comprehensive ppt on nec

1. Dr Afnan Shamraiz

2. Introduction:

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
intestine occurs.
 The incidence of NEC is 1–5% of infants in NICU.
 Although rare, the disease does occur in term infants (10%)

Birth weight
incidence,fatality
Gestational age

3. Epidemiology
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

5. Risk factors influencing NEC
prediposition
.

Enteral feeding:
 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

6. Prematurity
Deficient mucosal barrier (suppressed GI
hormones and mucosal enzymes)
 Dysfunctional intestinal host defense
system
 Decreased motility
 Dysregulation of intestinal microcirculation
(increased bacterial overgrowth)

6

7. Intestinal Ischemia





Term infants (polycythemia, asphyxia,
exchange transfusion, congenital heart
disease, IUGR)
PDA
Indocin
Cocaine exposure in utero
Gastroschisis
7

8. Risk Factors: in Term Babies
Limited to those that have some underlying illness or
condition requiring NICU admission.
 Congenital Heart Disease
 Intrauterine growth restriction
 Polycythemia
 Hypoxic-ischemic events

The mean gestational age of infants with NEC is 30 to
32 weeks,

9. 
PATHOLOGY AND PATHOGENESIS:
Distal part of the ileum
Involved most
frequently
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,
inflammation,
and the host's response to that injury like circulatory,
immunologic, inflammatory responses resulting in necrosis
of the affected area.

10. 
PATHOLOGY AND PATHOGENESIS: contd..

Various bacterial and viral agents, including

, have been recovered from cultures.
 However,
is identified.


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.

11. PRIMARY INFECTIOUS AGENTS
Bacteria, Bacterial toxin, Virus,
Fungus
CIRCULATORY INSTABILITY
Hypoxic-ischemic event
Polycythemia
MUCOSAL INJURY
INFLAMMATORY MEDIATORS
Inflammatory cells (macrophage)
Platelet activating factor (PAF)
Tumor necrosis factor (TNF)
Leukotriene C4, Interleukin 1; 6
ENTERAL FEEDINGS
Malabsorption, gaseous
distention H2 gas production,
Endotoxin production

12. Enteral feeding
Ischemic or toxic
mucosal damage
Bacterial proliferation
Loss of mucosal integrity
nvasion of mucosa and submucosa
Intramural gas
TransmuralnecrosisI
Perforation
Peritonitis

13. Microbiologic Flora and Infection
Several organisms have been accused, but non has been
proven to be causative:
 Enterobacteriaceae
 Enterobactersakazakii
 Coagulase-negative staphylococci: SIP
 Closrtidium perfringens
 Candida species: SIP
 Cytomegalovirus
 Torovirus
 HIV
 Mucormycosis

14. Mean Age at Presentation
Gestational age (weeks)
Age at onset (days)
< 30
20
31-33
14
34
5
Full term
2
14

15. Clinical Presentation

Course of the disease
 Fulminant presentation
 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
VLBW infants

16. Clinical Presentation

Abdominal (enteric)
signs:






Distension
Tenderness
Gastric aspirate, vomiting
Ileus
Abdominal wall
erythema, induration
 Ascites
 Abdominal mass
 Bloody stool
Systemic
signs:
 Respiratory







distress,
apnea,
bradycardia
Lethargy,
irritability
Temp.
instability
Poor feeding
Hypotension
Acidosis
Oligurea
Bleeding
diathesis

17. Stage I (suspected disease):
mild systemic signs
(apnoea, bradycardia, temperature
instability),
 mild GIT signs (abdominal distension,
large gastric aspirates, bloody stools),
 non-specific or normal radiological
signs)


18. 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)


19. Stage III (advanced disease):
severe systemic illness (with
haemodynamic instability), .
 additional GI signs (gross abdominal
distension, peritonitis),
 severe radiological signs
(pneumoperitoneum),
 additional laboratory findings (e.g.
metabolic and respiratory acidosis,
disseminated intravascular
coagulopathy


20. Staging NEC – Bell’s Classification
Stage Clinical findings
Radiographic findings
I: Suspected NEC
Ia
Temp instability, apnea, lethargy,
increased residuals, abd distention.
Ib
Normal or mild ileus.
See above. + grossly bloody stool.
II: Proven NEC
IIa
IIb
See above. + absent bowel sounds. +abd Intestinal dilation, ileus,
tenderness. Appear mildly ill.
ascites, pneumatosis
intestinalis.
See above. Appear moderately ill.
+metabolic acidosis. +thrombocytopenia.
III: Advanced NEC
IIIa
See II. Bowel intact. Hypotension,
bradycardia, apnea. +peritoneal signs.
DIC, neutropenia.
IIIb
See III. + Bowel perforation.
Portal venous gas.
Pneumoperitoneum
(football sign) – specific
for stage IIIb.

