GI surgical conditions in the NICU

Key points

1.
Long-term survival of children with intestinal failure has significantly improved with advances in management including the establishment of interdisciplinary intestinal rehabilitation centers.
2.
A fundamental goal of intestinal failure management is weaning from parenteral nutrition (i.e., attaining enteral autonomy) while ensuring adequate growth and development.
3.
There is a high mortality for spontaneous intestinal perforation (19%). Necrotizing enterocolitis requiring surgical intervention has a two-fold higher mortality (38%).
4.
Hepatoprotective parenteral nutrition has been associated with decreased intestinal failure–associated liver disease and has improved survival; however, a majority of children with intestinal failure dependent on parenteral nutrition have persistent transaminitis.
5.
For home parenteral nutrition patients, catheter-associated blood stream infections remain a major cause of morbidity and mortality. In addition to strict aseptic techniques and rigorous caregiver education, the institution of small molecule (e.g., ethanol) catheter locks appears to be of benefit.
6.
Medical management of intestinal failure must address problems of oral aversion, gastroesophageal reflux disease, small bowel bacterial overgrowth, dysmotility, and mucosal inflammation.
7.
The development of glucagon-like peptide 2 analogs, although costly, has shown promise in helping select patients achieve enteral autonomy.
8.
Important aspects of the surgical management of short bowel syndrome are preserving intestinal bowel length and establishing intestinal continuity. In appropriate patients, autologous intestinal reconstruction can be considered.
9.
The current overall patient survival of all types of intestine transplant is 60%. Over the past decade, there has been a 64% reduction in pediatric intestine, intestine-liver, and multivisceral transplants. This probably reflects the improved outcomes of pediatric intestinal rehabilitation.
10.
The advent of interdisciplinary pediatric intestinal failure centers has been associated with 5-year survivals of >90% for neonatal short bowel syndrome. Over three-quarters of these individuals will achieve enteral autonomy. A long lifespan is now expected; hence our focus must extend to optimizing neurodevelopmental outcomes and improving patient and family quality of life. Further, as this new cadre of complex pediatric patients enters adulthood, appropriate transitions of care become increasingly important. Currently, there are few adult analogs to pediatric intestinal failure centers.

Introduction

Short bowel syndrome (SBS) is a life-threatening condition that affects tens of thousands of children. Historically, SBS or intestinal failure due to resection or bowel loss was a condition that was almost always fatal. However, over the past several decades survival has improved significantly. The advent of parenteral nutrition (PN) in the 1960s reduced the number of deaths secondary to dehydration and malnutrition. ^, Although PN is life-saving, duration of PN support has been shown to directly correlate with morbidity and potentially life-threatening complications including intestinal failure–associated liver disease (IFALD), sepsis from central line–associated blood stream infection (CLABSI), and central venous thrombosis. With decreased neonatal mortality in both term and preterm neonates, more children are at risk of certain diseases that predispose them to SBS and its associated complications. ^, The economic burden of this population is significant, with more than $500,000 in medical expenses in just their first year of life. ^, More recent advances in management including the establishment of interdisciplinary intestinal rehabilitation centers, improved hepatoprotective strategies, and CLABSI prevention protocols have resulted in long-term survival of >90%. ^, ^, ^, ^, ^, Interestingly, despite these findings, a substantial proportion of providers still tend to recommend comfort care for neonates with significant bowel loss. This is even more surprising as >75% of adolescents with neonatal onset SBS reach enteral autonomy (e.g., weaning fully from PN) with intestinal rehabilitation.

Pediatric intestinal failure (PIF) , a term that includes SBS, is a condition defined as a reduction in gut function that results in an inability to sustain growth, hydration, or electrolyte homeostasis. ^, ^, SBS is the result of actual bowel loss or resection for acquired or congenital gastrointestinal diseases. Motility disorders (e.g., intestinal pseudo-obstruction) or mucosal defects (e.g., tufting enteropathy or microvillus inclusion disease) are causes of PIF that do not necessarily involve a diminution of bowel length. ^, A commonly used functional definition of PIF is PN dependence >90 days. ^, In 2021 the American Society for Parenteral and Enteral Nutrition (ASPEN) Pediatric Intestinal Failure Section suggested a consensus definition for PIF as dependence on PN for >60 days within a 74-consecutive day interval. Percentage of predicted bowel length using established norms is available and is especially useful in patients who develop SBS after the neonatal period. In animal models, the definition of SBS is usually a loss of 80% or greater of small bowel. ^, An alternative method to estimate the quantity of small intestine present is the plasma citrulline level. Citrulline is a free amino acid that is produced by the metabolism of glutamine and proline in the small intestinal mucosa and may be used as a biomarker that correlates with small bowel length and absorptive capacity. ^, Increased rates of CLABSI have also been associated with lower citrulline levels.

To obtain current state-of-the-art outcomes, a detailed understanding of SBS, etiology, pathophysiology, and appropriate nutritional, medical, and surgical management strategies is essential.

Etiology

Common etiologies of pediatric SBS include necrotizing enterocolitis (NEC), intestinal atresias, gastroschisis, and malrotation with volvulus. Rarer causes of SBS include Hirschsprung disease extending into the small intestine, iatrogenic injuries (e.g., tumor resections), and trauma. ^,

Necrotizing enterocolitis

Epidemiology

NEC is a major cause of morbidity and mortality in neonates and the most common cause of PIF. ^, ^, It is an umbrella diagnosis of similarly presenting, largely idiopathic disease processes that affect the neonatal intestine and hence specific subsets of NEC need to be considered separately. The classic form of NEC occurs in preterm neonates.

