Flashcards in Ischemic bowel disease Deck (45)
If pt presents with any belly pain esp older pt what should always be on your DDx?
- mesenteric ischemia
Incidence of ischemic bowel disease? Mortality rate? Patterns/
- incidence increases with age
- dx frequently is delayed, high mortality: 50-90%
small and/or large bowel
diffuse or localized
segmental or focal
superficial or transmural
What are the 4 major causes of acute mesenteric ischemia?
- SMA emobolism (50%)
- SMA thrombosis (15-25%): often superimposed on pts with progressive atherosclerotic disease, also occurs with trauma or infection
- nonocclusive ischemia: 20-30%
- mesenteric venous thrombosis: 5%
Occlusive causes of acute mesenteric ischemia?
arterial: usually SMA
- embolic: Afib, valves
- thrombotic: atherosclerosis, trauma, infection
Nonocclusive cuases of acute mesenteric ischemia?
hypoperfusion (low cardiac output or shock (MI, arrythmias, septic shock) - leading to splanchnic vasoconstriction
Circulation to the intestines?
- primarily SMA and IMA
- lots of collateral circulation
- reqrs 10-35% of CO
Regulation of intestinal circulation?
- perfusion pressure
- neura and hormonal mechanisms
- sympathetic nervous system, renin angiotensin system, vasopressin from the pituitary:
vasopressin - causes mesenteric (arterial) vasoconstriction and venous dilation
reduces portal venous pressure in pts bleeding from portal HTN
hallmarks of clinical presentation of ischemic bowel?
- severe cramping abdominal pain, out of proportion to physical findings, poorly localized
- worst pain of their life, may hear some bruits (if they have atherosclerotic disease)
clinical presentation of ischemic bowel?
- abdominal exam may be normal initially
- occult blood in stool
- as bowel ischemia worsens:
abdominal distension, absent bowel sounds, peritoneal signs, +/- feculant odor to the breath
Clincial syndromes of ischemic bowel (occlusive and non-occlusive)?
-mesenteric arterial embolism
- mesenteric arterial thrombosis
- mesenteric venous thrombosis
RFs assoc with acute mesenteric arterial embolism?
- advanced age
- coronary artery disease
- cardiac valvular disease
- hx of dysrhythmias - esp Afib
- post- MI mural thrombi
- hx of thromboembolic disease
- aortic surgery
- coronary angiography
- aortic dissection
- CHF (low output)
Main characteristics of mesenteric arterial embolism: who it effects? What is usually effected?
- median age: 70, 2/3 women (smaller vessels)
- SMA often involved and affects the jejunum
- 6-8 cm beyond arterial origin, near middle colic artery
- thrombus form L atrium, L ventricle or cardiac valves: over 20% of cases have mult emboli, arteriolar vasoconstriction also occurs
Clinical presentation of mesenteric arterial embolism?
- sudden onset of severe pain, that is out of proportion to physical findings 75%
- N/V, frequent BMs
- occult blood in stool 25%
- more favorable prognosis than SMA thrombosis
mesenteric arterial thrombosis - usual culprits?
- atherosclerotic disease
- does not appear to be assoc with coagulopathy
Characteristics of mesenteric arterial thrombosis?
- usually can elicit a hx of chronic mesenteric ischemia
- usual site of blockage is orign of SMA or celiac axis
- less favorable prognosis compared with embolic
- sxs don't develop until sig blockage (collateral circulation) which can complicate revascularization
What pop more commonly affected by mesenteric venous thrombosis? What tpye of clots are the most common? Onset?
- younger pop: 48-60
- primary 20%
- secondary clot 80%
- onset can be acute or develop over the course of a few weeks
- thrombosis of superior mesenteric vein or intestinal strangulation from hernia or volvulus: 30% of cases involve thrombosis of the portal vein
sxs in mesenteric venous thrombosis?
more insidious onset of sxs:
- pain diffuse and nonspecific initially, but later becomes constant
- anorexia 53-54%
- vomiting 41-77%
- diarrhea 36%, constipation 13-34%
- hematemesis 9-425
RFs for mesenteric venous thrombosis?
- **hypercoagulable state (upt to 75% have hypercoag. disorder)
- **portal HTN
- abdominal infections
- blunt abdominal trauma
- malignancy in portal region
- personal or family hx of DVT or PE
PP of intestinal ischemia in mesenteric venous thrombosis?
- decreased mesenteric venous blood flow
- results in bowel wall edema (how you can tell the diff b/t arterial and venous on CT)
- fluid efflux into bowel lumen
- results in systemic hypotension and increase in blood viscosity
- this results in diminished arterial flow
- leading to submucosal hemorrhage and bowel infarction
Cause of nonocclusive mesenteric ischemia? RF?
- result of splanchnic hypo perfusion and vasoconstriction
- RF: atherosclerotic disease
- often pt has a life-threatening illness/is being tx (ex: CHF, MI, sepsis)
- pathogenesis: mesenteric vasospasm - homeostatic mechanism maintains cardiac and cerebral blood flow, vasopressin and angiotensin involved
Mortality of nonocclusive mesenteric ischemia? Sxs?
