Small Bowel Obstruction

Dr Tom Leach

8 years ago

Contents

Accounts for 80% of cases of intestinal obstruction

Can be partial or complete:

These appear filmly strands of fibrous material

This obstructs the ileo-caecal valve and actually obstructs the small intestine. These patients will need surgery. The patient will often be anaemic.

Colicky abdominal pain – often felt around the umbilucs
- Tender abdomen only tends to be present in strangulation (complete obstruction)
Dilated loops of bowel may be palpable
Vomiting – often provides some pain relief
- Fermentation of the bowel products can produce a foul vomit (faeculant vomit), but faecal vomiting only occurs with fistulae
Abdominal distension – increases as the condition progresses
Absolute constipation (absence of flatus and stool) – Late sign
Auscultation – high pitched ‘tinkling’ bowel sounds
- ‘Rushing’ sounds may also be heard, and are particularly associated with peristalsis and cramp pain
Shock ± oliguria – may be present in late stage disease, and indicate severe, strangulated obstruction.

Obstruction results in the dilation of proximal bowel, and the collapse of distal bowel. The normal secretory and digestive functions of the mucosa become impaired.
Strangulated obstruction occurs when the blood supply to the obstructed region becomes impaired. It can lead to ischaemia and gangrene within 6 hours of onset!
Strangulated obstruction occurs in 25% of cases of small bowel obstruction
Typically venous obstruction occurs before arterial
Perforation typically occurs at the ischaemic segment

Catheter
Analgesia
TED stockings
NG Tube
Erect CXR
Abdo x-ray (supine)– look for distended bowel (>5cm – the normal size of the small bowel is 2.5cm)
- Gas in biliary tree – this is a sign of gallstone ileus. Often, the gallstone has fistulated into the small bowel – usually duodenum.
- Supine AXR is necessary to get the best view of the gas patterns in the abdomen. When erect, these are more difficult to discern
- Differentiating small and large bowel loops:
  - Small bowel loops are the width of the lumen
  - Large bowel loops are not the complete width of the lumen
Blood tests
- Full blood count (anaemia? – may be present in caecal carcinoma)
- U+E’s – Fluid and electrolyte disturbance (particularly with potassium) may be present
- Amylase
- Likely raised CRP

Laparotomy
- Is the only definitive diagnostic tool, but obviously should not be undertaken lightly!

Strangulation – Significant abdominal pain, or other features of ischaemic bowel – e.g. raised WCC or serum lactate
Obstruction due to adhesion rarely requires surgery – if Hx of no previous surgery, adhesions are rare
Closed-loop obstruction – as seen in some cases of large bowel obstruction

This is a ‘disordered neuromuscular transmission’ within the myenteric plexus
Usually occurs after abdo surgery and handling of the bowel. Normally, the different parts of the bowel take different amounts of time to start working properly again (e.g. peristalsis and digestion):
- Stomach: up to 24 hours
- Small bowel <24 hours
- Large bowel 24-48 hours
- Longer than this can indicate ileus
Can also be caused by intra-abdominal infection, metabolic disorders, or a reflux response to retroperitoneal surgery
It is usually treated conservatively, and should resolve within a week
When present without obstruction (as in the majority of cases), then it is often painless
Although it can be a cause of obstruction, it can also be a diagnosis in its own right. Distinguishing small bowel obstruction and paralytic ileus may be difficult:
- Both show distended bowel on x-ray
- Both can present with constipation
- Bowel sounds are absent in ileus, whilst characteristic in obstruction (depending on the location of the obstruction).