Bowel Obstruction Flashcards
What is a bowel/intestinal obstruction?
Interruption of the normal passage of bowel contents through the bowel, either due to functional or mechanical obstruction
What is an acute abdomen?
Sudden onset severe abdominal pain due to the presence of an abdominal pathology which if left untreated (within 72 hours), will result in patient morbidity and mortality.
- Requires rapid and specific diagnosis
Classification of bowel obstruction?
A. Anatomical
1. Small bowel obstruction
2. Large bowel obstruction
B. Pathological
1. Mechanical (dynamic) - peristalsis working again a mechanical obstruction
2. Functional (adynamic) - absence of peristalsis, without “obstruction” or non-propulsive peristalsis (pseudo-obstruction)
Symptoms of small bowel obstruction?
High
1. Early profuse vomiting, with dehydration
2. Minimal distension
Low
1. Predominantly central abdominal distension
2. Multiple central fluid seen
Symptoms of large bowel obstruction?
- Early and pronounced distension
- Mild pain
- Late vomiting and dehydration
- Proximal colon and cecum distended (competent ileo-cecal valve)
What is mechanical bowel obstruction?
physical barrier preventing movement of bowel contents
Exaples of mechanical intra-luminal bowel obstruction?
- Fecal Impaction (stools) – i.e. bed-ridden patients
- Gallstone ‘ileus’
- Foreign Body e.g bezoars, worms
Examples of intra-mural mechanical bowel obstruction?
- Masses- benign Vs malignant
- Inflammatory Strictures (TB / Crohn’s, diverticulitis, radiation colitis)
- Intestinal Atresia
Examples of extra-mural mechanical bowel obstruction?
- Intraperitoneal bands and adhesions
- Hernia
- Volvulus – sigmoid / cecum (more commonly sigmoid)
- Intussusception
Name 2 types of functional bowel obstruction?
- paralytic ileus
- pseudo obstruction
What is paralytic ileus?
- hypo-mobility w/o obstruction : accumulation of gas & fluids
- Failure of transmission of peristaltic waves due to NM failure (Myenteric (Auerbach’s) and submucosa (Meissner’s) plexuses
What are the causes of paralytic ileus?
- Post-operative (most common)
- Infection – intra-abdominal sepsis
- Reflex Ileus
- Metabolic – uraemia & hypokalaemia most common
What is pseudo obstruction?
Recurrent obstruction (usually colon) occurring without a mechanical cause or acute intra-abdominal disease
Examples of pseudo-obstructions?
- Small Intestinal Pseudo-obstruction (idiopathic or a/w familial visceral myopathy)
- Acute Colonic Pseudo Obstruction eg, Toxic Megacolon
- Chronic Colonic Pseudo Obstruction eg, Hirschsprung Disease
Pathophysiology of a bowel obstruction?
- Dilatation of bowel proximal to obstruction & collapse of distal bowel
2, Hyper-peristalsis
3
Pathophysiology of a bowel obstruction?
- Dilatation of bowel proximal to obstruction & collapse of distal bowel
- Hyper-peristalsis
- Strangulation
What is hyper peristalsis?
- Gas Accumulation - significant overgrowth of aerobic and anaerobic organisms from swallowed air(gas composition – O2 , CO2 , H2S & N2)
- Fluid Accumulation - impaired absorption from gut leading to sequestration of fluid in the bowel lumen (risk of dehydration and electrolyte imbalance)
What is strangulation?
Compromised venous return due to dilated bowel
- Increased capillary pressure
- Local mural distention due to fluid and cellular exudation
- Compromised artery supply -HAEMORRHAGIC INFARCTION
- Risk of translocation of intestinal bacterial and toxins into peritoneal cavity -PERITONITIS AND SEPTICEMIA
- When long segments of bowel are strangulated, sequestration of blood occurs in the strangulated segment -HYPOVALEMIC SHOCK
Presentation of a bowel obstruction?
- abdominal pain
- vomitting
- abdominal distension
- constipation/obstipation
- Fever
- Urine output
- GIT bleed or underlying disorder
- Past Surgical History: Previous surgery
- Past Medical History: Previous stroke, HIV
- Risk of Malignancy: Age, Loss of weight/appetite, Previous cancer, Family history of cancer
Describe the presentation of abdominal pain?
Visceral pain secondary to distention: colicky, 4-5 days duration
Centered on the umbilicus (small bowel) or lower abdomen (large bowel)
Complete obstruction: constant, sharp pain
Strangulation: pain is severe and constant
Volvulus: sudden, severe pain –
Paralytic ileus: no pain involved
Describe the presentation of vomiting?
Ask if projectile, bilious or fecal stained
Time and load of vomitus can determine if obstruction is proximal or distal
High SB: greenish blue, bile stained
Lower SB: brown and increasingly foul smelling (feculent = thick brown foul)
LB: uncommon esp. if competent ileocecal valve, usually late symptom
Describe the presentation of abdominal distention?
Prominent feature in large intestinal (distal) obstruction
Usually not seen in high obstruction, esp. if patient is vomiting
Closed loop: RIF bulge that is hyper-resonant
SB: distension in centre of abdomen
Describe the presentation of constipation/obstipation?
- Constipation (where flatus only is passed)
- Obstipation (where neither faeces nor flatus is passed) – cardinal feature of complete intestinal obstruction
- Ask patient about NORMAL BOWEL OUTPUT FREQUENCY
How can you tell the difference between SBO vs LBO in terms of presentation?
Vomiting first = high obstruction. Distention first = Low obstruction
