Obstruction

Question 1

What do the presenting features of (SB & LB) GI tract obstruction depend on ?

Answer 1

The level of obstruction within the GI tract

Question 2

What are the 2 main classification of obstruction ?

Answer 2

1. Small bowel obstruction
2. Large bowel obstruction

Question 3

What are the cardinal features of any GI obstruction?

Answer 3

1. Vomiting
2. Pain
3. Constipation - this may be incomplete (still some passage of faeces or flatus) or complete (no passage of either)
4. 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)

Question 4

What are the general physcial signs of obstruction ?

Answer 4

• 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

Question 5

What are the characterisitc features of a small bowel obstruction rather than a large bowel obstruction ?

Answer 5

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

Question 6

What are the characterisitc features of a large bowel obstruction rather than a small bowel obstruction ?

Answer 6

• 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

Question 7

The nature of vomiting gives a clue to where the obstruction is, what would the vomiting be like in the following obstruction types:

1. Gastric outlet obstruction
2. Upper SB obstruction
3. Distal SB/LB obstruction

Answer 7

1. Gastric outlet obstruction ==> semi-digested food (no bile)
2. Upper SB obstruction ==> copious bile stained food
3. Distal SB/LB obstruction ==> thicker brown, foul-smelling vomitius (faeculuent)

Question 8

What is the classical sounds heard of ascultation of bowel obstruction ?

Answer 8

• 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.

Question 9

If the bowel obstruction is incomplete what happens ?

Answer 9

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

Question 10

No passage of flatus or faeces is pathognomic for what ?

Answer 10

Bowel obstruction (complete)

Question 11

What is the most useful 1st line investigation for bowel obstruction ?

Answer 11

Supine AXR (also get an exerect CXR to rule out perforation)

Question 12

What else should you do for someone with osbtruction as part of the initial investigations ?

Answer 12

• PR exam
• Exam for hernias

Question 13

What is the 2nd line investigation after AXR has identified bowel obstruction ?

Answer 13

• 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)

Question 14

What is the inital management of someone with bowel obstruction ?

Answer 14

• 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’

Question 15

How long do you drip and suck someone with bowel obstruction?

Answer 15

Can’t drip and suck hernias and expect resolution. Only adhesional

Up to 72 hours is standard

Intervene earlier if:

• Strangulation
• Perforation
• Ischaemia

Question 16

Ignoring the site of obstruction what are the 3 different types of GI obstruction ?

Answer 16

1. Simple = one obstructing point, no vascular compromise
2. Closed loop = obstruction at 2 points forming a loop of grossly distended bowel at risk of perforation. Needs urgent decompression
3. Stragulated = blood supply compromised, patient is more ill than you would expect (sharper more constant pain), peritonism and other signs of mesenteric ischaemia

Question 17

What are the 2 main causes of small bowel obstruction ?

Answer 17

1. Adhesions - congenital or after surgery
2. Hernias

Question 18

What are the 4 main causes of large bowel obstruction ?

Answer 18

1. Colon cancer
2. Constipation/ bolus obstruction
3. Diverticular stricture
4. Volvulus - sigmoid or caecal

Question 19

List some of the rarer causes of bowel obstruction

Answer 19

• Crohns stricture
• Gallstone ileus
• Intussusception
• TB
• Foreign body

Question 20

What are the 4 different causes of bolus obstruction ?

Answer 20

1. Food bolus
2. Impacted faeces
3. Impacted ‘gallstone ileus’ (rare)
4. Trichobezoar (rare) - hairball

Question 21

What does pain over a hernia indicate ?

Answer 21

That it is a strangulated hernia

Question 22

What is shown in the AXR?

Answer 22

Sigmoid volvulus

Question 23

Just to look at and differentiate from a sigmoid volvulus

Question 24

What are the 2 types of non-mechanical bowel obstruction ?

Answer 24

1. Paralytic ileus
2. Pseudo-obstruction

Question 25

Describe what paralytic ileus is and its risk factors

Answer 25

Disruption of the normal propulsive activity (adynamic bowel) of the GI tract, due to failure of peristalsis. Risk factors: * Recent GI surgery * Any inflammation with localised peritonitis e.g. pancreatitis * Diabetic keto acidosis * Drugs e.g. TCA's

Question 26

What are the signs/symptoms of paralytic ileus and its management ?

Answer 26

* Symptoms and signs: similar to bowel obstruction although pain and high pitched bowel sounds are less common. * Treatment: ‘drip and suck’ while awaiting restoration of peristalsis.

Question 27

What is pseudo-obstruction (Ogilvie’s syndrome)?

Answer 27

Acute dilatation of the colon in the absence of colonic obstruction in acutely unwell patients. - it is like mechanical obstruction but with no cause found Associated with: * Hip replacement surgery * Coronary Artery Bypass Grafts * Spinal # * Pneumonia * Frail / elderly patients

Question 28

What is the typical presenting features of pseudo-obstruction ?

Answer 28

Features are similar to that of mechanical obstruction

Question 29

How is pseudo-obstruction diagnosed ?

Answer 29

AXR +/- CT confirms gaseous distension to distal rectum

Question 30

What is the treatment of pseudo-obstruction ?

Answer 30

Neostigime or colonoscopic decompression if distension is causing pain or respiratory compromise

Question 31

Describe what constipation is

Answer 31

A common primary functional disorder of the bowel but may, of course, develop secondary to another condition. It may be defined as defecation that is unsatisfactory because of infrequent stools (\< 3 times weekly), difficult stool passage (with straining or discomfort), or seemingly incomplete defecation.

Question 32

What are the clinical features of constipation ?

Answer 32

* The passage of infrequent hard stools * Sensation of incomplete evacuation * Manual manoeuvers needs to facilitate evaucation

Question 33

What are the risk factors for constipation ?

Answer 33

* Mainly poor diet & exercise, laxative abuse, old-age, opioids, * Motility disorders

Question 34

What is the treatment of constipation ?

Answer 34

* 1st line = reassurance - encourage drinking more, diet & excercise - high fibre diet * 2nd line = simulant (bisacodyl or senna) + bulking agent (bran powder or isphagulha husk) OR just an osmotic laxative e.g. lactulose * 3rd line = enema