Page 180 - Medicine and Surgery

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176 Chapter 4: Gastrointestinal system

Aetiology Complications
Underlying causes include strangulation of a hernia, in- Ischaemic strictures may result from scarring at the
tussusception, or a volvulus inwhichaloopofbowel splenic flexure or sigmoid colon. These are confirmed
twists on itself usually around a fibrous peritoneal band on barium studies and require resection.
or adhesion.
Investigations
A barium enema can be used to show oedema or mu-
Pathophysiology
cosal sloughing. Bleeding into the bowel wall produces
The ischaemia results from venous infarction due to
athumb print appearance. Mesenteric angiography will
strangulation. The thin draining veins are occluded by
demonstrate the stenosis or occlusion.
external pressure resulting in venous congestion and
hence a failure of arterial supply to the segment of bowel.
Management
The condition generally is self-limiting within a few days
Clinical features/management
with uncomplicated cases managed conservatively.
The underlying cause requires identification and treat-
ment. If blood flow is not restored, a progression to in-
farction and necrosis necessitates bowel resection. Chronic intestinal ischaemia
Definition
Ischaemic colitis Slow progressive ischaemia of the gut due to atheroma
generally occurring in the elderly.
Definition
Ischaemia of the colon due to interruption of its blood Aetiology
supply. Atheroma within the mesenteric vessels causes reduced
blood flow and ischaemia. Risk factors:
Aetiology Fixed: Age, sex, positive family history, familial hyper-
In most cases the underlying cause is thrombosis of the lipidaemia.
inferiormesentericartery,embolisationofmuralthrom- Modifiable: Smoking (direct relationship to the num-
bus in atrial fibrillation, or non-occlusive infarction. ber of cigarettes smoked), hypertension, diabetes mel-
litus, LDL and total cholesterol levels (HDL are pro-
tective).
Pathophysiology
In around half the ischaemia is transient with damage
Pathophysiology
confinedtothemucosaandsubmucosa.Thesplenicflex-
Progressive atheroma occludes the lumen of the vessels
ure is most often affected due to the territories of the
causing reduced blood flow. The clinical presentation
arteries supplying the bowel. If the blood supply is not
depends on the position and degree of occlusion and the
restored, ischaemia progresses to gangrenous ischaemic
presence of collateral blood supply.
colitis. The presentation and treatment is as for acute
intestinal failure (see page 177).
Clinical features
Patients describe pain occurring after food, weight loss,
Clinical features
malabsorption and signs of vascular disease.
The patient presents with lower abdominal pain, nausea,
vomiting and bloody diarrhoea. There is lower abdom-
Investigations
inal tenderness and guarding in the lower abdomen.
The diagnosis is made on angiography.
Microscopy Management
There is ischaemic loss of mucosa, ulceration and later Surgical revascularisation depends on the results of an-
healing with oedema and inflammatory infiltrate. giography. A variant of this condition is coeliac axis