Session 9 Flashcards
What is peritonitis?
Inflammation of the serosal membrane that lines the abdominal cavity
•The peritoneal cavity is normally a sterile environment (no bacteria)
Two types:
- Spontaneously (primary)
- Breakdown of the peritoneal membranes leading to ‘foreign’ substances entering cavity (secondary)
- Subsequent inflammation follows a fairly uniform pattern
- Peritonitis can be infectious or sterile
What is primary peritonitis?
Spontaneous bacterial peritonitis (SBP)
Most commonly seen in patients with end stage liver disease (patients with cirrhosis)
SBP is an infection of ascitic fluid that cannot be attributed to any intra-abdominal, ongoing inflammatory, or surgically correctable condition
- Arises from ascites, and ascites is a pathological collection of fluid within the peritoneal cavity
- In cirrhosis it is caused by a combination of portal hypertension causing increased hydrostatic pressure in the veins draining the gut; and decreased liver function resulting in less albumin production causing decreased intravascular oncotic pressure. The result is the net movement of fluid into the peritoneal cavity
- Symptoms of abdominal pain, fever and vomiting
- Commonly symptoms are mild
- Diagnosed by aspirating ascitic fluid- neutrophil count >250 cells/mm³
What is secondary peritonitis?
Secondary (surgical) peritonitis is a result of an inflammatory process in the peritoneal cavity secondary to inflammation, perforation, or gangrene of an intra-abdominal or retroperitoneal structure
•If a viscera perforates then the contents will enter the peritoneal cavity
Common causes of secondary bacterial peritonitis include: • Peptic ulcer disease (perforated) • Appendicitis (perforated) • Diverticulitis (perforated) • Post surgery
Non bacterial causes: • Tubal pregnancy that bleeds (the peritoneal cavity is not enclosed in females) • Ovarian cyst • Blood is highly irritant to the peritoneal cavity
Blood can move up under diaphragm which can irritate the diphragm and cause shoulder pain (phrenic nerve supplies diaphram, C3,4,5 refers pain to shoulder)
How does peritonitis present and how is it treated?
Abdominal pain is the most common symptom - patient will often be rigid.
- This may come on gradually or acutely
- Diffuse abdominal pain is common in perforated viscera •Patients often lie very still as any movement makes the pain worse
- Often have knees flexed
- Shallow breathing
- Treatment approaches
- Control the infectious source
- Surgery
- Eliminate bacteria and toxins
- Antibacterial therapy
- Maintain organ system function
- Intensive care
What is bowel obstruction and what are its common causes?
Bowel obstruction is a mechanical or functional problem that inhibits the normal movement of gut contents
- This can affect the large and small intestine
- All ages can be affected
- Common causes in children include: • Intussusception • Intestinal atresia
- Common causes in adults include: • Adhesions • Incarcerated hernias
What is intussusception? What causes it? How is it treated?
Intussusception is when one part of the gut tube telescopes into an adjacent section
- The cause is not well known
- Potential motility issues
- ‘Lead point’ (a mass that precipitates the telescoping action) - Meckel’s diverticulum or Enlarged lymph node
- The intussusception can extend quite far (even prolapse out of rectum)
- As soon as the lymphatic and venous drainage is impaired you get oedema
- Enough oedema can impede arterial supply (infarction) so can lead to ischaemia
- Classically you get abdominal pain, vomiting and haematochezia
- Treatment - Air enema or Surgery
How does small bowel obstruction present? What causes it?
Nausea and vomiting (bilious) are most common symptom (early) as it has shorter distance to travel.
- Abdominal distension •Absolute constipation (late) so no faeces or air.
- Caused by:
- Intra-abdominal adhesions (abnormal fibrous bands between organs or tissues or both in the abdominal cavity that are normally separated). These arise after more than 50% of abdominal surgeries - Greater omentum involved in 80%, bowel in 50%
- Damage to mesothelium can also cause adhesions (direct trauma, post operative infection) - Capillary bleeding leads to exudation of fibrinogen
- Other consequences of adhesions are Abdominal pain and secondary infertility
- Hernias can narrow lumen enough to cause obstruction - Incarcerated groin hernias most common
- Inflammatory bowel disease -Crohn’s causing repeated episodes of inflammation/healing also causes narrowing
- Diagnosis
- History- abdominal pain is crampy, intermittent due to movement of small bowel (more frequent compared to biliary colic)
- Physical examination- abdominal distension, increased/absent bowel sounds, presence of hernia
- Imaging
Large bowel obstruction?
Typically affects older generation
- Common causes include:
- Colon cancer (60% of mechanical obstructions) • Diverticular disease (20%) • Volvulus- Sigmoid, Caecal (5%)
- Symptoms often appear gradually if caused by cancer but are abrupt with volvulus
- Change in bowel habit (cancer) • Abdominal distension • Crampy abdominal pain • Nausea/vomiting (later) due to distane from obstruction.
If you have a competent ileocaecal valve then you will get less vomiting/nausea as its more difficult for gut contents to back track however this si more ofan emegency as pressure will rise more rapidly and will eventually lead to perforation so this is a surgical emergency.
What is a volvulus?
- Part of the colon twists around its mesentery
- Most common in sigmoid colon (60%) and caecum (but can technically occur anywhere) as these are more mobile.
- Results in obstruction
- Can result from overloaded sigmoid colon (constipation) - Extra mass predisposes elongates the sigmoid (relatively smaller mesenteric attachment) - High fibre diets can also lead to sigmoid overload and twisting
- Caecal volvulus results in small and large bowel obstruction
On x-ray will look like a coffee bean.
How does age factor into prevalence of small vs large bowel obstruction? How are the symptoms different between the two conditions?
