GI: AAA, Appendicitis, SBO & LBO Flashcards
1
Q
What diameter of the abdominal aorta defines an abdominal aortic aneurysm (AAA)?
A
> 3cm
2
Q
Morality rate of a ruptured AAA?
A
80%
3
Q
What diameter of the abdominal aorta is defined as a ‘significant risk of rupture’ and is treated as a time critical medical emergency?
A
> 5cm
4
Q
Give some risk factors for AAA
A
- Male (more often and at a younger age than women)
- Increased age
- Smoking (& COPD)
- HTN
- FH of AAA
- Existing CVD
5
Q
Risk of rupture in males vs females?
A
Despite AAA being more common in males, the risk of rupture is more common in females and can occur in aneurysms of a smaller diameter
6
Q
Screening programme for AAA?
A
Current NHS screening programme is only for men.
Current NICE guidance is that ALL men over 65 be offered screening and all women over 70 with risk factors be offered screening for AAAs.
7
Q
Do diabetics undergo AAA screening earlier?
A
No - diabetes mellitus does not confer a higher risk of developing a AAA or of it rupturing when diagnosed.
8
Q
Who is AAA screening routinely offered to?
A
Men aged >65 y/o
9
Q
What investigation is used for AAA screening?
A
US
10
Q
When can AAA screening be considered in women?
A
In women aged >70y with risk factors
11
Q
What aorta diameter is referred to a vascular team during screening?
A
> 3cm –> refer to vascular
> 5.5cm –> refer urgently
12
Q
Symptoms of an AAA (not ruptured)?
A
- often asymptomatic
- pulsatile and expansile mass in the abdomen when palpated with both hands
13
Q
what is investigation of choice in diagnosing AAA?
A
1st line: US.
CT angiogram gives a more detailed picture of the aneurysm and helps guide elective surgery to repair the aneurysm.
14
Q
Classfication of an AAA:
a) normal
b) small aneurysm
b) medium aneurysm
d) large aneurysm
A
a) <3cm
b) 3-4.4 cm
c) 4.5-5.4 cm
d) >5.5 cm
15
Q
Management of an AAA (not ruptured)?
A
1) Treat reversible risk factors (to reduce risk of progression):
- Stop smoking
- Healthy diet and exercise
- Optimising the management of hypertension, diabetes and hyperlipidaemia
2) Screening and surveillance programme (follow up scans)
3) Elective repair
16
Q
How often should patients have follow up scans if they have an AAA of 3-4.4cm?
A
Yearly
17
Q
How often should patients have follow up scans if they have an AAA of 4.5-5.4cm?
A
3 monthly
18
Q
Who is an elective repair for AAA considered in?
A
1) Symptomatic aneurysm
2) Diameter growing >1cm per year
3) Diameter >5.5cm
19
Q
What is involved in an elective surgical repair of an AAA?
A
Inserting an artificial “graft” into the section of the aorta affected by the aneurysm.
There are two methods for inserting the graft:
1) Open repair via a laparotomy
2) Endovascular aneurysm repair (EVAR) using a stent inserted via the femoral arteries
20
Q
Driving rules for AAA?
A
1) Inform the DVLA if they have an aneurysm above 6cm
2) Stop driving if it is above 6.5cm
3) Stricter rules apply to drivers of heavy vehicles (e.g., bus or lorry drivers)
21
Q
What size AAA must patients inform the DVLA?
A
> 6cm
22
Q
Presentation of a ruptured AAA?
A
1) Pain:
- May be back or loin pain
- May be severe abdo pain that radiates to the back
2) CVS failure:
- Significant haemorrhage
- Progressive tachycarida & hypotension (shock) - poorly responsive to fluid resuscitation
3) Pulsatile and expansile mass in the abdomen
4) Distal ischaemia
5) Collapse, LOC & death
23
Q
What is permissive hypotension?
A
The strategy of aiming for a lower than normal blood pressure when performing fluid resuscitation.
