Multidisciplinary evaluation of the distended abdomen in critically ill infants and children: the role of bedside sonography

Imaging for Diagnosis and Assessment of Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is inflammatory bowel necrosis of preterm and critically ill infants. The disease is seen in 6-10% of preterm infants who weigh less than 1500 g at birth and carries considerable morbidity, mortality, and healthcare cost burden. Efforts focused on timely mitigation remain restricted due to challenges in early diagnosis as clinical features, and available laboratory tests remain nonspecific until late in the disease. There is renewed interest in the radiological and sonographic assessment of intestinal diseases due to technological advances making them safe, cost-efficient, and supporting Web-based transmission of images, thereby reducing time to diagnosis by disease experts. Most of our experience has been with plain abdominal radiography, which shows characteristic features such as pneumatosis intestinalis in up to 50-60% of patients. Many patients with advanced disease may also show features such as portal venous gas and pneumoperitoneum. Unfortunately, these features are not seen consistently in patients with early, treatable conditions, and hence, there has been an unfulfilled need for additional imaging modalities. In recent years, abdominal ultrasound (AUS) has emerged as a readily available, noninvasive imaging tool that may be a valuable adjunct to plain radiographs for evaluating NEC. AUS can allow real-time assessment of vascular perfusion, bowel wall thickness, with higher sensitivity in detecting pneumatosis, altered peristalsis, and characteristics of the peritoneal fluid. Several other modalities, such as contrast-enhanced ultrasound (CEUS), magnetic resonance imaging (MRI), and near-infrared spectroscopy (NIRS), are also emerging. In this article, we have reviewed the available imaging options for NEC evaluation.

Bowel ultrasound for predicting surgical management of necrotizing enterocolitis: a systematic review and meta-analysis

BACKGROUND

Necrotizing enterocolitis (NEC) is a devastating inflammatory disease of the intestinal tract that represents a significant source of morbidity and mortality in preterm infants. Imaging of the abdomen is valuable for timely diagnosis and close monitoring of disease progression in NEC. Bowel ultrasound (US) is increasingly being recognized as an important imaging tool for evaluating NEC that provides additional detail than plain abdominal radiographs.

OBJECTIVE

To identify bowel US findings associated with surgical management or death in infants with NEC.

MATERIALS AND METHODS

We searched Embase, PubMed, and the Cumulative Index to Nursing and Allied Health Literature for studies investigating the association between bowel US findings and surgical management or death in NEC. Selected articles were evaluated for quality of study methodology using the Newcastle-Ottawa Scale, and aggregate statistics for odds ratio (OR) and 95% confidence interval were calculated.

RESULTS

Of 521 articles reviewed, 11 articles comprising 748 infants were evaluated for quality. Nine of the studies were retrospective and from single-center experiences. Pooled analysis showed that focal fluid collections (OR 17.9, 3.1-103.3), complex ascites (OR 11.3, 4.2-30.0), absent peristalsis (OR 10.7, 1.7-69.0), pneumoperitoneum (OR 9.6, 1.7-56.3), bowel wall echogenicity (OR 8.6, 3.4-21.5), bowel wall thinning (OR 7.11.6-32.3), absent perfusion (OR 7.0, 2.1-23.8), bowel wall thickening (OR 3.9, 2.4-6.1) and dilated bowel (OR 3.5, 1.8-6.8) were associated with surgery or death in NEC. In contrast, portal venous gas (OR 3.0, 0.8-10.6), pneumatosis intestinalis (OR 2.1, 0.9-5.1), increased bowel perfusion (OR 2.6, 0.6-11.1) and simple ascites (OR 0.54, 0.1-2.5) were not associated with surgery or death.

CONCLUSION

This meta-analysis identified several bowel US findings that are associated and not associated with surgery or death in NEC. Bowel US may be useful for early identification of high-risk infants with NEC who may benefit from more aggressive treatment, including surgery. Future studies are needed to determine whether the addition of bowel US in NEC evaluation would improve outcomes.

Point-of-Care Ultrasound in Acute Neonatal Ascites

We present a 4-week-old neonate with acute onset of bloody stools and abdominal distention. Point-of-care ultrasound performed in the emergency department allowed for rapid diagnosis of a large amount of free intra-abdominal fluid, which together with the physical findings, prompted emergent operative exploration revealing chylous ascites. Although no areas of active volvulus were identified intraoperatively, findings in the case were suggestive of small bowel volvulus and deemed as the most likely etiology for this patient's presentation. In this report, we review the relevant aspects of ultrasonography for ascites and discuss the diagnosis of chylous ascites.

Sonographic and radiographic imaging features of the neonate with necrotizing enterocolitis: correlating findings with outcomes

BACKGROUND

Abdominal radiography is the reference standard in imaging neonates with necrotizing enterocolitis (NEC); however, ultrasound of the abdomen including bowel may be of value in this setting.

OBJECTIVE

To correlate sonographic and radiographic findings with patient outcomes in NEC.

MATERIALS AND METHODS

We reviewed sonographic and radiographic exams, as well as clinical, pathological and laboratory records. Ultrasound images were reviewed for free intraperitoneal gas, peritoneal fluid, pneumatosis intestinalis, portal gas, bowel vascularity, bowel wall thickness and echogenicity, peristalsis and the presence of dilated bowel with anechoic contents. Contemporaneously acquired radiographs were reviewed for intraperitoneal gas, pneumatosis intestinalis, portal gas, the sentinel loop sign and gas pattern. Patients were categorized into two groups based on clinical outcome.

RESULTS

Forty-four neonates receiving 55 sonograms were included. Focal fluid collections, echogenic free fluid, increased bowel wall echogenicity and increased bowel wall thickness were statistically significant in predicting an unfavorable outcome. Other features approached significance in predicting poor outcomes: free peritoneal gas, pneumatosis intestinalis, aperistalsis, bowel wall thinning and absent bowel perfusion. Anechoic free peritoneal fluid predicted a good outcome. The sentinel loop sign on radiographs predicted an unfavorable outcome.

CONCLUSIONS

Abdominal sonography and radiography in patients with NEC can help prognosticate the outcome.

Necrotizing Enterocolitis: Review of State-of-the-Art Imaging Findings with Pathologic Correlation

Plain abdominal radiography is the current standard imaging modality for evaluation of necrotizing enterocolitis (NEC). Sonography is still not routinely used for diagnosis and follow-up, as it is not widely recognized that it can provide information that is not provided by plain abdominal radiography and that may affect the management of NEC. Like plain abdominal radiography, sonography can depict intramural gas, portal venous gas, and free intraperitoneal gas. However, the major advantages of abdominal sonography over plain abdominal radiography are that it can depict intraabdominal fluid, bowel wall thickness, and bowel wall perfusion. Sonography may depict changes consistent with NEC when the plain abdominal radiographic findings are nonspecific and inconclusive. Thinning of the bowel wall and lack of perfusion at sonography are highly suggestive of nonviable bowel and may be seen before visualization of pneumoperitoneum at plain abdominal radiography. The mortality rate is higher after perforation; thus, earlier detection of severely ischemic or necrotic bowel loops, before perforation occurs, could potentially improve the morbidity and mortality in NEC. The information provided by sonography allows a more complete understanding of the state of the bowel in patients with NEC and may thus make management decisions easier and potentially change outcome.