Intestinal obstruction & ileus (GI) Flashcards
Define bowel obstruction.
Interruption of normal passage of bowel contents through the bowel, either due to a functional or mechanical obstruction
Define functional bowel obstruction (paralytic ileus).
Temporary disturbance of peristalsis - common complication after bowel surgery
Define mechanical bowel obstruction.
Due to a structural barrier e.g. tumour or adhesions
Can be classified as SBO (80%) or LBO (20%)
What are some causes of a small bowel obstruction? (6)
- adhesions (from previous abdominal surgery) - most common
- incarcerated hernias (e.g. inguinal)
- gallstones (gallstone ileus)
- Crohn’s disease (inflammatory phlegmon causes obstruction)
- intestinal malignancy
- appendicitis
What are some causes of a large bowel obstruction? (3)
- malignant tumours e.g. colorectal carcinoma
- diverticular disease (strictures)
- sigmoid/caecal volvulus (360 degree twist –> closed loop obstruction –> ischaemia and necrosis)
How can bowel obstruction be classified (based on bowel wall)? (3)
- intraluminal - faecal impaction, gallstone ileus, ingested foreign body
- mural - Crohn’s disease, tumours, diverticulitis, inflammatory strictures, intussusception, lymphoma, Meckel’s diverticulum
- extramural - strangulated hernia, volvulus, adhesions, peritoneal metastasis
What type of bowel obstruction is common after surgery?
Functional bowel obstruction (paralytic ileus) - temporary disturbance of peristalsis
What causes colicky abdominal pain and vomiting in bowel obstruction?
Resulting proximal dilatation of intestine + peristalsis
What causes constipation (and diarrhoea) in bowel obstruction?
Distal interruption of faecal flow –> constipation, hyperperistalsis distal to obstruction –> diarrhoea
What are both small and large bowel obstructions?
Medical emergencies
LBO = surgical emergency
What should we consider in all patients who present with large bowel obstruction?
Malignancy
What are the cardinal clinical features of mechanical bowel obstruction? (5)
- colicky abdominal pain
- vomiting
- constipation (may be absolute - failure to pass flatus or stool)
- abdominal distension - worse in LBO vs SBO
- decreased bowel sounds (may be tympanic/high-pitched)
What signs are specific to small bowel obstruction? (2)
- early onset bilious vomiting
- tinkling bowel sounds (more common in early bowel obstruction)
What signs are specific to large bowel obstruction? (3)
- late onset vomiting - may progress to faecal vomiting
- absolute constipation (and earlier) - not passing wind/faeces
- very distended abdomen
What may there be a history of in large bowel obstruction?
Possible malignant symptoms like change in bowel habit, weight loss, rectal bleeding
What signs of peritonitis might there be in bowel obstruction? (6)
- localised or generalised guarding
- fever
- leukocytosis
- tachycardia
- metabolic acidosis
- continuous pain
When would symptoms from adhesions vs post-operative ileus present?
- adhesions - no symptoms until months/years after surgery
- post-operative ileus - may occur sooner
What is the main clinical difference between paralytic ileus and mechanical bowel obstruction?
- paralytic ileus (post-operative ileus) - complete absence of bowel sounds
- mechanical bowel obstruction - tinkling bowel sounds
What might DRE show in bowel obstruction?
Hard faeces on DRE - faecal impaction or empty rectum in proximal bowel obstruction
What are some risk factors for bowel obstruction? (5+3+2)
- adhesions
- incarcerated hernia
- gallstone ileus
- Crohn’s disease (also increased CRC risk)
- appendicitis
- malignancy - colorectal cancer
- diverticular disease
- volvulus
- malrotation (–> midgut volvulus –> necrosis and death)
- intussusception - ‘pinched off’ intestine
What is the gold standard diagnostic investigation for bowel obstruction?
CTAP with IV contrast - definitive Ix that helps establish cause, order ASAP
When is CTAP with IV contrast contraindicated?
Contrast agents contraindicated in AKI
What is the first-line investigation for bowel obstruction if patient is haemodynamically unstable?
Erect AXR
What does imaging show in small bowel obstruction?
Central finding, distended bowel in middle of abdomen with valvulae conniventes going all the way across
What does imaging show in large bowel obstruction?
Peripheral finding, distended bowel around outside of abdomen with haustra (do NOT go all the way across, only halfway)
What would imaging show in sigmoid volvulus (LBO)?
Coffee bean sign
What is the 3,6,9 rule in bowel obstruction?
Upper limits:
- small bowel: 3cm
- large bowel: 6cm
- caecum: 9cm
What do we monitor after surgery for post-operative paralytic ileus?
U&Es (deranged electrolytes can contribute to development of postoperative ileus so check K, Mg and PO4)
What other scan can we do in bowel obstruction?
Erect CXR to look for perforation (pneumoperitoneum)
What do we check in U&Es due to vomiting from bowel obstruction?
Hyponatraemia and hypokalaemic metabolic alkalosis
What bloods do we do in bowel obstruction to check for bowel ischaemia? (3)
- elevated lactate and metabolic acidosis
- leukocytosis
- amylase can be raised in SBO (not just pancreatitis)
What are some differential diagnoses for bowel obstruction? (11)
- SBO - colicky central pain, early onset bilious vomiting, late onset constipation
- LBO - colicky/constant pain, late onset bilious/faecal vomiting, very distended abdomen, constipation –> absolute constipation
- paralytic ileus - less cramping, often post-operative (/systemic infection/meds)
- infectious gastroenteritis - D&V
- intestinal pseudo-obstruction - chronic, constipation, neurological meds e.g. amitriptyline
- acute colonic pseudo-obstruction - distension w/o tenderness
- acute appendicitis - RLQ pain, N&V
- acute pancreatitis - epigastric pain –> back, vomiting, amylase&lipase
- toxic megacolon - initial colitis, sepsis, thumbprinting on AXR
- pseudomembranous colitis - Abx/immunosuppressant, foul-smelling diarrhoea
- endometriosis
When is thumbprinting seen on AXR?
Toxic megacolon
What do we do first when approaching bowel obstruction management?
ABCDE approach
What is the initial management for bowel obstruction? (5)
- NBM
- IV fluid resuscitation
- electrolyte replacement
- NG tube - decompression of bowel, prevents aspiration of vomit
- supportive care: analgesia (morphine) + anti-emetics
How can we remember the first-line medical management of small bowel obstruction?
‘Drip and suck’ - IV fluids and gastric decompression (NG tube)
What can we give for bowel obstruction patients not fit for surgery?
Gastrograffin
What definitive treatment is there for bowel obstruction?
Surgery (laparotomy) if complicated bowel obstruction (i.e. strangulation or ischaemic bowel signs)
What medication should we avoid in those with bowel obstruction?
Metoclopramide
When is laparoscopic surgery contraindicated in bowel obstruction?
Acute intestinal obstruction with dilated bowel loops
When is emergency surgery indicated in bowel obstruction?
Those with adhesional obstruction/signs of peritonitis, hernia strangulation, bowel ischaemia or perforation
Surgery type depends on cause
How do we manage volvulus (bowel obstruction)?
Flexible sigmoidoscopy
What can small bowel obstruction quickly lead to?
Peritonitis
What are some complications of bowel obstruction? (7)
- bowel ischaemia (–> necrosis)
- bowel perforation (secondary to necrosis)
- peritonitis
- sepsis
- intra-abdominal abscess
- short bowel syndrome (need supplemental nutrition)
- death
Describe the prognosis of bowel obstruction.
High risk of recurrence, mortality rate high in complicated bowel obstruction
