Necrotizing Enterocolitis: an acquired neonatal
acute intestinal necrosis of unknown etiology .
NEC is the most common life-threatening emergency of the
gastrointestinal tract in the newborn.
Various degrees of mucosal or transmural necrosis of the
The incidence of NEC is 1–5% of infants in NICU.
Although rare, the disease does occur in term infants (10%)
Incidence: 0.3-2.4 / 1000 live births
2-5 % of all NICU admissions
5-10 % of VLBW infants
Over 90 % of cases occur in preterm babies
About 10 % occur in term newborns: essentially limited
to those that have some underlying illness or condition
requiring NICU admission
Sex, race, geography, climate has no role in
determining the incidence of NEC
Risk factors influencing NEC
Aggressive advancement of feeding.
Non human milk feeding
Abnormal bacterial colonization
Prolonged emperical antibiotic therapy
Decreased commensal flora
Increased pathogenic bacteria
Maternal cocaine abuse – 2.5 times increases risk
Prematurity is the single greatest risk factor
Deficient mucosal barrier (suppressed GI
hormones and mucosal enzymes)
Dysfunctional intestinal host defense
Dysregulation of intestinal microcirculation
(increased bacterial overgrowth)
Risk Factors: in Term Babies
Limited to those that have some underlying illness or
condition requiring NICU admission.
Congenital Heart Disease
Intrauterine growth restriction
The mean gestational age of infants with NEC is 30 to
PATHOLOGY AND PATHOGENESIS:
Distal part of the ileum
Proximal segment of colon
In fatal cases, gangrene may extend from the stomach
to the rectum.
NEC probably results from an interaction between loss of
mucosal integrity due to factors like ischemia, infection,
and the host's response to that injury like circulatory,
immunologic, inflammatory responses resulting in necrosis
of the affected area.
PATHOLOGY AND PATHOGENESIS: contd..
Various bacterial and viral agents, including
, have been recovered from cultures.
NEC rarely occurs before the initiation of enteral feeding
and is much less common in infants fed human milk.
Coagulation necrosis is the characteristic histologic finding
of intestinal specimens.
Ischemic or toxic
Loss of mucosal integrity
nvasion of mucosa and submucosa
Microbiologic Flora and Infection
Several organisms have been accused, but non has been
proven to be causative:
Coagulase-negative staphylococci: SIP
Candida species: SIP
Mean Age at Presentation
Gestational age (weeks)
Age at onset (days)
Course of the disease
Slow, paroxysmal presentation
The onset of NEC usually occurs in the 1st 2
weeks of life (with a mean age at onset of 12
days) but can be as late as 3 months of age in
Stage I (suspected disease):
mild systemic signs
(apnoea, bradycardia, temperature
mild GIT signs (abdominal distension,
large gastric aspirates, bloody stools),
non-specific or normal radiological
Stage II (definite disease):
mild systemic signs
with additional GI signs (absent bowel
sounds, abdominal tenderness),
specific radiological signs (dilated loops
of intestines, pneumatosis intestinalis or
portal venous air),
abnormal laboratory investigations (e.g.
metabolic acidosis, thrombocytopenia)
Stage III (advanced disease):
severe systemic illness (with
haemodynamic instability), .
additional GI signs (gross abdominal
severe radiological signs
additional laboratory findings (e.g.
metabolic and respiratory acidosis,
Staging NEC – Bell’s Classification
Stage Clinical findings
I: Suspected NEC
Temp instability, apnea, lethargy,
increased residuals, abd distention.
Normal or mild ileus.
See above. + grossly bloody stool.
II: Proven NEC
See above. + absent bowel sounds. +abd Intestinal dilation, ileus,
tenderness. Appear mildly ill.
See above. Appear moderately ill.
+metabolic acidosis. +thrombocytopenia.
III: Advanced NEC
See II. Bowel intact. Hypotension,
bradycardia, apnea. +peritoneal signs.
See III. + Bowel perforation.
Portal venous gas.
(football sign) – specific
for stage IIIb.
MODIFIED BELL’S STAGING OF NEC:
1. Systemic Signs
2. Intestinal Signs
3. Radiological Signs
II. Definite :
A (Mildly ill) ,
B (Moderately ill)
A (Severely ill,bowel intact),
B (Severely ill,bowel perforated)
Initial work up: what to look for
No lab test is specific for NEC
↑WBC, ↓WBC, ↓PMN
Neutropenia (<1500/microL) –poor
DIC panel (PT/INR, PTT, Fibrinogen,
Elevated PT/INR, PTT, D-dimer
METABOLIC (may have values
similar to those found in sepsis)
Fecal occult blood test
Serial measurements of CRP –
diagnostic and prognostic
○ Abnormal gas pattern, ileus
○ Bowel wall edema
○ Pneumatosis intestinalis
○ Fixed position loop
○ Intra hepatic-portal venous gas ( in the
absence of UVC)
○ Pneumoperitonium - left lateral decubitus or
cross-table lateral views
hydrogen gas within the bowel wall
○ product of bacterial metabolism
a. linear streaking pattern
○ more diagnostic
b. bubbly pattern
○ appears like retained meconium
○ less specific
Supine AXR, The bowel is mildly dilated with
gas, mainly on the left side. The bubbly
pattern of gas seen mainly in the right lower
quadrant represents intramural gas.