The theory is that increasing the blood pressure may increase blood loss.
24
Q
What investigation is used to diagnose or exclude ruptured AAA in haemodynamically stable patients?
A
CT angiogram (gold standard imaging in patients with known AAA with suspected rupture)
25
Investigations in suspected ruptured AAA?
1) Imaging (CT angiogram)
2) FBC: to ascertain whether there is a low platelet count which may require transfusion and affect surgical bleeding risk.
3) U&Es: if treated endovascularly the patient will be exposed to large volumes of contrast and pre-existing renal failure may contraindicate this
4) Coagulation screen
5) Blood grouping
26
Differentials for an AAA?
- Back pain
- Acute pancreatitis: measure serum amylase or lipase in all patients presenting with acute abdominal or upper back pain.
- Renal colic: consider abdo US
- Lower limb ischaemia
27
What are the 3 main treatment options for ruptured AAAs?
1) open surgical repair
2) endovascular aneurysm repair (EVAR)
3) palliative care
28
What are classed as 'low rupture risk' AAAs?
Asymptomatic, aortic diameter < 5.5cm (i.e. small and medium aneurysms)
29
What is acute appendicitis typically caused by?
It is typically caused by infection secondary to luminal obstruction with faecolith, impacted normal stool, lymphoid hyperplasia or a tumour.
30
What is the most common abdominal surgical emergency worldwide?
Acute appendicitis
31
What is the appendix? What does it arise from?
a small, thin tube arising from the caecum.
32
Pathophysiology of appendicitis?
1) Pathogens can get trapped due to obstruction at the point where the appendix meets the bowel.
2) Trapping of pathogens leads to infection and inflammation.
3) The inflammation may proceed to gangrene and rupture.
4) When the appendix ruptures, faecal contents and infective material are released into the peritoneal cavity.
5) This leads to peritonitis, which is inflammation of the peritoneal lining.
33
Risk factors for appendicitis?
1) Male sex
2) Age 10-20 y/o
3) Positive FH
4) Caucasian
34
What are 4 causes of luminal obstruction of the appendix (that can lead to appendicitis)?
1) Faecaliths
2) Lymphoid hyperplasia
3) Foreign bodies
4) Tumours
35
What is the most common cause of luminal obstruction causing appendicitis?
Faecaliths
36
What are faecalith?
Hardened faecal matter
37
4 most common bacteria implicated in appendicitis?
1) E. coli
2) Bacteriodes
3) Streptococcus
4) Enterobacter species
38
Clinical features of appendicitis?
1) Abdominal pain:
- central that localises to the RIF
- tenderness at McBurney's point
- pain worse on coughing or going over speed bumps
2) N&V:
- once or twice but marked and persistent vomiting is unusual
3) Low grade fever: usually 37.5-38 degrees
4) Loss of appetite (anorexia)
5) Rovsing's sign
6) Guarding on abdominal palpation
7) Rebound tenderness in the RIF
8) Percussion tenderness
9) Psoas sign
39
What is Rovsing's sign?
Palpation of the left iliac fossa causes pain in the RIF)
40
What is MucBurney's point?
Tefers to a specific area one third of the distance from the anterior superior iliac spine (ASIS) to the umbilicus.
41
What is rebound tenderness?
Increased pain when suddenly releasing the pressure of deep palpation
42
What is percussion tenderness?
pain and tenderness when percussing the abdomen
43
What does rebound tenderness & percussion tenderness indicate?
Peritonitis: potentially indicating a ruptured appendix.
44
What is psoas sign?
pain on extending hip (if retrocaecal appendix)
45
How is a diagnosis of appendicitis typically made?
Raised inflammatory markers + compatible history and examination findings
46
Other potential investigations in appendicitis?
1) Inflammatory markers
2) CT scan: can be useful in confirming the diagnosis, particularly where another diagnosis is more likely.
