Intestinal obstruction and ischaemia Flashcards
What is the arterial blood supply of the colon?
.
What are the three types of intestinal ischaemia?
Acute mesenteric ischaemia, chronic mesenteric ischaemia, chronic colonic ischaemia (aka ischaemia colitis)
What is the epidemiology of intestinal ischaemia: age and gender?
Most common in elderly (60-80 y/o) with equal gender distribution.
What is acute mesenteric ischaemia?
Ischaemia of the small intestines (almost always) that presents acutely
What is the aetiology of acute mesenteric ischaemia? (x8)
o Superior mesenteric artery thrombosis
o Superior mesenteric artery embolism
o Mesenteric vein thrombosis (especially in younger patients with hypercoagulable states)
o Non-occlusive disease (low-flow states and usually reflects poor cardiac output, though there may be other factors such as recent cardiac surgery or renal failure) – from low BP or vasospasm
o Trauma
o Vasculitis
o Radiotherapy
o Strangulation (volvulus or hernia)
What are the risk factors of acute mesenteric ischaemia? (x7)
AF, heart failure, hypercoagulation, previous MI, cocaine (leading to vasospasm), cardiac surgery, renal failure.
What is chronic mesenteric ischaemia?
Aka intestinal angina. Ischaemia that presents over a longer period of time, almost always in the small intestines.
What are the risk factors of chronic mesenteric ischemia? (x4)
Smoking, hypertension, diabetes, high cholesterol.
What is the aetiology of chronic mesenteric ischaemia?
Low-flow state with atheroma (atherosclerosis of the mesenteric arteries).
What are the signs and symptoms of acute mesenteric ischaemia? (x3)
Classical clinical triad: acute severe abdominal pain, no/minimal abdominal signs, rapid hypovolaemia leading to shock. Pain tends to be constant, central, or around RIF.
What are the signs and symptoms of chronic mesenteric ischaemia? (x6)
There is a triad of severe, colicky, post-prandial abdominal pain (gut claudication), lose weight (because of fear of eating), upper abdominal bruit may be present, +/- PR bleeding, malabsorption, N&V.
What is colicky pain?
Starts and stops abruptly (usually due to muscular contractions).
What are the investigations for acute mesenteric ischaemia? (x3)
o BLOOD: increased Hb (due to plasma loss), increased WCC, modestly raised plasma amylase, metabolic acidosis (high lactic acid from ischaemia).
o AXR: ‘gasless’ abdomen early on.
o ANGIOGRAPHY.
What are the investigations for chronic mesenteric ischaemia?
CT ANGIOGRAPHY and CONTRAST-ENHANCED MR ANGIOGRAPHY.
What is ischaemic colitis?
Aka ischaemic colitis – inflammation of the COLON caused by decreased colonic blood supply.
What vessel is typically affected in ischaemia colitis?
IMA
What is the aetiology of ischaemic colitis? (x6) Note about younger patients.
o OCCLUSION of large vessels by thrombosis or embolism
o IATROGENIC ligation (through medical intervention; tying a band around a vessel to occlude it) e.g. AAA surgery
o HYPOVOLAEMIA
o Small vessel vasculitis
o Vasospasm e.g. from cocaine use
o Hypercoagulable states
o The latter three are typical in younger patients with intestinal ischaemia
What are the risk factors of ischaemia colitis? (x4)
Atherosclerosis, AF, AAA surgery, cocaine
What are the symptoms of ischaemic colitis? (x5) Range?
o Can range from mild ischaemia to gangrenous colitis
o Crampy abdominal pain – mostly lower left-sided
o Pain may be post-prandial (gut claudication – where blood supply is adequate when not digesting) giving ‘food fear’
o Fever
o Nausea
o Bloody diarrhoea – dark blood in later stages
What are the signs of ischaemic colitis? (x5)
o There may be a lack of signs
o Abdominal distension
o Tenderness
o Local peritonism (worse on the left)
o Fever
o Tachycardia
What are the possible investigations for ischaemic colitis? (x7)
o BLOOD: FBC (high WCC), increased CRP, U&Es, LFTs, increased LDH, increased CK, increased lactate (from ischaemia), ABG for metabolic acidosis, clotting screen. Evaluation of hypercoagulability more important in younger patients where this is more likely to be the cause of the ischaemia
o STOOL: cultures of Salmonella, Shigella, Campylobacter, Yersinia, E. Coli, and assay Clostridium difficile toxins to exclude infective colitis
o AXR: large bowel wall thickening, diffuse dilation, air in bowel wall, or thumbprinting.
o ERECT CXR: air under diaphragm indicates perforation
o CT: thickening of colonic wall, irregular lumen, intramural air (inside walls), portal or mesenteric venous air, occlusion in larger blood vessels
o COLONSCOPY: may show pale mucosa, petechial bleeding, blush haemorrhagic nodules, cyanotic mucosa, mucosal friability (break easily into smaller parts e.g. crumbly), and haemorrhagic ulcerations.
o ANGIOGRAPHY: may be normal or show attenuated (reduced) flow or site of occlusion.
What does thumbprinting on an AXR show? What does it look like?
Looks like thumbs protruding into the intestinal lumen and caused by submucosal oedema.
How can you differentiate whether obstruction is small or large bowel radiologically?
Small bowel obstruction (a): AXR shows CENTRAL gas shadows (dark/black) with VALVULAE CONNIVENTES that completely cross the lumen and no gas in the large bowel. Large bowel obstruction (b): AXR shows PERIPHERAL gas shadows proximal to the blockage but not in the rectum. HAUSTRA do not cross the width of the lumen.
What are the radiological signs of sigmoid volvulus?
Inverted ‘U’ loop of vowel that looks a bit like a coffee bean.
