GI emergencies Flashcards
What is peritonitis?
- Inflammation of serosal membrane that lines abdominal cavity
How does peritonitis occur?
- Peritoneal cavity is normally sterile
- Can occur spontaneously (primary)
- Or due to breakdown of peritoneal membranes leading to foreign substances entering cavity (secondary)
- Can be infectious or sterile
Summarise the structure of the peritoneal cavity
- Space between visceral and parietal layers of peritoneum
- Visceral and parietal components are continuous
- Parietal peritoneum lines abdominal wall
- Visceral peritoneum is any part that does not line abdominal wall
- Cavity contains a small amount of fluid
- Divided into greater sac and lesser sac
Which demographic of patients are more commonly affected by primary peritonitis?
- Patients with end stage liver disease
What is spontaneous bacterial peritonitis?
- Infection of ascitic fluid that cannot be attributed to any intra-abdominal, ongoing inflammatory, or surgically correctable condition
What is ascites?
- Pathological collection of fluid within peritoneal cavity
In cirrhosis, what causes ascites?
- Portal hypertension
- Causes increased hydrostatic pressure in veins draining the gut
- Decreased liver function results in less albumin production
- Decreased intravascular oncotic pressure
- Results in net movement of fluid into peritoneal cavity
What are the symptoms of primary peritonitis?
- Abdominal pain
- Fever
- Vomiting
- Commonly symptoms are mild
How is primary peritonitis diagnosed?
- Aspirating ascitic fluid
- Neutrophil count >250 cells/mm^3
What is secondary peritonitis?
- Result of an inflammatory process in peritoneal cavity
- Secondary to inflammation, perforation, or gangrene of an intra-abdominal or retroperitoneal structure
What are common causes of secondary bacterial peritonitis?
- Peptic ulcer disease (perforated)
- Appendicitis (perforated)
- Diverticulitis (perforated)
- Post surgery
What are the non-bacterial causes of secondary peritonitis?
- Tubal pregnancy that bleeds (ectopic pregnancy)
- Ovarian cyst
- Blood is highly irritant to peritoneal
What is the clinical presentation of peritonitis?
- Abdominal pain is most common symptom
- May come on acutely or gradually
- Diffuse abdominal pain common in perforated viscera
- Patients often lie very still as any movement makes pain worse
- Often have knees flexed and shallow breathing
What are the treatments for peritonitis?
- Control infectious source - surgery
- Eliminate bacteria and toxins - antibacterial therapy
- Maintain organ system function - intensive care
What is bowel obstruction?
- Mechanical or functional problem that inhibits normal movement of gut contents
- Can affect large and small intestine
- Can affect all ages
What are common causes of bowel obstruction in children?
- Intussusception
- Intestinal atresia
What are common causes of bowel obstruction in adults?
- Adhesions
- Incarcerated hernias
What is intussusception?
- When one part of the gut ‘telescopes’ into an adjacent section
What causes intussusception?
- Cause not well known
- Potential motility issues
- Lead point (mass precipitating telescoping action) e.g. Meckel’s diverticulum or enlarged lymph node
What can bowel obstruction result in?
- Can even prolapse out of rectum
- Get oedema as soon as lymphatic and venous drainage is impaired
- Can lead to infarction because arterial supply is impeded
What are the classic symptoms of intussusception?
- Abdominal pain
- Vomiting
- Haematochezia
How is intussusception treated?
- Air enema
- Surgery
What are the most common symptoms of small bowel obstruction?
- Nausea and vomiting (can contain bile) are most common symptom
- Abdominal distension
- Absolute constipation (late)
What can cause small bowel obstruction?
- Intra-abdominal adhesions
- Hernias (incarcerated groin hernias most common)
- IBD (repeated inflammation/healing causes narrowing)
What are intra-abdominal adhesions?
- Abnormal fibrous bands between organs, or tissues, or both in abdominal cavity that are normally separated
What causes intra-abdominal adhesions?
- Arise after more than 50% of abdominal surgeries
- Damage to mesothelium - capillary bleeding leads to exudation of fibrinogen
What are the consequences of adhesions?
- Abdominal pain
- secondary infertility
How is small bowel obstruction diagnosed?
- History - abdominal pain is crampy/intermittent
- Physical examination - abdominal distension, increased/absent bowel sounds, presence of hernia
- Imaging - CT abdo and pelvis
Which demographic of patients is most commonly affected by large bowel obstruction?
- Typically affects older generation
What are common causes of large bowel obstruction?
- Colon cancer
- Diverticular disease causing strictures
- Volvulus - sigmoid (older patients) or caecal (younger patients and rarer)
What are the symptoms of large bowel obstruction?
- Appear gradually if caused by cancer but are abrupt with volvulus
- Change in bowel habit
- Abdominal distension
- Crampy abdominal pain
- Nausea/vomiting
What is a volvulus?
- Part of colon twists around mesentery
- Most common in sigmoid colon and caecum
- Results in obstruction
- Caecal volvulus results in obstruction of large and small bowel
What causes volvulus?
