Mr Alay Tutorial 1 - Intestinal Obstruction Flashcards
(155 cards)
1
Q
Define intestinal obstruction
A
Failure of downward passage of intestinal contents
2
Q
What are the two subtypes of intestinal obstruction?
A
Dynamic
Adynamic
3
Q
Define dynamic intestinal obstruction
A
Increasing peristalsis working against an obstructive agent
4
Q
Define adynamic intestinal obstruction
A
Peristalsis is absent/ineffective and there are no effective propulsive waves
(no mechanical blockage)
5
Q
Define simple intestinal obstruction
A
Obstruction of the intestinal lumen without interference with its blood supply
6
Q
What is the commonest cause of simple intestinal obstruction?
A
Adhesions (usually due to prev. abdominal surgery)
7
Q
What are causes of simple IO?
A
Lumen: gallstones, impacted faeces
Wall: strictures (neoplastic/inflammatory)
Outside wall: adhesions/tumours
8
Q
What are causes of adhesions in the abdomen?
A
Usually due to surgery
Other: infections after surgery, infection due to primary pathology
9
Q
What kind of obstructions do adhesions generally causes?
A
Small IO
10
Q
How can you differentiate the most common cause of SBO based on the patients history?
A
Hx SBO + Hx abdominal surgery –> adhesions
Hx SBO = no Hx abdominal surgery –> tumour
11
Q
What does simple OI look like above and below the obstruction?
A
Above obstruction - bowel dilates, inc. peristalsis to overcome blockage, food builds up, distension as fluid + gas builds up
Below obstruction: collapsed bowel (immobile + pale)
12
Q
In IO what is the site between the collapse bowel and the dilated bowel known as?
A
Transition point - this is where the aetiology will be found
13
Q
What can occur at the site of the obstruction in simple IO?
A
Perforation
14
Q
What is the pathophysiology of simple IO?
A
Third space loss
Dehydration
Proliferation of bacterial proximal to obstruction
Impairment of barrier function of intestinal mucosa
15
Q
What is third space loss in simple IO?
A
Normally fluid is in intravascular/extravascular spaces
But in IO above the obstruction there is a compartment where fluid is secreted by the GIT and cannot be reabsorbed due to the pathology
16
Q
What is the clinical consequence of simple IO?
A
Dehydration
Patients require more fluid than you may think
17
Q
Define third space loss
A
Fluid sequestration inside the body (cavity) that cannot be used by the systemic circulation
18
Q
Explain why IO can lead to peritonitis
A
Bacteria above obstruction can proliferate and translocate (migrate) over the bowel wall into the peritoneum
19
Q
Why does bacteria not usually translocate in healthy individuals?
A
Active protective mucosal barrier of GIT which is disrupted in IO
20
Q
How long after the intestine becomes disrupted does translocation tend to occur?
A
Within 48h
21
Q
If bacteria translocates in IO what can occur?
A
Peritonitis
Sepsis
22
Q
What are causes of death in simple IO?
A
Fluid and electrolyte imbalance
Peritonitis
23
Q
Define strangulation
A
Intestinal obstruction with persistent interference with the blood supply
(once BS starts to decrease, do not wait until it is completely diminished)
24
Q
How long do you have to save the bowel before it dies in strangulation?
A
6h
25
Delay in the management of strangulation can lead to what?
Major resection of the bowel
| Death
26
What should you do if in A and E you suspect someone to have strangulation?
Call surgical team - Ex, CT scan, theatre rapidly
27
What can cause strangulation?
```
Strangulated hernia
Intussusception
Adhesive intestinal obstruction (late)
Volvulus
Vascular occlusions
```
28
What is the pathophysiology of strangulation?
Blockage of bowel also puts pressure on artery + vein supplying bowel
Vein low pressure and hence is blocked first --> venous return impaired so bowel appears dark and congested (as blood flows in but not out)
High venous pressure --> blood stained fluid (serosanguinous) filtration around bowel
Arterial supply impaired (bowel turns black)
29
What is serosanguinous fluid?
