Necrotising enterocolitis

Introduction Necrotizing enterocolitis (NEC) is a serious disease of unknown cause and is charaterised by various degrees of mucosal or transmural necrosis of intestine. Is the most common gastrointestinal medical/surgical emergency occurring in neonates.

Epidemiology There is no consistent association between gender/season/socioeconomic status and rates of NEC . However male VLBW babies have a higher mortality. Mortality is higher in black infants with NEC (even when matching for birthweight and other characteristics) . 95% of NEC occurs after enteral feeds have been introduced . Human milk is protective with a three to ten-fold reduction in NEC (compared to formula fed) .

Age at onset The age at onset is inversely related to birth weight and gestational age. mean age of 3 weeks in the <30 weeks 2 weeks for the 31-33 weeks 5 days for >34 weeks and 2 days for full-term infant

Incidence <1500gms 10% 1500-2500gms 5% >2500gms 2%

Pathogenesis: Despite many years of research, its pathogenesis remains unknown. Several factors appear to play either a primary or a secondary role: infectious agents/toxins, mesenteric ischemia/tissue hypoxia and prematurity .

Risk factors Prematurity Perinatal asphyxia Shock Cyanotic heart disease Hypertonic formula Too much – too fast formula feeding Exchange transfusion Congenital gi anomalies Polycythemia

Premature infants are at risk because of immaturity of: - Gastrointestinal motility - Digestive ability - Circulatory regulation - Intestinal barrier function: If this is immature, or reduced, bacteria are able to penetrate the mucosal barrier and cause inflammation more easily. Immature goblet cells and an immature mucin layer may lead to increased permeability and breaching of the intestinal epithelial barrier. - Immune defense

Infectious agents Occasional epidemics of NEC have occurred in some nurseries, and have been associated with Klebsiella, E. coli, Clostridia, coagulase negative Staphylococcus, rotavirus, and coronavirus.

Symptoms feeding intolerance abdominal distension bloody stools apnea lethargy temperature instability hypoperfusion

Signs Gastrointestinal Signs Systemic signs Respiratory failure Increased abdominal girth Visible intestinal loops Obvious abdominal distention and decreased bowel sounds Hematochezia (passage of bright red ) A palpable abdominal mass Erythema of the abdominal wall Systemic signs Respiratory failure Decreased peripheral perfusion Circulatory collapse

Criteria for diagnosis (any 2) Prefeed gastric aspirate volume of more than 50% of the last feed volume or abdominal distension ( increase in abdominal girth >2 cms). Frank or occult blood and/or reducing substance in stool. Radiological evidences of pneumatosis intestinalis /portal air /free air under the diaphgram.

Laboratory evaluation Common laboratory abnormalities include thrombocytopenia leukocytosis electrolytes imbalance metabolic acidosis hypoxia or hypercapnia NEC is associated with bacteremia in approximately 30% of the cases, and a blood culture should be obtained before antibiotics are started.

Radiographic findings  nonspecific diffuse gaseous distension asymmetric, disorganised bowel pattern ‘featureless’ loops dilated bowel loops bowel wall thickening increased peritoneal fluid diagnostic signs pneumatosis intestinalis (virtually pathognomonic) portal venous gas pneumoperitoneum (although may not be due to NEC)

Pneumatosis intestinalis

Pneumatosis intestinalis

Normal (top) versus necrotic section of bowel

Resected portion of necrotic bowel

Picture of acute bowel necrosis seen in NEC

Differential diagnosis Intestinal Volvulus Gastroesophageal Reflux Neonatal Sepsis Intestinal Malrotation Meningitis Hospital Acquired Infection

Complications Pneumoperitoniun Localised peritonitis Intestinal obstruction Lactose intolerance Short gut syndrome

Management Nil by mouth to rest the bowel . NG or OG tube to decompress the bowel with low intermittent orogastric suction . IV fluids TPN IV antibiotics for 10-14 days Ampicillin/gentamicin or cefotaxime Plus metronidazole or clindamycin Treat shock, DIC etc. Surgery if deteriorating or perforated/necrotic bowel suspected . Intubation/ventilation for apnoea . Serial bloods and abdominal x-rays. Can restart oral feeds 7-10 days after pneumatosis clears.

Surgical Care In acute illness Ischemic segment should be resected with construction of ileostomy or colostomy. It is better to just drain the abdomen and perform a defunctioning enterotomy until the acute inflammation subsides,when definite resection is easier. In recovery phase Stricture. Persistent malabsorption.

Patient Care Inpatient care Outpatient Care Prolonged parenteral nutrition is essential to optimize the baby's nutrition while the gastrointestinal tract is allowed enough time for recovery and return to normal functioning. Prolonged parenteral nutrition may be associated with cholestasis and direct hyperbilirubinemia. Outpatient Care If a baby goes home with a colostomy, parents need thorough instruction regarding the baby's care. Babies who have undergone intestinal resection may experience short-gut syndrome

Prognosis Overall the prognosis is poor. Mortality of those undergoing medical treatment is about 20% . Mortality of those coming to surgery is about 30% . Amongst survivors about 30% develop ischaemic colonic strictures .

Prevention Feeding human milk (Start feeds slowly using low volume). Small increments (20 ml/kg/day) when increasing feeds. Antenatal steroids . Ig A supplementation. Arginine supplementation. Oral antibiotics. Probiotics.

Corticosteroids Corticosteroids given to women in early labour help the babies' lungs to mature and so reduce the number of babies who die or suffer breathing problems at birth common serious neurological and abdominal problems, e.g. cerebroventricular haemorrhage and necrotising enterocolitis, that affect babies born very early. New concepts in necrotizing enterocolitis. Current opinion in Pediatrics 2001;13:111-5