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Obstruction, Large Bowel
Introduction
Background
Large-bowel obstruction (LBO) is an emergency condition
that requires early identification and intervention. The
etiology of LBO is age dependent.
LBO can result from either mechanical interruption of the
flow of intestinal contents or by the dilation of the colon in
the absence of an anatomic lesion (pseudo-obstruction).
Distinguishing between a true mechanical obstruction and a
pseudo-obstruction is important, as the treatment differs. 1
Pathophysiology
The prevalence of mechanical large-bowel obstruction (LBO)
increases with age as does it main causes, colon
cancer and diverticulitis. Sigmoid
volvulus and cecal
volvulus are also potential causes of this disorder.
Large-bowel obstruction.
Abdominal (KUB)
radiograph depicting
massive dilation of the colon
due to a cecal volvulus.
Radiograph courtesy of
Charles McCabe, MD.
Mechanical obstruction of the large bowel causes bowel
dilation above the obstruction. This causes mucosal edema
and impaired venous and arterial blood flow to the bowel.
Bowel edema and ischemia increase the mucosal
permeability of the bowel, which can lead to bacterial
translocation, systemic toxicity, dehydration, and electrolyte
abnormalities. Bowel ischemia can lead to perforation and
fecal soilage of the peritoneal cavity.
The pathophysiology of acute colonic pseudo-obstruction
(ACPO) is not clear, but it is thought to result from an
autonomic imbalance, which results from decreased
parasympathetic tone or excessive sympathetic output.
ACPO usually occurs in the setting of a wide range of medical
or surgical illnesses. If untreated, colonic ischemia or
perforation can occur. This syndrome is characterized by a
loss of peristalsis and results in the accumulation of gas and
fluid in the colon. The right colon and cecum are most
commonly involved. The risk of perforation for ACPO ranges
from 3-15%. The mortality rate is 15% with early care; this
increases to 36% if colonic ischemia or perforation develops.3
Clinical
History
1. Obtain history of bowel movements, flatus, obstipation
(ie, no gas or bowel movement), and symptoms.
 Major complaints include abdominal distention, nausea,
vomiting, and crampy abdominal pain.

Abrupt onset of symptoms makes an acute obstructive
event (eg, cecal or sigmoid volvulus) a more likely
diagnosis.
 History of chronic constipation, long-term cathartic use,
and straining at stools implies diverticulitis or carcinoma.
 Change in caliber of stools strongly suggests carcinoma.
When associated with weight loss, likelihood of
carcinoma increases.
2. Colonic lesion development history
 Right-sided colonic lesions can grow quite large before
obstruction occurs because of the large capacity of the
right colon and soft stool consistency.
 Sigmoid colon and rectal tumors cause colonic
obstruction much earlier in their development because
the colon is narrower and the stool is harder in that area.
3. Large-bowel obstruction prior to perforation
 Obstruction that dilates the colon causes vague, visceral
abdominal cramps. Pain receptors sense distention or
vigorous contraction.
 Peritonitis may ensue.
 When giving a history of obstipation, patients may state
that pants or belts are not fitting properly.
 Intervention is necessary to prevent perforation.
4. Obstruction secondary to intussusception
 Patients may describe intermittent, crampy abdominal
pain that is colicky and relieved by assuming fetal
position.
 Weight loss and fatigue are common.
5. Obstruction secondary to ACPO
 Symptoms are similar to LBO and usually develop over 37 days, or less commonly, over 24-48 hours.
 Eighty-three percent of patients complain of
mild/moderate pain, which is typically diffuse and colicky
in nature.
 Nausea and vomiting are not predominate complaints.
 Fever may be present in the setting of colonic ischemia
or perforation.
6. Pneumaturia, mucinuria, or fecaluria may occur when
fistulization of the sigmoid colon to the bladder occurs
secondary to diverticulitis or cancer.
Physical
1. Abdominal distention may be significant in patients with
a large-bowel obstruction.
 Bowel sounds may be normal early on but usually
become quiet.
 Abdomen is hyperresonant to percussion.
2. Palpation of the abdomen reveals tenderness. Fever,
severe tenderness, and abdominal rigidity are ominous
signs that suggest peritonitis secondary to perforation.
3. The cecum is the area most likely to perforate (following
the Laplace law). Sigmoid diverticulitis and a perforated
sigmoid secondary to carcinoma are clinically difficult to
differentiate.
4.
Guaiac-positive stool may be seen with carcinoma or
diverticulitis.
5. Rectal or lower sigmoidal mass may be palpated on
rectal examination. An abdominal mass or fullness may
be palpated if a tumor is present in the cecum.