Blood stained fluid
30
What is serosanguinous fluid indicative of if found in the abdomen?
Ischaemic/necrotic bowel
31
How does the third space loss in strangulation differ from simple IO?
Blood + fluid are lost
Blood is trapped due to venous congestion
This is blood lost from the systemic circulation and hence in strangulation more likely to present as unwell + shocked
Dehydration is big issue!
32
Why is translocation of bacteria much faster in strangulation as compared to simple IO?
Ischaemic bowel is easier for the bacteria to translocate over
33
What are causes of death in strangulation?
Peritonitis due to perforation
Hypovolaemic shock
Sepsis
34
At how many points is the bowel usually obstructed?
1
35
If the bowel is obstructed at 2 points what is this known as?
Closed loop obstruction
36
Give examples of closed loop obstructions
Hernias
Volvulus
Competent ileocaecal valve + sigmoid obstruction
37
Explain why sigmoid obstructions can lead to a closed loop obstruction
In most people the ileocaecal valve is competent + allows things only to move from SB --> LB
And therefore in sigmoid blockage this is a normal physiological blockage that leads to a closed loop obstruction
38
What % of people have a competent ileocaecal valve?
75%
39
How do sigmoid tumours often present?
Closed loop obstruction
40
In sigmoid tumours where is the most common place for a perforation to occur and why?
Caecum
| CLO forms and the wall at the caecum is thinnest
41
When the caecum is ____cm there is eminent risk of perforation of the caecum.
10cm
42
What are the only two kinds of operations done during the night?
L + L
| Life saving and limb saving
43
What are the 4 clinical features of IO?
Pain
Vomiting
Abdominal distension
Absolute constipation
44
What can the timing of the symptoms tell you about where the obstruction is in IO?
If order of onset of symptoms is pain --> vomiting --> distension --> constipation = small IO
and if opposite = large IO
45
What kind of pain is experienced in IO?
Generalised colicky abdominal pain
| Attacks of pain lasting a few min with periods of relief
46
What happens to the pain as time progresses in IO?
Attacks of pain become longer, more painful and less spread out
47
What causes colicky pain?
Obstructed bowel, ureter, gallbladder
| Is due to peristalsis
48
How can you tell where the obstruction is in IO based on the timing of the vomiting?
Jejunal - early vomiting, vomiting with each attack
| Ileal - delayed for a few hours, vomiting with each attack
49
What does bile stained vomiting suggest?
Jejunal contents are in the vomit
50
What is faeculent vomit?
Dark brown, v. offensive vomit
51
What does faeculent vomit suggest?
Partly digested food from the TERMINAL ileum
52
If the obstruction in IO is higher up why do you get more vomit as compared to if it is lower down?
The higher up the obstruction, the less time there is for fluids (both ingested + secreted) to be absorbed hence there is a higher volume of vomit
53
What is the most important point about vomiting in IO to remember?
The higher the level of obstruction, the more SEVERE and EARLY the vomiting is
54
Why don't people normally vomit faeces if they have a large IO?
Ileocaecal valve usually is competent
55
What type of constipation do you get in complete obstruction?
Absolute
56
Define absolute constipation
Inability to pass stools and flatus
57
What kind of constipation would you get in partial obstruction?
Continued passage of flatus +/or stools beyond 6-12h after onset of symptoms
58
What type of constipation is more indicative of IO?
Complete
59
What kind of abdominal distension do you get in jejunal obstruction?
Minimal
60
What kind of abdominal distension do you get in ileal obstruction?
Central
| Flanks complete collapsed
61
What kind of abdominal distension do you get in large bowel obstruction?
Flanks
62
What types of IO may lead to generalised abdominal distension?
Distended small bwel + colon, e.g. LBO with incompetent ileocaecal valve
63
Give examples where IO presents without absolute constipation
Ritcher's hernia
Gallstone ileus
Mesenteric vascular occlusion
Intestinal obstruction associated ith a pelvic abscess
64
Define Richter's hernia
Bowel caught in v small hernia so that a section of it is strangulated but not full circumference of bowel is in hernia so there isn't a complete obstruction
65
What is the issue with Richter's hernia?