3) US scan: often used in female patients to exclude ovarian and gynaecological pathology (or in children where CT scan is less appropriate)
4) Urine analysis: exclude pregnancy in women, renal colic and urinary tract infection
47
When a patient has a clinical presentation suggestive of appendicitis, but investigations are negative, what is the next investigation?
Perform a diagnostic laparoscopy: to visualise the appendix directly.
48
Key differentials of appendicitis?
Gynae:
1) Ectopic pregnancy
2) Ovarian cysts
3) Ovarian torsion
4) PID
GI:
1) Mesenteric adenitis
2) Meckel's diverticulum
3) IBD
4) Acute cholecystitis
Urology:
1) Testicular torsion
2) Ureteric stones
3) UTI
49
Important test in any female of reproductive age presenting with abdo pain?
Pregnancy test
50
What investigation can be used to differentiate between appendicitis and gynaecological conditions?
US scan
51
Similarities & differences between appendicitis and ectopic pregnancy?
Similarities: both can cause right iliac fossa pain, nausea/vomiting and fever
Differences: ectopic pregnancies typically present with a 6-8 week history of amenorrhoea with or without vaginal bleeding and a positive pregnancy test
52
Similarities & differences between appendicitis and ovarian torsion?
Similarities: both can cause right iliac fossa pain and nausea and vomiting
Differences: a palpable adnexal mass is felt in 50-70% of cases of ovarian torsion
53
Similarities & differences between appendicitis and acute mesenteric adenitis?
Similarities: both can cause lower abdominal pain with guarding
Differences: mesenteric adenitis typically occurs in children after a viral upper respiratory tract infection and it does not cause localised tenderness
54
Who does mesenteric adenitis typically affect?
children and young adults under 20 years old.
55
What does mesenteric adenitis typically follow?
Viral URTI or tonsilitis
56
Similarities & differences between appendicitis and meckel's diverticulitis?
Similarities: both can cause periumbilical pain which localises to the right iliac fossa and peritonitis
Differences: Meckel's diverticulitis is clinically indistinguishable from acute appendicitis and is often identified when a normal appendix is found during laparoscopic appendicectomy
57
What is Meckel's diverticulum?
Meckel’s diverticulum is a malformation of the distal ileum that occurs in around 2% of the population.
It is usually asymptomatic and does not require any treatment. However, it can bleed, become inflamed, rupture or cause a volvulus or intussusception.
58
What is mesenteric adenitis?
Mesenteric adenitis describes inflamed abdominal lymph nodes.
59
What is an appendix mass?
An appendix mass occurs when the omentum surrounds and sticks to the inflamed appendix, forming a mass in the right iliac fossa.
60
Management of an appendix mass?
This is typically managed conservatively with supportive treatment and antibiotics, followed by appendicectomy once the acute condition has resolved.
61
Management of acute appendicitis?
1) emergency admission under surgical team
2) appendicectomy (typically done laparoscopically)
3) if perforation: copious abdominal lavage.
62
What are some complications of appendicitis?
1) Perforation
2) Abscess formation
3) Phlegmon
4) Peritonitis
5) Post op complications
6) Sepsis
63
What is a phlegmon?
A phlegmon is an inflammatory mass formed by a localized infection and oedema, often seen in the early stages of appendiceal perforation.
It can cause localized tenderness, and fever.
64
Signs of peritonitis?
severe abdominal pain, tenderness, guarding, and fever.
65
Management of peritonitis?
Prompt surgical intervention (appendectomy and peritoneal lavage), intravenous antibiotics, and supportive care, including fluid resuscitation and analgesia.
66
Examples of post appendicectomy complications?
- Bleeding, infection, pain and scars
- Damage to bowel, bladder or other organs
- Removal of a normal appendix
- Anaesthetic risks
- Venous thromboembolism (deep vein thrombosis or pulmonary embolism)
67
Are small or large bowel obstructions more common?
Small
68
Cause of vomiting in SBO?
