GI - Bowel Obstruction: Causes and investigations Flashcards
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
