Bowel Obstruction

Question 1

… … refers to complete or partial disruption of the normal flow of gastrointestinal content.

Answer 1

Bowel obstruction refers to complete or partial disruption of the normal flow of gastrointestinal content.

Question 2

… obstruction: no fluid or gas is able to pass beyond the site of obstruction.

Answer 2

Complete obstruction: no fluid or gas is able to pass beyond the site of obstruction.

Question 3

Types of bowel obstruction

Answer 3

Complete obstruction: no fluid or gas is able to pass beyond the site of obstruction.
Partial/incomplete obstruction: some fluid or gas is able to pass beyond the site of obstruction.
Mechanical obstruction: physical blockage to the flow of gastrointestinal content.
Non-mechanical obstruction (ileus): obstruction to flow secondary to neuromuscular dysfunction (e.g. failure in peristaltic activity).
Closed loop obstruction: the bowel is obstructed at two points, this prevents proximal or distal decompression of contents. High-risk of rapid necrosis and perforation.

Question 4

Small bowel

The most common cause of mechanical small bowel obstruction within the western world is …

Answer 4

Small bowel

The most common cause of mechanical small bowel obstruction within the western world is post-operative adhesions. These refer to strands of fibrous tissue that form following surgery and can lead to the abnormal adhesion between intra-abdominal tissue.

Question 5

Another major cause of mechanical small bowel obstruction are … (after adhesions)

Answer 5

Another major cause of mechanical small bowel obstruction are hernias (e.g. inguinal hernias). Loops of bowel can become trapped within the hernial sac leading to obstruction and potentially strangulation and infarction if not managed urgently.

Question 6

Other causes of small bowel obstruction: (apart from adhesions and hernias?)

Answer 6

Inflammatory bowel disease
Malignancy
Radiation enteritis
Intussusception
Gallstone ileus
Other

Question 7

It is estimated that 60% of patients with mechanical large bowel obstruction occurs secondary to …

Answer 7

It is estimated that 60% of patients with mechanical large bowel obstruction occurs secondary to colorectal malignancy.

Question 8

Other causes of mechanical large bowel obstruction are listed below: (aside from colorectal malignancy)

Answer 8

Diverticular stricture (approx. 20% of mechanical large bowel obstruction)
Volvulus (approx. 5% of mechanical large bowel obstruction)
Hernia

Question 9

Non-mechanical (or adynamic) bowel obstruction refers to a dilatation of the bowel in the abscence of mechanical blockage through failure of normal ….

Answer 9

Non-mechanical (or adynamic) bowel obstruction refers to a dilatation of the bowel in the abscence of mechanical blockage through failure of normal peristalsis.

Question 10

Define paralytic ileus

Answer 10

Paralytic ileus is the general slow-down of the intestines and affects the entire intestinal tract (small and large bowel).

Its aetiology is poorly understood though it is commonly seen post-operatively. Other triggers include abnormal electrolytes and systemic upset.

Question 11

Acute colonic pseudo-obstruction - what is this?

Answer 11

Also termed Ogilvie syndrome, ACPO refers to the dilations of the colon in the absence of mechanical obstruction. Its aetiology is poorly understood and likely multifactorial. A combination of systemic illness, medications and biochemical abnormalities are implicated.

The condition is also often seen in the post-partum setting, particularly following caesarian section.

Question 12

The classical features of bowel obstruction include … (4)

Answer 12

The classical features of bowel obstruction include abdominal pain, distension, vomiting & obstipation (Obstipation is when a person cannot pass stool or gas, usually due to an obstruction or blockage of hard, difficult-to-pass stool.)

Question 13

… is when a person cannot pass stool or gas, usually due to an obstruction or blockage of hard, difficult-to-pass stool.

Answer 13

Obstipation is when a person cannot pass stool or gas, usually due to an obstruction or blockage of hard, difficult-to-pass stool.

Question 14

Symptoms of bowel obstruction (6)

Answer 14

Abdominal pain
Nausea
Vomiting
Anorexia
Small volume diarrhoea
Obstipation

Question 15

Signs of bowel obstruction (5)

Answer 15

Abdominal tenderness / peritonism
Rebound
Abdominal distention
Abdominal mass (e.g. hernia)
Dehydration

Question 16

Signs and symptoms of…

Answer 16

Bowel obstruction

Question 17

Biochemical abnormalities frequently seen in bowel obstruction include a raised .. and ..

Answer 17

Biochemical abnormalities frequently seen in bowel obstruction include a raised lactate and inflammatory markers.