1) Obstruction results in a build up of gas and faecal matter proximal to the obstruction
2) This causes back-pressure, resulting in vomiting and dilatation of the intestines proximal to the obstruction.
69
Cause of hypovolaemia & shock in SBO?
1) The GI tract secretes fluid that is later absorbed in the colon.
2) When there is an obstruction, and fluid cannot reach the colon, it cannot be reabsorbed
3) As a result, there is fluid loss from the intravascular space into the GI tract --> hypovolaemia & shock
70
How does location of SBO affect fluid loss?
The higher up the intestine the obstruction, the greater the fluid losses as there is less bowel over which the fluid can be reabsorbed.
71
What is the most common cause of SBO?
Adhesions (68%)
72
What is the 2nd most common cause of SBO?
Incarcerated hernias
73
Most common causes of SBO in adults?
Mneumonic: HANG IVs
H - Hernias
A - Adhesions (commonly colorectal and gynaecological surgery)
N - Neoplasms (malignant, benign, primary or secondary)
G - Gallstone ileus
I - Intussusception
V - Volvulus
s - Strictures e.g. Crohn's
74
What are the 4 most common causes of SBO in children?
1) Appendicitis
2) Intussusception
3) Intestinal atresia
4) Volvulus
75
Clinical features of SBO?
1) Absence of passing flatus or stool
2) Abdominal pain
3) N&V: may be bilious
4) Abdo distension
5) Abdo tenderness
6) Bowel sounds: tinkling (high pitched) & increased frequency
7) Fever & tachycardia: if hernia strangulation is the cause of obstruction
76
Describe the abdo pain in SBO
- Ranges in severity
- Often cramping/colicky in nature
- Intermittent every 3-4 minutes. Constant pain may indicate bowel ischaemia.
- Often precedes vomiting (constant pain may indicate bowel ischaemia)
77
What causes the colicky pain seen in SBO?
It is the combination of the dilation of the intestine, and the continuing intestinal peristalsis
78
Describe the N&V seen in SBO
- Often green & bilious in nature
- Leads to loss of fluid, Na+, K+, H+ and Cl-
- Results in a metabolic alkalosis, hypokalemia and hypovolemia
79
What are the main 3 causes of intestinal obstruction (small and large bowel)?
1) Adhesions (small bowel)
2) Hernias (small bowel)
3) Malignancy (large bowel)
80
what to ask about in potential bowel obstruction presentation (when trying to establish cause)?
- hernias
- bowel cancer red flags: weight loss, PR bleeding, change in bowel habits
- previous abdo surgery
81
Does abdo pain come before or after vomiting in SBO?
Before (constant pain may indicate bowel ischaemia)
82
Presentation of proximal vs distal SBO?
Proximal:
- patients tend to present earlier
- abdominal pain and vomiting are the predominant symptoms.
Distal:
- patients usually present after 2-3 days of abdominal pain
- predominant symptoms are abdominal distension and constipation.
83
In the case of a severe, complete and/or complicated obstruction, what are the common features?
- Complete obstipation
- Severe lethargy
- Fevers and rigors
- Bilious vomiting
- Tachycardia and tachypnoea
84
What are adhesions?
Adhesions are pieces of scar tissue that bind the abdominal contents together.
They can cause kinking or squeezing of the bowel, leading to obstruction
85
Do adhesions typically cause obstruction in the small or large bowel?
Small bowel
86
What are the main causes of intestinal adhesions?
- Abdominal or pelvic surgery (particularly open surgery)
- Peritonitis
- Abdominal or pelvic infections (e.g., pelvic inflammatory disease)
- Endometriosis
87
What is a closed loop obstruction?
Closed-loop obstruction describes a situation where there are two points of obstruction along the bowel; meaning that there is a middle section sandwiched between two points of obstruction.
88
What may lead to a closed loop obstruction?
1) Adhesions that compress two areas of bowel
2) Hernias that isolate a section of bowel blocking either end
3) Volvulus where the twist isolates a section of intestine
4) A single point of obstruction in the large bowel, with an ileocaecal valve that is competent
89
What is a competent ileocaecal valve? How can this lead to a closed loop obstruction?
