Bowel obstruction

Question 1

what is bowel obstruction?

Answer 1

mechanical blockage of the bowel

Question 2

what is functional bowel obstruction? what else is it known as?

Answer 2

bowel is not mechanically blocked but does not work properly, for example due to inflammation, electrolyte derangement or recent surgery.
a.k.a paralytic ileus

Question 3

what are the most common causes of small bowel obstruction?

Answer 3

adhesions

herniae

Question 4

what are the most common causes of large bowel obstruction?

Answer 4

malignancy - this until proven otherwise
diverticular disease
volvulus

Question 5

describe the pathophysiology of third spacing in bowel obstruction

Answer 5

• Bowel segment becomes occluded
‣ Causes gross dilatation of the proximal limb of bowel
‣ Causes increased peristalsis of the bowel
‣ Leads to secretion of large volumes of electrolyte-rich fluid into the lumen

Question 6

what is needed in the management of bowel obstruction due to third spacing?

Answer 6

urgent fluid resuscitation and close attention to fluid balance

Question 7

what is a ‘closed-loop’ obstruction?

Answer 7

if there are two bowel obstructions, one distal to the other, e.g. due to a twist in the bowel or in the large bowel if the ileocaecal valve is competent

Question 8

what is the complication of a closed-loop obstruction?

Answer 8

the bowel will continue to distend, stretching it until it becomes ischaemic and perforates
** surgical emergency

Question 9

what are the possible features of bowel obstruction in a patient’s history?

Answer 9

• abdominal pain (colicky or cramping) due to bowel peristalsis
• vomiting -> gastric, then bilious, then faeculent
• abdominal distension
• absolute constipation (wind and faeces)

Question 10

what is a red flag sign with the pain that is experienced in bowel obstruction?

Answer 10

any pain that is originally colicky in nature that is now constant or worse on movement is a sign that ischaemia is developing

Question 11

what are the clinical signs of intestinal obstruction?

Answer 11

• abdominal distension
• possible underlying cause, such as surgical scars, cachexia from malignancy or hernia
• focal and rebound tenderness -> indicates ischaemia
• on percussion, tympanic sounds
• on auscultation, tinkling bowel sounds

Question 12

what are the differential diagnoses for intestinal obstruction?

Answer 12

paralytic ileus
toxic megacolon
constipation

Question 13

what investigations are done when suspecting bowel obstruction?

Answer 13

• laboratory tests (FBC, U&Es, CRP, lactate and group and save)
• CT imaging
• abdominal Xray (CT used more now)

Question 14

why is CT imaging a good modality for bowel obstruction?

Answer 14

• more sensitive
• can differentiate between mechanical obstruction and pseudo-obstruction
• can demonstrate the site and cause of obstruction
• may show metastases

Question 15

what can be seen on an abdominal XRay in small bowel obstruction?

Answer 15

• dilated bowel (>3cm)
• central abdominal location
• valvulae conniventes visible (lines completely crossing the bowel)

Question 16

what can be seen on an abdominal X-ray in large bowel obstruction?

Answer 16

• dilated bowel (>6 cm)
• peripheral location
• haustral lines visible (indents go halfway there)

Question 17

what are the signs of bowel ischaemia?

Answer 17

• pain worsened by movement
• focal tenderness (rebound and guarding)
• pyrexia

Question 18

briefly describe the management of bowel obstruction

Answer 18

• • urgent fluid resuscitation and careful attention to fluid balance
• if no signs of ischaemia or strangulation, initial management is conservative
• patient with closed loop bowel obstruction or evidence of ischaemia require urgent surgery

Question 19

what is the conservative management of bowel obstruction?

Answer 19

• Nil-by-mouth
• nasogastric tube to decompress the bowel
• start IV fluids and correct electrolyte imbalances
• urinary catheter and fluid balance
• analgesia and anti-emetics

Question 20

how is adhesional small bowel obstruction treated usually?

Answer 20

conservatively - usually resolves this way

Question 21

what is the surgical management of bowel obstruction?

Answer 21

nature if the management depends on the underlying cause but usually involves laparotomy
if resection is necessary, the bowel ends can be re-joined or a stoma may be necessary

Question 22

when is surgical management needed for bowel obstruction?

Answer 22

• suspicion of intestinal ischaemia
• closed loop bowel obstruction
• small bowel obstruction in a virgin abdomen (no surgery)
• cause that requires surgical correction (e.g. strangulated hernia or obstructing tumour)
• patient fails to improve on conservative methods (after >48 hours)

Question 23

what are the complications of bowle obstruction?

Answer 23

• bowel ischaemia
• bowel perforation-> faecal peritonitis
• dehydration and renal impairment due to 3rd spacing

Question 24

what is volvulus?

Answer 24

torsion of the bowel

- twisting of a loop of intestine around its mesenteric attachment, resulting in a closed loop bowel obstruction

Question 25

where does a volvulus most commonly occur?

Answer 25

sigmoid colon

Question 26

why is this part of the intestine most commonly affected by volvulus?

Answer 26

because the sigmoid colon has a long mesentery so is prone to twisting around it

Question 27

what are the risk factors fo volvulus?

Answer 27

• Neuropsychiatric disorders
• Advanced age
• Male gender
• Constipation or laxative use
• Previous abdominal surgery
• Diabetes mellitus

Question 28

what are the clinical features of a volvulus?

Answer 28

features of bowel obstruction

Question 29

which investigations are carried out when suspecting volvulus?

Answer 29

same as for bwoel obstruction

Question 30

what is seen on an abdominal Xray when there is a volvulus?

Answer 30

coffee-bean sign