Bowel Obstruction Flashcards
What is bowel obstruction?
- Mechanical blockage of bowel
- Can present as acute abdomen
- Can be small bowe, large bowel or both
What occurs to fluid when bowel obstructed?
- 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
What is closed loop obstruction?
- 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
Most common causes of bowel obstruction
- SB - adhesions or hernia
- LB - malignancy, diverticular disease, volvulus
3 types of causes of BO
- Intraluminal
- Mural
- Extramural
Intraluminal causes of BO
- Gallstone ileus
- Ingested foreign body
- Faecal impaction
Mural causes of BO
- Cancer
- Strictures eg inflammatory from Crohns or Diverticular
- Intussusception - children
- Meckels diverticulum
- Lymphoma
Extramural causes of BO
- Hernias
- Adhesions
- Peritoneal mets
- Volvulus
Cardinal features of bowel obstruction
- 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
Examination findings of BO
- Signs of underlying cause eg scars, hernia
- Abdominal distension
- Assess fluid status - SIGNIFICANT 3rd spacing
- Focal tenderness - not rebound or guarding unless ischaemia occuring
Bedside and bloods for BO
- Urgent bloods - routine inc U&E - third spacing can derange
- Group and save
- VBG - evaulate for end organ damage (lactate) and metabolic derangement?
Imaging for BO
- CT scan + IV contrast of abdomen and pelvis
- Confirms presence and can show cause
- X-rays sometimes used
Findings on abdo x-ray of SBO
- Dilated bowel >3cm
- Central abdominal location
- Valvulae conniventes visible - complete lines crossing bowel
Abdo x-ray findings for LBO
- Dilated bowel >6cm or >9cm if caecum
- Peripheral location
- Haustral lines visible - not completely crossing bowel halfway haustra
Initial management
- IV fluids
- Make NBM
- NG tube placement - decompress
- Urinary catheter + fluid balance
- Analgesia as required + antiemetics
- Closed loop or evidence ischaemia = urgent surgery
What can be performed if BO does not resolve with initial conservative management?
- 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
When is surgery done for BO
- 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
Surgery for BO
- Depends on cause
- Lapartomy usually
- If resection needed, rejoining is often not possible so may need defunctioning stoma
Complications BO
- Ischaemia
- Perforation –> faecal peritonitis
- Intravascularly deplete –> AKI or end organ injury
SBO vs LBO
- SBO - early vomitting, late constipation, colicky pain every 3-4 mins due to peristalsis, improves with vomitting
- LBO - early constipation, late vomitting, continious pain
Causes of bowel obstruction (if there are no signs of peritonitis) which are mananged conservatively - one for SBO and LBO
- LBO - sigmoid volvulus - flexible sigmoidoscopy to decompress
- SBO - adhesions