Question 18

Bedside tests in bowel obstruction (5)

Answer 18

Observations
ECG
Fluid balance
PR examination
Pregnancy test

Question 19

Bloods in bowel obstruction presentation

Answer 19

VBG/ABG
FBC
UE
Magnesium
Bone profile
LFTs
Amylase
CRP
Group and saves

Question 20

Imaging in suspected bowel obstruction

Answer 20

Erect chest radiograph (check for free air)
Abdominal radiograph
CT abdomen/pelvis

Question 21

NOTE: … is a key biochemical marker in bowel obstruction, acting as an indicator for ischaemia. DO NOT however be deceived by a normal .. which can be found despite significant ischaemia having occurred. As always it must be interpreted in the wider clinical context.

Answer 21

NOTE: Lactate is a key biochemical marker in bowel obstruction, acting as an indicator for ischaemia. DO NOT however be deceived by a normal lactate which can be found despite significant ischaemia having occurred. As always it must be interpreted in the wider clinical context.

Question 22

Small bowel: Identification of the small bowel is based on the presence of the … …. These are circular folds, which help increase the surface area of the small intestines. On radiograph, these are seen as white lines which cross the lumen of the small bowel.

Answer 22

Small bowel: Identification of the small bowel is based on the presence of the valvulae conniventes. These are circular folds, which help increase the surface area of the small intestines. On radiograph, these are seen as white lines which cross the lumen of the small bowel.

Question 23

Large bowel: Identification of the large bowel is based on the presence of …. These give the large intestines its sacculated appearance. On radiograph, these are seen as white lines, which do not cross the lumen of the large bowel.

Answer 23

Large bowel: Identification of the large bowel is based on the presence of haustra. These give the large intestines its sacculated appearance. On radiograph, these are seen as white lines, which do not cross the lumen of the large bowel.

Question 24

… rule: As a general rule of thumb, dilatation of the small bowel > ..cm, the large bowel > …cm or the caecum > …cm, is suggestive of abnormal dilatation.

Answer 24

3, 6, 9 rule: As a general rule of thumb, dilatation of the small bowel > 3cm, the large bowel > 6cm or the caecum > 9 cm, is suggestive of abnormal dilatation.

Question 25

Identifying small vs large bowel on imaging?

Answer 25

Small bowel: Identification of the small bowel is based on the presence of the valvulae conniventes. These are circular folds, which help increase the surface area of the small intestines. On radiograph, these are seen as white lines which cross the lumen of the small bowel. Large bowel: Identification of the large bowel is based on the presence of haustra. These give the large intestines its sacculated appearance. On radiograph, these are seen as white lines, which do not cross the lumen of the large bowel.

Question 26

What is the 3, 6, 9 rule?

Answer 26

3, 6, 9 rule: As a general rule of thumb, dilatation of the small bowel > 3cm, the large bowel > 6cm or the caecum > 9 cm, is suggestive of abnormal dilatation

Question 27

Sigmoid volvulus: typical ‘…’ sign is described. Arises from left lower quadrant, haustra cannot be identified. Multiple air-fluid levels may be seen. Classical appearances often not present and a simple x-ray may not be diagnostic.

Answer 27

Sigmoid volvulus: typical ‘coffee bean’ sign is described. Arises from left lower quadrant, haustra cannot be identified. Multiple air-fluid levels may be seen. Classical appearances often not present and a simple x-ray may not be diagnostic.

Question 28

Caecal volvulus: arises from the … … quadrant, haustral pattern tends to be maintained. One air-fluid level seen. Classical appearances often not present and a simple x-ray may not be diagnostic.

Answer 28

Caecal volvulus: arises from the right lower quadrant, haustral pattern tends to be maintained. One air-fluid level seen. Classical appearances often not present and a simple x-ray may not be diagnostic.

Question 29

It is important to note that if bowel obstruction is still suspected in patients with an equivocal X-ray, they may require further imaging in the form of …

Answer 29

It is important to note that if bowel obstruction is still suspected in patients with an equivocal X-ray, they may require further imaging in the form of computed tomography (CT).

Question 30

Computed tomography in bowel obstruction

Answer 30

CT imaging of the abdomen provides a more comprehensive assessment of the specific site, severity, underlying aetiology and complications in bowel obstruction. The additional benefit of CT imaging is that it helps to differentiate from the many other causes of acute abdominal pain, which present through the emergency department. The finer details of CT imaging in patients with bowel obstruction is beyond the scope of these notes.

Question 31

The … records and reviews emergency laparotomies and identifies ways in which practice can improve.

Answer 31

The National Emergency Laparotomy Audit records and reviews emergency laparotomies and identifies ways in which practice can improve.

