Small Bowel Obstruction Flashcards
Extrinsic bowel lesion causes of SBO
Extrinsic bowel causes
- Adhesions: commonest cause, previous laparotomy
- Strangulation in hernia or pockets of abdo cavity
- Volvulus: torsion of bowel around its mesentery
- Masses: extrinsic neoplasm, aneurysm, endometriosis, intra-abdo abscess
Intrinsic bowel lesion wall causes of SBO
Intrinsic bowel wall causes:
- Stricture: IBD, irradiation, surgery
- Tumour (rare)
- Intussusception: one part of the bowel is pull into itself by peristalsis (95% in children)
Luminal occlusion causes of SBO
- Neoplasm (adenocarcinoma, carcinoid, lymphoma)
- Inflammation: Crohn’s, TB
- Intestinal ischaemia
- Swallowed: foreign body; trichobezoar (hairball)
- Gallstone
What is the diagnostic triad of SBO
DxT = colicky central pain + vomiting + distension
The more proximal the obstruction, the more ___ the pain
Severe
Where is the colicky pain predominantly?
Mainly periumbilical, also epigastric
How long do the spasms last for?
Spasms last about 1 minute
List the clinical features of SBO
Severe colicky epigastric and perumbilical pain
Spasms app 1 min
Spasms every 3-10 min
Vomiting
Absolute constipation
No flatus (obstipation)
Abdo distension (especially if lower SBO)
Difference between high and low SBO: frequency of spasms
High: 3-5 mins
Low: 6-10 mins
Difference between high and low SBO: intensity of pain
High: +++
Low: +
Difference between high and low SBO: vomiting and content
High: Early, frequent, violent with gastric juices, then green
Low: Later, less severe that is faeculent (later)
Difference between high and low SBO: dehydration and degree of illness
High: Marked
Low: Less prominent
Difference between high and low SBO: distension
High: Minimal
Low: Marked
How will the patient appear on initial inspection?
Patient weak and sitting forward in distress
Abdomen is soft on palpation except with ___?
Strangulation
Abdomen is tender when ____?
Distended
What sounds are heard on auscultation?
Initially there is an increased sharp, tinkling bowel sounds (hyperactive and high pitched). Then later, secondary ileus can occur and eventually bowel can be silent
Findings on PR?
Empty rectum, may be tender
What x-rays should be ordered and what are the findings?
- Upright CXR: gas underneath diaphragm
- Supine AXR: distended loops of bowel > 3cm
- Upright AXR: air-fluid levels; string of pearls sign
Explain the air fluid levels and string of pearls sign on a upright AXR.
Air fluid level: both fluid and gas collect in the intestine, that produce a characteristic ‘air fluid level’ pattern. Air rises above the fluid and there is a flat surface at the ‘air-fluid’ interface
* stepladder fluid levels ‘air-fluid levels’ (4-5 for Dx) in 3-4 hours
String of pearls sign: small pockets of gas in fluid filled small bowel (usually sign of higher grade mechanical obstruction)
If Dx by XR is unclear, what should be ordered next?
CT - more sensitive
Outline the general pathogenesis of SBO
Small bowel obstruction leads to rapid accumulation of fluid and gas in the bowel proximal to the site of obstruction. In typical cases, there is initial active peristalsis proximal to the obstruction.Within a few hours, the peristaltic activity declines. Oedema and increasing distension supervene. Stasis and bacterial overgrowth make the fluid faeculent. Appearance of faeculent fluid with a foul odour in the vomitus or from a nasogastric tube confirms the diagnosis of obstruction.
Rx of SBO
If stable: IV fluids and bowel decompression with NGT
with anti-emetics and analgesics.
Consider surgery if:
- peritonitis or perforation
- Laparotomy or hernia repair
Complications of SBO
Increasing severity:
- unable to PO intake (due to vomiting)
- fluid loss into peritoneum (oedema)
- ischaemia and then perforation (in severe cases of oedema)
Why is SBO pain epigastric/periumbilical?
small bowel origin is mid gut