Causes
1. Approximately 60% of mechanical large-bowel
obstructions (LBOs) are caused by malignancies, 20% are
caused by diverticular disease, and 5% are the result
of colonic volvulus.4,1,5
 Obstructions caused by tumors tend to have a gradual
onset and result from tumor growth narrowing the
colonic lumen.
Large-bowel
obstruction.
Contrast study demonstrates
colonic obstruction at the
level of the splenic flexure,
in this case due to
carcinoma.
Radiograph
courtesy of Charles McCabe,
MD.
are caused by tumors. Two main types of
intussusception affect the large bowel.
 Enterocolic intussusceptions involve both the small
bowel and the large bowel. These are composed of
either
ileocolic
intussusceptions
or
ileocecal
intussusceptions, depending on where the lead point is
located.
 Colocolic intussusceptions involve only the colon. They
are classified as either colocolic or sigmoidorectal
intussusceptions.
Acute colonic pseudo-obstruction (ACPO), or Ogilvie
syndrome, has many etiologies. This disorder is typically seen
in elderly patients who are hospitalized with a severe illness.
In a retrospective review of more than 1400 cases of ACPO,
the most common predisposing conditions were operative
and nonoperative trauma (11%), infections (10%), and
cardiac disease (10-18%).
Differential Diagnoses

Laboratory Studies
Obtain a blood sample for a CBC, electrolyte levels, lactate
level, prothrombin time (PT), and type and crossmatch.
Imaging Studies
1. Obtain an upright chest radiograph and flat and upright
abdominal radiographs. Chest radiographs demonstrate
free air if perforation has occurred; abdominal
radiographs may be diagnostic of sigmoid or cecal
volvulus (ie, kidney bean appearance on the radiograph).
Large-bowel
obstruction.
This
chest
radiograph
demonstrates free
air
under
the
diaphragm,
indicating
bowel
perforation.


Diverticulitis is associated with muscular hypertrophy of
the colonic wall. Repetitive episodes of inflammation
cause the colonic wall to become fibrotic and thickened,
leading to luminal narrowing.
Colonic volvulus results when the colon twists on its
mesentery. This impairs the venous drainage and arterial
inflow. Symptoms are usually abrupt.
Sigmoid volvulus typically occurs in older, debilitated
individuals with a history of chronic constipation, or
those living in an institutionalized setting.
Large-bowel
obstruction.
Massive dilation of the colon
due to a sigmoid volvulus.
Radiograph courtesy of
Charles McCabe, MD.
Abdominal Pain in Elderly Persons
Constipation
Diverticular Disease
Obstruction, Small Bowel
Workup
2.
3.

2.
Cecal volvulus is caused by a congenital defect in the
peritoneum, which results in inadequate fixation of the
cecum, and increased cecal mobility.1 Patients usually
present with this disorder in the sixth decade of life.6
Intussusception is primarily a pediatric disease. It is
estimated that between 5% and 16% of all
intussusceptions in the western world occur in adults.
Approximately two thirds of adult intussusception cases
4.
Intramural air is an ominous sign that suggests colonic
ischemia.
The absence of free air does not exclude perforation
(this finding may be absent in half of all perforations).
Additional contrast studies include an enema with watersoluble contrast (ie, Gastrografin) or CT with intravenous
and oral or rectal contrast.
Large-bowel
obstruction.
Gastrografin study in a
patient with obstipation
reveals colonic obstruction at
the
rectosigmoid
level.
Radiograph
courtesy
of
Charles McCabe, MD
5.
Contrast studies that reveal a column of contrast ending
in a "bird's beak" are suggestive of colonic volvulus.
Large-bowel
obstruction.
Contrast study of patient
with cecal volvulus. The
column of contrast ends in a
"bird's beak" at the level of
the volvulus. Radiograph
courtesy of Charles McCabe,
MD.
Procedures
 Insert a nasogastric tube if the patient has been
vomiting. Intravascular volume usually is depleted,
and early intravenous fluid resuscitation with
isotonic saline or Ringer lactate solution is
necessary.
Treatment
Emergency Department Care
Initial therapy includes volume resuscitation, appropriate
preoperative antibiotics, gastric decompression, and timely
surgical consultation.
Consultations
Obtain early consultation from a general surgeon. Surgical
intervention is frequently indicated, depending on the cause
of the obstruction.
1. Carcinoma
 Left colon9
 Surgical treatment includes resection without primary
anastomosis or resection with primary anastomosis and
intraoperative lavage.
 Endoscopically placed expandable metal stents can be
used to relieve the LBO, thus allowing for a primary
colorectal anastomosis.
