GI Flashcards
1
Q
What is the aetiology of small-bowel obstruction?
A
- Adhesions (60%): usually secondary to previous abdo surgery
- Hernia
- Malignancy
- Crohn’s disease
2
Q
What is the pathophysiology of small-bowel obstruction?
A
- Mechanical obstruction is most common
- Obstruction leads to bowel distension above the block with increased fluid secretion into the distended bowel
- Also leads to proximal dilatation above the block (causes increased secretion and swallowed air in the SB)
- More dilatation causes decreased absorption and mucosal wall oedema
- Increased pressure with the intramural vessels becoming compressed, resulting in ischaemia and/or perforation
- Untreated obstruction leads to ischaemia, necrosis and perforation
3
Q
What is the presentation of small-bowel obstruction?
A
- Pain – initially colicky then diffuse (higher in abdo than large bowel obstruction)
- Profuse vomiting following pain (occurs earlier than in large bowel obstruction)
- Less distension than large bowel obstruction
- Nausea and anorexia
- Tenderness suggests strangulation and urgent surgery is required
- Constipation with no passage of wind occurs late
- Increased bowel sounds
4
Q
How is small-bowel obstruction investigated?
A
- Abdominal x-ray: central gas shadows that completely cross the lumen, no gas in large bowel, distended loops of bowel proximal to obstruction, increased bowel sounds
- Examination of hernia orifices and rectum
- FBC essential
- CT is gold standard to localise lesion accurately
5
Q
How is small-bowel obstruction managed?
A
- Aggressive fluid resuscitation
- Bowel decompression
- Analgesia and antiemetic
- Antibiotics
- Surgery to remove obstruction
6
Q
What is the aetiology of large bowel obstruction?
A
- 90% due to colorectal malignancy
- Volvulus is most common cause in African countries
7
Q
What is the pathophysiology of large bowel obstruction?
A
- Similar to SBO, but colon proximal to obstruction dilates
- Increased colonic pressure and decreased mesenteric blood flow results in mucosal oedema
- Can compromise arterial blood supply and cause mucosal ulceration
In colonic volvulus: - 360o axis rotation results in a closed loop obstruction
- Fluid and electrolytes shifts into the closed loop
- Results in increased pressure and tension in the loop causing impaired colonic blood flow
8
Q
What is the presentation of large bowel obstruction?
A
- Abdominal pain is more constant than in SBO
- Abdominal distension
- Bowel sounds normal then increased then quiet later
- Palpable mass e.g. hernia, distended bowel loop or caecum
- Late vomiting which is more faecal like (suggestive of LBO)
- Vomiting may be absent
- Constipation
- Fullness/ bloating/ nausea
9
Q
How is large bowel obstruction investigated?
A
- DRE (empty rectum, hard stools, blood)
- FBC is essential (see low Hb if chronic occult blood loss)
- Abdominal XR (peripheral blood shadows proximal to the blockage, caecum and ascending colon distended)
10
Q
How is large bowel obstruction managed?
A
- Aggressive fluid resuscitation
- Bowel decompression
- Analgesia and antiemetic
- Antibiotics
- Surgery to remove obstruction (if due to malignancy, then colorectal stents followed by elective surgery)
11
Q
What is the aetiology of bowel pseudo-obstruction?
A
- 80% is a complication of other conditions:
- Intra-abdominal trauma, pelvic, spinal and femoral fractures
- Postoperative states e.g. abdominal, pelvic, cardiothoracic, orthopaedic, neuro
- Intra-abdominal sepsis
- Pneumonia
- Drugs e.g. opiates and antidepressants
- Metabolic disorders e.g. electrolyte disturbances, malnutrition
12
Q
What is the presentation of bow pseudo-obstruction?
A
- Rapid and progressive abdominal distension with pain
13
Q
How is bow pseudo-obstruction investigated?
A
- XR shows gas-filled large bowel
14
Q
How is bowel pseudo-obstruction managed?
A
- Treat underlying problem e.g. withdrawal of opiate analgesia
- IV neostigmine
15
Q
What is the pathophysiology of diverticulitis?
A
- Low fibre diet increases intestinal transit time and decreases stool volume resulting in increased intraluminal pressure and colonic segmentation, which predisposes to diverticular formation
- Commonly form where vasa recti penetrate the colonic all, and food particle or faecal material may contribute to the development of infection
