Obstruction Flashcards
What do the presenting features of (SB & LB) GI tract obstruction depend on ?
The level of obstruction within the GI tract
What are the 2 main classification of obstruction ?
- Small bowel obstruction
- Large bowel obstruction
What are the cardinal features of any GI obstruction?
- Vomiting
- Pain
- Constipation - this may be incomplete (still some passage of faeces or flatus) or complete (no passage of either)
- Abdo distension - hear active ‘tinkling’ bowel sounds if mechanical obstruction +/- a mass may be palpable. On percussion abdo may be ressonant
- Borborygmi (rumbling or gurgling noise made by the movement of fluid and gas in the intestines.)
- May also have anorexia (WL)
What are the general physcial signs of obstruction ?
- Dehydration (dry mouth, loss of skin turgor and elasticity)
- Abdominal distension
- Visible peristalsis
- Relative lack of abdominal tenderness (obstruction with tenderness may indicate bowel strangulation)
- Obstructing abdominal mass may be palpable
- On percussion the centre of the abdomen tends to be resonant due to gaseous distension
- Groins must be examined for an obstructing hernia
What are the characterisitc features of a small bowel obstruction rather than a large bowel obstruction ?
Small bowel obstruction:
- Vomiting occurs earlier (within hours) and is of large volume (gastric, pancreatic, biliary secretions)
- Distension is less marked and pain is colicky in nature and experienced centrally and higher in the abdomen
- AXR will show central gas shadows with valvulae conniventes (folds of small intestine) that cross SB lumen & no gas will be seen in the large bowel/ distal from blockage site
What are the characterisitc features of a large bowel obstruction rather than a small bowel obstruction ?
- Pain is more constant and lower down
- If ileocaecal valve stays shut (in 50% of cases) i.e. no reflux, pain may be felt over a distended caecum
- Vomiting is faeculent and more gradual onset
- AXR shows peripheral gas shadows (LB always peripheral & SB always central) proximal to the blockage. Haustra do not cross the whole lumen of LB
The nature of vomiting gives a clue to where the obstruction is, what would the vomiting be like in the following obstruction types:
- Gastric outlet obstruction
- Upper SB obstruction
- Distal SB/LB obstruction
- Gastric outlet obstruction ==> semi-digested food (no bile)
- Upper SB obstruction ==> copious bile stained food
- Distal SB/LB obstruction ==> thicker brown, foul-smelling vomitius (faeculuent)
What is the classical sounds heard of ascultation of bowel obstruction ?
- Bowel sounds are traditionally described as high-pitched and tinkling.
- In practice they may be absent at the time of auscultation, echoing (cavernous quality), or may sound like water lapping against a boat.
If the bowel obstruction is incomplete what happens ?
The clinical features may be less clearly defined.
- Vomiting may be intermittent and bowel habit erratic.
- Pain is more colicky in nature compared to complete obstruciton
No passage of flatus or faeces is pathognomic for what ?
Bowel obstruction (complete)
What is the most useful 1st line investigation for bowel obstruction ?
Supine AXR (also get an exerect CXR to rule out perforation)
What else should you do for someone with osbtruction as part of the initial investigations ?
- PR exam
- Exam for hernias
What is the 2nd line investigation after AXR has identified bowel obstruction ?
- Contrast CT
- Oral gastrograffin studies may be done also (if gastrograffin present in colon within 24hrs then obstruction is likely to resolve with just conservative measures)
What is the inital management of someone with bowel obstruction ?
- Nil by mouth.
- Insert IV cannula and send bloods (FBC, LFT’s, Bone group, Us & Es, amylase)
- Blood gases
- Resuscitate with IV fluids with hartmans or saline, replacing electrolyte losses.
- Pass a NG tube (ryles not a feeding tube) to decompress the stomach.
Think ‘drip & suck’
How long do you drip and suck someone with bowel obstruction?
Can’t drip and suck hernias and expect resolution. Only adhesional
Up to 72 hours is standard
Intervene earlier if:
- Strangulation
- Perforation
- Ischaemia
Ignoring the site of obstruction what are the 3 different types of GI obstruction ?
- Simple = one obstructing point, no vascular compromise
- Closed loop = obstruction at 2 points forming a loop of grossly distended bowel at risk of perforation. Needs urgent decompression
- Stragulated = blood supply compromised, patient is more ill than you would expect (sharper more constant pain), peritonism and other signs of mesenteric ischaemia
What are the 2 main causes of small bowel obstruction ?
- Adhesions - congenital or after surgery
- Hernias
What are the 4 main causes of large bowel obstruction ?
- Colon cancer
- Constipation/ bolus obstruction
- Diverticular stricture
- Volvulus - sigmoid or caecal
List some of the rarer causes of bowel obstruction
- Crohns stricture
- Gallstone ileus
- Intussusception
- TB
- Foreign body
What are the 4 different causes of bolus obstruction ?
- Food bolus
- Impacted faeces
- Impacted ‘gallstone ileus’ (rare)
- Trichobezoar (rare) - hairball
What does pain over a hernia indicate ?
That it is a strangulated hernia
What is shown in the AXR?
Sigmoid volvulus
Just to look at and differentiate from a sigmoid volvulus
What are the 2 types of non-mechanical bowel obstruction ?
- Paralytic ileus
- Pseudo-obstruction