 Right colon
 Palliative colorectal stents are an option in patients who
are poor surgical candidates or have advanced cancer.
 Right colonic obstructions are treated with a right
colectomy and a primary anastomosis between the
ileum and the transverse colon. Patients with high-risk
features for surgery (advanced age, complete
obstruction, or severe comorbidities) may benefit from
stent placement until patient can be optimized for a
surgical procedure.10
2. Diverticulitis
 Patients with persistent obstruction despite appropriate
medical management are treated surgically. Surgical
resection follows the same principles as the treatment of
carcinomas.
 Elective colonic resection is offered to patients with
recurrent disease.
3. Volvulus
 Sigmoid volvulus1
 First choice is sigmoidoscopy with volvulus reduction.
 Second choice is sigmoid colectomy.
 Cecal volvulus1
 The primary treatment is surgical, often a cecopexy
needs to be performed to prevent recurrence.
 Second choice is colonoscopy, due to the high risk of
colonic perforation.
4. Intussusception: Adult colonic intussusception is treated
with primary colon resection without prior reduction.
5. Acute colonic pseudo-obstruction
 Underlying precipitant factors must be identified and
corrected. If no perforation, pseudo-obstruction is
treated with conservative management for the first 24
hours. This includes bowel rest, hydration, and
management of underlying disorders.
 Electrolyte abnormalities should be corrected, and
medications that slow colonic motility (eg, narcotics,
anticholinergics) should be stopped, if possible.
 Pharmacologic treatment with neostigmine or
colonoscopic decompression may be effective in cases
that do not resolve with conservative management.
Colonoscopic decompression may be successful in as
many as 80% of patients with ACPO.7
 Surgical intervention is is associated with a high
mortality and morbidity and is reserved for refractory
cases or cases complicated by perforation.7
Medication
Bowel obstruction frequently necessitates surgical
intervention. However, antibiotics should be started in the
ED. Coverage must include gram-negative aerobic and gramnegative anaerobic organisms. The following antibiotics do
not represent an all-inclusive list.
Antibiotics
Therapy must cover all likely pathogens in the context of this
clinical setting.
Clindamycin (Cleocin)
A lincosamide useful to treat serious skin and soft-tissue
infections caused by most staphylococcal strains. Also
effective against aerobic and anaerobic streptococci, except
enterococci.
Inhibits bacterial protein synthesis by inhibiting peptide chain
initiation at bacterial ribosome, where it preferentially binds
to 50S ribosomal subunit, inhibiting bacterial growth.
Adult: 450-900 mg IV q8h
Pediatric: 20-40 mg/kg/d IV divided tid/qid
Metronidazole (Flagyl)
Imidazole ring-based antibiotic active against various
anaerobic bacteria and protozoa. Used in combination with
other antimicrobial agents (used alone in Clostridium
difficile enterocolitis).
Adult” 1 g IV loading dose, followed by 0.5 g IV q6h or 1 g IV
q12h
Aztreonam (Azactam)
Monobactam that inhibits cell wall synthesis during bacterial
growth. Active against gram-negative bacilli. Effective against
aerobic gram-negative organisms.
Adult: 2 g IV q8h
Pediatric: 30 mg/kg IV q6h or q8h
Cefoxitin (Mefoxin)
Second-generation cephalosporin indicated for management
of infections caused by susceptible gram-positive cocci and
gram-negative rods. Effective against aerobic and anaerobic
gram-negative organisms.
Adult: 2 g IV q8h
Pediatric: 80-100 mg/kg/d IV divided tid/qid
Cefotetan (Cefotan)
Second-generation cephalosporin indicated for management
of infections caused by susceptible gram-positive cocci and
gram-negative rods.
Adult: 2 g IV q12h
Imipenem and cilastatin (Primaxin)
Effective against aerobic and anaerobic gram-negative
organisms.
Adult: 0.5 g IV q6h
Pediatric
<12 years: Not recommended
>12 years: Administer as in adults
Meropenem (Merrem)
Bactericidal broad-spectrum carbapenem antibiotic that
inhibits cell-wall synthesis. Effective against most grampositive and gram-negative bacteria.
Adult: 1 g IV q8h
Pediatric: 40 mg/kg IV q8h
Follow-up
Complications
 Perforation
 Sepsis
 Intra-abdominal abscess
 Death
Prognosis
1. If treated early, outcome is generally good.
2. If secondary to carcinoma, outcome is dependent on the
carcinoma prognosis.
Miscellaneous
Medicolegal Pitfalls
1. Suspect bowel perforation in patients with persistent
unexplained tachycardia, fever, or abdominal pain.
2. Malignancy should be considered for all patients who
present with LBO.