Intestinal Obstruction

Question 1

Define an intestinal obstruction.

Answer 1

Arrest/blockage of onward propulsion of intestinal contents through the bowel.
Can be a surgical emergency.

Question 2

Classifications of obstruction according to:
- Site.

Answer 2

Large bowel/small bowel/gastric

Question 3

Classifications of obstruction according to:
- Extent of luminal obstruction.

Answer 3

• Partial
• Complete - volvulus can result in this, resulting in overflow and sickness

Question 4

Classifications of obstruction according to:
- Mechanism.

Answer 4

• Mechanical
• True (intraluminal/extraluminal)
• Functional:
• Paralytic ileus - a dynamic bowel due to the absence of normal
  peristaltic contractions, caused by abdominal surgery or acute
  pancreatitis

Question 5

Classifications of obstruction according to:
- Pathology.

Answer 5

• Simple
• Closed loop
• Strangulation
• Intussusception - one hollow structure into its distal hollow structure, usually seen in children as bowel is softer

Question 6

Intestinal obstruction: what is intussusception?

Answer 6

Intussusception is when part of the intestine invaginates into another section of the intestine -> telescoping. It is caused by force in-balances.

Question 7

What are most intestinal obstructions due to?

Answer 7

Most intestinal obstruction is due to a mechanical block

Question 8

Name the 3 broad categories that describe the causes of intestinal obstruction.

Answer 8

1. Blockage.
2. Contraction.
3. Pressure.

Question 9

Intestinal obstruction: give 3 causes of blockage.

Answer 9

1. Tumour.
2. Diaphragm disease.
3. Gallstones in ileum (rare).

Question 10

Intestinal obstruction: what is thought to cause diaphragm disease?

Answer 10

NSAIDS.

Question 11

Intestinal obstruction: give 3 causes of contraction.

Answer 11

1. Inflammation.
2. Intramural tumours.
3. Hirschprung’s disease.

Question 12

Intestinal obstruction: what can cause inflammation to cause contraction for intestinal obstruction?

Answer 12

1. Crohn’s disease.
2. Diverticulitis.

Question 13

Describe how Crohn’s disease can cause intestinal obstruction.

Answer 13

Crohn’s disease -> fibrosis -> contraction -> obstruction.

Question 14

What is Hirschprung’s disease?

Answer 14

A congenital condition where there is a lack of nerves in the bowel = so without complete innervation of the colon to rectum.

• Motility is affected
• Results in gut dilatation and the filling of faeces
• Since there are no ganglion cells, no peristalsis or movement of content
• Results in gross dilatation and obstruction of the bowel

Question 15

Intestinal obstruction: give 3 causes of pressure.

Answer 15

1. Adhesions.
2. Volvulus.
3. Peritoneal tumour.

Question 16

Intestinal obstruction: what are adhesions?

Answer 16

Adhesions often form secondary to abdominal surgery.

It is the sticking together of abdominal structures to one another, bowel loops, omentum, other solid organs or the abdominal wall
by fibrous tissue, leading to the bowel being pulled and distorted.

Question 17

Intestinal obstruction: what causes adhesions?

Answer 17

Adhesions often form secondary to abdominal surgery.

Question 18

Intestinal obstruction: what is volvulus?

Answer 18

Volvulus is a twist/rotation in the bowel; closed loop obstruction. There is a risk of necrosis.
- Looks like a coffee-bean!

Question 19

Intestinal obstruction: which areas of the bowel are most likely to be affected by volvulus?

Answer 19

Volvulus occurs in free floating areas of the bowel e.g. bowel with mesentery. The sigmoid colon has a long mesentery and so can twist on itself.

Question 20

What is the most common cause of obstruction in adults?

Answer 20

Adhesions

Question 21

Name 3 categories of bowel obstruction.

Answer 21

1. Small bowel obstruction (most common)
2. Large bowel obstruction
3. Pseudo-obstruction

Question 22

Which is more common: small bowel obstruction or large bowel obstruction?

Answer 22

Small bowel obstruction is more common; it makes up 75% of intestinal obstruction.

Question 23

Give 4 common causes of small bowel obstruction in adults.

Answer 23

1. Adhesions from previous abdominal / gynecological surgery.
2. Hernias.
3. Crohn’s disease.
4. Malignancy.

Question 24

Give 3 common causes of small bowel obstruction in children.

Answer 24

1. Appendicitis.
2. Volvulus.
3. Intussusception.

Question 25

Give 5 symptoms of small bowel obstruction.

Answer 25

1. Colicky abdominal pain (pain higher up) 2. Abdominal distension (less severe than LBO) 3. Vomiting first (bilious) 4. Followed by constipation with no pass of wind 5. ‘Tinkling’ bowel sounds 6. Tenderness 7. Nausea + anorexia

Question 26

Would dilatation, distension and increased secretions be seen proximal or distal to an intestinal obstruction?

Answer 26

Proximal.

Question 27

Give 4 signs of small bowel obstruction.

Answer 27

1. Vital signs e.g. increased HR, hypotension, raised temperature. 2. Tenderness and swelling. 3. Resonance. 4. Bowel sounds.

Question 28

What investigations might you do in someone who you suspect to have a small bowel obstruction?

