Appendicitis and Small bowel obstruction

Question 1

Pathophysiology of appendicitis

Answer 1

Appendicitis describes acute inflamation and bacterial infection of the appendix. This occurs due to luminal obstruction by a faecolith (hard mass of stool), foreign body, lymphoid hyperplasia of Peyer’s patches, or fibrous strictures.

Question 2

The veriform appendix may occupy a variety of positions in relation to the caecum, which are the most common?

Answer 2

Most commonly the descending intraperitoneal or retrocaecal position

Question 3

Mechanisms of pain in appendicitis:

Answer 3

• Peri-umbilical pain: inflammation fo the appendix and visceral peritoneum irritates autonomic nerves of the embryological midgut resulting in referred pain to the umbilical region
• Right iliac fossa pain: due to localised inflammation of the parietal peritoneum

Question 4

Appendicitis is the most common acute abdomen condition in the UK requiring surgery. What are the risk factors?

Answer 4

• Young age (the highest incidence is between 10-20 years of age)
• Male
• Frequent antibiotic use (causes an imbalance in gut flora and a modified response to subsequent infection which may trigger appendicitis)
• Smoking

Question 5

Classic history in appendicitis

Answer 5

• Periumbilical pain which migrates to the right iliac fossa (McBurney’s point)
• Low grade fever
• Anorexia

Question 6

Where is McBurney’s point?

Answer 6

1/3 of the way from the anterior superior iliac spine to the umbilicus

Question 7

Signs for appendicitis:

Answer 7

• Right iliac foss tenderness (suggests localised peritonism)
• Tachycardia, hypotension and generalised peritonism (suggests perforation)
• Rovsing’s sign: pain in the right iliac fossa is worsened by pressing on the left iliac fossa; now thought to be of limited diagnostic value
• Psoas sign: pain is worsened by extending the hip
• Obturator sign: pain is worsened by flexing and internally rotating the hip

Question 8

Which score is used to predict the likelihood of appendicitis?

Answer 8

Alvarado score (a score of 7 or more)

Question 9

Primary investigation for appendicitis:

Answer 9

• FBC: leukocytosis and neutrophila is seen in up to 90% of patients
• CRP: raised due to inflammation
• U&Es: acute kidney injury in dehydration secondary to vomiting
• Group & save: important prior to surgical intervention
• Urinalysis: to exclude renal colic, a UTI or pregnancy; in appendicitis, there may be a mild leukocytosis without nitrates

Question 10

Imaging investigations in appendicitis

Answer 10

• CT abdomen/pelvis with contrast: 95% sensitivity and specificity
• Abdominal ultrasound: preferred in children, pregnancy and breastfeeding women; however the appendix can often not be visualised
• MRI abdomen/pelvis: mainly reserved for pregnant women when ultrasound is non-diagnostic

Question 11

Initial management of appendicitis:

Answer 11

• Fluids (due to fluid losses as well as being nil by mouth prior to surgery)
• Analgesia (patients can be in considerable pain)
• Antiemetics (eg ondansetron)
• Preoperative antibiotics (prophylactic antibiotics associated with reduced wound infection eg ceftriaxome and metronidazole)

Question 12

Definitive management of appendicitis:

Answer 12

• Prompt laparoscopic appendectomy
• Post oeratative antibiotis usually given for 24 hours

Question 13

Pathophysiology of perforation in appendicitis

Answer 13

Inflammation, reduced vascular supply, distension, and tissue death, may result in perforation.

This can result in peritonitis, profound sepsis, and death.

Question 14

What is small bowel obstruction?

Answer 14

Small bowel obstruction is a mechanical or functional obstruction of the small intestine that prevents the normal passage of digestive contents.

Question 15

Describe the pathophysiology behind the symptoms seen in a mechanical small bowel obstruction:

Answer 15

When peristalsis occurs against a mechanical obstruction, this results in the characteristic symptoms of abdominal pain, distension, and absolute constipation.

Dilation of the proximal bowel leads to compression of meseteric vessels. This results in transudation of large volumes of electrolyte-rich fluid into the bowel.

As arterial supply is compromised, bowel ischamia occurs with risk of perforation and subsequent faecal peritonitis and sepsis.

Question 16

Causes of mechanical small bowel obstruction

Answer 16

• Bowel adhesions: (most common cause) occurs due to previous abdominal surgery
• Incarcerated hernia: most commonly femoral and inguinal hernias
• Crohn’s disease: due to stricture formation
• Volvulus: a rare cause of SBO; commonly causes large bowel obstruction
• Intussusception: more common in children

Question 17

Causes of function small bowel obstruction

Answer 17

• Paralytic ileus: due to failure of peristalsis
  
  • occurs post abdominal surgery
  • can occur due to electrolyte imbalances, particularly hypokalaemia

Question 18

Symptoms of small bowel obstruction

Answer 18

• Colicky, central or generalised abdominal pain
• Nausea and vomiting: early symptom
• Abdominal distension
• Absolute constipation: no passing of faeces or flatus; a late symptoms is SBO

Question 19

Signs of small bowel obstruction

Answer 19

• Abdominal tenderness and distension
• Tinkling bowel sounds (absent bowel sounds may be present in paralytic ileus)
• Rectal examination:
  
  • rectum may be empty
  • blood suggests strangulation and ischamaemia
• Tachycardia and hypotension:
  
  • third spacing of fluid
  • significant hypotension may indicate ischameia, perforation or sepsis

Question 20

Primary investigations for small bowel obstruction

Answer 20

• Bloods:
  
