Bowel Obstruction

Question 1

What is bowel obstruction?

Answer 1

• Mechanical blockage of bowel
• Can present as acute abdomen
• Can be small bowe, large bowel or both

Question 2

What occurs to fluid when bowel obstructed?

Answer 2

• Gross dilation of proximal segment
• Increased peristalsis
• = secretion of large volumes of electrolyte rich fluid into bowel (third spacing)
• Can have deficit of up to 10L inc normal maintenance fluids = VERY HIGH RISK OF SHOCK

Question 3

What is closed loop obstruction?

Answer 3

• If there is a second obstructing point proximally eg competent ileocaecal valve in LBO
• = closed loop
• Surgical emergency as if not corrected bowel will continue to distend, stretching until becomes ischaemic and can then perforate

Question 4

Most common causes of bowel obstruction

Answer 4

• SB - adhesions or hernia
• LB - malignancy, diverticular disease, volvulus

Question 5

3 types of causes of BO

Answer 5

• Intraluminal
• Mural
• Extramural

Question 6

Intraluminal causes of BO

Answer 6

• Gallstone ileus
• Ingested foreign body
• Faecal impaction

Question 7

Mural causes of BO

Answer 7

• Cancer
• Strictures eg inflammatory from Crohns or Diverticular
• Intussusception - children
• Meckels diverticulum
• Lymphoma

Question 8

Extramural causes of BO

Answer 8

• Hernias
• Adhesions
• Peritoneal mets
• Volvulus

Question 9

Cardinal features of bowel obstruction

Answer 9

• Abdominal pain - colicky or cramping (from peristalsis)
• Vomitting - early in proximal and late in distal
• Abdominal distension
• Absolute constipation - early in distal, late in proximal

Question 10

Examination findings of BO

Answer 10

• Signs of underlying cause eg scars, hernia
• Abdominal distension
• Assess fluid status - SIGNIFICANT 3rd spacing
• Focal tenderness - not rebound or guarding unless ischaemia occuring

Question 11

Bedside and bloods for BO

Answer 11

• Urgent bloods - routine inc U&E - third spacing can derange
• Group and save
• VBG - evaulate for end organ damage (lactate) and metabolic derangement?

Question 12

Imaging for BO

Answer 12

• CT scan + IV contrast of abdomen and pelvis
• Confirms presence and can show cause
• X-rays sometimes used

Question 13

Findings on abdo x-ray of SBO

Answer 13

• Dilated bowel >3cm
• Central abdominal location
• Valvulae conniventes visible - complete lines crossing bowel

Question 14

Abdo x-ray findings for LBO

Answer 14

• Dilated bowel >6cm or >9cm if caecum
• Peripheral location
• Haustral lines visible - not completely crossing bowel halfway haustra

Question 15

Initial management

Answer 15

• IV fluids
• Make NBM
• NG tube placement - decompress
• Urinary catheter + fluid balance
• Analgesia as required + antiemetics
• Closed loop or evidence ischaemia = urgent surgery

Question 16

What can be performed if BO does not resolve with initial conservative management?

Answer 16

• Water soluble contrast study (eg Gastrograffin)
• Abdo X-ray 6hrs after oral contrast
• Check to see if ongoing obstruction vs resolution - if contrast passess distal to obstruct = good

Gastrograffin can also have osmotic effect on bowel wall oedema and be therapeutic but evidence not quite there

Question 17

When is surgery done for BO

Answer 17

• Intestinal ischaemia
• Or closed loop bowel obstruction
• Or cause that requires surgical correction eg strangulated hernia
• Or if patients fail to improve with conservative management after 48hrs

Question 18

Surgery for BO

Answer 18

• Depends on cause
• Lapartomy usually
• If resection needed, rejoining is often not possible so may need defunctioning stoma

Question 19

Complications BO

Answer 19

• Ischaemia
• Perforation –> faecal peritonitis
• Intravascularly deplete –> AKI or end organ injury

Question 20

SBO vs LBO

Answer 20

• SBO - early vomitting, late constipation, colicky pain every 3-4 mins due to peristalsis, improves with vomitting
• LBO - early constipation, late vomitting, continious pain

Question 21

Causes of bowel obstruction (if there are no signs of peritonitis) which are mananged conservatively - one for SBO and LBO

Answer 21

• LBO - sigmoid volvulus - flexible sigmoidoscopy to decompress
• SBO - adhesions