Intestinal Ischaemia

Adventure of the day- on my way home from firms, I noticed that my hospital ID/access card was not on my lanyard so figured I must had dropped it along the way. So, I retrace my steps, go all the way back to the tube station I got off at, and do not find it. The tube station worker hasn’t seen it. So, I’m stressing- not exam level stress or even ‘it’s my turn to order and I don’t know what starter to get’ sort of stress, but mild stress. I’ve lost it before and my consultant gave it to me before I even noticed it was missing and I don’t want him to find it again and think I am a totally ditsy irresponsible human being that can’t be trusted with a cannula. And the bother of having to let the hospital know and waiting for a new one. And I hope they’ve saved my photo because I looked really cute in that photo and I don’t think I can look that good again, even though I was totally unprepared the first time. And- this one was my sister’s contribution- what if someone finds your card and pretends to be you and has total access to the hospital for their illegal doings.

And it was in my bag. No idea how it got there.

Now, how about some more bowel disease…


 Intestinal Ischaemia

Definition: inflammation of the intestines caused by decreased intestinal blood supply. There are three main types of bowel ischaemia: acute mesenteric ischemia, chronic mesenteric ischaemia and ischaemic colitis/chronic colonic ischaemia.

Aetiology/risk factors:

Acute mesenteric ischaemia:

Almost always involves the small bowel and may follow:

superior mesenteric artery (SMA) thrombosis or embolism (70%)- e.g. due to AF

Consider mesenteric ischaemia in anyone with AF presenting with abdominal pain.

-mesenteric vein thrombosis (more common in younger patients with hypercoagulable state, affects smaller lengths of bowel) (5%)

-non-occlusive disease (occurs in low-flow states and usually reflects poor cardiac output, there may be other factors such as recent cardiac surgery or renal failure) (20%)

Other: trauma, vasculitis, radiotherapy, strangulation e.g. volvulus (bowel twists on itself) or hernia, vasospasm (cocaine)

Chronic mesenteric ischaemia:

-usually caused by a combination of a low-flow state  with diffuse atherosclerotic disease in all 3 mesenteric arteries

-associated with other vascular disease

Ischaemic colitis/ chronic colonic ischaemia:

Usually follows low flow in the inferior mesenteric artery (IMA) territory (because a low flow-state e.g. hypovolaemia following surgery, will affect the IMA most as it is the last of the mesenteric arteries that blood reaches)

Ranges from mild ischaemia to gangrenous colitis (dead bowel).

Image result for anatomy blood supply to git

-Ischaemia leads to mucosal inflammation, oedema, necrosis, and ulceration. The splenic flexure- the watershed between superior and inferior mesenteric artery territories, is the most common area affected.

Epidemiology:

Intestinal ischaemia is most common in the elderly (60-80) with equal gender distribution.

Symptoms & Signs:

Acute mesenteric ischaemia:

classical triad =acute severe abdominal pain + no abdominal signs + rapid hypovolaemia⇒ shock

Pain usually constant, central, or around RIF.

Degree of illness often far out of proportion with clinical signs.

Chronic mesenteric ischaemia: a.k.a intestinal angina

classic triad: severe, colicky post-prandial abdominal pain + weight loss (eating hurts, so you don’t) + upper abdominal bruit may be present

+/- PR bleeding, malabsorption, nausea, vomiting

Ischaemic colitis/ chronic colonic ischaemia:

Lower, left-sided abdominal pain +/- blood diarrhoea

Gangrenous ischaemic colitis = peritonitis (guarding, rebound tenderness) + hypovolaemic shock (low BP, tachycardic, cold peripheries)

Investigations:

General:

Bloods: WCC, CRP↑, U&Es, LFTs, LDH, CK, lactate, clotting screen (check for hypercoagulability in young patients and those with recurrent ischaemia)

Stool culture- Salmonella, Shigella, Campylobacter, Yersinia, E.coli, assay C.diff toxins- exclude infective cause

AXR- bowel wall thickening or diffuse dilation, air in bowel wall, thumbprinting (submucosal oedema)

Erect CXR- air under diaphragm if perforation

CT- thickening of colonic wall, irregular lumen, intramural air, occlusion of large blood vessels

Colonoscopy- may show pale mucosa, petechial bleeding, bluish haemorrhagic nodules, cyanotic mucosa, mucosal friability and haemorrhagic ulcerations

Angiography- may be normal or show attenuated flow or site of occlusion

Acute mesenteric ischaemia:

Bloods: Hb may be high due to plasma loss, ↑WCC, ↑amylase (moderate rise)

-Persistent metabolic acidosis- showing an anion gap, due to lactate rise

AXR: shows gasless abdomen early on (i.e. no black bits- there are other causes of gasless abdomen and it may be normal in some people)

Mesenteric ischemia. Plain abdominal radiograph in

Acute Mesenteric Ischaemia- gasless abdomen and ‘thumb-printing’

Arteriography: may help visualise vessel occlusion

CT/MR angiography: non-invasive alternative to simple arteriography

Laparotomy: many diagnoses are only made on finding a nasty necrotic bowel when you open up the abdomen

Related image

(Measurement of mucosal oxygen tension and MR oximetric measurements of superior mesenteric vein flow are emerging diagnostic tools)

Chronic mesenteric ischaemia:

CT angiography/ contrast enhanced MR angiography- visualise mesenteric vasculature. Replacing traditional angiography.

Image result for chronic mesenteric ischemia ct angiography

Doppler ultrasound– may be useful in assessing blood flow in the mesenteric vasculature

Ischaemic colitis/ chronic colonic ischaemia:

CT- may be helpful

 

Image result for ischemic colitis ct

Thickened bowel wall in ischaemic colitis

 

Colonoscopy + biopsy- GOLD-STANDARD

Barium-enema- shows characteristic ‘thumb-printing’ of thickened, submucosal swelling

Management:

Acute mesenteric ischaemia:

-Fluid resuscitation

-Antibiotics- gentamicin + metronidazole (to prevent bacterial translocation across dying gut wall)

Heparin, or if arteriography is done, thrombolytic may be infused locally via the catheter.

-Surgically remove dead bowel

-Revascularisation may be attempted on potentially viable bowel but difficult and often needs 2nd laparotomy.

Chronic mesenteric ischaemia:

-consider surgery due to ongoing risk of infarction (cell death due to ischaemia)

-percutaneous transluminal angioplasty + stent insertion- replacing open revascularisation

Ischaemic colitis/ chronic colonic ischaemia:

Conservative

-fluid replacement

-antibiotics

If gangrenous ischaemic colitis

-resuscitation

-resection of affected bowel and stoma formation

Complications:

Acute mesenteric ischaemia:

-Septic peritonitis

-Systemic Inflammatory Response Syndrome (SIRS)

-Multi-Organ Dysfunction Syndrome (MODS)

-Gangrene

-Perforation

-Toxic megacolon, pyocolon (colon full of pus)- occasionally

Chronic mesenteric ischaemia:

-Mesenteric infarction

-Restenosis after revascularisation

Ischaemic colitis/ chronic colonic ischaemia:

-strictures following recovery –> intestinal obstruction

Prognosis:

Prognosis depends on severity, extent and timing of ischaemic insult and comorbidities. Prognosis is poor for acute mesenteric ischaemia caused by arterial thrombosis and non-occlusive disease with less than 40% surviving; prognosis is not so bad for venous and embolic ischaemia.

References: Cheese & Onion, Rapid Medicine

 

 

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