Necrotising Enterocolitis

Necrotising enterocolitis (NEC) is one of the most common neonatal surgical emergencies and is a potentially life-threatening condition.

Introduction 

NEC is characterised by variable intestinal damage, including inflammation, cellular death and sometimes perforation of the intestinal walls.

The morbidity and mortality associated with severe NEC is high. Mortality is reported to be between 10-50% and of those surviving, half go onto develop long term complications.(1)

Epidemiology 

The incidence of NEC in the UK is reported to be 1 in 250 live births but disproportionately affects premature and low birth weight infants. Up to 90% of cases occur in premature infants and up to 7% of infants with a birth weight of 500-1500g are affected.

NEC classically presents in the first three weeks of life and is associated with commencement of enteral feeds. Feeding with breast milk and probiotics are identified as being preventative.

The exact pathophysiology of NEC is not fully understood, but it is hypothesised to be multi-factorial with contribution of genetic predisposition, altered microbiota and intestinal barrier immaturity. (2-4)

Signs and Symptoms 

Signs and symptoms of NEC can be subtle, highly variable, and difficult to identify. 

Common signs and symptoms include:

  • Abdominal distention with prominent veins and discolouration
  • Umbilical flaring
  • Poor feeding
  • Bilious vomiting
  • Abdominal tenderness
  • Bowel changes, including diarrhoea, blood and mucus
  • Lethargy, apnoea, bradycardia
  • Sepsis
  • Risk factors of low birth rate, prematurity and formula feeding. (1, 3-6)
NEC 1

Distended, veiny abdomen with discolouration and umbilical flare

Investigations 

The most important investigation for diagnosing NEC is an abdominal radiograph.

If you are clinically concerned about perforation, you should request left-lateral decubitus views in addition to supine to identify free air indicative of perforation (with the baby lying on their left side, so the free air rises above the liver and is easily visible on x-ray). Often in an unstable neonate a lateral beam view may be utilised. 

Features that are indicative of NEC are:

  • Distended bowel loops
  • Bowel oedema +/- thumb printing
  • Intramural gas (pneumatosis intestinalis) 
  • Gas in the portal tract
  • Pneumoperitoneum (if perforated) (3,7)
Abdominal Radiographs

Double wall sign (Rigler sign), telltale triangle sign, football sign, falciform ligament sign, and many more

NEC 2

Pneumatosis intestinalis – gas within wall of the bowel

NEC 3

Pneumatosis intestinalis – gas within wall of the bowel

NEC 4

Rigler Sign (gas is outlining both sides of the bowel wall)

NEC 5

Falciform ligament sign (ligament outlined by gas) + football sign (abdominal cavity outlined by gas forming oval shape, falciform/median umbilical ligaments are sometimes included as sutures of the football)

NEC 6

Telltale triangle (radiolucent triangle of gas formed between three loops of bowel or between two loops of bowel and the abdominal wall)

Left Lateral Decubitus Abdominal Radiographs

Used to detect free intraperitoneal gas in neonates (pneumoperitoneum) as they are unable to be positioned for an erect chest x-ray.

NEC 8

Example of pneumoperitoneum following perforated NEC

Other Investigations

Blood tests and abdominal ultrasound.

Bloods may show anaemia, thrombocytopenia, leukocytosis/leukopenia, hyponatraemia, raised CRP, metabolic acidosis.

Abdominal ultrasound may show bowel wall thickening, altered vascular state and free fluid.

Management 

It is useful to be aware of Bell’s modified staging for NEC for deciding on treatment. Below is a simplified version.

StageClassificationSystemic SignsAbdominal signsRadiological signs
IA    Suspected    Temperature instability, apnoea, bradycardia, lethargyGastric retention, abdominal distention, emesis, heme-positive stool  Normal or mild intestinal dilation, mild ileus
IBGrossly bloody stool
IIA    Definite+ absent bowel sounds +/- abdominal tendernessIntestinal dilation, ileus, pneumatosis intestinalis
IIB+ metabolic acidosis and thrombocytopenia+ definite tenderness +/- abdominal cellulitis or RLQ mass  + ascites
IIIA    Advanced+ hypotension, bradycardia, severe apnoea, combined respiratory and metabolic acidosis, DIC, and neutropenia  + signs of peritonitis, marked tenderness and abdominal distension
IIIB  + pneumoperitoneum

Generally speaking, Stage I & II are managed medically, whereas Stage III is managed surgically. (1, 3-4, 7-8, 12)

Medical Management :

Nil by mouth (NBM) to rest the bowel.

Supportive intravenous fluids and total parenteral nutrition (TPN) as NBM

Nasogastric tube to decompress the bowel 

Triple IV antibiotics for 10-14 days according to local guidance

Surgical Management:

Laparotomy to remove perforated or necrotic bowel with diversion (stoma formation) is most commonly utilised.

Peritoneal drainage is possible in the acute setting and can be used as a stabilisation method. Clip and drop with relook is also an approach to diffuse necrosis.

Infants who recover from medically managed NEC may develop late complications including stricture formation, which could also lead to surgical intervention.

Complications 

  • Short bowel syndrome (following significant resection, and more common following removal of the ileocaecal valve)
  • Intestinal stricture
  • Sepsis / shock
  • DIC
  • Intestinal perforation
  • Mortality (1, 3)

References

  1. Ginglen JG, Butki N. Necrotizing Enterocolitis. [Updated 2022 Aug 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK513357/
  2. Allin, B. S. R., Long, A.-M., Gupta, A., Lakhoo, K. & Knight, M. One-year outcomes following surgery for necrotising enterocolitis: a UK-wide cohort study. Arch. Dis. Child. – Fetal Neonatal Ed. fetalneonatal-2017-313113 (2017).
  3. https://patient.info/doctor/necrotising-enterocolitis
  4. Neu J, Walker WA. Necrotizing enterocolitis. N Engl J Med. 2011 Jan 20;364(3):255-64. doi: 10.1056/NEJMra1005408
  5. Tasker RC, McCLure RJ, Acerini CL. Oxford handbook of paediatrics. 2nd ed. England: Oxford University Press; 2013.
  6. Afzal B, Elberson V, McLaughlin C, Kumar VH. Early onset necrotizing enterocolitis (NEC) in premature twins. J Neonatal Perinatal Med. 2017;10(1):109-112.
  7. Weerakkody Y, Worsley C, Bell D, et al. Necrotising enterocolitis. Reference article, Radiopaedia.org (Accessed on 16 Jan 2023)
  8. Bell MJ, Ternberg JL, Feigin RD, Keating JP, Marshall R, Barton L, Brotherton T. Neonatal necrotizing enterocolitis. Therapeutic decisions based upon clinical staging. Ann Surg. 1978 Jan;187(1):1-7. doi: 10.1097/00000658-197801000-00001.
  9. Jones J, Niknejad M, Hartung M, et al. Intramural bowel gas. Reference article, Radiopaedia.org (Accessed on 13 Mar 2023) https://doi.org/10.53347/rID-6168.
  10. Epelma, M. et al. Necrotizing Enterocolitis: Review of State-of-the-Art Imaging Findings with Pathologic Correlation. 2007.
  11. Jones J, Shah V, Botz B, et al. Pneumoperitoneum. Reference article, Radiopaedia.org (Accessed on 13 Mar 2023) https://doi.org/10.53347/rID-6165
  12. Neu J. Necrotizing enterocolitis: the search for a unifying pathogenic theory leading to prevention. Pediatr Clin North Am 1996; 43:409.

Written by Dr James Mackintosh, GPST1, reviewed by Mr David Corbett, Paediatric Surgical Registrar

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