It does not allow any movement back into the ileum from the caecum.
When there is a large bowel obstruction and a competent ileocaecal valve, a section of bowel becomes isolated and the contents cannot flow in either direction.
90
Management of closed loop obstruction?
Emergency surgery
91
Are tinkling bowel sounds heard in early or late bowel obstruction?
Early
92
1st line investigation in SBO?
Abdo XR
93
What findings on an abdo XR are consistent with SBO?
1) Dilated bowel loops with/without air-fluid levels (considered dilated if small bowel is >3cm diameter)
2) Proximal bowel dilation and distal bowel collapse
3) Absence of gas in the abdomen: due to complete filling of bowel loops with sequestered fluid
94
What diameter indicates dilated small bowel loops?
>3cm diameter
95
What are the upper limits of the normal diameter of the bowel?
3 cm: small bowel
6 cm: colon
9 cm: caecum
96
What are valvulae conniventes?
Mucosal folds that form lines extending the full width of the bowel that are present in the small bowel.
These are seen on an abdominal x-ray as lines across the entire width of the bowel.
97
Are valvulae conniventes seen in the small or large bowel?
Small
98
What are haustra?
Haustra are like pouches formed by the muscles in the walls of the large bowel.
They form lines that do not extend the full width of the bowel.
These are seen on an abdominal x-ray as lines that extend only part of the way across the bowel.
99
Are haustra seen in the small or large bowel?
Large
100
Differentials for a SBO?
1) LBO
2) Paralytic ileus
3) Appendicitis
4) Pseudo-obstruction
101
Similarities and differences for SBO and LBO?
Similarities:
- Similar aetiologies to SBO e.g. adhesions, hernias
- Both present with colicky abdominal pain and vomiting
Differences:
- LBO more frequently caused by malignant tumours and volvulus
- Faeculent vomiting is more frequently associated with LBO (late symptom)
- Abdominal distention is more common in LBO
- Typically the interval at which cramping pain occurs is longer
102
Is faeculent vomiting more common in LBO or SBO?
LBO (late sign)
103
Similarities and differences for SBO and paralytic ileus?
Similarities
- Present with abdominal pain, vomiting and constipation
- Both commonly caused by abdominal surgery
Differences
- More frequently caused by recent abdominal surgery and medications (e.g. opioids)
- Presents with diffuse, continual abdominal pain (rather than colicky abdominal pain)
- Bowel sounds tend to be absent
104
Further investigations in SBO?
1) AXR (depending on the signs and symptoms, this may be skipped, and the patient sent straight for a CT scan)
2) Erect CXR: can demonstrate air under the diaphragm when there is an intra-abdominal perforation
3) Contrast abdominal CT scan: usually required to confirm the diagnosis of bowel obstruction and establish the site and cause of the obstruction
4) Bloods:
- FBC
- U&Es
- VBG: metabolic alkalosis due to vomiting stomach acid
- Lactate: raised
105
Management of SBO?
1) ABCDE approach
2) 'Drip and suck':
3) Conservative management in stable patients with obstruction secondary to adhesions or volvulus.
4) Surgery
106
What complications of SBO would require an ABCDE approach?
- Hypovolaemic shock due to fluid stuck in the bowel rather than the intravascular space (third-spacing)
- Bowel ischaemia
- Bowel perforation
- Sepsis
107
What is the 'drip and suck' approach in bowel obstruction?
1) Nil by mouth (don’t put food or fluids in if there is a blockage)
2) IV fluids to hydrate the patient and correct electrolyte imbalances
3) NG tube with free drainage to allow stomach contents to freely drain and reduce the risk of vomiting and aspiration
108
Who is 'non-operative management' appropriate in in SBO?
This is appropriate for patients with partial obstruction or complete obstruction without signs of strangulation or peritonitis.
109
Non-operative management of SBO?