In a study with 71,808 very-low-birth-weight infants (≤1500 g), the incidence of NEC for neonates weighing between 501 g and 750 g was 12% with a decrease in incidence of 3% for each 250-g increase in weight. ^, Birth weight was the most significant predictor of mortality in this cohort. A more recent study evaluating 473,895 very-low-birth-weight infants from 2006 to 2017 revealed a 4.1% and 5.1% decline in all-cause mortality of medical and surgical NEC, respectively. Although this trend was encouraging, particularly in light of decreasing median birth weights for very-low-birth-weight neonates, the overall mortality for the last year of the investigation was still 16.8% for medical NEC and 31.6% for surgical NEC. This same study also observed an overall reduction in NEC incidence, with medical NEC decreasing from 5.3% in 2006 to 3.0% in 2017 and surgical NEC decreasing from 3.4% in 2006 to 3.1% in 2017. The reason for this reduction in incidence and mortality may be secondary to use of human breast milk, careful feeding advancement, and antenatal corticosteroid use. ^, It is also important to note that although overall mortality has decreased, the mortality of very-low-birth-weight neonates with surgical NEC (receiving primary peritoneal drainage [PPD] or laparotomy) is still at least 30%.

Term infants with NEC-like diseases have a considerably lower mortality. In an analysis of 1629 such neonates, 45% of >2500-g birth weight neonates had a major congenital anomaly, most commonly gastrointestinal defects, followed by congenital heart defects and then chromosomal anomalies.

Diagnosis

Bell’s criteria have historically been used to define neonates with NEC, however these criteria are imprecise. The Vermont Oxford Network (VON) has an alternative method for defining NEC. NEC diagnosis is determined at laparotomy, postmortem, or by specific clinical and radiologic criteria. NEC is clinically defined as the presence of one or more physical findings: bilious gastric aspirate or emesis, abdominal distension, or occult/gross fecal blood in the absence of an anal fissure and at least one diagnostic imaging finding: pneumatosis intestinalis, portal venous gas, or pneumoperitoneum. ^, The VON has historically differentiated NEC from spontaneous intestinal perforation (SIP) only if the neonate has had a laparotomy or at postmortem.

Pathophysiology

The pathophysiology of NEC is multifactorial. It is currently believed to be affected by two main factors: prematurity and microbial dysbiosis. ^, ^, The intestinal epithelium provides a barrier against the external environment through epithelial cells and tight junctions. Prematurity affects the tight junctions leading to increased permeability and bacterial translocation. This causes a release of cytokines which in turn can cause microvascular constriction and intestinal ischemia. ^, The timing of NEC resembles that of retinopathy of prematurity and this similarity suggests that host maturity is a factor in the pathophysiology of NEC. Microbial dysbiosis may also play a significant role in the pathogenesis of NEC. ^, ^, The gut microbiome in premature infants has fewer bacterial species and microbial diversity with an increased proportion of pathogenic bacteria compared to full-term infants. Many elements can alter the gut microbiome leading to microbial dysbiosis including antibiotics and the acid-base environment of the intestine. ^, ^, Formulas can cause a higher intestinal pH compared to human milk and acidified formulas have been associated with a lower incidence of NEC. ^, ^, ^, It has also been described that the use of H2 blockers leads to increased Proteobacteria over Firmicutes and this may be important in the genesis of NEC. ^,

Clinical presentation

The typical presentation of NEC is a preterm infant with feeding intolerance, abdominal distention, and bloody stools around 2 to 8 weeks after birth. ^, Abdominal radiographs are the standard imaging used to diagnose NEC. Pathognomonic signs include pneumatosis intestinalis and/or portal venous gas. Abdominal ultrasound can also be used to evaluate peristalsis, intestinal wall thickness, presence of free fluid, decreased intestinal blood flow, and portal venous gas. ^, Laboratory tests may be of utility in supporting the diagnosis of NEC and assessing its progression. Common laboratory findings associated with NEC include thrombocytopenia, absolute neutrophil count (ANC) less than 1500 cell/μL, acidosis, and hyperglycemia. ^,

Management

Medical management of NEC includes broad-spectrum antibiotics, bowel rest and gastric decompression, initiation of PN, and supportive care. Most neonates will recover with medical management alone, however 25% to 50% will require surgical intervention. ^, An absolute indication for surgical management of NEC is bowel perforation as indicated by free air. Clinical decompensation despite optimal medical management may also be an indication for surgery in an infant with NEC.

Operative approaches depend on the condition of the patient and clinician preference. A laparotomy with resection of necrotic bowel followed by proximal diversion is typical, but PPD is often utilized either as a stabilizing intervention or as attempted definitive management. In a recent multicenter randomized clinical trial of 310 premature infants with NEC or isolated intestinal perforation, there was no difference in death or neurodevelopmental impairment at 18 to 22 months corrected age between initial laparotomy versus PPD. Primary anastomosis may also be done in stable patients with limited disease, while the clip and drop technique may be used as a salvage operation in extensive NEC. For severe NEC, temporary silo closure of the abdomen to avoid the sequelae of abdominal compartment syndrome may be necessary. It is important to note that infants who survive after only receiving PPD likely have minimal NEC or SIP. SIP differs from NEC in several ways. It usually presents as an isolated perforation without associated ischemia within 10 days of birth whereas NEC usually occurs between 2 and 8 weeks after birth. In a study of 177,618 very-low-birth-weight infants from 2006 to 2010, infants with laparotomy-confirmed SIP had a mortality of 19% whereas laparotomy-confirmed NEC had a mortality twice that at 38%.

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