THINK ABOUT MESENTERIC ISCHEMIA

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THINK ABOUT MESENTERIC ISCHEMIA

• SEVERE ABDOMINAL PAIN OUT OF PROPORTION TO
  FINDINGS ON EXAMINATION

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• Sudden reduction in arterial perfusion of the
  small bowel results in immediate central
  abdominal pain
• Progressive involvement of muscular layer
• Serosa
• Peritoneal signs

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Acute mesenteric ischemia

• Thrombotic
• Embolic
• Non-occlusive

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Thrombotic

• Due to an acute arterial thrombosis which
  occludes the orifice of the superior mesenteric
  artery (SMA), resulting in massive ischemia of
  the entire small bowel plus the right colon

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Embolic

• Due to a shower of embolic material originating
  proximally from the heart (AF, post MI,
  diseased valve) or aneurysmal or atherosclerotic
  aorta.
• Emboli lodge at the proximal SMA, below the
  entry of the middle colic artery, therefore the
  most proximal segment of the jejunum is spared.
• Emboli tend to fragment and re-emboli distally
  producing a patchy type of ischemia

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Non-occlusive

• Low flow state no documented thrombosis or
  emboli
• Low cardiac output (cardiogenic shock), reduced
  mesenteric flow (increased intra-abdominal
  pressure) or mesenteric vasoconstriction
  (administration of vasopressors)
• Usually develops in the setting of pre-existent
  critical illness

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Mesenteric Venous Thrombosis

• Can also produce small bowel ischemia
• Clinical features and management completely
  different from the above three

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• The problem in clinical practice mesenteric
  ischemia is usually recognized too late, after it
  has led to intestinal gangrene, sepsis and organ
  failure
• Even if the patient survives - development of
  short bowel syndrome
• Therefore early diagnosis and treatment are
  crucial

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Clinical picture

• The early clinical picture is non-specific
  severe abdominal pains, minimal abdominal
  findings
• Preceding symptoms mesenteric angina (pain with
  meals, weight loss)
• History of IHD
• Source of emboli
• Low flow state in moribund patients due to
  underlying critical disease
• If peritonitis usually signifies dead bowel

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• Abdominal x-rays in the early course of the
  illness are normal. Later adynamic ileus
• Laboratory tests initially normal. As bowel
  ischemia progresses leukocytosis,
  hyperamylasemia, lactic acidosis
• Therefore high level of suspicion and active
  search for the diagnosis in the early phase to
  prevent bowel necrosis

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• Abdominal CT-Angio
• Mesenteric Angiography
• Contraindicated in the presence of acute abdomen

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Mesenteric Angiography

• Invasive, takes time and requires experienced
  personnel only if CT-Angio non diagnostic and
  there is still high probability of vascular event
• To rule out non-occlusive disease
• Advantage can be therapeutic
• Occluded ostium of SMA Thrombosis, immediate
  operation unless good collateral flow. The angio
  provides road map for reconstruction.
• In Emboli, the first few cm of SMA are patent

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Non-operative Treatment

• Only if no peritoneal signs, usually in emboli
• Selective infusion of thrombolytic agent,
  papaverine to relieve the associated mesenteric
  vasospasm
• Only cessation of abdominal symptoms and
  angiographic resolution can be regarded as a
  success
• In non-occlusive mesenteric ischemia attempt to
  improve intestinal flow by restoring altered
  hemodynamics. Selective intra-arterial infusion
  of vasodilator.
• In emboli long term anti-coagulation

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Operative Treatment

• Peritoneal signs
• Failure of non-operative regimen
• Two possibilities
• Frank gangrene
• Ischemia, questionable viability

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Frank Gangrene

• Gangrene of the entire small bowel and right
  colon signifies SMA thrombosis.
• Total resection TPN for life not practical
• Shorter gangrene or multiple segments
  emboli. Excision of all dead bowel and evaluation
  of the rest. Less than 1 meter of small bowel
  will require in half of patients TPN for life

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Questionable viability

• Possibility of embolectomy in emboli or vasculoar
  reconstruction only if bowel questionably
  viable.
• Consider second-look operation if remaining
  questionable bowel too long and massive resection
  required
• Signs of viability color, peristalsis,
  pulsation in mesenterium
• Anastomosis selectively. Stable patient, fair
  nutritional status, remaining bowel
  unquestionably viable, no severe peritonitis.
  Anastomosis after massive resection intractable
  diarrhea
• The main reason not to anastomose the
  possibility that further ischemia may develop
• If anastomosis not safe exteriorize both end of
  the bowel as end-ileostomy and mucous fistula for
  a later re-anastomosis

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Second-look Operation

• A planed re-operation has to be decided during
  the first operation
• Allows to re-assess intestinal viability
• Allows to preserve the greatest possible length
  of viable intestine
• Has to be done after 24-48 hours to prevent SIRS

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Mesenteric Vein Thrombosis

• Occlusion of the venous outflow of the bowel.
• Rare, may be idiopathic or secondary to
  hypercoagulable state or sluggish portal flow
  (cirrhosis)
• Clinical presentation non-specific, may last
  several days until the intestine is compromised
  and peritoneal signs develop
• CT may be diagnostic intra-peritoneal fluid,
  thickened segment of small bowel, thrombus in the
  SMV

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MVT - Treatment

• If no peritoneal signs full anticoagulation
  may result in spontaneous resolution and avoid
  surgery
• Failure to improve on heparin or peritoneal signs
  mandate an operation
• At operation the involved segment of small
  bowel is thick, edematous, dark blue, arterial
  pulsation present, thrombosed veins.
• Resection of the involved segment, the same
  considerations as for arterial ischemia regarding
  anastomosis or second look.
• Postoperative anticoagulation to prevent thrombus
  progression