Intestinal obstruction Flashcards
Define intestinal obstruction
Normal flow on normal flow of intestinal contents is interrupted. It can be classified pathologically into mechanical
obstruction (dynamic) or function obstruction (adynamic)
Mechanical : there is obstruction
Functional : there is no obstruction
mechanical (peristalsis working against a mechanical obstruction)
functional (absence of peristalsis without obstruction)
Small bowel obstruction is more common than large bowel. What is the common causes of SBO ?
Adhesion , hernia , strictures and cancers
How bowel obstruction manifestated ?
simple obstruction > bowel ischemia > gangrenous bowel > perforation
Bowel ischemia is resulted from compromised arterial supply .
4 cardinal symptoms of IO (AbCDV)
Abdominal pain
Constipation
Distension (Abdominal)
Vomiting
Pathophysiology of abdominal pain
- Visceral pain secondary to distention – colicky in nature
- Centred on the umbilicus (small bowel) or lower abdomen (large bowel)
- Progression to more focal, constant pain → need to rule out complications (i.e. perforation / peritonitis)
In term of vomiting , what is the different between small bowel and large bowel?
▪ Proximal Small Bowel Obstruction: greenish blue, bile stained (obstruction distal to ampulla of vater)
▪ Distal Small Bowel Obstruction: brown and increasingly foul smelling (feculent = thick brown foul)
▪ Large Bowel: uncommon to have vomiting esp. if competent ileocecal valve, usually late symptom
Proximal : distal to ampulla -> bile is released into duodenum
Distal : foul smell and brown color arise due to the stagnation and decomposition of intestinal contents in the affected portion of the bowel
Ileocecal valve : the valve that separate the small and large intestine
Abdominal distension :
does it prominent in large bowel or distal small bowel obstruction ? and why
Prominent in large bowel ,
because :
i)large bowel contents are typically solid , consisting of feces which can cause noticeable distension
ii) large intestine has a wider diameter than the small intestine ,when obstruction occur here , enlargement is more noticeable
Differential diagnosis of IO
-mechanical causes
Mechanical causes :
-gallstones
-parasites
-foreign body
-stricture (abnormal narrowing of a tubular structure within the body)
-intraperitoneal bands and adhesions
-hernia
-volvulus (twisted intestine)
hernia cause IO when there is strangulation
Differential diagnosis of IO
-functional causes
Paralytic ileus
-Hypo-mobility w/o obstruction leading to accumulation of gas & fluids with associated distention,
vomiting, absence of bowel sounds and obstipation
Pseudoobstruction
-Recurrent obstruction (usually colon) that occurs in the absence of a mechanical cause or acute intraabdominal disease
-eg : toxic megacolon
How to differentiate SB and LB in abdominal X ray
Small intestine
: centrally located
:circular or transverse folds of mucosa ( valvulae conniventes)
Large intestine
:peripherally located
:haustration (d/t contraction of colon muscles)
Investigation - Biochemical
Biochemical (FAULBIA)
- FBC: leukocytosis with left shift may indicate complications
- U/E/Cr: any dehydration/electrolyte imbalances due to (or acute renal failure from dehydration)
- ABG: acidosis from bowel ischemia or alkalosis due to vomiting (more for pyloric stenosis in children)
- Lactate (trend): surrogate measurement for anaerobic respiration, important if suspecting of ischemic bowel
- Inflammatory markers – CRP, procalcitonin
- Blood cultures (if fever, tachycardia, hypotension)
- Amylase – ? acute pancreatitis (AXR may just show small bowel dilatation)
Imaging Investigation
i)erect CXR
-to look for free air under diaphragm , any aspiration pneumonia
ii) abdominal CXR
- In general ≥ 5 fluid levels are diagnostic of intestinal obstruction
-Assess for complications: Rigler’s Sign / double-wall sign → pneumoperitoneum. Thumb-print sign / pneumatosis
intestinalis → ischemic bowel
iii)CT abdomen and pelvis
-▪ Able to identify transition point, severity of obstruction, any fecalization in small bowel proximal to transition, closed-loop
obstruction
▪ Able to identify complications – pneumoperitoneum, ischemic bowel (no bowel wall enhancement), necrotic bowel
(pneumatosis intestinalis)
▪ Target sign – intussusception
▪ Whirl sign – rotation of SB mesentery in volvulus
▪ Air in distal bowel with no transition point – paralytic ileus
Management
i)ABC - give supplemental oxygen oxygenation may be affected due to splinting of the diaphragm
ii)Keep NBM - because bowel rest can help the recovery of the patient
iii)NG tube insertion - large bore to prevent small diameter tube blocked
iv)IV fluid rehydration
