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3- Large bowel obstruction:
a. Mild abdominal pain
b. Distention is early and pronounced
c. Vomiting and dehydration are late
d. Abdominal x ray: distention of proximal colon and caecum
* Intestinal obstruction is also classified according to the onset of
presentation into: Acute, chronic, acute on chronic and subacute
I- Acute obstruction:
a. Usually in small bowel obstruction
b. Sudden, severe, colicky, central abdominal pain
c. Early vomiting
d. Abdominal distention and constipation
II- Chronic obstruction:
a. Usually in large bowel obstruction
b. Lower abdominal colic
c. Absolute constipation is early symptom
d. Distention at the periphery of the abdomen
e. Vomiting is late to occur
III- Acute on chronic:
a. Chronic constipation and mild pain
b. Abdominal distention and vomiting
IV- Subacute: when there is incomplete obstruction of the lumen
** Intestinal obstruction can be classified according to the
condition of blood supply to the bowel:
1- Simple intestinal obstruction: blood supply of the bowel is intact
2- Strangulated bowel: bowel is obstructed with interference with
blood supply of the bowel usually by hernial rings or intraperitoneal
adhesions.
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Etiology
Condition after small bowel obstruction.
Overall, the most common causes of mechanical obstruction are
adhesions, hernias, and tumors. Other general causes are diverticulitis,
foreign bodies (including gallstones very rare), volvulus (twisting of
bowel on its mesentery), intussusception (telescoping of one segment
of bowel into another) commonly in neonates and infants, and fecal
impaction. Specific segments of the intestine are affected differently.
Causes of Intestinal Obstruction
Location Causes
1- Colon: Tumors (usually in left colon), diverticulitis
(usually in sigmoid), volvulus of sigmoid or
cecum, fecal impaction, Hirschsprung's disease
2- Duodenum
a- Adults Cancer of the duodenum or head of pancreas,
ulcer disease
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b- Neonates Atresia, volvulus, bands, annular pancreas
3- Jejunum and ileum
a- Adults Hernias, adhesions (common), tumors, foreign
body, Meckel's diverticulum, Crohn's disease
(uncommon), Ascaris infestation, midgut
volvulus, intussusception by tumor (rare)
b- Neonates Meconium ileus, volvulus of a malrotated gut,
atresia, intussusceptions
Small bowel obstruction.
222
Strangulating obstruction of small bowel.
Pathophysiology
In simple mechanical obstruction, blockage occurs without vascular
compromise. Ingested fluid and food, digestive secretions, and gas
accumulate above the obstruction. The proximal bowel distends, and
the distal segment collapses. The normal secretory and absorptive
functions of the mucosa are depressed, and the bowel wall becomes
edematous and congested. Severe intestinal distention is selfperpetuating and progressive, intensifying the peristaltic and secretory
derangements and increasing the risks of dehydration and progression
to strangulating obstruction. Strangulating obstruction is obstruction
with compromised blood flow; it occurs in nearly 25% of patients
223
with small-bowel obstruction. It is usually associated with hernia,
volvulus, and intussusception. Strangulating obstruction can progress
to infarction and gangrene in as little as 6 h. Venous obstruction occurs
first, followed by arterial occlusion, resulting in rapid ischemia of the
bowel wall. The ischemic bowel becomes edematous and infarcts, leading
to gangrene and perforation. In large-bowel obstruction, strangulation is
rare (except with volvulus).
Perforation may occur in an ischemic segment (typically small bowel)
or when marked dilatation occurs. The risk is high if the cecum is
dilated to a diameter ≥ 13 cm. Perforation of a tumor or a diverticulum
may also occur at the obstruction site.
* Factors causing distention:
1- Gas: sources of gas in the gastrointestinal tract are:
a. bacterial over growth (aerobes and anaerobes) result in considerable
gas production.
b. swallowed gas: the oxygen (O2) and carbon dioxide (CO2) are
absorbed, and the intraluminal gas is formed mainly of nitrogen
(90%) and hydrogen sulfide.
2- Fluid: various digestive juices (8000 ml), after obstruction fluid
accumulate in the lumen,absorption retarded, dehydration and
electrolyte loss due to:
a. Reduced oral intake
b. Defective intestinal absorption
c. Losses due to vomiting
d. Sequestration into the lumen
Symptoms and Signs:
Obstruction of the small bowel causes symptoms shortly after onset:
224
abdominal cramps centered around the umbilicus or in the epigastrium,
vomiting, and - in patients with complete obstruction - constipation.