  • FBC: elevated white cell count with neutrophilia
  • U&Es: assess for pre-renal acute kidney injury secondary to hypovolaemia, additionally hypokalaemai is a cause of ileus
  • CRP: raised as part of the general inflammatory response
  • Group and save: patients may go for surgery and require blood products
  • Venous blood gas: to assess the degree of metabolic acidosis and lactate level, which may be suggestive of bowel ischameia
• Abdominal X-ray:
  
  • Reveals dilated small bowel loops (>3cm) with fluid levels
• CT abdomen and pelvis with contrast:
  
  • Gold standard, can identify dilated loops of bowel, evidence of ischamia and peroration, as well as the underlying cause

Question 21

Initial conservative management of small bowel obstruction

Answer 21

• IV resuscitation: ‘third space’ fluid in the lumen of the bowel segment proximal to the obstruction results in hypovolaemia
• Nasogastric tube: for abdominal decompression
• IV antibiotics: broad spectrum antibiotics if going for surgery to prevent wound infection, eg cefotaxime and metronidazole
• Analgesia and anti-emetics

Question 22

Other non-surgical management of small bowel obstruction:

Answer 22

• Gastrograffin: as well as being diagnostic, evidence suggests that oral gastrograffin (eg 100ml with repeat abdominal X-rays) may be used therapeutically in adhesional obstruction

Question 23

Surgical management of small bowel obstruction and indications for surgery:

Answer 23

• Emergency laparotomy to treat the underlying cause with bowel resection. Indicated if:
  
  • evidence of bowel ischameia regardless of the cause
  • a non-adhesional cause (eg strangulated hernia)
  • failure of conservative management for adhesional obstruction
• Adhesiolysis performed for adhesional obstruction, and recurrent adhesional obstruction may require repeat adhesiolysis

Question 24

What is large bowel obstruction?

Answer 24

Occurs due to mechanical or functional obstruction of the large intestine that prevents the normal passage of contents.

Question 25

What are the three most common causes of large bowel obstruction?

Answer 25

* Colorectal cancer (most common cause) * Stricture (a complication of diverticulitis, IBD, or post-anastomosis * Volvulus: sigmoid or caecal

Question 26

What is a volvulus? Which type of vovulus is the most common?

Answer 26

* Volvulus is **torsion** of the **colon** around its **mesentery** * This results in **compromised blood flow** and a **closed loop obstructio**n * Sigmoid volvulus is the most common (80%)

Question 27

Risk factors for volvulus

Answer 27

* **Sigmoid volvulus** typically affects elderly patients, as well as those with chronic constipation or neuropsychiatric conditions, such as Parkinson's disease and schizophrenia * **Caecal volvulus** is associated with adhesions, more common in females and can occur at any age

Question 28

Symptoms of large bowel obstruction

Answer 28

* Colicky, generalised abdominal pain * Bloating * Absolute constipation: no faeces or flatus (occurs earlier than in SBO) * Vomiting: may be faeculent in nature, a late symptom in LBO

Question 29

Signs of large bowel obstruction

Answer 29

* Abdominal tenderness and distension * Tinkling bowel sounds * Rectal examination: empty rectum * Tachycardia and hypotension * Third spacing of fluid * Significant hypotension may indicate ischaemia, perforation or sepsis

Question 30

Primary investigation for large bowel obstruction

Answer 30

* **FBC**: elevated white cell count with neutrophiliA * **U&Es**: assess for pre-renal acute kidney injury secondary to hypovolaemia (third spacing) * **CRP**: raised as part of the general inflammatory response * **Venous blood gas**: to assess the degree of metabolic acidosis and lactate level, which may be suggestive of bowel ischaemia * **Group and save**: patients may go for surgery and require blood products **Abdominal X-ray**: * Dilated large bowel may be visible (\> 6cm in the colon; \> 9cm in the caecum) * Sigmoid volvulus: a large, dilated loop of colon, with coffee bean sign * Caecal volvulus: small bowel obstruction may be seen (\> 3 cm in the small bowel) **CT abdomen and pelvis with contrast**: gold-standard imaging as it can identify dilated bowel loops, evidence of ischaemia and perforation, as well as the underlying cause

Question 31

Initial management of large bowel obstruction

Answer 31

* **IV resuscitation**: third space fluid in the lumen of the bowel segment proximal to obstruction causes hypovolaemia * **Nasogastric (Ryle's) tube**: for abdominal decompression * **IV antibiotics**: prophylactic antibiotics due to risk of bacterial translocation across the inflamed bowel wall * **Analgesia and anti-emetics**

Question 32

Further management of large bowel obstruction depends on the cause. How would you treat LBO caused by: 1) Colon cancer 2) Rectal cancer 3) Diverticular disease 4) Sigmoid volvulus 5) Caecal volvulus 6) Unclear cause

Answer 32

1. **Colon cancer**: stenting or surgical resection eg Hartmann's procedure 2. **Rectal cancer**: defunctioning colostomy 3. **Diverticular** **disease**: Hartmann's procedure or resection, with or without a stoma 4. **Sigmoid** **volvulus**: rigid sigmoidoscopy with flatus tube insertion 5. **Caecal** **volvulus**: usually requires surgery; right hemicolectomy is often performed 6. **Unclear** **cause**: exploratory surgery

Question 33

Complications of large bowl obstruction

Answer 33

* Bowel ischameia and perforation * Sepsis * Aspiration pneumonia: the risk is reduced with NG tube decompression * Dehydration (due to third spacing of fluid)