21. 
MODIFIED BELL’S STAGING OF NEC:
Based on:
1. Systemic Signs
2. Intestinal Signs
3. Radiological Signs
Classified into:
I. Suspected:
II. Definite :
A (Mildly ill) ,
B (Moderately ill)
III. Advanced:
A (Severely ill,bowel intact),
B (Severely ill,bowel perforated)

23. Initial work up: what to look for
No lab test is specific for NEC


CBC
↑WBC, ↓WBC, ↓PMN
 Thrombocytopenia
 Neutropenia (<1500/microL) –poor
prognosis

DIC panel (PT/INR, PTT, Fibrinogen,
D-dimer)
 Elevated PT/INR, PTT, D-dimer
 Decreased Fibrinogen

METABOLIC (may have values
similar to those found in sepsis)
 Hyponatremia (<130)
 Hyperglycemia
 Hyperkalemia

Blood gas
 Metabolic acidosis


Blood culture
Fecal occult blood test
Serial measurements of CRP –
diagnostic and prognostic

24. Blood studies:
Thrombocytopenia
COMMON TRIAD
OF SIGNS
Persistent
Hyponatremia
Severe Refractory
Metabolic Acidosis

25. Radiology studies

Abdominal X-ray:
○ 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

28. RADIOLOGICAL FINDINGS

Pneumatosis Intestinalis
 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

29. Pneumatosis Intestinalis

30. 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.

31. Fixed Loop Sign
The finding of a single
loop or several loops
of dilated(enlarged)
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
intestine

32. RADIOLOGICAL FINDINGS

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
mortality

33. Portal Air
Dilated stomach &
loops of bowel

35. RADIOLOGICAL FINDINGS

Pneumoperitoneum
 free air in the peritoneal cavity secondary to
perforation
○ falciform ligament may be outlined
 “football” sign
 surgical emergency

36. Example of football sign:

38. 

Intestinal perforation.
Abdominal Xray in NEC demonstrates marked distention and massive
pneumoperitoneum
Free air below the anterior abdominal wall.
Example of cross-table lateral
x-ray with free air

39. NEC with perforation

40. Rigler sign
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.

41. 
Abdominal ultrasound:
 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
liver.
 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
hypoechoic rim

42. 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
hyperechoicfoci (arrows),
which represent intramural
gas

43. 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
posterior artifact.

44. Pneumatosis
Necrosis

45. Histopathology
Normal
small
bowel
NEC:
Hemorrhagic
necrosis
beginning at
the mucosa
and working
its way down
into the wall
http://library.med.utah.edu/WebPath/PEDHTML/PED045.html

46. Histopathology
Pneumatosis in
the submucosa
of the small
bowel
http://library.med.utah.edu/WebPath/PEDHTML/PED049.html

47. 
Differential diagnosis of NEC :

Specific infections (systemic or intestinal)- Pneumonia,
Sepsis.

Gastrointestinal obstruction, volvulus, malrotation,

Isolated intestinal perforation.

Severe Inherited Metabolic disorders. (e.g., galactosemia
with Escherichia coli sepsis)

Feeding intolerance

Idiopathic focal intestinal perforation can occur
spontaneously or after the early use of postnatal steroids
and indomethacin.

48. 
TREATMENT:

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
immediately.

49. Algorithm for the treatment of necrotizing enterocolitis

51. 
TREATMENT: Contd..
Umbilical catheters if present should be removed.

Ventilation should be assisted as required.

Intravascular volume replacement with crystalloid or blood
products.

Cardiovascular support with volume and/or inotropes.

Correction of hematologic, metabolic, and electrolyte
abnormalities.

Careful attention to respiratory status, coagulation profile,
and acid-base and electrolyte balance are important.


52. 
MONITORING:

Sequential abdominal grith measuremet

Sequential anteroposterior and cross-table lateral or
lateral decubitus abdominal x-rays to detect intestinal
perforation;

Serial determination of hematologic status,

Serial determination of electrolyte status, and

Serial determination of acid-base status.

53. 
Indications for surgery :
Absolute indications:
 Evidence of perforation on abdominal roentgenograms
(pneumoperitoneum) or
 Positive abdominal paracentesis (stool or organism on
Gram stain from peritoneal fluid).

Relative indications:
 Failure of medical management,
 Single fixed bowel loop on roentgenograms,
 Abdominal wall erythema, or
 A palpable mass.


54. 
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
perforation.

55. Initial signs of possible NEC (bell’s stage I )
•NPO
•GI decompression- low constant sucton, replace output with electrolytes
•CBC with differentials, blood culture, CRP, S.Electrolytes
•Abdominal radiograph
•Begin antibiotics
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
•Monitor electrolytes
•Monitor electrolytes
•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
•Hemodynamic support
•Monitor coagulation abnormalities and
correct
Indications for surgery
•Intestinal perforation
•Fixed adynamic loop – necrotic gut
•Signs suggestive of necrotic gut –persistent severe thrombocytopenia, severe
metabolic acidosis

56. 
PROGNOSIS.:

Medical management fails in about 20–40% of patients
with pneumatosis intestinalis at diagnosis; of these, 10–
30% die.

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.

57. 
complications….

After massive intestinal resection,
-Complications from postoperative NEC include
short-bowel syndrome (malabsorption, growth
failure, malnutrition),

Premature infants with NEC who require surgical
intervention or who have concomitant bacteremia are at
increased risk for adverse growth and
neurodevelopmental outcome.

The overall mortality is 9% to 28% regardless of surgical
or medical intervention.

58. 
PREVENTION:

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
therapy.

Alteration of the immunologic status of the intestine using
immunoglobulin A (IgA) and immunoglobulin G (IgG)
supplementation.