Fixed Loop Sign
The finding of a single
loop or several loops
small intestine that
remain unchanged in
position for 24 to 36
hours is referred to as
the persistent “rigid”
loop sign and
suggests lack of
movement of the
intestine due to death
of a segment of
Portal Venous Gas
extension of pneumatosis intestinalis into the
portal venous circulation
○ linear branching lucencies overlying the liver
and extending to the periphery
○ associated with severe disease and high
Abdominal Xray in NEC demonstrates marked distention and massive
Free air below the anterior abdominal wall.
Example of cross-table lateral
x-ray with free air
Rigler's sign, also known as the double wall sign, is seen
on an x-ray of the abdomen when air is present on both sides
of the intestine, i.e. when there is air on both the luminal and
peritoneal side of the bowel wall.
Thick-walled loops of bowel with hypomotility.
Intraperitoneal fluid is often present.
Intramural gas can be identified in early-stage NEC
In the presence of pneumatosis intestinalis, gas is
identified in the portal venous circulation within the
Color Doppler US is more accurate than abdominal
radiography in depicting bowel necrosis in NEC.
Gas bubbles in hepatic parenchyma
Pseudo-kidney sign- central echogenic focus and
Sonogram of a bowel loop
shows differentiation of
inter luminal gas from
intramural gas. The
intraluminal gas (L) is
surrounded by a thickened
bowel wall. Within the
bowel wall are multiple
which represent intramural
Sonogram shows a bowel
loop with a large amount of
intramural gas (arrows) in the
more dependent and
vertically oriented parts of the
loop. This gives the bowel
wall a typical granular
appearance and causes a
its way down
into the wall
of the small
Differential diagnosis of NEC :
Specific infections (systemic or intestinal)- Pneumonia,
Gastrointestinal obstruction, volvulus, malrotation,
Isolated intestinal perforation.
Severe Inherited Metabolic disorders. (e.g., galactosemia
with Escherichia coli sepsis)
Idiopathic focal intestinal perforation can occur
spontaneously or after the early use of postnatal steroids
Rapid initiation of therapy is required for suspected as well
as proven NEC cases.
There is no definitive treatment for established NEC and,
therapy is directed at supportive care and preventing
further injury with
-Cessation of feeding,
-Nasogastric decompression, and
-Administration of intravenous fluids.
Once blood has been drawn for culture, systemic
antibiotics (with broad coverage for gram-positive, gramnegative, and anaerobic organisms) should be started
Algorithm for the treatment of necrotizing enterocolitis
Umbilical catheters if present should be removed.
Ventilation should be assisted as required.
Intravascular volume replacement with crystalloid or blood
Cardiovascular support with volume and/or inotropes.
Correction of hematologic, metabolic, and electrolyte
Careful attention to respiratory status, coagulation profile,
and acid-base and electrolyte balance are important.
Sequential abdominal grith measuremet
Sequential anteroposterior and cross-table lateral or
lateral decubitus abdominal x-rays to detect intestinal
Serial determination of hematologic status,
Serial determination of electrolyte status, and
Serial determination of acid-base status.
Indications for surgery :
Evidence of perforation on abdominal roentgenograms
Positive abdominal paracentesis (stool or organism on
Gram stain from peritoneal fluid).
Failure of medical management,
Single fixed bowel loop on roentgenograms,
Abdominal wall erythema, or
A palpable mass.
Ideally, surgery should be performed after
intestinal necrosis develops, but before
perforation and peritonitis occurs.
Peritoneal drainage may be helpful for patients
with peritonitis who are too unstable to
undergo surgery. Peritoneal drainage is more
successful in patients with isolated intestinal
Initial signs of possible NEC (bell’s stage I )
•GI decompression- low constant sucton, replace output with electrolytes
•CBC with differentials, blood culture, CRP, S.Electrolytes
Mild to Moderate (Bell’s stage II)
Advanced (Bell’s Stage III)
•Serial abdominal radiographs
•Serial abdominal radiographs
•Broad spectrum antibiotics for 7- 10 days •Broad spectrum antibiotics for 7- 10 days
•NPO for 5-10 days, parentaral nutrition •NPO for 10-14 days, parentaral nutrition
•Serial CBCs every 12h to 24h for 2-3 days
•Serial CBCs every 12h to 24h for 2-3 days
•Co-mangement with paediatric surgeon
•Monitor coagulation abnormalities and
Indications for surgery
•Fixed adynamic loop – necrotic gut
•Signs suggestive of necrotic gut –persistent severe thrombocytopenia, severe
Medical management fails in about 20–40% of patients
with pneumatosis intestinalis at diagnosis; of these, 10–
Early postoperative complications : Wound infection,
dehiscence, and stomal problems (prolapse, necrosis).
Later complications : Intestinal strictures develop at the
site of the necrotizing lesion in about 10% of surgically or
medically managed patients.
After massive intestinal resection,
-Complications from postoperative NEC include
short-bowel syndrome (malabsorption, growth
Premature infants with NEC who require surgical
intervention or who have concomitant bacteremia are at
increased risk for adverse growth and
The overall mortality is 9% to 28% regardless of surgical
or medical intervention.
Always better than cure!
Newborns exclusively breast-fed have a reduced risk of NEC.
Early initiation of aggressive feeding may increase the risk of NEC
in VLBW infants.
Gut stimulation protocol of minimal enteral feeds followed by
judicious volume advancement may decrease the risk.
Probiotic preparations have also decreased the incidence of NEC.
. Induction of GI maturation.
Incidence of NEC is significantly reduced after prenatal steroid
Alteration of the immunologic status of the intestine using
immunoglobulin A (IgA) and immunoglobulin G (IgG)