Pathophysiological Basis of Clinical
Dr Imran Javed.
MBBS, FCPS Surgery.
Associate Professor Surgery.
Fiji National University.
• Intestinal Obstruction: A mechanical blockage
arising from a structural abnormality that
presents a physical barrier to the progression
of gut contents.
• Partial or complete
• Simple or strangulated
• Ileus: is a paralytic or functional variety of
• A 50 year old gentleman presents with
abdominal pain, distension and absolute
constipation with repeated episodes of
• His vital sign were stable, abdomen distended
with diffuse tenderness but minimal
peritonism. Bowel Sounds are hyperactive.
• Is this bowel obstruction or ileus?
• Is this a small or large bowel obstruction?
• Is this proximal or distal obstruction?
• What is the cause of this obstruction?
• Is this a complex or simple obstruction?
• How should I start investigating my patient?
• What is the role of other supportive investigations?
• What is my immediate/ intermediate treatment plan?
• What are the indications for surgery?
• 8L of isotonic fluid received by the small intestines (saliva,
stomach, duodenum, pancreas and hepatobiliary )
• 6L re-absorbed
• 2L enter the large intestine and 200 ml excreted in the
• Air in the bowel results from swallowed air ( O2 & N2) and
bacterial fermentation in the colon ( H2, Methane & CO2),
600 ml of flatus is released
• Enteric bacteria consist of coliforms, anaerobes and
• Normal intestinal mucosa has a significant immune role
• Distension results from gas and/ or fluid and
can exert hydrostatic pressure.(Laplace Law)
• In case of Bowel Obstruction, Bacterial
overgrowth can be rapid
• If mucosal barrier is breached it may result in
translocation of bacteria and toxins resulting
in bactaeremia, septaecemia and toxaemia.
Pathological Basis of clinical events.
• Initial overcoming of the obstruction(CONSTIPATION) by increased
peristalsis(COLICKY ABDOMINAL PAIN)
• (ABDOMINAL DISTENTION) & (VOMITING)Increased intraluminal
pressure by fluid and gas, sequestration of fluid into the lumen from
the surrounding circulation
• Lymphatic and venous congestion resulting in edematous tissues
• Vomiting result in hypovolemia and electrolyte imbalance (ILEUS).
• Further: anoxia, mucosal necrosis and perforation and
• Bacterial over growth with translocation of bacteria and it’s toxins
causing bacteremia and septicemia.(SYSTEMIC SIGNS)
Principles of Management
SUCK & DRIP.
• Decompress with Naso-gatric Tube or Flatus Tube.
• Replace lost fluid in vomiting or 3rd space.
• Correct electrolyte abnormalities (Hypcholremic,
Hyopnatremic, Hypokalemic, metabolic Alkalosis)
• Recognize strangulation (Hernia) and perforation
• Systemic antibiotics (Broad Spectrum).
Causes of Small Bowel Obstruction.
• Luminal Causes:
• Foreign Body
• Gall stone
• Food Particles
• Ascaris lumbricoides
Causes of Small Bowel Obstruction
• Postoperative adhesions.
• Congenital adhesions & Bands.
• Hernia (External & Internals, Incisional)
• Volvulus (Around base of Mesentery)
Small Bowel Adhesions
• Accounts for 60-70% of All Small Bowel Obstructions.
• Results from peritoneal injury, platelet activation and fibrin
• Associated with starch covered gloves, intraperitoneal sepsis,
haemorrhage and wash with irritant solutions iodine and other
• As early as 4 weeks post laparotomy. The majority of patients
present between 1-5 years
• Colorectal Surgery 25%
• Gynaecological 20%
• Appendectomy 14%
• 70% of patients had a single band
• Patients with complex bands are more likely to be readmitted
• Readmission in surgically treated patients is 35%
• Accounts for 20% of SBO
• Commonest 1. Femoral hernia 2. ID inguinal 3.
Umbilical 4. Others: incisional and internal H.
• The site of obstruction is the neck of hernia
• The compromised viscus is with in the sac. Ischemia
occurs initially by venous occlusion, followed by edema
and arterial compromise.
• Attempt to distinguish the difference between:
• Incarceration, Sliding, Obstruction.
• Strangulation is noted by: Persistent pain,
Discoloration, Tenderness, Constitutional symptoms
Other Common causes of Small Bowel
• Intussusception: part of the intestine has
invaginated into another section of intestine.
• Gall stone Ileus: caused by an impaction of a
gallstone within the lumen of the small
intestine. Which enters the gut lumen via
• Crohn’s Disease:is a type of inflammatory
bowel disease (IBD)
Large Bowel Obstruction
• Distinguishing ileus from mechanical
obstruction is challenging
• According to Laplace's law: maximum pressure
is at the it’s maximum diameter. Cecum is at
the greatest risk of perforation
• Perforation results in the release of formed
feaces with heavy bacterial contamination
Causes of Large Bowel Obstructions.