1) Nasogastric tube: Decompression of the upper gastrointestinal tract should be initiated early to avoid vomiting, as well as to reduce gastric and small bowel distention
2) IV fluids and electrolyte repletion: To correct dehydration and electrolyte imbalances.
3) Nil by mouth
4) Observation
5) Serial examinations: To assess for signs of worsening obstruction or development of complications that would necessitate surgery.
110
Who is operative management indicated in in SBO?
Patients with complete obstruction with signs of strangulation, peritonitis, or ischemia, as well as in those who fail to improve with non-operative management after 48-72 hours
111
Complications of SBO?
1) Bowel ischaemia
2) Sepsis
3) Short bowel syndrome
112
Surgical options in bowel obstruction?
Either laparoscopy or laparotomy to correct the underlying cause:
1) Exploratory surgery in patients with an unclear underlying cause
2) Adhesiolysis to treat adhesions
3) Hernia repair
4) Emergency resection of the obstructing tumour
5) Stents: may be inserted into the bowel (during a colonoscopy) in patients with obstruction due to a tumour to hold the tumour out of the way, creating space for the bowel contents to move through.
113
What may indicate bowel ischaemia in SBO?
A change in the character of the pain (e.g. intermittent to continuous pain, increase in severity) or worsening of abdominal signs (e.g. rebound tenderness, guarding)
114
What can bowel ischaemia lead to?
Perforation, leakage into abdo cavity, peritonitis, abdo sepsis & death
115
What is short bowel syndrome?
Occurs if surgical management of SBO is necessary, and requires a large portion of small intestine to be removed for appropriate management
116
Complications of short bowel syndrome?
With reduction in the surface area and distance for absorption of gastric nutrients, it essentially may lead a patient to require lifelong supplemental nutrition or intestinal transplantation.
117
What is the main cause of LBO?
Carcinoma (60%)
LBO is the initial presenting complaint of colonic malignancy in approximately 30% of cases.
118
LBO is the initial presenting complaint of colonic malignancy in approximately 30% of cases.
What location of tumours if this more common in? Why?
This is particularly the case in more distal colonic and rectal tumours, as these tend to obstruct earlier due to the smaller lumen diameter.
119
What is the most common site of malignancy causing LBO?
Rectosigmoid (70%)
120
What are the 3 most common sites of malignancy causing LBO?
Rectosigmoid (70%)
Rectal (10%)
Anal (5%)
Other (15%)
121
Why are right sided obstructions rare in LBO?
Right sided obstructions are rare due to large diameter of the lumen and liquid consistency of faecal material
(note: the features of these obstructions will mimic a distal small bowel obstruction more)
122
What is the most common BENIGN cause of LBO?
Volvulus (10%)
123
What is volvulus?
Volvulus occurs when a loop of intestine twists around itself and the mesentery that supplies it, causing a bowel obstruction.
124
Volvulus of what part of the colon is most common causing LBO?
Volvulus of the sigmoid colon
125
Complications of volvulus in LBO?
Twisting of the bowel on the mesentery leads to ischaemia and subsequent increased risk of perforation
126
What are the causes of LBO?
1) malignancy
2) volvulus
3) diverticular disease
4) post-op adhesions
5) others:
- Hernia with colonic incarceration (2.5%)
- Benign strictures (inflammatory, ischaemic, radiation-induced, anastomotic)
- Severe faecal impaction
- Intussusception
- Intra-luminal foreign body
127
Where does diverticular disease normally occur?
Sigmoid colon
128
How can diverticular disease cause LBO?
Repeated bouts of diverticulitis can lead to subsequent scarring and muscular hypertrophy, eventually leading to formation of strictures and subsequent obstruction.
129
Are adhesions more likely to cause SBO or LBO?
SBO
130
Complications of LBO?
1) Dilation & pressure proximal to obstruction
2) Blood flow to the bowel through the mesenteric system is reduced
3) Bowel mucosal ulceration, full thickness wall necrosis, and potentially subsequent perforation.
