter-directed intraarterial papaverine infusion, 30-60 mg/hr, is intraarterial papaverine infusion, 30-60 mg/hr, is begun. begun. After resolution of peritoneal signs, papaverine After resolution of peritoneal signs, papaverine infusion is temporarily replaced with saline solution for infusion is temporarily replaced with saline solution for 30 minutes followed by repeat angiography. If relief of 30 minutes followed by repeat angiography. If relief of vasospasm is documented angiographically, vasospasm is documented angiographically, papaverine infusion is continued for 24 hours and final papaverine infusion is continued for 24 hours and final arteriography performed. arteriography performed. Operative intervention in NOMI is reserved for patients Operative intervention in NOMI is reserved for patients with peritoneal signs who do not respond to with peritoneal signs who do not respond to intraarterial papaverine. These patients should intraarterial papaverine. These patients should undergo exploration and resection of nonviable bowel, undergo exploration and resection of nonviable bowel, and papaverine infusion is continued throughout the and papaverine infusion is continued throughout the entire intraoperative and perioperative periodentire intraoperative and perioperative period..

MESENTERIC VENOUS THROMBOSIS (MVT)MESENTERIC VENOUS THROMBOSIS (MVT) MVT is responsible for 10% of AMI events. MVT is responsible for 10% of AMI events. MVT causes acute ischemia through the limiting of MVT causes acute ischemia through the limiting of venous return from the SMA distribution. Compromised venous return from the SMA distribution. Compromised venous return leads to interstitial swelling in the bowel venous return leads to interstitial swelling in the bowel wall, distension, impeded arterial inflow, and eventual wall, distension, impeded arterial inflow, and eventual infarction.infarction. Conditions predisposing to thrombosis include one or Conditions predisposing to thrombosis include one or more of the following: hypercoagulable states, portal more of the following: hypercoagulable states, portal hypertension, intraabdominal infections, cirrhosis, hypertension, intraabdominal infections, cirrhosis, pancreatitis, malignancy, and blunt trauma.pancreatitis, malignancy, and blunt trauma. Symptoms are more commonly prolonged and insidious Symptoms are more commonly prolonged and insidious

than those associated with other causes of AMIthan those associated with other causes of AMI..

In contrast to other causes of mesenteric ischemia, CT In contrast to other causes of mesenteric ischemia, CT scanning is the diagnostic test of choice in MVT and scanning is the diagnostic test of choice in MVT and will often demonstrate thrombus within the superior will often demonstrate thrombus within the superior mesenteric vein (SMV), pneumatosis, and bowel wall mesenteric vein (SMV), pneumatosis, and bowel wall thickening. In such settings, angiography is less thickening. In such settings, angiography is less sensitive than CT and relies on indirect evidence of sensitive than CT and relies on indirect evidence of venous obstruction such as reflux of contrast into the venous obstruction such as reflux of contrast into the aorta during selective arterial injection and nonfilling aorta during selective arterial injection and nonfilling of the SMV during the venous phase.of the SMV during the venous phase.Treatment of MVT involves long-term anticoagulation, Treatment of MVT involves long-term anticoagulation, broad-spectrum antibiotics, and fluid resuscitation. broad-spectrum antibiotics, and fluid resuscitation. Testing for hypercoagulable states should also be Testing for hypercoagulable states should also be undertaken. undertaken. Operative intervention is reserved for patients Operative intervention is reserved for patients suspected of having ischemic bowel, and resection is suspected of having ischemic bowel, and resection is performed under therapeutic heparinization to prevent performed under therapeutic heparinization to prevent

further thrombosisfurther thrombosis..

))aa .( .(CT scan shows partially occluding thrombus in the superior CT scan shows partially occluding thrombus in the superior mesenteric vein mesenteric vein

(arrow). (arrow). (b). CT scan obtained 4 months later reveals complete resolution of (b). CT scan obtained 4 months later reveals complete resolution of

thrombusthrombus (arrowhead)(arrowhead)..

OTHER CAUSES OF AMIOTHER CAUSES OF AMI Vasculitic syndromes (Takayasu's arteritis, polyarteritis Vasculitic syndromes (Takayasu's arteritis, polyarteritis nodosa, fibromuscular dysplasia) can affect the nodosa, fibromuscular dysplasia) can affect the mesenteric arteries and may progress to cause AMI.mesenteric arteries and may progress to cause AMI. Ergotism may similarly cause AMI and can be treated Ergotism may similarly cause AMI and can be treated either via oral calcium channel blockers or, in more either via oral calcium channel blockers or, in more severe cases, with intraarterial vasodilators such as severe cases, with intraarterial vasodilators such as nitroprusside, prostacyclin, or prostaglandin E2.nitroprusside, prostacyclin, or prostaglandin E2.Either aortic dissection or isolated SMA dissection may Either aortic dissection or isolated SMA dissection may result in bowel ischemia. Treatment involves surgical result in bowel ischemia. Treatment involves surgical bypass, though endovascular stenting has been bypass, though endovascular stenting has been successfully performed. successfully performed. Finally, iatrogenic causes of AMI include post-coronary Finally, iatrogenic causes of AMI include post-coronary artery bypass graft SMA thrombosis, post-aortic artery bypass graft SMA thrombosis, post-aortic surgery thrombosis, and vasopressor-induced SMA surgery thrombosis, and vasopressor-induced SMA

ischemia/thrombosisischemia/thrombosis . .

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