Summary about bowel obstruction including Hx, examinations, ddx & Tx

1. Bowel obstruction
• Mechanical bowel obstruction “dynamic”( tumor, adhesions)
• functional bowel obstruction “adynamic”(Temporary functional impairment of peristalsis)
Failure of propulsion of intestinal contents
Etiology
Etiology of bowel obstruction
SBO LBO
Most common
causes
•Bowel adhesions
◦ history of abdominal surgery, abdominal tuberculosis
•Incarcerated hernias: second most common cause of SBO
•Malignant tumors (colorectal
carcinoma)
•Diverticulitis
•Volvulus
Other causes
•Strictures (e.g., Crohn disease)
•Malignant tumors or metastases
•Gallstone ileus
•Foreign body impaction
•Adhesions
•Strictures (e.g., ibd)
•Foreign body impaction
Functional (adynamic):
Paralytic ileus
Mesentric vascular occlusion (MVO)
Bowel obstruction → stasis contents and gas proximal to the obstruction
→ ↑ intraluminal pressure
• Gaseous abdominal distention → sequestration of fluids within the distended bowel loops
(third spacing) → dehydration and hypovolemia
• Vomiting → loss of fluid and Na+, K+, H+, and Cl- → hypokalemia, metabolic
alkalosis, and hypovolemia
• Compression of intestinal veins and lymphatics → bowel wall edema → compression of
intestinal arterioles and capillaries → bowel ischemia
↑ Bowel wall permeability → translocation of microbes to the peritoneal cavity → sepsis
Necrosis and perforation of the bowel wall → peritonitis
Pathophysiology
Clinical features
features associated with the site of bowel obstruction
Clinical feature SBO LBO
Abdominal pain • Colicky, periumbilical • Colicky or constant
Vomiting and/or nausea
• Early onset
• Larger volume of vomitus than in LBO
• Bilious
• Late onset
• Initially bilious
• Progresses to fecal vomiting (presence of feces in vomitus)
Constipation or obstipation • Late onset in proximal SBO • Early onset in distal LBO
Abdominal distention • Typically less severe than in LBO • Early and significant abdominal distention
Examination findings
• Dehydration and possible hypovolemia (hypotension, dry mucous membranes)
• Diffuse abdominal tenderness
• Tympanic percussion
• Increased high-pitched bowel sounds (early) or the absence of any bowel sounds (late)
• Collapsed, empty rectum on digital rectal examination (complete bowel obstruction); or impacted feces
Yellow - green fluid
Paralytic ileus (No colic)

2. Diagnostics
A- Imaging
• Initial imaging modality (depends on type of bowel obstruction and hemodynamic
stability of the patient)
1- Acute bowel obstruction
Stable patients (CT abdomen and pelvis + IV contrast)
Unstable patients (X-ray erect position or abdominal U/S first)
1- Dilation
2- Multiple air fluid level
3- For detecting SBO or LBO
• Transverse diameter
Small bowel > 3 cm
Large bowel > 6 cm
Cecum > 9 cm
• Site
SBO (Dilated loops are central)
LBO (Dilated loops are Peripheral)
• Mucosal Folds
SBO (Plicae Circulares)
LBO (Haustra)
2- Subacute bowel obstruction
• Preferred: CT abdomen and pelvis with IV contrast
• Alternatives: MRI with and/or without IV contrast
Barium Study
Barium enema
• Bird beak sign (volvulus)
• Apple core sign (colonic malignancy)
Barium Swallow
Barium follow-through
Barium meal
B- Laboratory investigations
1- CBC (WBC Increase in cases of strangulation)
2- Serum electrolytes (decreased sodium and potassium levels)

3. Differential diagnoses
vomiting or Constipation
abdominal pain
Abdominal distention
Abdominal tenderness
◦ Bowel perforation
◦ Mesenteric ischemia
◦ Inflammatory bowel disease
◦ Acute appendicitis
Mechanical bowel obstruction vs. paralytic ileus
Mechanical bowel obstruction Paralytic ileus
Definition • structural barrier • impairment of peristalsis
Etiology
• Small bowel obstruction
◦ Bowel adhesions
◦ Incarcerated hernias
• Large bowel obstruction
◦ Malignant tumors (colorectal carcinoma)
◦ Volvulus
• Recent abdominal surgery
• Atherosclerotic disease
• Abdominal infections or inflammatory conditions
• medications (opioids, anticholinergics, antiparkinsonian
agents)
Clinical
features
• Colicky abdominal pain
• Vomiting
• Obstipation or constipation
• Abdominal distention
• High-pitched bowel sounds (early)
• Absent bowel sounds (late)
• Diffuse, continuous abdominal pain
• Vomiting
• Obstipation or constipation
• Marked abdominal distention
• Absent bowel sounds
Findings on
imaging
• Dilated bowel loops proximal to obstruction
• Collapsed bowel loops distal to obstruction
• Multiple air-fluid levels
• Cause of obstruction (e.g., tumor)
• Pendular peristalsis on ultrasound (absent in late
mechanical bowel obstruction)
• Diffusely dilated small and large bowel loops
• No evidence of mechanical obstruction
• Absent peristalsis
◦ Acute pancreatitis
◦ Diverticulitis
◦ Toxic megacolon
◦ Chronic megacolon
Treatment
1- Non-operative management
• Early postoperative bowel obstruction (within 6 weeks of abdominal surgery)
• Partial bowel obstruction with no evidence of complications
1- ABCDE Approach
2- Tow lines IV
3- NPO (Bowel Rest)
4- IV Fluid & Electrolyte & analgesics (nonopioid analgesics)
5- NG Tube (if vomiting & Distention)
6- Imaging according to approach
2- Interventional management
• Complicated BO (signs of ischemia, perforation)
• Closed-loop BO (volvulus, Irreducible hernia)
• patients with hemodynamic instability (heart rate, blood pressure)
• Failure of nonoperative management (i.e., no improvement after 3 days of NOM)
• Procedure (Exploratory laparotomy)

4. 3- Endoscopic intervention
Can be considered for bowel obstruction with no signs of strangulation or perforation
Complications
• Bowel ischemia
• Bowel perforation
• Peritonitis
Preoperative
• Decompression
• Relieves congestion & oedema of the intestines and helps return of tone & peristalsis
Operative
• For anaesthesia (prevents vomiting & aspiration pneumonia)
• For surgeon (Easy closure of the abdomen)
Postoperative
• prevent massive toxic absorption after release of obstruction
• Reduces postoperative paralytic ileus (distention and vomiting)
NG Tube Benefits: