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*Medicine: Gastrointestinal > Peritonitis & Intestinal obstruction > Flashcards

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
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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
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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
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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
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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)
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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
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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)
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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
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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
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10
Q

What are the ways to classify a mechanical obstruction?

A
  1. speed of onset
  2. anatomical site
  3. simple vs strangulating
  4. open vs closed loop
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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)
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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
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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.
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14
Q

What is an open loop obstruction?

A

occurs when intestinal flow is blocked but proximal decompression is possible through vomiting

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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
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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
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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
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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
Q

Describe the presentation of colorectal cancer as bowel obstruction

A
  • 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
Q

Describe how Crohn’s disease can cause bowel obstruction

A
  • 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
Q

Why does absolute constipation occur in bowel obstruction?

A
  • 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
Q

Why does a colickly pain occur in bowel obstruction?

A
  • bowel proximal to obstruction exhibits increased peristalsis
  • in an attempt to overcome obstruction
  • results in colickly pain
29
Q

Why does abdominal distension occur in bowel obstruction?

A
  • 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
Q

Why does vomiting occur in bowel obstruction?

A
  • due to ejection of accumulated intestinal secretions + contents
31
Q

What happens to the blood supply in the intestine as it distends?

A
  • 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
Q

What is the definition of gangrene?

A
  • infarction w/ superimposed bacterial invasion and putrefaction of tissue
34
Q

What are the cardinal clinical features of mechanical bowel obstruction?

A
  • 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

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
Q

What are other clinical features of bowel obstruction?

A
  • 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
Q

What features is it important to look for on examination for the most common causes of bowel obstruction?

A
  • hernias
  • abdominal scars (indicating prev surgery + therefore post-op adhesions)
  • a palpable mass (eg. caecal mass representing a caecal cancer)
37
Q

How do you distinguish between a simple and strangulating obstruction?

A

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
Q

What is the medical management of mechanical bowel obstruction?

A
  • 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
Q

Is surgery required for mechanical bowel obstruction?

A
  • 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
Q

What is paralytic ileus?

A
  • when luminal contentsf cannot pass through intestine
  • bc of cessation of normal gut peristalsis (usually there is paralysis)
41
Q

What is the aetiology (causes) of paralytic ileus?

A
  • post-operative state
  • generalised peritonitis of any cause eg. perforation, severe acute pancreatitis
  • drugs eg. opiates, anticholinergics
  • electrolyte imbalances eg. hypokalaemia, uraemia

n.b. ‘gallstone ileus’ is a complete misnomer since a gallstone causes a mechanical obstruction

42
Q

Why does paralytic ileus result in the post-operative state?

A
  • 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
Q

What is the pathophysiology of paralytic ileus?

A
  • 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
Q

What are the clinical features of paralytic ileus?

A
  • 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
Q

What is the difference between a colicky and constant abdominal pain?

A
  • 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

*Medicine: Gastrointestinal (29 decks)

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