Patients with partial obstruction may develop diarrhea. Severe, steady
pain suggests that strangulation has occurred. In the absence of
strangulation, the abdomen is not tender. Hyperactive, high-pitched
peristalsis with rushes coinciding with cramps is typical. Sometimes,
dilated loops of bowel are palpable. With infarction, the abdomen
becomes tender and auscultation reveals a silent abdomen or minimal
peristalsis. Shock and oliguria are serious signs that indicate either late
simple obstruction or strangulation. Obstruction of the large bowel
usually causes milder symptoms that develop more gradually than those
caused by small-bowel obstruction. Increasing constipation leads to
symptoms of constipation and abdominal distention. Vomiting may
occur (usually several hours after onset of other symptoms) but is not
common. Lower abdominal cramps unproductive of feces occur.
Physical examination typically shows a distended abdomen with loud
borborygmi. There is no tenderness, and the rectum is usually empty.
A mass corresponding to the site of an obstructing tumor may be
palpable. Systemic symptoms are relatively mild, and fluid and
electrolyte deficits are uncommon.
Picture of volvulus.
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Volvulus often has an abrupt onset. It is twisting or axial rotation of
portion of bowel about its mesentery, it is a form of closed loop
obstruction. Pain is continuous, sometimes with superimposed waves
of colicky pain..
A. Volvulus of small bowel, usually occurs in the lower ileum, secondary
to adhesions to the parietes or to female pelvic organs Treatment:
· Untwisting of the involved loop.
· Treatment of the cause (adhesion).
· Excision of gangrenous segment
B. Volvulus of the caecum:
Lax freely mobile caecum, twist is usually clockwise. More common in
females.
Clinical features: classical of acute intestinal obstruction, palpable
tympanic mass in the midline or left side of the abdomen.
· Plain x ray: gas filled ileum and occasionally distended caecum.
· Barium enema: diagnostic (absence of barium in the caecum).
·
]
Strangulation of small bowel.
226
Treatment:
laparotomy. Untwisting of the caecum, decompression may be needed.
Caeopexy (fixation of caecum to the RIF). Caecostomy or Rt
haemicolectomy if gangrene present.
Diagnosis
Abdominal x-ray series
Supine and upright abdominal x-rays should be obtained and are usually
adequate to diagnose obstruction. Although only laparotomy can
definitively diagnose strangulation, careful serial clinical examination
may provide early warning. Elevated WBCs and acidosis may indicate
that strangulation has already occurred.
Small bowel obstruction
227
Radiological diagnosis:
1- Erect and supine abdominal X ray
- The diameter of the distended viscus is not diagnostic
- In obstructed small bowel: straight segments of bowel, centrally
located and lie transversely, and no gas seen in the colon
- Jejunum is characterized by presence of valvulae conniventes,
across the wall, regularly spaced giving a ladder effect
- Ileum: is featureless
- Caecum: round gas shadow in the right iliac fossa (RIF)
- Large bowel are characterized by haustral fold, spaced irregularly,
indentations are not placed opposite each others
- Volvulus of the sigmoid: dilated colon loop (with or without
haustration) arising from the pelvis and extending obliquely across
the spine to the upper abdomen
- Fluid levels:
· They appear later than the gas
· Below 2 years of age: few fluid levels are physiological
· In adults: 2 inconstant fluid levels may be normal one at duodenal
cap and the other at the terminal ileum.
· Fluid levels are more in advanced cases, maximum when paralysis
occur, the number of fluid levels is directly proportional to the
degree of obstruction and its site ( the number increasing the
more distal the lesion) resulting in the stepladder pattern.
· Low colonic obstruction: does not produce fluid levels in the
small bowel unless advanced
· High colonic obstruction: produce fluid levels if the iliocaecal
valve is incompetent
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· Colonic obstruction: is associated with large amount of gas in the
caecum
· Fluid levels are also seen in paralytic ileus, pseudo- obstruction,
and in non obstructing conditions e.g. inflammatory bowel
disease (IBD), acute pancreatitis and intra-abdominal sepsis
- Impacted foreign body can be visualized on abdominal x ray
- Gall stone ileus (rare): gas in the biliary tree with stone visible in
the RIF.
2- Water soluble enema: differentiate colonic obstruction from pseudo-
obstruction
3- Barium follow through is contraindicated in intestinal obstruction.
Air fluid levels
229