Page 179 - Medicine and Surgery

P1: KOA
BLUK007-04 BLUK007-Kendall May 25, 2005 7:57 Char Count= 0

Chapter 4: Vascular disease of the bowel 175

Age High intermuscular abscesses cause pain exacerbated
Most common 20–40 years. on defecation, a boggy tender swelling is felt on rectal
examination.
Sex Management
2M : 1F Perianal and ischiorectal abscesses are drained under
general anaesthetic and de-roofed by making a cruci-
Aetiology ate incision and excising the resultant 4 triangles of skin.
In the majority of patients there is no apparent cause for 25% of abscesses recur.
abscess formation. Recurrent abscesses occur in inflam-
matory bowel disease, HIV and rectal carcinoma.
Vascular disease of the bowel
Pathophysiology
Infection of an anal gland may cause a tracking down Intestinal ischaemia
to form a perianal abscess, or tracking out to form a Intestinal ischaemia results from a failure of the blood
ischiorectal abscess, or upwards to produce a high inter- supply to the bowel. Certain areas of bowel are more
muscular abscess. susceptible to ischaemia (e.g. the splenic flexure) due to
the pattern of blood supply. Three underlying patholo-
gies are in operation resulting in a number of clinical
Clinical features
entities all with three possible outcomes (see Fig. 4.9).
Perianal abscess is common and presents in well pa-

tients with an acute tender swelling at the anal verge. Focal ischaemia of the bowel
Ischiorectal abscess present with a diffuse hard painful

swelling lateral to the anus, which may extend behind Definition
the anal canal to form a horseshoe abscess. Patients Localised bowel pathology may result in focal area of
have significant systemic upset. ischaemia.

Arterial occlusion Non-occlusive infarction Venous occlusion
Atheroma, Embolus, Aortic disease, Arteritis
Extrinsic pressure:
Thrombosis: Superimposed on atheroma, Ventricular failure, Intussusception,
Disseminated intravascular coagulation Cardiac failure Strangulated hernia,
Sickle cell disease, Polycythaemia Volvulus

Superior mesenteric Inferior mesenteric Generalised reduction in Focal blockage
artery occlusion artery occlusion blood flow
Acute intestinal failure Ischaemic colitis Chronic intestinal ischaemia Focal ischaemia

POSSIBLE OUTCOMES: Full recovery if flow is restored within 6 hours
Slow resolution, with stricture formation
Progression of necrosis, gangrene, perforation

Figure 4.9 Intestinal ischaemia.