Bowel Obstruction

Question 1

What are the most common causes of small bowel obstruction?

Answer 1

Adhesions

Hernias

Question 2

What are the most common causes of large bowel obstruction?

Answer 2

Malignancy
Diverticular disease
Volvulus
Constipation

Question 3

How can causes of bowel obstruction be divided?

Answer 3

Intraluminal, mural, extramural

Question 4

What are intraluminal, mural and extramural causes of bowel obstruction?

Answer 4

Gallstone ileus, ingested foreign body, faecal impaction

Caricnoma, inflammatory stricture, intususception (inversion of one portion of bowel in to another - in children), diverticular strictures, Meckel’s diverticulum, lymphoma

Hernias, adhesions, peritoneal metastasis, volvulus

Question 5

What is the pathophysiological process in bowel obstruction?

Answer 5

Once the bowel segment becomes occluded, there is gross dilatation of the proximal limb of the bowel, which in turn results in increased peristalsis of the bowel. This leads to secretion of large volumes of electrolyte rich fluid into the bowel - urgent fluid resuscitation and close attention to fluid balance is essential.

If there is a 2nd obstruction proximally (as occurs if the obstruction is due to a twist in the bowel) this is a closed-loop obstruction. The bowel will continue to distend, stretching the bowel wall until it becomes ischaemic and perforates.

Question 6

What are the cardinals features of bowel obstruction?

Answer 6

Vomiting - gastric contents, before becoming bilious and eventually faeculent

Abdominal pain: colicky or cramping in nature - if becomes constant, red flag for ischaemia

Absolute constipation - no faces or flatus passed - in distal obstruction, later in proximal obstruction

Abdominal distension - increases as the obstruction progresses with tinkling bowel sounds, tympanic sound on percussion

Question 7

What does focal tenderness indicated? What test should you do?

Answer 7

Ischaemia
(guarding and rebound tenderness)
Serum lactate is raised

Question 8

What are some differential diadnoses for bowel obstruction?

Answer 8

Paralytic ileus
Toxic megacolon
Contipation
Adhesions
Hernia
Malignancy
Diverticular stricture
Volvulus

Question 9

What investigations for bowel obstruction?

Answer 9

FBC< CRP, U&E, G&S VBG - for ischaemic bowel (high lactate and for dehydration due to vomiting)

CT imaging
AXR

Question 10

How to differentiate functional from mechanical bowel obstruction on examination?

Answer 10

Mechanical - tinkling bowel sounds

Functional - absent bowel sounds

Question 11

What are the differences between small bowel obstruction and large bowel obstruction on AXR?

Answer 11

Small bowel obstruction:
Dilated bowel > 3cm
Central abdominal location
Valvulae conniventes visible (lines completely crossing the bowel)

Large bowel obstruction:
Dilated bowel (>6cm) or >9cm at the caecumPeripheral gas shadow location
Haustral lines visible - lines not completely crossing the bowel (HALFWAY HAUSTRA)

Question 12

What is sigmoid volvulus? What does sigmoid volvulus look like on AXR? Management?

Answer 12

Bowel twists on its mesentery which can produce severe rapid strangulated obstruction - closed loop.
Occurs in elderly, constipated.

Inverted U loop of bowel showing coffee bean sign

Managed by insertion of flatus tube or sigmoidoscopy. Sigmoid colectomy is sometimes required

Question 13

Describe management of bowel obstruction

Answer 13

note: urgent surgery if evidence of ischaemia

Conservative: drip and suck
NBM
NG tube to decompress bowel (suck)
Start IV fluids and correct electrolyte disturbance (drip)
URinary catheter and fluid balance
Analgesia with suitable anti-emetics

Surgical:
Indicated if:
Suspicion of intestinal ischaemia or closed loop bowel obstruction
Small bowel obstruction in patient with virgin abdomen (no previous surgery)
Cause that requires surgery - strangulated hernia or obstructing tumour)
Conservative management fails after 48 hours

Usually laparotomy
If resection of bowel is required and rejoining of obstruct bowel is not possible, stoma may be necessary

Question 14

What are the complications of bowel obstruction?

Answer 14

Bowel ischaemia
Bowel perforation –> faecal peritonitis
Dehydration and renal impairment

Question 15

Difference between paralytic ileus and pseudo-obstruction?

Answer 15

Paralytic ileus is dynamic bwoel due to absence of normal peristaltic contractions
Abdo srugery, pancreatitis, spinal injury, hypokalaemia, hyponatraemia, uraemia, peritonitis and drugs can cause

Pseudo-Obstruction resembles mechanical obstruction with no obstructing lesion.