Peritonitis & Intestinal obstruction Flashcards
1
Q
What is peritonitis?
A
- inflammation of the peritoneum
- may be localised or generalised
- generalised = surgical emergency, requires resuscitation and immediate surgery
2
Q
What is peritonism?
A
- refers to specific features found on abdominal examination in those w/ peritonitis
- characterised by tenderness w/ guarding, rebound/percussion tenderness on examination
- peritonism is eased by lying still and exacerbated by any movement
- maybe localised or generalised
3
Q
The most common cause of peritonitis is bacterial/infective. What are some infective causes?
A
- secondary to gut disease eg. appendicitis
- perforation of any organ
- chronic peritoneal dialysis
- spontaneous, usually in ascites w/ liver disease
- tuberculosis
4
Q
What are the clinical features of peritonitis?
A
- abdominal pain (constant and severe, worse on mvmt)
- signs of ileus (more in generalised)
- distension, vomiting, tympanic abdomen w/ reduced bowel sounds
- signs of systemic shock
- tachycardia, tachypnoea, hypotension, low urine output
- more prominent w/ generalised than localised
5
Q
Diagnosis for peritonitis is most often made on history and examination. What are investigations for localised peritonitis?
A
- acute abdomen investigations pictured below
- all patients get simple investigations
- complex investigations are requested depending on suspected diagnosis (remember that some diagnoses do not require complex investigations and are entirely based on history and examination eg. appendicitis)
6
Q
How do you diagnose generalised peritonitis?
A
- surgical emergency - will require emergency op
- following investigations:
- bloods: FBC, U+E, LFT, amylase, CRP, clotting, G+S, ABG
- AXR + erect CXR
-
CT scan
- only if this can be performed urgently + pt stable
- if not, then surgery without delay
- does not change management (pts will need surgery regardless) but useful to identify cause
- other time consuming complex investigations should not be performed as they will only delay definitive treatment + add very little
7
Q
What is the emergency resus of generalised peritonitis?
A
- ABC
- oxygen
- fluid resuscitation (large bore cannulae, bloods, IV fluids, catheter)
- IV antibiotics (augmentin + metronidazole)
- Analgesia
- Surgery (with or without preceeding CT depending on availability and stability of patients)
8
Q
Give a differential diagnosis for bowel obstruction
A
- Ileus
- Infectious gastroenteritis
- Intestinal pseudo-obstruction
- Appendicitis
- Pancreatitis
- Chronic/idiopathic megacolon
- Toxic megacolon
- Endometriosis
- Pseudomembranous colitis
9
Q
What is intestinal obstruction?
A
refers to a restriction of normal passage of intestinal contents along the intestines
two main types:
- mechanical obstruction - luminal contents cannot pass through the intestine bc the lumen is physically blocked, either completely or partially
- paralytic obstruction (=ileus) - luminal contents cannot pass through the intestine bc of cessation of normal gut peristalsis (usually there is paralysis) - some call this functional obstruction
10
Q
What are the ways to classify a mechanical obstruction?
A
- speed of onset
- anatomical site
- simple vs strangulating
- open vs closed loop
11
Q
What is meant by the speed of onset?
A
- ie. acute, chronic or acute-on-chronic
- in acute obstruction - onset is rapid and symptoms severe
- in chronic - symptoms are insidious and slowly progressive (eg. large bowel carcinoma)
12
Q
What is meant by the anatomical site?
A
- ie. small or large bowel (which is roughly synonymous to high and low obstruction)
- small bowel obstruction is much more common than large bowel obstruction + is often rapid in onset
- large bowel obstruction may be gradual or intermittent in onset
13
Q
What is meant by simple vs strangulating obstruction?