Progresses v. quickly to gangrene
As very small hernia, no vomiting, constipation etc. may mistakenly think it is fine to leave it
66
What is NEVER normal for a hernia?
For it to be painful/tender
67
What should you do if a patient has a tender/painful hernia?
Refer to surgery immediately
68
What is the commonest presentation of a Richter's hernia?
Small femoral hernia in elderly women that is not fully obstructed (i.e. no vomiting, constipation)
69
What will you see on general examination on someone with IO?
Dehydration
| Tachycardia + shock (may indicate strangulation)
70
Why are patients with IO dehydrated?
Third space loss
| Vomiting
71
What should you look for on inspection of the abdomen in suspected IO?
Scars for prev. surgeries (adhesions)
Visible non-reducible hernia
Visible peristalsis
Step ladder appearance due to distended loops of bowel over each other
72
What must you always check for in patients with suspected IO?
Hernias
| i.e. check groin for femoral hernias
73
What will tenderness/rigidity on palpable in suspected IO indicate?
Strangulation (do not get tenderness/rigidity in simple IO)
74
What will you ascultate in early IO?
Loud and frequent intestinal sounds
75
What will you ascultate in late IO?
Silent abdomen (ileus/peritonitis)
76
What other examination should you always do in suspected IO?
PR
77
What will PR in IO show in most cases?
Empty rectum (they have cleared the faeces and it is now empty due to the occlusion)
78
What may PR reveal in IO if the rectum is not empty?
Rectal tumour, faecal impaction etc.
79
What signs/symptoms should make you suspect strangulation as opposed to simple IO?
Pain - more severe, background pain in between attacks
Shock - present + progressive
Tenderness + rigidity
NG suction for 1-2h fails to relieve the pain (unlike in simple IO)
80
What causes the background pain in strangulation?
Ischaemia
81
What are the two types of strangulation?
Internal - inside chest/abdominal cavity
| External (hernia)
82
What features of a hernia should make you think it has strangulated?
Tense, tender, irreducible, no expansible impulse on cough
83
What investigations should be done for suspected IO?
```
(fiBloods - FBC, UE, LFTs, ?ABG
AXR
CT
Water soluble oral contrast/enema
Erect CXR
```
84
What useful information can be derived from the FBC in suspected IO?
Hb - anaemic (if elderly think colon cancer as colon tumours bleed)
WCC - if high early - could be strangulation, if high after day or 2 could indicate strangulation
85
If an elderly patient presents with SBO and anaemia where is the tumour most likely to be and why?
```
Right side (caecal tumour)
Blood mixes with the faeces and hence pt doesn't know they are bleeding and present late and by this point are anaemic
```
L sided tumour present with rectal bleeding and hence present earlier before anaemia has occured
86
What useful information can be derived from the U+E in suspected IO?
Dehydration puts pt at risk of AKI
| Check eGFR and also K level (fix hypokalaemia ASAP as pt cannot be anaesthesised if hypokalaemic
87
Why should you do LFTs in a pt with IO?
To see what drugs anaesthetist can use
| If abnormal LFTs in certain pts may indicate liver mets
88
Why do you do an erect CXR in suspected IO?
To check for free air (perforations)
89
How can you differentiate between the large bowel and small bowel on AXR?
Small bowel - complete lines over circumference of bowel (valulae conniventes)
Large bowel - incomplete lines (haustrations)
Terminal ileum is featureless tube
90
What is the sensitivity of AXR in picking up IO?
60-90%
91
Why is use of AXR in IO limited?
Cannot reliably find site/cause of obstruction
| Normal AXR does not exclude IO (may have to do CT)
92
Summarise the clinical presentation of a high proximal SBO
Early vomiting
Minimal distension
Minimal small bowel loops on AXR
93
Summarise the clinical presentation of a low (distal) SBO
Pain + distension
Vomiting late
Dilated small bowel loops on AXR
94
Summarise the clinical presentation of a high LBO
Marked distension
Pain + vomiting late
Dilated large bowel loops on AXR
95
What is CT used for in IO?
Confirm diagnosis
| Identify level of obstruction, find cause, ischaemia, perforations
96
What agent is used in water soluble oral contrast scans?
Gastrografin (orally or via NG tube)
97
What is predictive of a non-surgical resolution of adhesive small bowel obstruction?
Contrast in caecum within 6h of giving gastrografin (i.e. it can be therapeutic!)
98
What can water soluble enemas be used for?
Confirming diagnosis of LBO (rarely)
99
What are the most common causes of IO in newborns?
Imperforate anus
Congenital atresia
Stenosis of the gut
Volvulus
100
What are the most common causes of IO in 2-3m olds?
Strangulated hernias
101
What are the most common causes of IO in 3-12m olds?
Intussusception
102
What are the most common causes of IO in young adults?
Strangulated hernia
| Post-op adhesions
103
What are the most common causes of IO in older adults?
Strangulated hernias
Post-op adhesions
Colon cancer
Colonic volvulus
104
What are the general principles of treatment of IO?
NG tube
Reus - IV fluids
Early surgery in some cases
105
What are indications for early surgery in IO?
```
Obstructed hernia
Suspected strangulation
SBO in virgin abdomen
Failure of conservative Rx in adhesive SBO
Obstructing tumours on CT
```
106
What does a virgin abdomen mean?
Abdomen that has never been operated on
107
Why do you want to do surgery early on a virgin abdomen in IO?
Likely to be tumour
108
Why do you want to use an NG tube in all patients with IO?
Avoid risk of aspiration
109
What are the two types of intussusception?
Adult
| Paediatric
110
Define intussusception
Invagination of an intestinal segment into adjacent loop
111
What are causes of intussusception in adults?
Polyp, submucosa lipoma, polypoidal tumours, inverted Meckle's diverticulum
(protrusion invites intussusception)
112
What is the difference between adult and paediatric intussusception?
Adult - always an underlying cause + hence req. surgery
| Children - no cause, avoid surgery
113
What is the treatment of adult intussusception?
Laparotomy, resection +/- anastomosis
114
How does intussusception present in paediatrics?
Dying spells - recurrent episodes of screaming + drawing legs up
Vomiting
Redcurrant jelly stools
O/e - sausage shaped mass
115
What investigations are usually done for intussusception?
USS - target sign
116
How is intussusception managed in paediatrics?
Air enema reduction
| Surgery if failed reduction/suspected strangulation
117
Define volvulus
Axial rotation of the gut
| i.e. bowel twisted on itself
118
What are the 4 types of volvulus?
Volvulus Neonatorum
Volvulus of Small Intestine in Adults
Volvulus of the Caecum
Sigmoid Volvulus
119
What causes volvulus of small intestine in adults?
Post-op adhesions between the intestine and anterior abdominal wall which acts as an axis for the bowel to twist on
120
What occurs in caecal volvulus?
Usually caecum covered on front and sides by mesentery
| In 10% individuals it is covered on all surfaces and this means the caecum can twist on itself
121
How is caecal volvulus managed?
R hemicolectomy +/- ileo-colic anastomosis
122
Why do you not just untwist the bowel in caecal volvulus and leave it?
Recurrence is v. high
123
Who is sigmoid volvulus most common in?
Elderly females
124
What is the typical presentation of sigmoid volvulus?
Sudden L sided abdominal pain
| Abdominal distension, absolute constipation
125
What do you see on AXR in sigmoid volvulus?
Dilated colon - 'coffee bean sign'
126
How is sigmoid volvulus managed?
Emergency - endoscopic decompression
| May do sigmoid resection in fit pts but most of these pts v. frail and will just req. frequent decompressions
127
How are adhesive IO managed?
```
NG tube
IV fluids
Pain relief
Gastrografin
Give bowel time for symptoms to calm down itself
```
128
What is the issue with doing surgery for adhesive IO?
