壞死性腸炎(NEC)
壞死性腸炎（NEC）是指嬰兒的腸道出現嚴重受損和炎症。雖然所有嬰兒都有機會患上此病，但這在早產嬰兒中較為常見。這是因為他們的腸道尚未發育成熟，以致容易受損。高風險的因素包括：出生週數較早、出生體重較輕以及腸道血液流動不穩定[1] (如低血壓、心臟問題和飲用配方奶)[2]。研究顯示，相對飲用配方奶粉的嬰兒，接受母乳餵哺的嬰兒患上壞死性腸炎的風險較低。[3]
壞死性腸炎可在出生後幾天至幾週內發病。[4] 患有壞死性腸炎的嬰兒可能會出現餵食不耐、嘔吐、腹部脹大、血便等病徵。部分的患者亦可能會出現一些非特定的病徵，例如：發燒、疲倦、呼吸停頓和血壓不穩。由於腹部脹大，有些嬰兒可能會出現呼吸不暢順。醫生需為患者進行腹部X光檢查和血液測試，以確定壞死性腸炎的診斷並密切監測嬰兒的狀況。
壞死性腸炎的治療包括停止餵食，使用抗生素來對抗感染和在嚴重的情況下，由兒科外科醫生將腸道壞死的部分切除。停止進食能讓嬰兒的腸道有充份的時間休息（為期14天左右，視乎嬰兒的臨床情況而決定)。 病情較輕的嬰兒主要通過腸道休息和服用抗生素來讓身體康復，無需接受手術。然而，若嬰兒的病情較為嚴重（如對藥物治療無反應或出現腸穿孔），則需要接受手術以清除腸內壞死的部分。
病情嚴重的嬰兒可能會因此而死亡。在出生體重較輕、出生週數較早和需要接受手術的嬰兒中，死亡率會相對較高。[5] 在一項研究中，壞死性腸炎的死亡率在出生體重少於1.5公斤的嬰兒中為16-21％，在出生體重少於1公斤的嬰兒中則為29-42％。[6]
當嬰兒痊癒後，他們可以慢慢恢復餵哺量。因為餵食的過程需要循序漸進，他們一般也需要一段時間的靜脈營養治療（另稱為腸外營養），然後才能過渡到完全透過腸道餵食和消化。亦有部分嬰兒因手術後剩餘的腸道不足，腸道內的餵養就變得更加困難。這些嬰兒可能需要較長時間甚至終身依賴靜脈營養治療來幫助成長。長遠的預後結果則取決於手術後剩餘的腸道有多少、剩餘的腸道在哪個位置以及身體其後的適應。
Necrotizing enterocolitis (NEC)
Necrotizing enterocolitis (NEC) describes a serious condition when there is severe injury and inflammation in the baby’s gut. NEC can happen in all babies but is more common in preterm babies as their intestines are immature and more susceptible to injury. Higher risks are observed in babies who are born at lower gestational age, with a lower birth weight, those with unstable blood flow to the gut[1] e.g. hypotension, heart problem and those on formula milk[2]. It has been shown that babies who are on breastfeeding have a lower risk of developing NEC compared with those on exclusive formula feed.[3]
NEC can happen from the first few days to weeks of life.[4] Babies with NEC may present with poor feeding tolerance, vomiting, abdominal distension, blood in stool etc. They may develop non-specific features such as fever, tiredness, apnoea and unstable blood pressure. Some may not breathe well due to the distended abdomen. Serial radiographs of the gut and blood tests are performed to look for features of NEC and monitor the progress of the baby.
The treatment of NEC includes withholding feeding, using antibiotics to fight the infection and in severe cases, removing the dead parts of the bowel by the paediatric surgeon. Babies are not allowed to eat in order to let the gut rest, which may be required up to 14 days or more. Babies with a milder course may recover with bowel rest and antibiotics, without the need of surgery. However, babies who run a more severe course, i.e., unresponsive to medical treatment, or develop perforation of bowel, will require surgery to remove the dead parts of the bowel.
Babies who are seriously ill may die from this condition; the mortality rate increases with decreasing birth weight, decreasing gestational age and in those who required surgery.[5] In one study, the mortality rate of NEC was found to be 16-21% in babies whose birth weight were 1500g and 29-42% in those who were 1000g.[6]
Feeding is resumed gradually in small steps for babies who recover from NEC. They often require parenteral nutrition for some time before achieving full enteral feeding. Some babies may rely on parenteral nutrition for up to years or even life-long if they have insufficient healthy bowel left after surgery and are unable to tolerate enteral feeds. The long-term prognosis depends on the length, site of remaining bowel and how the body adapts afterwards.
Written by Dr. Sharon Lau
Resident, Department of Paediatrics
Prince of Wales Hospital
Reference:
[1] Samuels N, van de Graaf RA, de Jonge RCJ, et al. Risk factors for necrotizing enterocolitis in neonates: a systematic review of prognostic studies. BMC Pediatr 2017; 17:105.
[2] Niño DF, Sodhi CP, Hackam DJ. Necrotizing enterocolitis: new insights into pathogenesis and mechanisms. Nat Rev Gastroenterol Hepatol 2016; 13:590.
[3] Bode L. Human Milk Oligosaccharides in the Prevention of Necrotizing Enterocolitis: A Journey From in vitro and in vivo Models to Mother-Infant Cohort Studies. Front. Pediatr. 2018; 6:385.
[4] Yee WH, Soraisham AS, Shah VS, et al. Incidence and timing of presentation of necrotizing enterocolitis in preterm infants. Pediatrics 2012; 129: e298.
[5] Hull MA, Fisher JG, Gutierrez IM, et al. Mortality and management of surgical necrotizing enterocolitis in very low birth weight neonates: a prospective cohort study. J Am Coll Surg 2014; 218:1148.
[6] Fitzgibbons SC, Ching Y, Yu D, et al. Mortality of necrotizing enterocolitis expressed by birth weight categories. J Pediatr Surg 2009; 44:1072.