• 1. Carcinoma: The commonest cause, 18% of colonic
carcinomas present with obstruction
• 2. Benign stricture: Due to Diverticular disease,
Ischemia, Inflammatory bowel disease.
• 3. Volvulus:
A. Sigmoid Volvulus: Results from long redundant,
faecaly loaded colon with a narrow pedicle
B. Caecal Volvulus
• 4. Hernia.
• 5.Congenital:Hirschusbrung, anal stenosis and agenesis
Diagnosis of Intestinal Obstruction
• Clinical Features:
Colicky Abdominal Pain, Absolute Constipation,
Vomiting & Abdominal Distension.
Plain X-ray Films (Erect & Supine).
Contrast studies (Single & Double) Diagnostic as
well as therapeutic.
Ultrasound Scan & Doppler Studies.
CT Scan (Plain & Contrast).
CBC, ESR, Electrolytes, Urea & Creatinine Levels,
LFTs, RFTs, Blood Glucose level, Serum Amylase
level, cultures etc.
• Pathological: Urine Analysis & Cultures, FNAC
or Biopsy for enlarged Lymph Nodes.
• Laparoscopic: Diagnostic as well as
Comparative Features in History
• Pre-existing change in bowel habit
•Colicky in the lower abdomen
•Vomiting is late
•Cecum ? distended
•Distal small bowel
•Pain: central and colicky
•Vomitus is feculent
•Distension is severe
•May continue to pass flatus and feaces before absolute constipation
•Pain is rapid
•Vomiting copious and contains bile jejunal content
•Abdominal distension is limited or localized
• Abdominal distension and it’s
• Hernial orifices
• Visible peristalsis
• Cecal distension
• Tenderness, guarding and
• Bowel sounds
• High pitched
• Rectal examination
• Vital signs:
• P, BP, RR, T, Sat
• Anaemia, jaundice, LN
• Assessment of vomitus if
• Full lung and heart
• Systemic examination
If deemed necessary.
• Views: Supine, Erect and CXR
• Gas pattern: Gastric, Colonic and 1-2 small
• Fluid Levels: Gastric, 1-2 small bowel
• Check gasses in 4 areas: Caecal, Hepatobiliary,
Free gas under diaphragm, Rectum
• Look for soft tissue masses, psoas shadow
• Look for fecal pattern
The Difference between small and
large bowel obstructionCentral ( diameter 5 cm max)
Ileum: may appear tubeless
Peripheral ( diameter 8 cm max)
Presence of haustration
US Scan & Doppler Studies
• Free fluid,
• Abdominal Masses,
• Intestinal mucosal folds,
• Intestinal pattern of peristalsis,
• Doppler of mesenteric vasculature,
• Solid organs evaluation.
Role of CT in Diagnosis
• Used with iv contrast, oral and rectal contrast
• Able to demonstrate abnormality in the bowel
wall, mesentery, mesenteric vessels and
• Ensure: patient vitally stable with no renal
failure and no previous allergy to iodine.
Findings on CT Scan Abdomen
It can define
• the level of obstruction
• The degree of obstruction
• The cause: volvulus, hernia, luminal and mural
• The degree of ischemia
• Free fluid and gas
Barium & Gastrografin studies
• Barium should not be used in a patient with
• As: follow through, enema: Limited use in the
• Gastrografin is used in acute abdomen but is
• Useful in recurrent and chronic obstruction
• May able to define the level and mural causes.
• Can be used to distinguish adynamic and
Indications for Surgery
• Evidence of strangulation (hernia….etc)
• Signs of peritonitis resulting from perforation or ischemia
In the next 24-48 hours:
• Clear indication of no resolution of obstruction ( Clinical,
• Diagnosis is unclear in a virgin abdomen
• The cause has been diagnosed and the patient is stabilized
Causes of Intestinal Ileus
• Postoperative and bowel resection
• Intraperitoneal infection or inflammation
• Extra-abdominal: Chest infection, Myocardia infarction
• Endocrine: hypothyroidism, diabetes
• Spinal and pelvic fractures
• Retro-peritoneal haematoma
• Metabolic abnormalities:
• Bed ridden
• Drug induced: morphine, tricyclic antidepressants
Is this an ileus or obstruction
• Is there an under lying cause?
• Is the abdomen distended but tenderness is not marked.
• Is the bowel sounds diffusely hypoactive.
• Is the bowel diffusely distended
• Is there gas in the rectum
• Are further investigations (CT or Gastrografin studies)
helpful in showing an obstruction.
• Does the patient improve on conservative measures
Initial Management in the ER
• Air way (O2 60-100%)
• Insert 2 lines if necessary
• IVF : Crytloids at least 120 ml/h. (determined by estimated fluid loss
and cardiac function). Add K+ at 1mmmol/kg
• Draw blood for lab investigations
• Decompress with Naso-gastric tube and secure in position
• Insert a urinary catheter (hourly urinary measurements) and start a
fluid input / output chart
• Intravenous antibiotics (no clear evidence)
• If concerns exist about fluid overloading a central line should be
• Follow-up lab results and correction of electrolyte imbalance