More surgery = more adhesions
129
What are indications for surgery in IO?
Suspected strangulation
| Failure of conservative treatment (48h - risk of bacterial translocation)
130
What is an ABG likely to show in strangulation and why?
Severe metabolic acidosis
| Bowel undergoing anaerobic respiration and producing large amounts of lactic acid
131
What is the pathophysiology of gallstone ileus?
Gallbladder sits on jejunum
LARGE stone causes pressure necrosis through wall of gallbladder and jejunum
Large stone passes into jejunum and causes blockage in SBO
132
What does gallstone ileus ALWAYS result from?
Cholecystoduodenal fistula
133
Why can small stones passing through the CBD not cause gallstone ileus?
Stone passing through CBD would be too small to cause a SBO
134
What signs will you see on AXR in gallstone ileus?
SBO
Air in biliary tree
Stone may be seen
135
Why do you get air in the biliary tree in gallstone ileus?
Due to fistula between gallbladder and jejunum
136
How is gallstone ileus managed?
Enterotomy + removal of gallstone (enterolithotomy)
137
Should you do a cholecystectomy in gallstone ileus?
No - do as minimal as possible in emergency situations
138
What is the aetiology of mesenteric vascular occlusion?
Occlusion of the superior (rarely the inferior) mesenteric vessels or one of its branches
139
What are causes of mesenteric vascular occlusion?
```
Arterial embolism (e.g. in AF, SBE)
Arterial thrombosis (e.g. polycythaemia, artherosclerosis, COCP)
Venous thrombosis (portal HTN)
```
140
What patients tend to get mesenteric vascular occlusion?
Elderly
| Those with an aetiological RF (cardiac hx)
141
What is a classical presentation of mesenteric vascular occlusion?
Sudden onest severe pain out of proportion with physical signs
May get passage of blood/mucous per rectum
Shock
Abdominal tenderness/ridigity
142
Why is the pain of mesenteric vascular occlusion out of keeping with the physical signs?
No peritonitis yet (happens after about 6-8h)
143
What is the prognosis of mesenteric vascular occlusion?
Very poor
| Usually a life ending event
144
How do you investigate suspected mesenteric vascular occlusion?
ABG if severe metabolic acidosis then do -
| CT angiogram
145
How should you manage mesenteric vascular occlusion?
Discussion with pt/family re options
Can do GI suction, IV fluids, antibiotics
laparotomy (embolectomy if early case)
Late case may be treated by resection
146
Define paralytic ileus
Cessation of peristalsis due to failure of neuromuscular mechanism of intestine
147
What does paralytic ileus lead to?
Accumulation of gas + fluid in intestine --> distension, vomiting, failure of pass flatus, absent intestinal sounds
148
What are causes of paralytic ileus?
```
Post-abdominal surgery
Perionitis
Reflex following spinal fracture/retroperitoneal haemorrhage
Uraemia
Hypokalaemia
```
149
What electrolytes should you check in paralytic ileus?
K, Mg, Ca
150
What is a typical presentation of paralytic ileus?
```
Hx underlying disorder
Vomiting/increased NG tube output
Absolute constipation
NO PAIN
False shifting dullness
Dead silent abdomen
```
151
What do you see on AXR/CT in paralytic ileus?
Dilated small bowel loops
| No transition point
152
How do you treat paralytic ileus?
NG tube
Restoration of fluid and electrolyte balance
Mx underlying cause
153
Define large bowel pseudo-obstruction (Ogilvie syndrome?
Signs, symptoms + AXR appearance of LBP bit with no identifiable mechanical obstruction
154
Who does Ogilvie syndrome tend to occur in?
Elderly patients +/- recent surgery
155
What are associated features/causes of Ogilvie syndrome?
```
Severe pulmonary or CV disease
Severe electrolyte disturbance:
Hyponatraemia
Hypokalaemia
Hypomagnesaemia
hypo/hypercalcaemia
Malignancy
Systemic infection
Medications:
Opioids, anticholinergics, clonidine, amphetamines, phenothiazines, steroids
```
