What is small bowel obstruction?
mechanical disruption of the small bowel, resulting in bilious or faeculent vomiting, abdominal pain and distension as well as complete constipation
What is the most common causes of small bowel obstruction in the western world?
adhesions
What are 3 groups of causes of small bowel obstruction?
- Factors outside of the bowel
- Factors relating to the bowel wall
- Factors relating to inside the bowel
What are 2 examples of factors outside the bowel that can cause small bowel obstruction?
- Adhesions
- Intra-abdominal hernia: incarcerated hernias cause acute obstruction
What is the main risk factor for development of adhesions?
previous intra-abdominal operations - the larger the operation, the more likely the development of adhesions
What are 2 causes of small bowel obstruction relating to the bowel wall?
- Crohn’s disease
- Appendicitis
What are 3 causes of small bowel obstruction relating to the inside of the bowel?
- Malignancy
- Foreign body ingestion
- Gallstone ileus
What are 4 examples of diseases causing small bowel obstruction in children?
- Intussusception
- Volvulus
- Intestinal atresia
- Appendicitis
What are 6 key features that small bowel obstruction commonly presents with?
- Abdominal pain with distension (initially colicky pain that becomes continuous)
- Bloating and vomiting (often bilious)
- Failure to pass flatus or stool
- History of abdominal / gynaecological surgery or hernia
- Tympanic, high-pitched bowel sounds on examination (tinkling)
- Empty rectum on examination in complete bowel obstruction
What is the nature of the abdominal pain in small bowel obstruction?
initially colicky, becomes continuous
What is often the nature of vomiting in small bowel obstruction?
often bilious
What is likely to be present in the history of someone with small bowel obstruction?
abdominal/gynaecological surgery or hernia
What are 4 things that may be present on examination in small bowel obstruction?
- Tympanic, high-pitched bowel sounds on auscultation
- Empty rectum on PR if complete bowel obstruction
- May have a fever
- May be significantly fluid depleted
What complication can severe small bowel obstruction lead to?
peritonitis
can lead to ischaemic or necrotic bowel as well as perforation
What is likely to happen to passage of stool/flatus in small bowel obstruction?
simple or partial small bowel obstruction will generally continue to pass some flatus/stool with a mild temperature
What are the initial investigations to perform in a patient with SBO who may have peritonitis? 3 key things
- Basic blood tests: FBC, U+Es, lactate, amylase
- Abdominal x-ray
- Chest x-ray
What are 4 blood tests that should be performed as part of the initial assessment in small bowel obstruction and what is the reason behind each?
- FBC: looking for leucocytosis or anaemia
- U+Es: organ dysfunction or signs of hypovolaemia
- Lactate: to establish if bowel ischaemia/necrosis
- Amylase: for all cases of acute abdomen
Why should an AXR be performed as part of the initial investigations for small bowel obstruction?
look for absence of air in rectum - can indicate complete obstruction
Why should an CXR be performed as part of the initial investigations for small bowel obstruction?
upright position to look for pneumoperitoneum
Once a patient with small bowel obstruction has been stabilised, what are 5 types of investigation to perform?
- CT abdomen and pelvis
- Small bowel contrast study using gastrograffin
- MRI abdomen - instead of CT in young patients (radiation)
- US abdomen - children
- Diagnostic laparotomy/laparoscopy
What is the best diagnostic test in small bowel obstruction, to perform once the patient is stabilised?
CT abdomen and pelvis
What are 3 benefits of performing CT-AP in patients with small bowel obstruction?
- Establishes underlying cause
- Establishes site of obstruction
- Establishes partial vs. complete obstruction
What are 2 advantages to performing a small bowel contrast study with gastrograffin in small bowel obstruction?
- Can be used a therapeutic measurement in partial SBO
- Presence of contrast in rectum 24h after ingestion of substance establishes resolving partial SBO - hence reducing need for surgery
How is the contrast agent gastrograffin thought to play a therapeutic role in early small bowel obstruction?
moves water into the small bowel lumen, thus diluting the bowel contents, decreasing bowel wall oedema, and enhancing smooth muscle contractility
What is the use for diagnostic laparotomy/ laparoscopy as an investigation in small bowel obstruction?
used to distinguish between partial and complete obstruction if no clear evidence on imaging
What are 4 aspects of the management of small bowel obstruction?
- Initially resuscitation protocols: ABCDE
- Correction of fluid and electrolytes to reduce operative risk before surgery for obstruction
- Fluid resuscitation and NG tube to aspirate content for decompression (‘Drip and suck’)
- Surgery if conservative measures fail
What is the purpose of drip and suck in the management of small bowel obstruction?
for decompression
What are 4 types of surgery which may be performed to manage small bowel obstruction?
- Adhesionolysis
- Bowel resection
- Closure of hernias
- Tumour resection
What is the second most common cause of small bowel obstruction following intra-abdominal adhesions?
hernias
What is an abdominal film likely to show in small bowel obstruction?
small bowel loops with fluid levels
may show rectum with no air if complete obstruction