A
-
simple refers to bowel obstruction without compromise to blood supply of the involved segment of intestine, it may be:
- complete (total occlusion of lumen)
- incomplete (partial occlusion, permitting distal passage of some fluid/air)
- strangulating refers to bowel obstruction with compromise to blood supply of involved segment of intestine (as may occur, for example, in strangulated hernia, volvulus, inussusception or when a loop of intestine is occluded by a band). Strangulation may lead to bowel infarction, perforation and peritonitis. Strangulation usually implies that the obstruction is complete but some forms of partial obstruction can also be complicated by strangulation.
14
Q
What is an open loop obstruction?
A
occurs when intestinal flow is blocked but proximal decompression is possible through vomiting
15
Q
What is a closed loop obstruction?
A
- obstruction occurs when inflow AND outflow from obstructed loop of bowel are both blocked
- this results in accumulation of gas and secretions in the obstructed segment
- without a means to decompression
- bowel wall dilates resulting in increased pressure in wall
- this stretches + compresses the blood vessels within wall
- compromises the blood supply to affected segment, resulting in strangulation + its consequences
16
Q
What are examples of closed loop obstruction?
A
- torsion of a loop of small intestine around an adhesion
- incarceration of bowel in a hernia
- volvulus
- large bowel obstruction with a competent ileocaecal valve
- competent ICV means it closely completely
- so therefore obstruction cannot decompress
- causes bowel wall to distend (most pronounced at caecum)
- other hand, an incompetent ICV will decompress large bowel obstruction
17
Q
The common causes of small and large bowel obstruction in adults are different.
What are the common causes of small bowel obstruction?
A
- adhesions (usually post-op)
- hernias
- intussusception
- volvulus
- Crohn’s stricture
18
Q
What are common causes of large bowel obstruction?
A
- colorectal cancer (adenocarcinoma)
- diverticular strictures
- sigmoid volvulus
19
Q
What is the most common cause of bowel obstruction in the UK?
A
adhesions
20
Q
What is an adhesion and when do they form? How do they result in bowel obstruction?
A
- band of fibrous (scar) tissue that binds together normally separate anatomical structures
- the scar tissue forms as part of healting by repair following inflammation
- an important cause of localised peritoneal inflammation is the handling + manipulation of bowel during surgery which causes damage to delicate peritoneum -> inflammation + scarring -> post-operative adhesions
- less commonly, adhesions may form secondary to ther causes eg. healing of infective peritonitis, post-radiotherapy
- adhesions can kink, twist or pull intestines out of place causing small bowel obstruction. Acute large bowel obstruction due to post-op adhesions usually does not occur bc the large bowel is mostly retroperitoneal unlike the small bowel which gets easily kinked on its loose mesentery
21
Q
What are abdominal hernias? How do they result in bowel obstruction?
A
- hernias second most common cause of bowel obstruction in UK (but most common cause worldwide)
- hernias are abnormal protrusions of peritoneal-lined sacs through defects in the abdominal wall
- eg. inguinal and femoral canals, umbilicus, surgical scars
- if a segment of bowel protrudes into the sac and becomes trapped, it may lead to a closed loop strangulating bowel obstruction and consequent infarction
22
Q
What is intussusception and how does it cause bowel obstruction?
A
- occurs when segment of small bowel prolapses into immediately adjoining bowel
- prolapsing bowel is called the intussusceptum
- different portions of intestine may form apex of intussusception
- commonest form is ileocolic - extends through the ileocaecal valve into the colon
- over 95% cases occur in infancy or young children in whom there is no obv cause
- in adults, it’s usually associated w/ an intraluminal mass (such as the base of a Meckel’s diverticulum, a polyp or tumor) that serves as the initiating point of traction
- the intussusceptum has its blood supply cut off by direct pressure of the outer layer and by stretching of its supplying mesentery resulting in strangulating obstruction
23
Q
What is a volvulus and how can it lead to obstruction?