Answer 28

1. Take a good history - ask about previous surgery (adhesions)! 2. Bloods - FBC (essential!), U+E, lactate. 3. 1st line: Abdominal XRay (dilation of the small bowel >3 cm, coiled-spring appearance ) 4. Gold standard: CT abdomen and pelvis with/without contrast

Question 29

What is the management of stable patients with small bowel obstruction?

Answer 29

Conservative management (stable patients): A-E assessment. ‘Drip and suck’: - Insert IV cannula → Resuscitate with IV fluids - Nil-by-mouth (NBM) - Insert nasogastric (NG) tube to decompress stomach - Catheter (monitor urine output) - Analgesia, antiemetics, antibiotics

Question 30

What is the management of unstable patients with small bowel obstruction?

Answer 30

Surgical (unstable patients): Treat according to cause - Laparotomy - Adhesiolysis for adhesions - Hernia repair - Tumour resections - Bowel resection

Question 31

Give 2 common causes of large bowel obstruction.

Answer 31

1. Colorectal malignancy. 2. Sigmoid volvulus (especially in the developing world). 3. Diverticulitis.

Question 32

Give 5 symptoms of large bowel obstruction.

Answer 32

1. Tenesmus. 2. Constipation first 3. Follwed by vomiting (initially bilious, then faecal fluid) 4. Continuous Abdominal discomfort/pain 5. Severe abdominal distension 6. Bloating. 7. Absent bowel sounds. 6. Weight loss.

Question 33

What investigations might you do in someone who you suspect to have a large bowel obstruction?

Answer 33

1. 1st line: Abdo XRay - Dilation of the large bowel > 6cm - Dilation of the caecum > 9cm 2. Gold standard: CT of the abdomen and pelvis with contrast 3. Digital rectal exam: * Empty rectum * Hard stools * Blood 4. FBC = essential - see low Hb sign of chronic occult blood loss

Question 34

What is the management of stable patients with large bowel obstruction?

Answer 34

Conservative management (stable patients): A-E assessment. ‘Drip and suck’: - Insert IV cannula → Resuscitate with IV fluids - Nil-by-mouth (NBM) - Insert nasogastric (NG) tube to decompress stomach - Catheter (monitor urine output) - Analgesia, antiemetics, antibiotics

Question 35

What is the management of unstable patients with large bowel obstruction?

Answer 35

Surgical (unstable patients): Treat according to cause - Laparotomy - Adhesiolysis for adhesions - Hernia repair - Tumour resections - Bowel resection

Question 36

Give 3 consequences of untreated intestinal obstructions.

Answer 36

1. Ischaemia. 2. Necrosis. 3. Perforation.

Question 37

Give 2 indications for the need of immediate surgical intervention in someone with a small bowel obstruction.

Answer 37

1. Signs of perforation (peritonitis). 2. Signs of strangulation.

Question 38

What is the difference between SBO and LBO for the symptom of pain?

Answer 38

SBO: colicky abdominal pain LBO: continuous abdominal pain

Question 39

What is the difference between SBO and LBO for the symptom of vomiting?

Answer 39

SBO: early onset bilious vomiting LBO: late onset vomiting, first bilious followed by faecal

Question 40

What is the difference between SBO and LBO for the symptom of constipation?

Answer 40

SBO: late onset LBO: early onset

Question 41

What is the difference between SBO and LBO for the symptom of abdominal distension?

Answer 41

SBO: less severe LBO: significant

Question 42

What is the difference between SBO and LBO for the symptom of bowel sounds?

Answer 42

SBO: 'tinkling' bowel sounds LBO: absent

Question 43

What is the difference between SBO and LBO for the abdominal X-ray?

Answer 43

SBO: Dilation of the small bowel >3cm Coiled-spring appearance Centrally located multiple dilated loops of gas filled bowel (arrowheads) Valvulae conniventes (arrow) are visible - confirming this is small bowel LBO: Dilation of the large bowel >6cm or the caecum >9cm

Question 44

What is pseudo-obstruction?

Answer 44

Also known as Ogilvie syndrome Clinical picture mimicking colonic dilation + obstruction but with no mechanical cause of obstruction.

Question 45

Give 4 causes of pseudo-obstruction.

Answer 45

1. Post-operative (paralytic ileus) 2. Medications (opioid, calcium channel blockers, antidepressants) 3. Neurological (Parkinson’s, multiple sclerosis, Hirschsprung's) 4. Electrolyte imbalance 5. Recent trauma/surgery

Question 46

Explain the pathophysiology of pseudo-obstruction.

Answer 46

Parasympathetic nerve dysfunction → absent smooth muscle Complication: bowel ischaemia and perforation

Question 47

What investigations might you do in someone who you suspect to have a pseudo-obstruction?

Answer 47

1. 1st line: Abdominal X-ray (megacolon → dilation > 10cm) - Shows a gas-filled large bowel 2. Gold standard: CT of the abdomen and pelvis with contrast (no transition zone)

Question 48

What is the management for pseudo-obstruction?

Answer 48

1. ‘Drip and suck’ management 2. Treat underlying cause e.g. withdrawal of opiate analgesia 3. IV neostigmine 4. Surgical decompression for unstable patients (caecostomy, ileostomy)