Age: Small bowel obstruction more common in younger age group - Large bowel obstruction older age group
• Causes explain this: (often large bowel obstruction will develop over time) •Competence of the ileo-caecal valve is of great importance - If it is competent then the colon cannot decompress proximally - Closed loop obstruction- ischaemia and perforation are more likely
For small bowel obstruction abdominal pain will be colicky (every3-4 minutes) whereas it will still be colicky in large bowel obstruction but every 10-15 minutes.
In sbo vomiting will be relatively early compared to lbo which will have vomiting relatively late
In sbo constipation will be relatively late whereas in lbo it will present relatively early.
How does the imaging differ between small and large bowel obstruction?
Often CT scans will be used to determine cause of obstruction
Howver X-ray still sometimes used:
Large bowel will have haustra (partial folds) whereas small bowel will have full folds (plicae circulares)
What is acute mesenteric ischaemia?
Symptomatic reduction in blood supply to the GI tract
- More common in females (75%) and if you have a history of peripheral vascular disease
- Acute occlusion (70% of cases) - Arterial embolism in SMA (50%)
- Non occlusive mesenteric ischaemia (20%) - Low cardiac output - watershed areas- areas at risk of hypoxia when blood flow is limited - e.g splenic flexure (large bowel)
- Mesenteric venous thrombosis (5-10%) - Systemic coagulopathy, malignancy (increases resistance so more diffcult for arterial blood to get through)
Most cases are in more elderly patients with a cardiovascular risk factors
- Can be difficult to diagnose because the symptoms can be fairly non-specific
- Abdominal pain (if present) is disproportionate to the clinical findings
- Classically pain comes on 30 minutes after eating (and last 4 hours) as this is when blood flow increases to bowel
- Nausea and vomiting are often present
- Pain can often left sided because the blood supply to the splenic flexure is most fragile
- Investigations
- Blood tests
- Metabolic acidosis/increased lactate levels
- Erect chest x-ray (to check for perforation)
- CT angiography is used (sensitivity is >90%) –intravenous contrast
Treatment
- Surgery- resection of ischaemic bowel
- bypass graft
- Thrombolysis/angioplasty if caught early
- Mortality is high (arterial thrombosis up to 70% mortality) - Often older patients with comorbidities
What can cause major upper GI bleeding?
peptic ulceration leading to perforation causing damge to slenicartery or gastroduodenal artery - duodenal ulcers mostcommon
Oesophageal varices - portosystemic anastomoses - often as a result of portal hypertension. portal drainage normally into left gastric vein which drains into portal vein - can reverse. Systemic drainage into azygous vein which drains into SVC
Splenomegally also caused as portal vein is normmaly contributed to by splenic vein so can acktrack to spleen.
Both cause Haematemesis (vomiting blood)
To treat oesophageal varices:
Band ligation
If bleeding not controlled by banding:
- TIPS (Transjugular intrahepatic portosystemic shunt) • An expandable metal is placed within the liver • Bridges the portal vein to an hepatic vein • Decompresses the portal vein pressure • Reduction in variceal pressure • Reduction in ascites
- Drug treatment • Terlipressin • Reduces portal venous pressure
What is an abdominal aortic aneurysm?
Abdominal aortic aneurysm (AAA) is a permanent pathological dilation of the aorta with a diameter >1.5 times the expected anteroposterior (AP) diameter of that segment, given the patient’s sex and body size.
The most commonly adopted threshold is a diameter of 3 cm or more.
More than 90% of aneurysms originate below the renal arteries.
- Usually due to the degeneration of the media layer of the arterial wall
- Media- smooth muscle cells with elastin and collagen
- AAAs form due to degradation of elastin and collagen
- Lumen gradually starts to dilate
- Risk factors • Male • Inherited risk • Increasing age • Smoking
- Most AAAs are asymptomatic
Most AAAs are infrarenal (>90%)
Normally asymptomatic until acute expansion or rupture
- Can cause symptoms by compressing other nearby structures • Stomach, bladder, vertebra • Nausea, urinary frequency and back pain
- Usual presentation of rupture: • Abdominal pain (+/-flank and groin pain) • Back pain • Pulsatile abdominal mass • Transient hypotension • Syncope
- Retroperitoneum can temporarily tamponade the bleed
- Sudden cardiovascular collapse (65% of ruptured AAAs die before hospital)
How do we diagnose abdominal aortic aneurysm?
- Physical examination - Presence of a pulsatile abdominal mass (less than 50% of cases)
- Ultrasonography - Non invasive and in the right hands very sensitive and specific - Can also detect free peritoneal blood
- Computed Tomography (CT) - Can detect a lot of surrounding anatomy that may be relevant - Planning for elective surgery
- Plain x-rays - If aneurysm has calcified then can be seen on plain x-rays
GI infections – approach to history taking and examination
Presenting complaint & history of presenting complaint:
- Diarrhoea – onset, duration, frequency, consistency (Bristol Stool Chart 1-7 from separate hard lumps to watery, no solid pieces), mucous/blood
- Vomiting – onset, frequency
- Pain – site, radiation, intermittent/continuous
Past Medical History:
- Immunodeficiency/immunocompromised state - HIV, steroids, transplant???
- Other GI conditions - Inflammatory bowel disease, crohns, coeliac?
Travel history:
- Where, when, how long
- Activities
- Food and drink
- Animal contact
- Travel companions & household contacts
Drug history:
- Recent antibiotics
- Proton pump inhibitors
- Laxatives
- Immunosuppressant medications
Social History:
• Occupation - e.g farmer has igher risk of salmonella and e.coli - also public health like are they going to spread their pathogen to the food then distribute it?
