Bowel obstruction Flashcards
Describe bowel obstruction?
- Mechanical impedance to the normal propulsive action through the intestine
- Once occluded, dilatation of the proximal bowel occurs
- This leads to secretion of large volumes of electrolyte-rich fluid into the bowel
- Can be mistaken for diarrhoea
What is a closed loop obstruction?
- If there is a second obstruction proximally
- eg volvulus or obstruction with a competent ileocaecal valve
- Surgical emergency as the bowel will continue to distend until the bowel wall becomes ischaemic and perforates
What is functional obstruction / paralytic ileus?
- When the bowel is not mechanically blocked but does not work properly
- eg inflammation, electrolyte derangement, recent surgery
What are the most common causes of obstruction in the small bowel?
- Adhesions
- Obstructed hernia
- Malignancy
What are the most common causes of obstruction in the large bowel?
- Colonic adenocarcinoma
- Diverticular disease
- Volvulus
How can causes of bowel obstruction be otherwise divided?
- Intraluminal
- Faecal concretion
- Intramural
- Colonic adenocarcinoma, crohns, diverticular strictures, volvulus
- Extramural
- Massive hernia, compression by tumour mass
Which cause of bowel obstruction are most commoon in children?
What cause of bowel obstruction is most common in people with crohns disease?
Intussusception
Inflammatory strictures
What are the cardinal clinical features of a bowel obstruction?
- Abdominal pain
- colicky or cramping, secondary to peristalsis, worse with movement
- Vomiting
- (less common with large bowel obstruction)
- Constipation
- Abdominal distension
Name some findings from examination that may be present in someone with bowel obstruction?
- Focal tenderness on palpation
- Guarding and rebound tenderness
- Tympanic sound of percussion
- Tinkling sounds on auscultation
Name some differentials for bowel obstruction?
- Paralytic ileus
- Toxic megacolon
- Constipation
Describe the investigations which should be performed for suspected bowel obstruction?
- FBC, CRP, U&Es, LFTs, Group and Save (G&S)
- Venous blood gas (high lactate may indicate ischaemia)
- CT with contrast of abdomen and pelvis
- Abdominal x-ray (AXR)
- Contrast fluoroscopy (in small bowel obstruction caused by adhesions from pervious surgery)
Why is CT imaging more useful than AXRs?
- More sensitive for bowel obstruction
- Can differentiate between mechnical and pseudo-obstruction
- Can demonstrate site and cause of obstruction
- May demonstrate the presence of metastases if caused by a malignancy
What are the AXR findings with someone who has a small bowel obstruction?
- Dilated bowel >3cm
- Central location
- Valvulae conniventes visible
- (lines completely crossing the bowel)
What are the AXR findings with someone who has a large bowel obstruction?
- Dilated bowel (>6cm, or >9cm if at the caecum)
- Peripheral location
- Haustral lines visible
- (lines not completely crossing the bowel)
Describe the management of bowel obstruction?
- Urgent fluid resuscitation
- Make patient nil by mouth
- Insert NG tube to decompress the bowel
- Analgesia + antiemetics
- SURGERY may be required
How should patients with an adhesional small bowel obstruction from a previous surgery be managed?
- Treated conservatively in the first instance
- Unless evidence of strangulation or ischaemia
- Obstruction in a patient who has not had previously surgery rarely settles without surgery
What should be done if a patient’s bowel obstruction does not resolve within 24 hours?
- A water soluble contrast study
- If contrast does not reach colon by 6 hours then it is unlikely to resolve without surgery
When is surgical intervention indicate in bowel obstruction?
- Suspicion of ischaemia or closed loop obstruction
- Small bowel obstruction in a patient with a virgin abdomen
- Cause that requires surgical correction
- (strangulated hernia or obstructing tumour)
- Patients fail to improve with conservative measures within >48 hours
Name some complications of bowel obstruction?
- Bowel ischaemia
- Bowel perforation, leading to faecal peritonitis
- Dehydration and renal impairment
Describe the digestive system components which receive blood from the Coeliac trunk? (T12)
- Coeliac trunk -> hepatic artery
- Hepatic artery -> gastroduodenal artery
- Gastroduodenal artery
- Blood to pylorus of the stomach and duodenum
Describe the components of the digestive system which are supplied by the SMA? (L1)
- Inferior pancreaticoduodenal artery supplies pancreas and distal duodenum
- Jejunal and ileal arteries supply their namesakes
- Ileocolic artery supplies terminal ileum, caecum and appendix
- Right colic artery supplies the ascending colon
- Middle colic artery supplies transverse colon
Describe the compoennts of the digestive system which are supplied by the ingerior mesenteric artery? (L3)
- Left colic artery supplies descending colon
- Sigmoid artery supplies the sigmoid colon
- Superior rectal artery supplies rectum to level of internal anal sphincter
What is pictured here?
- CT
- Large bowel obstruction
- Secondary to splenic flexure carcinoma
What is pictured here?
- AXR
- Large bowel obstruction
What is pictured here?
- AXR
- Small bowel obstruction
Describe a major differential diagnosis for bowel obstruction?
- Pseudo-obstruction
- Exact mechanism unclear
- Autonomic imbalance from decreased parasympathetic tone or excessive sympathetic output
Management of pseudo-obstruction?
- Stimulant enemas
- Colonoscopic deflation
Read the presentation of someone with large bowel obstruction
How can you differentiate between pseudo-obstruction and obstruction?
- Pseudo-obstruction has impressive abdominal distension with very little abdominal tenderness
- Contrast enema can exclude mechanical causes almost always
Differentials for small bowel obstruction?
- Ileus
- Less crampy abdominal pain
- CT shows passage of contrast throughout small bowel and into retum
- Large bowel obstruction
- Very distended abdomen
- X-ray shows dilated colon
Read the presentations of small bowel obstruction
