GI pathology II Flashcards
what is peritonitis?
Inflammation of the peritoneum
what is the peritoneum?
a Thin layer of cells that covers the external surface of all abdominal and pelvic organs
In peritonitis what normally causes the damage to the peritoneum?
Bacterial Infection
what are typical clinical features of peritonitis?
- tachycardia
- pyrexia
- constant abdominal pain
- abdo tenderness and guarding
- rebound tenderness
- localised pain during distant palpitation
- abscent bowel sound
what investigations can be done for peritonitis?
- clinical history
- FBC
- serum amylase (will show if pancreatitis is a problem)
- X RAY
- CT
what are basic management principles for peritonitis?
- IV fluid
- antibiotic therapy
- gastric aspiration
what are the two types of intestinal obstruction?
- mechanical
2. paralytic
what is mechanical obstruction?
The luminal contents can’t pass through the intestine due to a physical blockage
what is paralytic obstruction of the intestine?
The luminal contents can’t pass due to cessatation of normal gut peristalsis
what is simple obstruction of the intestine?
obstruction refers to bowel obstruction without compromise to the blood supply of the affected segment
what is a strangulating obstruction of the bowel?
bowel obstruction with compromise to the blood supply
what is open loop obstruction?
The intestinal flow is blocked but proximal decompression is possible through vomiting.
what is a closed loop obstruction?
Both inflow and outflow are obstructed causing a build up of gas and secretion in the affected part
what are examples of closed loop obstruction?
- torsion of a loop of s.intestine around an adhesion
- incarceration of bowel in a hernia
- volvulus
what are common causes of small bowel obstruction?
- adhesions
- hernia
- intussusception
- volvulus
- crohns
what re common causes of large bowel obstruction?
- colorectal cancer
- diverticular strictures
- sigmoid volvulus
what is an adhesion?
A band of fibrous tissue that binds together normally separate anatomical structures
what is the first two common causes of bowel obstruction in the uk?
- adhesions
2. abdominal hernia
what is intussusception?
a segment of small bowel prolapses into the immediately adjoining bowel.
what is a volvulus?
An abnormal twisting of a segment of bowel around it’s site of mesenteric attachment.
what are precipitating factors for a volvulus?
- an abnormally mobile loop of intestine
- ## an abnormally loaded loop
where is the most common site for volvulus to form?
Sigmoid colon
what is the most common type of bowel cancer?
Adenocarcinoma
what are common causes of bowel obstruction in neonates?
- congenital stenosis
- volvulus
- hirschsprungs disease
- meconium ileus
what are common causes of bowel obstruction in infants?
- intussusception
- hirschsprungs disease
- strangulated hernia
- mechels diverticulum
what causes colicky pain in bowel obstruction?
The bowel proximal to the obstruction has increased peristalsis in an attempt to overcome the obstruction
what causes bowel dilatation in a blockage?
- accumulation of gas
2. accumulation of intestinal secretions
what happens to the pressure in the wall as the bowel distends?
due to laplaces law it increases
how does strangulation occurs due to laplaces law in obstruction?
The radius becomes increased meaning more tension. This causes veins to collapse and then arteries
what is the order of events from strangulation to death due to bowel obstruction?
Strangulation –> ischaemia
- -> infarction
- -> perforation –> peritonitis
- -> death
what is ischaemia?
a reversible process due to blood flow interference disrupting tissue function
what is infarction?
Irreversible
tissue death due to interruption with blood flow
what is necrosis?
cell death due to a pathological process
what is gangrene?
infarction with super imposed bacterial invasion of the tissue
what are the four cardinal clinical features of mechanical bowel obstruction?
- colickly pain
- abdominal distension
- vomit
- absolute constipation
where is the colicky pain in mechanical bowel obstruction?
small bowel colick in the central abdo
large bowel colic in the lower 1/3 of the abdo
How can you tell if its a simple obstruction or a strangulating obstruction?
strangulation features are similar to peritonitis
- a toxic appearance with tachycardia and fever
- colicky pain
- tenderness, guarding and rebound pain
- abscent bowel sounds
when is surgery indicated in bowel obstruction?
- if the underlying cause needs surgical treatment
- the patient doesn’t improve with conservative management over 2 days
- signs of strangulation and peritonitis
what are some causes of paralytic ileus?
- post operative state
- generalised peritonitis
- drugs
- electrolyte imbalance
what drugs can cause paralytic ileus?
- opiates
- anticholinergics
what causes colicky abdominal pain?
stretching or contracting a hollow viscus
what are major risk factors for developing Ogilvie syndrome?
- severe blunt trauma
- orthopaedic trauma
- joint replacement
- cardiac events
what is Ogilvie syndrome?
A type of paralytic ileus which affects the large bowel due to interference with autonomic nerve supply to the gut
what is infarction?
Tissue necrosis due to interference with the blood supply
what are the main causes of bowel infarction?
- strangulating bowel obstruction
- occlusion of a mesenteric artery by an embolus
- occlusion of a mesenteric artery by a thrombus
- occlusion of a mesenteric artery by an aortic dissection extending into the mesenteric artery
- compression of veins in the bowel wall
what is the triad of symptoms seen in bowel infarction?
Acute colicky abdo pain
rectal bleeding
shock
what is the general management of bowel infarction?
- IV fluids
- broad spectrum antibiotics
- laparotomy to remove dead bowel
where is the most common place for diverticular disease to develop?
The sigmoid colon
what is a diverticulum?
.A pouch of colonic mucosa that has herniated through the muscularis propria and now lies in the fat outside the bowel wall
what two factors are important for diverticula formation?
- areas of weakness in the colonic wall
2. raised intraluminal pressure
An important factor for developing diverticulas is the increase intraluminal pressure what can cause this?
Insufficient fibre in the diet
why is the sigmoid colon the most common place to develop diverticula?
It has the smallest diameter so intraluminal pressure is more likely to be high here
what is diverticulosis?
Diverticula are present but asymptomatic
what is diverticulitis?
An acutely flamed diverticulum
what initiates acute diverticulitis?
Faecal matter impacts and obstructs the neck of a diverticulum leading to bacteria trapping and mucosal injury
what is the presentation of acute diverticulitis?
Abdominal pain (often left iliac fossa) Malaise Fever localised tenderness No peritonitis
how can acute diverticulitis lead to abscess formation?
There is an acute inflammatory response to the diverticula that can extend past the diverticula to the surrounding tissue leading to abscess
how can a diverticula lead to bacterial peritonitits?
acute diverticulitis –> pericolic abscess develops due to inflammatory response –> abscess perforates into the abdominal cavity
how can a diverticula lead to faecal peritonitis instead of bacterial?/
If the inflamed diverticulm perforates into the abdominal cavity directly before developing an abscess.
why can strictures form because of diverticular disease?
- there is smooth muscle hypertrophy and hyperplasia
- fibrosis is around the diverticula
this leads to a reduced diameter
why can diverticular disease mimic colorectal cancer?
- intermittent abdominal pain and altered bowel habit
- affect similar age groups
- positive FOB and iron deficient anaemia
