Small and large bowel obstruction Flashcards
Definition
Partial or complete blockage of the small or large intestine preventing normal flow of gastrointestinal content
What is a closed loop obstruction?
SURGICAL EMERGENCY
2nd obstruction proximally, such as volvulus or competent ileocaecal valve in large bowel obstruction – bowel will continue to extend until ischaemia or perforation
Is small or large bowel obstruction more common?
Small - accounts for 80% intestinal obstruction
How common?
Account for 15% acute abdomens
Who’s affected?
can occur at any age
What happens in bowel obstruction?
Mechanical or functional obstruction –> gross dilation of proximal bowel –> increased peristalsis of bowel –> secrete large volumes of electrolyte rich fluid (third spacing) –> can lead to hypovolaemia
Most common causes of bowel obstruction
ADHESIONS (small bowel) HERNIAS (small bowel) MALIGNANCY (large bowel) Diverticular disease (large bowel) Volvulus (large bowel)
Adhesions, hernias and malignancy account for 90%
Mechanical obstruction
Physical blockage, obstruction is either simple, closed loop or strangulated
Most common = adhesions (usually post-surgery)
Other causes = hernias, volvulus, tumours, diverticular disease/strictures, inflammatory strictures (e.g. secondary to Crohn’s), intussusception (children), constipation/impacted faeces, foreign body
Functional obstruction
Adynamic bowel due to absence of normal peristaltic contractions (neuromuscular dysfunction)
Paralytic ileus
Mesenteric vascular occlusion
Medication related e.g. opioid
Risk factors
- Hx of abdominal surgery (–> adhesions)
- Hx of hernia
- Cancer
- IBD
- Hx of foreign body ingestion
Symptoms/history
VOMITING (esp. green bilious) – early in SBO, late in LBO
ABDOMINAL DISTENTION
Diffuse ABDOMINAL PAIN – colicky, cramping (constant or worse on movement = red flag for ischaemia)
ABSOLUTE CONSTIPATION (no stool or flatus) – early in LBO, late in SBO
Signs/examination
Abdominal distention
Abdominal tenderness
Tinkling bowel sounds (decreased bowel sounds in functional obstruction)
Tympanic sounds on percussion
Evidence of underlying cause e.g. surgical scars, cachexia, hernia
Dehydration –> hypotension, tachycardia
Differentials
- Gastroenteritis
- Gut perforation
- Toxic megacolon
Investigations
BLOODS: U&Es, FBC, CRP, LFTs, G&S
VBG: lactate increased in bowel ischaemia, assess for metabolic derangement secondary to dehydration or excessive vomiting e.g. metabolic alkalosis due to vomiting
ABDOMINAL CT WITH IV CONTRAST: confirm diagnosis, establish site and cause of obstruction
PLAIN ABDOMINAL X-RAY
ERECT CXR: assess for free air under diaphragm suggesting bowel perforation
WATER SOLUBLE ENEMA (GASTROGRAFIN): may help demonstrate site of obstruction (aka contrast fluoroscopy). Used in small bowel obstruction caused by adhesions to determine likelihood of obstruction resolving without surgery
Signs of AXR
Small bowel: dilated >3cm, central abdo location, valvulae conniventes
Large bowel: dilated >6cm (or >9cm if at caecum), peripheral location, haustral lines
Bowel proximal to obstruction dilated and filled with air, bowel distal to obstruction collapsed with absent gas
Gas seen throughout bowel in functional obstruction
Management
Drip and suck (conservative) management Surgery Anti-emetics Analgesia Consider Abx prophylaxis
Drip and suck management
- Nil by mouth
- Nasogastric tube to decompress bowel
- IV fluids for hydration and correction of electrolytes
- Catheterise to monitor fluid balance
- Usually resolves after a few days
Indications for surgery
closed loop obstruction ischaemia strangulated hernia obstructing tumour no improvement with conservative management (>48hrs)
Examples of surgery
adhesiolysis
hernia repair
emergency resection of obstructing tumour
inserting stent if obstructing tumour
Prognosis
Mortality 25% in SBO if surgery delayed beyond 36hrs (8% if under 36hrs)
50% sigmoid volvulus recur within 2yrs
Prognosis
Mortality 25% in SBO if surgery delayed beyond 36hrs (8% if under 36hrs)
50% sigmoid volvulus recur within 2yrs
Complications
Bowel perforation and/or ischaemia –> peritonitis, septicaemia
Dehydration/fluid and electrolyte imbalance –> AKI
Explaining bowel obstruction to patient
So we think that the cause of your stomach pain is a bowel obstruction - I’ll now try and explain this to you. So normally your intestines are a tube where the food you eat and the fluid you drink passes through. In bowel obstruction, there is something blocking this flow within the tube so your stomach contents can no longer pass through and this is what is causing your symptoms. Many different things can cause there to be an obstruction, and we would like to take some bloods and do some scans to try and work out what is causing this so that we can treat it.
