GI - Bowel Obstruction: Causes and investigations Flashcards Preview

Year 3- Surgery > GI - Bowel Obstruction: Causes and investigations > Flashcards

Flashcards in GI - Bowel Obstruction: Causes and investigations Deck (19)
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1
Q

What is bowel obstruction?

A

-Mechanical blockage of bowel -blockage of normal passage of intestinal contents

2
Q

-Aetiology - commonest causes

A
  • SBO: adhesions (60%) and herniae
  • LBO: colorectal neoplasia (60%), Diverticular disease (20%), volvulus (5%)
  • GI malignancy is primary LBO Dx until proved otherwise
3
Q

Presentation of BO 0- 4 cardinal features

A
  • Abdominal pain: colicky, central (but depends on gut region), constant/localised pain (suggests strangulation/ impending perf)
  • Distension: especially with lower obstruction
  • Vomiting: early in high obstruction vs late/absent in lower obstruction
  • Absolute constipation: flatus and faeces
4
Q

Pathophysiology

A
  • Bowel segment becomes occluded
  • Gross dilation of proximal limb = increased peristalsis of bowel
  • This leads to increased secretion of large vols of electrolyte rich fluid into bowel (3rd spacing)
  • *Urgent fluid resus/ and I/O moniting essential
  • Closed loop: 2nd obstruction proximally (eg ileocaecal valve competent) = surgical emergency as bowel will continue to distend, stretch bowel wall until ischaemic and perforates
5
Q

What should you say in differential Dx?

A
  • Paralytic ileus
  • Toxic megacolon
  • Constipation
6
Q

Other causes of BO: non mechanical

A

Non mechanical = paralytic ileus, which can occur as a result of:

  • post op
  • peritonitis
  • pancreatitis or any localised inflammation
  • poisons/drugs: anti AChM (eg TCAs)
  • pseudo-obstruction
  • Metabolic (low K+/Na/Mg/uraemia)
  • Mesenteric ischaemia
7
Q

Other causes of BO- mechanical - intra-luminal

A
  • Impacted matter: faeces, worms
  • untussusception
  • gallstones
8
Q

Other causes of BO- mechanical - intra-mural

A
  • Benign stricture (IBD, surgery, ischaemic colitis, diverticulitis, radiotherapy)
  • neoplasia
  • congenital atresia
9
Q

Other causes of BO- mechanical - extra-mural

A
  • Hernia
  • Adhesions
  • Volvulus
  • extrinsic compression (pseudocyst, abscess, haematoma, tumour, congenital bands)
10
Q

Examination: signs and cause

A
  • Raised HR: hypovolaemia and strangulation
  • Dehydration, hypovolaemia
  • Fever: suggests inflammatory disease or strangulation
  • Surgical scars: possible source of strictures
  • hernias: check all
  • mass: neoplastic or inflammatory
  • bowel sounds: increased (mechanical obstruction) vs decreased (ileus)
  • PR: empty rectum, rectal mass, hard impacted stool, blood from higher pathology
11
Q

Ix- lab tests

A
  • Bloods: FBC (raised WCC), U&Es (dehydration/electrolyte abnormalities), amylase (raised in strangulation/perforation), ABG (raised lactate in strangulation)
  • *Remember to do group and save as may need surgery
12
Q

Ix- imaging and others

A
  • CT: modality of choice in suspected BO
  • AXR
  • CXR (erect for gas)
  • Contrast fluoroscopy: useful in SBO caused by adhesions from previous surgery
13
Q

Ix- imaging: AXR specifics

A
  • SBO: dilated bowel (>3cm), central abdominal location, valvulate conniventes (lines completely crossing bowel) are visible
  • LBO: dilated bowel (<6cm or >9cm if at caecum), peripheral location, haustral lines (lines not completely crossing bowel) visible
14
Q

Mx- conservative

A
  • Resus: NBM, IV fluids, catheter and I/O, NGT (decompresses upper GIT, stops vomiting and presents aspiration)
  • Adhesions in SB: resolve with conservative Rx (if not ischaemic/strangulated) in 80% of cases - perform water soluble contract study - if it doesn’t reach colon by 6h then unlike to resolve alone and pt needs surgical intervention.
  • Pt with SBO/LBO who has not had previous surgery - rarely settles without surgery
15
Q

Mx- Therapy

A
  • Analgesia: may need strong opioid
  • ABX: ceftriaxone + metronidazole if strangulation/perforation
  • Gastrograffin study: oral or via NGT
  • Consider need for parenteral nutrition
16
Q

What signs can indicate resolution of obstruction?

A
  • Reducing pain
  • Reducing NGT aspirate volumes
  • Passage of flatus
  • Resolution of signs on repeat xray
17
Q

Mx- Surgical indications

A
  • Closed loop obstruction (caecum >10cm)
  • Obstructing neoplasm
  • Strangulation/perforation
  • failure of concervative Mx (up to 72h)
18
Q

Mx - Surgical principals

A
  • Aim to treat cause
  • typically involves resection of obstructing lesion
  • if unresectable, pt may be offered bypass solution
  • colon not been cleansed before surgery t/f most surgeons do proximal ostomy post-resection
  • endoscopically placed expanding metal stents offer palliation or a bridge to surgery allowing optimisaation
19
Q

Mx - Surgery options

A
  • **Must consent pt for possible resection and possible stoma
  • SBO: adhesiolysis
  • LBO: Hartmann’s, colectomy (plus primary anastomosis), palliative bypass procedure, caecostomy, transverse loop colostomy or loop ileostomy

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