- high mortality (up to 70%)
- severity and location of pain may be different than occlusive mesenteric ischemia:
going to have progressive abdominal pain, bloating, N/V, mental status changes
- up to 25% of pts don't have abdominal pain
- listen for bowel sounds!!
Ischemia in the colon presentation?
- 90% of pts over age of 60
- acute precipitating cause is rare
- pts don't appear severely ill
- mild abdominal pain, tenderness present
- rectal bleeding, bloody diarrhea typical
- colonoscopy is procedure of choice
Main cause of arterial emboli?
- afib, MI
Main cause of arterial thrombosis?
- atherosclerotic disease
Main cause of venous thrombosis?
- underlying disorder in coagulation (hypercoagulable), neoplasm
Main cause of nonocclusive mesenteric ischemia?
- nonocclusive mesenteric ischemia: low flow states
Work up of ischemic bowel disease?
- imaging: plain abdominal xrays, CT scan of abdomen
What will you see on labs in ischemic bowel disease?
- increase in WBCs with predominance of immature cells
- increased HCT (hemoconcentration)
- increase in amylase (50%), increase phosphate (80%)
- increase in serum lactate
77-100% sensitivity/42% specificity
- metabolic acidosis: any pt with abdominal pain and metabolic acidosis has intestinal ischemia until proven otherwise
What will you see on plain x-rays?
- pneumatosis intestinalis
- portal venous gas
- thickened bowel wall with thumb-printing
- air fluid levels
- dilated bowel loops (can look like a bowel obstruction)
- gasless abdomen
In cases of surgiclly proven acute mesenteric ischemia - this is what is seen?
- air fluid levels (67%)
- dilated bowel loops (18%)
- gasless abdomen (10%)
- pneumatosis (2%)
- portal venous gas (2%)
What is pneumatosis intestinalis?
- gas cysts in bowel wall
- it isn't gas in the bowel lumen
- suggestive of necrotizing enterocolitis
What is portal venous gas?
- accum of gas in portal vein and its branches
- a variety of causes such as ischemic bowel, intra-abdominal sepsis and other
Imaging for dx ischemic bowel disease - steps?
- upright and supine plain abdominal x-rays are the first step in eval of acute abdomen
- free air, obstruction, ileus, intusseception, volvulus
- mesenteric ischemia is diff to dx on plain films alone
- CT is next step if dx isn't made on plain fims and if pt is stable
Preferred imaging? How will appearance vary?
- oral and IV contrast, do IV first
- oral necessary for eval of mucosal thickening of bowel wall
- if just ordering CTA may not want oral contrast b/c it can obscure view of mesenteric vessels
- appearance will vary based on:
extent and distribution
Presence and degree of submucosal or intramural hemorrhage, superimposed bowel wall infection, or bowel wall perf
Findings on CT?
- bowel wall thickening: most common finding in ischemic colitis, colonic infarction, and venous occlusion
- bowel dilation (can be assoc with wall thinning)
- fat stranding and ascites
- varying degrees of attenuation: high attenuation (white), low (black)
- pneumatosis and portomesenteric gas
When is a CTA or MRA indicated?
- CTA: good study for eval of suspected intestinal ischemia but don't do if planning on percutaneous angiography too (excessie contrast with 2 studies)
- MRA: better at dx venous occlusions
When is a mesenteric percutaneous arteriography used? When can you not use this?
- if dx is in doubt after non-invasive radiologic eval
- if dx is fairly certain and need consideration for percutaneous tx or for surgical planning
- can't be used for venous occlusions
Dx and Tx process of ischemic bowel disease?
- hemodynamic monitoring and support: correct hypotension, hypovolemia
- correction of metabolic acidosis
- broad spectrum abx
- NG tube for gastric decompression
- vasopressors that have less effect on mesenteric perfusion: dobutamine, low dose dopamine, milrinone
- anticoag unless actively bleeding
- correction of arrhythmias
- then imaging
- may start with plain films or CT but if strong clinical suspicion should go directly to angiography
- at angiography can give papaverine (potent vasodilator) directly to relieve mesenteric vasoconstriction
- if peritoneal signs, may proceed directly to the OR for surgical repair
What is the gold std dx study for acute arterial ischemia?
- mesenteric angiography
Tx for MAE?
- surgery and embolectomy or local infusion of thrombolytic therapy
Tx for MAT?
- surgery with thrombectomy + revascularization or heparinization
Tx for MVT?
- heparinization + resection of infarcted bowel
Tx for nonocclusive mesenteric ischemia?
- papaverine infusion during angiography
- reverse underlying conditions
- repeat angiography can be done in 24 hrs
- surgical exploration reserved for pts with peritoneal signs
tx goal: reverse underlying cause
Basic care guidelines for these ischemic bowel pts?
- cardiac monitor, venous access, O2
- may reqr fluid resuscitation
- broad spectrum abx