Ischemic bowel disease Flashcards Preview

GI > Ischemic bowel disease > Flashcards

Flashcards in Ischemic bowel disease Deck (45):
1

If pt presents with any belly pain esp older pt what should always be on your DDx?

- mesenteric ischemia

2

Incidence of ischemic bowel disease? Mortality rate? Patterns/

- incidence increases with age
- dx frequently is delayed, high mortality: 50-90%
- patterns:
small and/or large bowel
diffuse or localized
segmental or focal
superficial or transmural

3

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%

4

Occlusive causes of acute mesenteric ischemia?

arterial: usually SMA
- embolic: Afib, valves
- thrombotic: atherosclerosis, trauma, infection

5

Nonocclusive cuases of acute mesenteric ischemia?

hypoperfusion (low cardiac output or shock (MI, arrythmias, septic shock) - leading to splanchnic vasoconstriction

6

Circulation to the intestines?

- primarily SMA and IMA
- lots of collateral circulation
- reqrs 10-35% of CO

7

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

8

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)

9

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

10

Clincial syndromes of ischemic bowel (occlusive and non-occlusive)?

occlusive:
-mesenteric arterial embolism
- mesenteric arterial thrombosis
- mesenteric venous thrombosis

non-occlusive:
hypoperfusion

11

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
- aortography
- coronary angiography
- aortic dissection
- CHF (low output)

12

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

13

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

14

mesenteric arterial thrombosis - usual culprits?

- atherosclerotic disease
- trauma
- infection
- does not appear to be assoc with coagulopathy

15

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

16

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

17

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

18

RFs for mesenteric venous thrombosis?

- **hypercoagulable state (upt to 75% have hypercoag. disorder)
- **portal HTN
- abdominal infections
- blunt abdominal trauma
- pancreatitis
- splenectomy
- malignancy in portal region
- personal or family hx of DVT or PE
- dehydration

19

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

20

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

21

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!!

22

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

23

Main cause of arterial emboli?

- afib, MI

24

Main cause of arterial thrombosis?

- atherosclerotic disease

25

Main cause of venous thrombosis?

- underlying disorder in coagulation (hypercoagulable), neoplasm

26

Main cause of nonocclusive mesenteric ischemia?

- nonocclusive mesenteric ischemia: low flow states

27

Work up of ischemic bowel disease?

- lab
- imaging: plain abdominal xrays, CT scan of abdomen

28

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

29

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

30

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%)

31

What is pneumatosis intestinalis?

- gas cysts in bowel wall
- it isn't gas in the bowel lumen
- suggestive of necrotizing enterocolitis

32

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

33

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

34

Preferred imaging? How will appearance vary?

- CT
- 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:
cause
severity
localization
extent and distribution
Presence and degree of submucosal or intramural hemorrhage, superimposed bowel wall infection, or bowel wall perf

35

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

36

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

37

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

38

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

39

What is the gold std dx study for acute arterial ischemia?

- mesenteric angiography

40

Tx for MAE?

- surgery and embolectomy or local infusion of thrombolytic therapy

41

Tx for MAT?

- surgery with thrombectomy + revascularization or heparinization

42

Tx for MVT?

- heparinization + resection of infarcted bowel

43

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

44

Basic care guidelines for these ischemic bowel pts?

- cardiac monitor, venous access, O2
- may reqr fluid resuscitation
- broad spectrum abx
- surgery

45

Characteristics of chronic mesenteric ischemia?

- intestinal angina
- episodic or constant intestinal hypoperfusion
- secondary to atherosclerosis
- strongly assoc with meals
- pts generally have sxs for a year, have unintentional wt loss, hurts to eat
tx: stents to open up blocked areas