- Overloaded sigmoid colon e.g. due to constipation
- Extra mass elongates sigmoid colon
- High fibre diet also results in sigmoid overload and twisting
How is volvulus investigated?
- CT abdo and pelvis
Compare ages in small vs large bowel obstruction
- Small bowel obstruction more common in younger age group
- Large bowel obstruction more common in older age group
Why is competence of the ileo-caecal valve important in bowel obstruction?
- If valve is very competent, obstruction is made worse
- Pressure increases in colon, making ischaemia and perforation more likely
Compare the symptoms of large and small bowel obstructions
- Abdominal pain is colicky for both but lasts longer in large bowel obstruction
- Vomiting occurs relatively early in small bowel obstruction and relatively late in large bowel obstruction
- Constipation occurs relatively late in small bowel obstruction but relatively early in large bowel obstruction
How is bowel obstruction imaged?
- CT scan
What might a presentation of acute mesenteric ischaemia look like?
- Intermittent diffuse abdominal pain
- Worse after eating
- Present for a while but recently worsened
- Significant weight loss
What is acute mesenteric ischaemia?
- Symptomatic reduction of blood supply to GI tract
- Worse after meals because blood is diverted to gut
Which area of the gut is most commonly affected by acute mesenteric ischaemia?
- Splenic flexure: superior and inferior mesenteric artery watershed
- Rectosigmoid junction: inferior mesenteric and hypogastric artery watershed
Outline arterial compromise of acute mesenteric ischaemia
- Occlusion in 70% of cases
- Arterial embolism/thrombosis usually affects SMA
- Vasculitis can narrow artery (not acute)
- Low cardiac output can also cause ischaemia
Outline venous compromise of acute mesenteric ischaemia?
- Mesenteric venous thrombosis (5-10%)
- Systemic coagulopathy, malignancy
What are the symptoms of acute mesenteric ischaemia?
- Most cases are in more elderly patients with cardiovascular risk factors
- Can be difficult to diagnose - symptoms are non-specific
- Abdominal pain is disproportionate to clinical findings
- Nausea and vomiting often present
- Pain often left sided because blood supply to splenic flexure is most fragile
What are the investigations for acute mesenteric ischaemia?
- Blood tests for metabolic acidosis/increased lactate levels
- CT abdo/pelvis
- CT angiography
How is acute mesenteric ischaemia treated?
- Surgery - resection of ischaemic bowel (bypass graft)
- Thrombolysis/angioplasty
- Mortality is high
Outline peptic ulceration
- Cause of 20-50% upper GI bleeding
- Disruption in gastric/duodenal mucosa going through to submucosa
- Duodenal ulcers most common
- Gastro-duodenal artery most commonly affected
- Gastric ulcers commonly found in lesser curve or antrum of stomach
Summarise portal hypertension
- Caused by anything that slows blood through portal vein
- Due to pressure than 10 mmHg
- Can cause issues in sites of porto-systemic anastomosis are areas that have venous drainage through portal vein and systemic veins
Outline venous drainage of oesophagus
- Portal drainage - oesophageal veins drain into left gastric vein which then drains into portal vein
- Oesophageal veins drain into azygous vein, drains into superior vena cava
How are oesophageal varices treated?
- Transjugular intrahepatic portosystemic shunt
- Expandable metal placed within liver to bridge portal vein into hepatic vein
- Decompresses portal vein pressure
- Reduction in variceal pressure and ascites
- Terlipressin (reduces portal venous pressure)
What is an abdominal aortic aneurysm?
- Permanent pathological dilation of aorta
- Diameter >1.5 times expected (3cm or more)
- More than 90% of aneurysms originate below renal arteries
What usually causes AAAs?
- Due to degeneration of media layer of arterial wall
- Made up of smooth muscle cells with elastin and collagen
- AAAs form due to degradation of elastin and collagen
- Lumen gradually starts to dilate
- Most AAAs are asymptomatic
What are the risk factors for AAAs?
- Male
- Inherited risk
- Increasing age
- Smoking
What are the symptoms of AAAs?
- Normally asymptomatic until acute expansion or rupture
- Can cause symptoms by compressing other nearby structures e.g. stomach, bladder, vertebra
- E.g. nausea, urinary frequency, back pain
How does a ruptured AAA present?
- Abdominal pain (+/- flank and groin pain)
- Back pain
- Pulsatile abdominal mass
- Transient hypotension
- Syncope
- Retroperitoneum can temporarily tamponade the bleed
- Sudden cardiovascular collapse
How do ruptured AAAs get diagnosed?
- Presence of pulsatile abdominal mass
- Ultrasonography (non-invasive, very sensitive, very specific)
- CT
How is an AAA treated?
- Smoking cessation
- Hypertension control
- Surveillance of AAA - if greater than 5.5 cm - refer to vascular surgeon
- Surgery
- Endovascular repair - relining aorta using an endograft
Outline how surgery is used to treat AAA?
- Stent inserted through femoral artery to seal renal arteries and common iliacs
- Or open surgical repair
- Clamp aorta
- Open aneurysm to remove thrombus and debris
- Suture in a synthetic graft to replace diseased segment