131
Danger of bowel perforation?
Perforation of the bowel results in release of faecal matter into the peritoneal cavity. This can lead to widespread bacterial infection and subsequent sepsis.
132
What are the 3 most common bacteria causing infection in bowel perforation?
1) Escherichia coli (most common)
2) Enterococcus faecalis
3) Bacteroides species
133
How can LBO lead to metabolic acidosis?
1) Ongoing increases in bowel colonic pressure causes compression of intestinal veins and lymphatics, leading to worsening bowel wall oedema.
2) Such oedema further causes compression of intestinal arterioles and capillaries, leading to worsening of bowel ischaemia.
3) Ongoing ischaemia leads to subsequent anaerobic metabolism, and lysis of the ischaemic cells causes increase in LACTIC ACID and release of intracellular potassium, potentially resulting in metabolic acidosis and hyperkalemia.
134
How does LBO affect potassium?
Hyperkalaemia: due to release of intracellular potassium
135
What are some symptoms of LBO?
1) Absence of passing flatus or stool:
- In complete obstruction this is absolute
- Passing of some flatus or faeces may suggest a partial obstruction
2) Abdo pain
3) Abdo distension
4) N&V (late symptoms)
136
Describe abdo pain in LBO
- Continuous, rather than intermittent and colicky
- Usually infra-umbilical region
- Sudden relief of pain followed by progressive worsening may suggest perforation
137
Would would a sudden relief of pain followed by progressive worsening suggest in LBO?
Perforation
138
If N&V is present in LBO, what is it likely to be like?
If present, is likely intermittent and faeculent in nature
More suggestive of proximal LBO
139
What are some signs of LBO?
1) Abdo distension
2) Tender abdomen
3) Peritonism (if vascular compromise or perforation):
- Guarding
- Rebound tenderness
- Abdominal rigidity
- Signs suggestive of shock (hypotension, tachycardia, fever)
4) Hypoactive bowel sounds (due to cessation of peristalsis)
140
what clinical features may suggest colonic malignancy as the cause of LBO?
- Unexpected weight loss and loss of appetite
- History of rectal bleeding mixed with stools
- History of altered bowel habits
141
what clinical features may suggest volvulus as the cause of LBO?
- More rapid symptom onset
- May have a previous history of prior volvulus
142
what clinical features may suggest sigmoid diverticulitis as the cause of LBO?
- History of recurrent episodes of abdominal pain and tenderness
- Left lower quadrant pain
- Fever
- Palpable mass
143
1st line imaging in diagnosing LBO?
Abdo XR (or CT scan)
144
Investigations in LBO?
1) AXR
2) FBC:
- Microcytic anaemia may be present as a result of colonic malignancy
- Presence of leukocytosis may suggest peritonitis and sepsis
3) U&Es:
- May be normal in early stages of obstruction
- Hypokalaemia may be present in late stages due to fluid shifts and disruption in normal exchange of electrolytes in the colon
4) Blood gases:
- Low serum bicarbonate levels, low blood pH and high lactic acid levels may be suggestive of intestinal ischaemia
5) LFTs:
- To exclude biliary or hepatic pathology as cause of abdominal pain
- Usually normal in LBO
6) Carcinoembryonic antigen (CEA):
- To consider, not normally first line
- Elevated CEA is suggestive of malignancy, and may guide diagnosis
145
Purpose of FBC in LBO?
- Microcytic anaemia may be present as a result of colonic malignancy
- Presence of leukocytosis may suggest peritonitis and sepsis
146
AXR features of LBO?
