Intestinal Pathology Part II Flashcards
80% of intestinal obstructions are due to what? (4)
- Herniations
- Adhesions
- Intussusception
- Volvulus
10-20% of intestinal obstructions are caused by what?
Tumors or infarcts
Intestinal obstruction is due to distention of the intestine caused by what?
Accumulation of gas and fluid proximal to and within the obstructed segment
With an intestinal obstruction, loss of fluid and electrolytes may be extreme, causing what? (3)
- Hypovolemia
- Renal insufficiency
- Shock
What may fluid loss be from?
- Vomiting
- Accumulation of fluids in the lumen
- Sequestration of fluid into the intestinal wall and peritoneal cavity
Where do most mechanical obstructions occur? Why?
Small bowel - smaller lumen, smaller diameter
Weakness or defect in the abdominal wall causing protrusion of peritoneum?
Hernia
What happens once the bowel has become trapped in a herniation? (5)
- Venous outflow obstructed
- Swelling of bowel
- Increased intramural pressure
- Decreased arterial perfusion
- ISCHEMIC BOWEL
How are intestinal herniations named?
Based on location - inguinal, femoral, umbilical
Trapped bowel?
Incarceration
Trapped and ischemic bowel?
Strangulation
Most frequent cause of obstruction worldwide?
Intestinal herniation
Risk factors for intestinal hernia? (3)
- Chronic cough
- Chronic straining
- Overweight
Clinical features of herniation? (4)
- Acute or chronic pain
- Bulges under the skin
- Nausea and vomiting
- Constipation
What usually occurs due to a tumor in the small bowel that disrupts motility?
Intussusception (telescoping)
What are usually due to an inflammatory process that link two segments of bowel together or compress it from the outside?
Adhesions
What are common causes of adhesions?
- Crohn’s, diverticulitis
- Abdominal surgery, cancers, infections
What tend to occur around a mesenteric point of attachment - both the vascular supply and the lumen are occluded at the site of twisting?
Volvulus
What presents similarly to a strangulated hernia and is a surgical emergency?
Severe acute mechanical obstruction
If blood flow is impaired, as in with a volvulus, it can cause mild hypoxia/ischemia and impaired function or __________
Food intolerance
Def. Ileus?
Bowel experiences greatly decreased motility - functional obstruction
Causes of functional bowel obstructions? (5)
- Post-surgical
- Intra-abdominal inflammation, hemorrhage, ischemia
- Metabolic or electrolyte abnormalities
- Medications that impair bowel motility
- Sepsis or peritonitis
What are some causes of Intestinal Ischemia? (5)
- Atrial fibrillation, valvular disease, embolic disease
- Hypercoagulable states
- Global hyperfusion
- Severe atherosclerosis
- Post-vascular surgery
Two phases of intestinal ischemia?
- Hypoxic injury
- Reperfusion injury
Hypoxic injury?
Epithelium, muscular layers are relatively resistant to ischemia, so damage is relatively limited early on
Reperfusion injury?
Free radical production, neutrophil infiltration, and release of inflammatory mediators, such as complement
proteins and TNF = more severe damage
What do acute and complete arterial obstruction tend to cause?
Transmural infarction
What does coagulative necrosis cause?
Perforation and inflammation of the serosa or peritoneum
Vulnerable intestinal areas?
Watershed zones
Splenic flexure?
Where the superior and inferior mesenteric arterial circulations terminate
Sigmoid colon and rectum?
Where the inferior mesenteric, pudendal, and iliac arterial circulations terminate
Population that intestinal ischemia tends to occur in?
Older individuals with co-existing cardiac or vascular disease
Typical presentation of acute transmural infarction?
- Sudden, severe abdominal pain and tenderness
- Nausea and vomiting
- Bloody diarrhea
- Grossly melanotic stool
Signs of intestinal ischemia overlap with what?
Acute appendicitis, perforated ulcer, and acute cholesystitis
Malformed submucosal and mucosal blood vessels?
Angiodysplasia
Where does angiodysplasia most often occur?
Cecum or right colon
Angiodysplasia accounts for ____ of major episodes of lower intestinal bleeding
20%
Pathogenesis of angiodysplasia contributing to mechanical and congenital factors?
- Focal dilation and tortuosity of overlying submucosal and mucosal vessels
- Cecum develops greatest wall tension
- Degenerative vascular changes
Clinical features of angiodysplasia?
- Hematochezia, melena, or iron deficiency
- Often asymptomatic if bleeding mild
Most common abdominal surgical emergency?
Appendicitis
Major complication of appendicitis?
Perforation
Traditional model of appendicitis?
A fecalith obstructs the lumen of the appendix, resulting in bacterial and mucous “build up”
Appendicitis can lead to distention and ischemia, which may be severe enough to cause?
Gangrene
______ infiltrate the full thickness of the mucosa and ____ can accumulate and fill the appendiceal lumen
Neutrophils; pus
In cases of perforation, the wall “bursts” or leaks ______, ________, and _______ into the peritoneum causing peritonitis
Fecal material, mucous, and bacteria
Encapsulation of the appendix and leaked material can lead to?
Abscess formation (greater omentum may encapsulate the “mess”)
“Free” perforation into the peritoneal cavity can cause? (4)
- 3rd spacing
- Vascular collapse
- Sepsis
- Portal vein thrombosis (rare)
What else can cause appendicitis?
- Mesenteric adenitis (big lymph nodes) from IBD or infection
- Cancer (rarely)
Appendicitis pain?
RLQ pain at McBurney’s point - often accompanied by nausea, vomiting, and anorexia
During pregnancy, where is appendix located?
RUQ
Symptoms of pelvic appendicitis?
Inguinal or suprapubic pain accompanied by dysuria. urinary frequency, diarrhea, tenesmus
Symptoms of perforation?
- High temp
- Hypotension
Diagnosis of appendicitis?
CT (best sensitivity and specificity) or ultrasound
Treatment for appendicitis?
Immediate surgical removal