A
- an abnormal twisting of a segment of the bowel around its site of mesenteric attachment
- resulting in closed loop obstruction
- there is also occlusion of the main vessels at base of involved mesentery -> strangulation
- precipitating factors include
- abnormally mobile loop of intestine (eg. long sigmoid loop)
- abnormally loaded loop eg. chronic constipation
- a loop fixed at its apex by adhesions, around which it rotates
- a loop of bowel with a narrow mesenteric attachment
- volvulus most commonly occurs in the sigmoid colon but it may also occur in the caecum and small intestine
24
Q
How might volvulus be treated?
A
- by passing a long soft rectal tube through sigmoidoscope
- advancing it into sigmoid colon
- this often untwists an early volvulus and is accompanied by passage of vast amounts of flatus + liquid faeces
- if this fails, the volvulus is untwisted at laparotomy and bowel is decompressed via a rectal tube threaded up from anus
- if infarction/gangrene has occurred, affected segment is resected and two open ends are brought out as a double-barreled colostomy which is later closed
25
Describe the presentation of colorectal cancer as bowel obstruction
* bowel cancer (almost always _adenocarcinoma_) may present as large bowel obstruction
* this is more common with **left-sided tumours** because the bowel contents are more solid by the time they reach left side
* the obstruction may be **chronic** w/ insidious onset and slowly progressive symptoms
* a chronic obstruction may develop acute symptoms as the obstruction **suddenly** **becomes complete**
* this is often termed acute-on-chronic obstruction
* don't forget that **colorectal cancer presents as an emergency (such as bowel obstruction) in around 20 cases**
26
Describe how Crohn's disease can cause bowel obstruction
* transmural inflammation heals by **fibrosis**
* results in **_stricture_** formation
* presents as bowel obstruction
* Crohn's disease most commonly affects **terminal ileum**
* so typically causes _small bowel_ obstruction rather than large bowel obstruction
27
Why does absolute constipation occur in bowel obstruction?
* when bowel is obstructed by a simple occlusion
* the intestine **_distal_** to obstruction exhibits **normal peristalsis**
* enabling any residual content to be passed out
* the bowel empties and collapses
* results in **absolute constipation** as neither faltus nor faeces are passed
28
Why does a colickly pain occur in bowel obstruction?
* bowel **_proximal_** to obstruction exhibits increased peristalsis
* in an attempt to overcome obstruction
* results in **colickly pain**
29
Why does abdominal distension occur in bowel obstruction?
* bowel **proximal** to obstruction gradually becomes dilated
* **dilation** due to a combo of:
* accumulation of **gas** (swallowed air mainly)
* accumulation of intestinal secretions due to breakdown in normal fxn of mucosa, the accumulation of fluid and electrolytes in the bowel lumen represents a **third space loss**
30
Why does vomiting occur in bowel obstruction?
* due to ejection of accumulated intestinal secretions + contents
31
What happens to the blood supply in the intestine as it distends?
* as bowel distends, **pressure** in wall increases
* as a consequence, **vessels** in wall collapse
* resulting in **compromise to blood supply** to intestine
* ie. obstruction is now **strangulating**
* the _veins_ collapse first leading to interference w/ venous drainage
* as bowel distends further, intraluminal pressure rises, _arteries_ collapse -\> intereference w/ arterial supply
* if unrelieved, bowel infarction, perforation + peritonitis can develop
33
What is the definition of gangrene?
* infarction w/ superimposed bacterial invasion and putrefaction of tissue
34
What are the **cardinal** clinical features of mechanical bowel obstruction?
* _colickly_ abdominal pain (a severe gripping pain that comes and goes in waves; small bowel colic is felt in the central part of the abdomen and large bowel colic felt in lower third of abdomen)
* abdominal distension
* vomiting
* absolute constipation
## Footnote
*not all 4 cardinal features are necessarily present in every case, the severity and time of onset of each of these symptoms will depend on level of obstruction*
35
What are **other** clinical features of bowel obstruction?
* **bowel sounds**: at first hyperactive/loud/frequent, then as bowel distends sounds become more resonant and high-pitched and eventually tinkling
* **dehydration** + **loss of skin turgor**
* **hypotension**, **tachycardia**
* **empty rectum** on PR exam
* pulse and temp are frequently normal (a raised tempt + tachycardia suggests strangulation)
36
What features is it important to look for on examination for the most common causes of bowel obstruction?
* hernias
* abdominal scars (indicating prev surgery + therefore post-op adhesions)
* a palpable mass (eg. caecal mass representing a caecal cancer)
37
How do you distinguish between a _simple_ and _strangulating_ obstruction?
signs of strangulation are generally same as peritonitis:
* toxic appearance w/ tachycardia + fever
* colickly pain becoming _continuous_ as peritonitis develops
* tenderness, guarding and rebound tenderness
* absent bowel sounds
38
What is the **medical** management of mechanical bowel obstruction?
* iv fluid/electrolyte replacement important
* close monitoring also important (fluid balance chart, urinary catheter, regular review)
* NG suction used to decompress gut, helps to decompress bowel and to lessen risk of inhalation of gastric contents during induction of anaesthesia - *combo of nasogastric suction and iv fluids = '**_drip and suck'_***
* iv antibiotics commenced if strangulation is suspected
* investigations appropriate to identify likely cause requested eg. contrast CT
39
Is surgery required for mechanical bowel obstruction?
* depends on clinical scenario
* small bowel obstruction due to adhesions may settle w/ conservative 'drip and suck' management without need for surgery
* however, surgical intervention is indicated if clinical features of **strangulation** or **peritonitis** develop or there is **failure to respond to conservative management**
* surgery may also be indicated in other cases of small + large bowel obstruction:
* if underlying cause needs _surgical treatment_, eg. hernia, colonic carcinoma
* if pt does not improve w/ _conservative_ mgmt over 24-48hrs
* if there are signs of _strangulation_ and/or _peritonitis_
40
What is paralytic ileus?
* when luminal contentsf cannot pass through intestine
* bc of _cessation of normal gut peristalsis_ (usually there is paralysis)
41
What is the aetiology (causes) of paralytic ileus?
* **post-operative state**
* **generalised peritonitis** of any cause eg. perforation, severe acute pancreatitis
* **drugs** eg. opiates, anticholinergics
* **electrolyte imbalances** eg. hypokalaemia, uraemia
## Footnote
*n.b. 'gallstone ileus' is a complete misnomer since a gallstone causes a mechanical obstruction*
42
Why does paralytic ileus result in the post-operative state?
* **any handling of bowel at surgery will cause an ileus**
* this is main reason why pts are kept _nil by mouth_ after abdo surgery until bowel regains function
* ileus is a **normal** physiological event after abdo surgery
* usually resolves spontaneously within 2-3 days of procedure
* in this context, paralytic ileus is defined as ileus of the intestine persisting **_more than 3 days_** after surgery
* in this context, another aetiological factor is prob present
43
What is the pathophysiology of paralytic ileus?
* effects of paralytic ileus are similar to those of simple mechanical obstruction
* **lack of coordinated peristalsis** results in a *functional* obstruction
* gas (mainly swallowed air) and fluid/electrolytes **accumulate** in bowel lumen
* as bowel **dilates**, blood supply to bowel is **compromised** resulting in _ischaemia_
* if not reversed, may result in infarction (gangrene) and perforation
44
What are the clinical features of paralytic ileus?
* mimics mechanical obstruction as also causes **constipation** + **vomiting**
* however, ileus does **not** usually cause _colickly_ pain since bowel not contracting
* nevertheless, there is **often pain** (which is usually not colickly) due to underlying disorder causing ileus
45
What is the difference between a **colicky** and **constant** abdominal pain?
* **colicky** (visceral) abdo pain is caused by stretching or **contracting** of a hollow viscus eg. gallbladder, ureter, ileum
* **constant** localised (somatic) pain is due to peritoneal irritation and indicates the presence of **inflammation** eg. pancreatitis, cholecystitis, appendictis
