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Intestinal obstruction/ileus
Intestinal obstruction/ileus

Intestinal obstruction/ileus

In this topic, we will take a look at intestinal obstruction and ileus. One is of mechanical obstruction aetiology while the other is a functional obstruction.

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INTESTINAL OBSTRUCTION

We will be looking at obstruction for both small and large bowel. There is a lot of overlap but we will discuss some of the key differences, especially on aetiology, imaging and clinical features.

Obstruction occurs in 15% of acute abdomens.

Pathophysiology

Depending on whether it is small bowel, or large bowel, the aetiology may differ entirely:

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Small bowel 🥇 Adhesions are the most common cause 🥈 Hernias
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😷 Presentation

4 cardinal signs of obstruction are:

  1. Pain - colicky in nature
  2. Vomiting - happens earlier in small bowel obstruction and later on in large bowel
  3. Distension
  4. Constipation - happens earlier in large bowel obstruction and later in small bowel
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Large bowel 🥇 Tumours are the main cause for large bowel obstruction Volvulus and diverticular disease are also potential causes.
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Location
Causes
Intraluminal
Gallstones, ileus, foreign body, faecal impaction
Mural
Cancer, inflammatory strictures (in Crohn’s), intussusception (in kids), diverticular strictures, Meckel’s diverticulum, lymphoma
Extramural
Hernias, adhesions, peritoneal metastasis, volvulus
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On examination:
  • Palpation - tenderness. Rebound tenderness and guarding would indicate that there is ischaemia developing.
  • Percussion - tympanic sound
  • Auscultation - tinkling bowel sounds

💭 Differential diagnosis

  • Pseudo-obstruction
  • Ileus
  • Toxic megacolon
  • Constipation

🔍 Investigations

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Imaging: 🏆 CT scan with IV contrast is the first line choice. It can show the site and cause of obstruction and may indicate metastasis if there is malignancy. 👍🏽 AXR is still used as a first-line investigation sometimes. Let’s discuss what we’d look for in an AXR:re
  • Small bowel
    • Dilation >3cm
    • Central in location
    • Valvulae conniventes visible
  • Large bowel obstruction
    • Dilation >6cm (or >9cm if in the caecum)
    • Peripheral
    • Haustra visible
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Laboratory: Urgent bloods are required looking for electrolyte changes and hypovolemia Venous blood gas may be used to look for raised lactate ⬆️ 
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🧰 Management

Management depends on the aetiology of the disease and the complications.

Of course if they are third spacing, IV fluid resuscitation and often a urinary catheter.

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Conservative management NBM + NG tube - decompresses bowel IV fluids Urinary catheter Broad-spectrum antibiotics - if there are any signs of sepsis Analgesia Anti-emetics if needed If the aetiology is adhesions due to a previous surgery, these will be treated conservatively too. Stenting of descending colon is also an option. Fluoroscopy should be performed if it doesn’t resolve within 24 hours and if the contrast does not reach the colon within 6 hours then the patient needs surgical management.
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Surgical management Surgery is indicated when there is:
  • Ischaemia
  • Closed loop obstruction (emergency as it can lead to perforation)
  • Hernia
  • Obstructing tumour
  • Refractory to conservative management

Often it is a laparotomy. If resectioning is required, then a stoma will be needed.

⛔️ Complications

  • Third spacing - when the bowel is obstructed, the proximal portion becomes increasingly dilated and has increased peristalsis, thus we have more secretion of electrolyte-rich fluids into the bowel and out of the vascular/cellular spaces. It will cause hypovolemia, hypotension, oedema and will require urgent fluid resuscitation.
  • Renal impairment (2º to third spacing)
  • Perforation and peritonism - peritonitis patients are usually rigid and don’t move. Marked tenderness upon percussion is also a good sign (rebound tenderness can be tough to assess).
  • Ischaemia
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ILEUS

Pathophysiology

A paralytic ileus is an adynamic bowel due to functional obstruction. It is common after abdominal or pelvic operations and spinal trauma (to thoracic or cervical spine).

It is harmless in most patients but in other patients it is an indicator of an underlying cause that is more sinister.

It is normal post-operatively for a certain amount of time usually:

  • Small bowel: 0-24 hours
  • Stomach: 24-48 hours
  • Colon: 48-72 hours

⚠️ Risk factors

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Surgical risk factors
  • Opioid usage
  • Pelvic surgery
  • Handling intestines extensively throughout the operation
  • Peritoneal contamination with pus or faeces
  • Resection of intestine

Other risk factors include:

  • Increasing age
  • Electrolyte derangement
  • Dementia, Parkinson’s or other neurological disorders
  • Anti-cholinergics (e.g. atropine, oxybutynin)

😷 Presentation

  • Inability to pass faeces or flatus
  • Feeling bloated/distended
  • Nausea and vomiting
  • On examination we may notice absent bowel sounds.

🔍 Investigations

We need to ensure that other pathologies are ruled out (e.g. anastomotic leak).

This will entail:

  1. FBC + CRP
  2. Electrolytes (K+, Mg2+, Ca2+, phosphate specifically)
  3. 🏆 CT abdo-pelvis with oral contrast often confirms diagnosis.

🧰 Management

Conservative management once again (unless it is due to a serious pathology of course). Prolonged ileus needs exclusion of complications such as an anastomotic leak.

This includes:

  1. NBM
  2. Checking bloods and electrolytes daily
  3. Mobilisation
  4. Reducing opiates

🔮 Prophylaxis

  • Minimising intra-operative handling of intestines
  • Avoiding fluid overload
  • Minimising opiates
  • Early mobilisation