Question 32

The NELA risk calculator can be used to give an estimate of a patient's…

Answer 32

The NELA risk calculator can be used to give an estimate of a patient's 30-day mortality. This also helps guide decisions such as the level of post-operative and the need for consultant anaesthetic support (though increasingly evidence shows the presence of a consultant anaesthetist and post-operative ITU/HDU care improves outcomes in all patient groups). Most importantly it helps us to explain risks of the operation to the patient and their family.

Question 33

….: this commonly used phrase refers to the administration of IV fluid (…) and the placement of an NG tube (…). The use of a nasogastric tube (with regular aspirations) helps decompress the stomach and prevent aspiration. Fluid resuscitation is essential due to the inability to maintain oral hydration and the large amount of third spacing that occurs in bowel obstruction.

Answer 33

‘Drip and suck’: this commonly used phrase refers to the administration of IV fluid (drip) and the placement of an NG tube (suck). The use of a nasogastric tube (with regular aspirations) helps decompress the stomach and prevent aspiration. Fluid resuscitation is essential due to the inability to maintain oral hydration and the large amount of third spacing that occurs in bowel obstruction.

Question 34

Other essential aspects in the management of patients with bowel obstruction include: (apart from ‘drip and suck’) - 6

Answer 34

Analgesia Urethral catheter and fluid balance monitoring Anti-emetics Antibiotics as needed Cardiac monitoring (esp. in patients with multiple co-morbidities due to the fluctuations in intravascular status) Correction of electrolytes

Question 35

Malignant obstruction: Surgical options (almost always via laparotomy) include defunctioning stoma and resection with primary …. Non-surgical options include endoscopic ... In non-surgical candidates this may represent the ‘definitive’ therapy, otherwise elective intervention should be planned.

Answer 35

Malignant obstruction: Surgical options (almost always via laparotomy) include defunctioning stoma and resection with primary anastomosis. Non-surgical options include endoscopic stenting. In non-surgical candidates this may represent the ‘definitive’ therapy, otherwise elective intervention should be planned.

Question 36

… stricture: Typically require surgical intervention (large bowel obstruction)

Answer 36

Benign stricture: Typically require surgical intervention.

Question 37

Volvulus: A sigmoid volvulus may resolve with a …

Answer 37

Volvulus: A sigmoid volvulus may resolve with a promptly placed flatus tube. Following this the patient should be considered for a definitive surgical procedure particularly if recurrent. Caecal volvulus more commonly requires immediate surgical intervention. Immediate surgical intervention is also indicated if there is evidence of perforation or ischaemia.

Question 38

Small bowel - Obstructing lesions/complications: An obstructing lesion, evidence of ischaemia or perforation, or a closed-loop are all indications for surgical management. Options include … and primary anastomosis or resection with a defunctioning …. Surgery may be laparoscopic or via a laparotomy.

Answer 38

Small bowel - Obstructing lesions/complications: An obstructing lesion, evidence of ischaemia or perforation, or a closed-loop are all indications for surgical management. Options include resection and primary anastomosis or resection with a defunctioning stoma. Surgery may be laparoscopic or via a laparotomy.

Question 39

Small bowel Uncomplicated adhesional obstruction: Most will trial conservative management, with early administration of an oral contrast agent (such as …). If the … passes to the colon, there is evidence of resolving obstruction, and the patient should be closely monitored. If there is deterioration or no resolution of the obstruction then surgical management with adhesiolysis (+/- bowel resection) is indicated.

Answer 39

Uncomplicated adhesional obstruction: Most will trial conservative management, with early administration of an oral contrast agent (such as gastrografin). If the gastrografin passes to the colon, there is evidence of resolving obstruction, and the patient should be closely monitored. If there is deterioration or no resolution of the obstruction then surgical management with adhesiolysis (+/- bowel resection) is indicated.

Question 40

Paralytic ileus management

Answer 40

Reversible causes should be considered and treated. Any electrolyte abnormality should be corrected and adequate IVF administered. NG tube decompression is often indicated. Exacerbating agents such as opiate analgesia should be reviewed. Commonly seen in the postoperative setting, it tends to settle with conservative management.

Question 41

Acute colonic pseudo-obstruction management

Answer 41

The treatment of ACPO involves the identification and treatment of any underlying cause. Neostigmine, a cholinesterase inhibitor, may be given to encourage motility. Endoscopic colonic decompression can be used in those failing to respond. Those at increasing risk of or who have developed complications (e.g. necrosis, perforation) will typically need surgical management if they are appropriate candidates.