Large bowel obstruction Flashcards
What is the definition of a large bowel obstruction
It is a surgical emergency
Mechanical interruption (complete or partial) to the flow of intestinal contents
Important to distinguish between mechanical and functional obstruction
Most occurs at/distal to transverse colon
Explain the different classification of large bowel obstruction
- Mechanical - Malignant or benign
- Extrinsic
- Intrinsic: mural or intra-luminal
Functional:
- Due to abnormal intestinal physiology
What are the most common causes of mechanical large bowel obstruction
Malignant causes:
- Cancer
- Extra-colonic neoplasms
Benign:
- Volvulus especially sigmoid volvulus
- Diverticulitis
- Ischaemic colitis
- IBD
Why is the left sided colon more commonly obstructed by malignancy
Narrower lumen
Solid content in the left colon
Annular constricting nature of tumours
What is a volvulus and which part of the colon is more commonly affected
A volvulus is when the colon twists on its mesentry and it then impairs the evenous drainage and arterial inflow.
Sigmoid colon is most commonly affected
Explain how Diverticulitis leads to large bowel obstruction
Diverticulitis is associated with muscular hypertrophy of the colonic wall and multiple episodes of inflammation causes the colon to become fibrotic and thickend which leads to luminal narrowing
Explain what is Ogilvie syndrome
It is a functional obstruction characterised by acute dilatation in the abscence of anatomic lesion obstructing flow of intestinal content.
Often occurs in elderly patients and is associated with severe illness and after surgery
Explain the pathophysiology of how mechanical LBO can lead to peritonitis
Mechanical LBO leads to dilatation of the proximal part and this results in mucosal oedema, impaired venous outflow and ultimatelyt impaired arterial inflow.
Ischaemia and oedema leads to an increased permeability which results in fluid shifts, bacterial translocation and electrolyte abnormalities.
Due to bacterial translocation peritonitis can develop
Explain how the patient history will present if there is a luminal obstruction
Abdominal pain - colicky in nature
Obstipation may be preceded with constipation
Distention
Vomiting
Change is bowel habits
Features of malignancy - LOW, anaemia, PR bleeding
LLQ pain may suggest previous episode of diverticulitis
What shoudl you ask if a patient presents with an LBO history
Previous diagnosis of adenomas/polyps
Known colorectal or pelvic malignancy
Hx of diverticular disease
Hx suggestive of IBD
Risk factors for malignancy
How will patient present on examination with a LBO
General - anaemia, dehydration
Inspection - Distented abdomen
Percussion - hyper resonance
Tenderness - may indicate ischaemia, perforation
Tachycardia, fever - perforation
Whata re the investigations done for a LBO
X-rays
CT scan
Barium enema
Laboratory investigations: U&E, FBC
Endoscopy
What are the general principles of management of a LBO
Bowel rest
IV fluid resus
Correct electrolyte abnormalities
Gastric decompression if nausea and vomiting
Identify features sugesting immediate surgery: Tachycardia, hypotension, acidosis
Whata re the definitive management options for LBO
Volvulus - pneumatic decompression followed by semi-elective resection or immediate surgery
Resection
Proximal diversion alone
Stenting
Dilatation/ trans anal stricturoplasty with electrocautery or laser (anastamotic strictures)
Decompression of pseudo-obstruction
Whata re the definitive management options for LBO
Volvulus - pneumatic decompression followed by semi-elective resection or immediate surgery
Resection
Proximal diversion alone
Stenting
Dilatation/ trans anal stricturoplasty with electrocautery or laser (anastamotic strictures)
Decompression of pseudo-obstruction