1) Marked colonic distension
2) May reveal particular aetiologies e.g. sigmoid volvulus, colonic volvulus, presence of free intra-peritoneal gas
147
What are the normal diameter limits of the large bowel?:
a) caecum
b) ascending colon
c) recto-sigmoid
a) 10-12cm
b) 8cm
c) 6.5cm
148
Describe appearance of sigmoid volvulus in LBO
- Distended sigmoid colon in right upper quadrant
- Dilated inverted U-shaped loop of colon projected towards the right side of abdomen
149
Describe appearance of colonic volvulus in LBO
'Coffee bean sign', whereby apposition of the medial walls of the dilated bowel form the cleft of the coffee bean, and the lateral walls form the outer walls of the coffee bean
150
What investigation is useful to differentiate between a mechanical LBO and a pseudo-obstruction?
Contrast enema
151
How can a contrast enema define the level of obstruction?
Contrast will flow freely to the point of obstruction, with minimal or no flow past the site of obstruction.
152
Who is a contrast enema contraindicated in?
This investigation is contraindicated in cases of perforation due to leakage of contrast into the abdominal cavity and subsequent irritation.
153
3 key differentials for a LBO?
1) SBO
2) Pseudo-obstruction
3) Toxic megacolon
154
In 15% of cases, why may a LBO present with features more classical of a SBO?
As 15% of people have an incompetent ileo-caecal valve, therefore this will decompress the large bowel into the distal small bowel, therefore resembling a distal SBO instead.
155
Similarities and differences of SBO vs LBO
Similarities:
- Similar symptoms e.g. abdominal pain, tenderness, vomiting and constipation
- Similar risk factors and aetiology (e.g. volvulus, adhesions, malignancy)
Differences:
- SBO tends to present more acutely, whilst in LBO the majority of cases will present with a more gradual onset of symptoms
- In SBO, abdominal pain tends to be intermittent and colicky, whilst in LBO the pain is more continuous
- Vomiting is more common in SBO and is bilious in nature, whereas this is a late sign in LBO and tends to be faeculent when present
- Abdominal tenderness is more focal in SBO, whilst generally is more diffuse in LBO
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What is a pseudo-obstruction typically caused by?
Is likely caused by an impairment of the autonomic nervous system and resulting functional obstruction.
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What is there often a history of in a pseudo-obstruction?
Recent severe illness, injury or surgery e.g. severe chest infection, orthopaedic trauma, electrolyte imbalance
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What is toxic megacolon often associated with?
C. diff infection (likely a history of Abx use)
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Similarities between toxic megacolon and LBO
- Both may present with abdominal pain and distention
- Both will show evidence of colonic dilatation on abdominal imaging, although in toxic megacolon this is usually of the entire colon whilst in LBO is usually only proximal to the obstruction
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Colonic dilatation on AXR in LBO vs toxic megacolon?
Both will show evidence of colonic dilatation on abdominal imaging, although in toxic megacolon this is usually of the entire colon whilst in LBO is usually only proximal to the obstruction.
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Differences in LBO vs toxic megacolon?
- Usually toxic megacolon is associated with a Clostridium difficile infection, therefore likely a history of antibiotic use
- Patients are usually very unwell with signs of shock (e.g. fever, tachycardia, hypotension, poor capillary refill), while this is usually only present in LBO with perforation
- Normally will present with diarrhoea, whilst this is uncommon in LBO
- Toxic megacolon affects all age groups, whilst LBO is far more common in the elderly population
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Management of LBO?
1) Nil by mouth
2) IV fluids: to prevent dehydration, as well as to correct any potential electrolyte imbalances
3) NG tube insertion:
- Required to decompress the bowel
- To reduce flow of gas and gastric contents further towards the site of obstruction
4) Abx: if signs of perforation or pre-ob
5) Surgery (emergency if overt peritonitis or evidence of bowel perforation)
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Management options if malignancy is cause of LBO?
1) 1st line: surgery (elieving the bowel obstruction as well as resecting the malignant tumour)
2) Colonic stenting may be used again as form of bowel decompression and as palliation (if patients not suitable for surgery)
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Management options if sigmoid volvulus is cause of LBO?
1) 1st line: endoscopic decompression
2) Surgery if evidence of ischaemia, perforation or mucosal gangrene
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