Neonatologist performed point-of-care bowel ultrasound: Is the time right?

Abstract

Introduction: This review acquaints neonatal clinicians using point-of-care ultrasound with a range of pathological bowel ultrasound findings, with the aim to promote utility of this skill as a diagnostic assessment tool in diseased neonatal intestinal states.

Overview: A range of normal and pathological bowel ultrasound findings are illustrated with case examples from our neonatal intensive care unit. The technical challenges of lack of familiarity with sonographic appearance of bowel (healthy and diseased), occurrence of gas artefacts and requirements of high-resolution linear transducer probes are described to allow the development of skills amongst neonatologists trained in point-of-care ultrasound. Plain abdominal radiography continues to remain the standard investigation to differentiate benign bowel states such as continuous positive airway pressure (CPAP) belly syndrome in preterm infants from life-threatening pathological intestinal states such as necrotising enterocolitis. Although plain radiography is the gold standard modality in the evaluation of neonatal diseased bowel states, real-time point-of-care bowel ultrasound performed in conjunction can provide valuable information on bowel peristalsis, bowel wall thickness and bowel vascularity. Abnormal configuration of superior mesenteric vessels on colour Doppler can alert the clinician to the diagnosis of neonatal intestinal malrotation-a time critical emergency.

Conclusion: Further research is needed to explore true-negative and true-positive predictive values of bowel ultrasound. However, with expansion of knowledge, appropriate training of techniques, neonatologists will be able to enhance their diagnostic acumen by performing point-of-care bowel ultrasound in conjunction with plain radiography in the evaluation of broad array of neonatal intestinal states.

Keywords: bowel ultrasound; neonatologists; point of care.

Figure 1

(a) Illustration of the Layers of Normal Bowel Wall. (b) Normal BUS Image in 38‐week Infant on Day 2 of Life. The Hypoechoic Layer Represents Muscularis Propria. (c) Normal BUS Image in 26‐week Infant on Day 6 of Life Showing Highly Echogenic Dots within the Bowel Representing Normal Intraluminal Gas.

Figure 2

(a, b) Bowel Ultrasound Image Showing Bowel Wall Thickening and Thinning.

Figure 3

(a) Plain Abdominal Radiograph Performed on a 27‐week Preterm Infant at 48 h of Life for Abdominal Distention. The Plain Radiograph Image Showing Non‐specific Dilatation of the Bowel Loops. (b) Bowel Ultrasound Performed Concurrently Showed a Localised Bowel Segment with Loss of Gut Signature with Significant Dilatation and Thinning of the Surrounding Bowel Loops. There was Free Fluid Noted in the Abdominal Cavity. This Patient was Diagnosed with Ileal Atresia on Diagnostic Laparoscopy, Underwent Surgical Resection of the Atretic Segment with End to End Ileal Anastomosis.

Figure 4

(a) Plain Abdominal Film Showing Loss of Normal Distribution of the Bowel Gas Pattern with Few Abnormally Distended Sausage‐shaped Bowel Segments. (b) Real‐time BUS Showed Significant Dilatation and Thinning of the Bowel Loops Surrounding the Atretic Segment with Loss of Normal Gut Signature. (c) Significant Dilatation and Thinning of the Surrounding Bowel Loop. The Echogenic Dots with Dilated Bowel Lumen Represent Intraluminal Gas which is Normal. This Patient was Confirmed to have Ileal Atresia on Laparotomy.

Figure 5

(a, b) Bowel Colour Doppler (CD) Study Images in a 24‐week Infant Diagnosed to have NEC Requiring Surgical Intervention on day 24 of Life. Increased Bowel Wall Perfusion seen During Bowel Inflammation in NEC Producing the Specific Hyperaemic Flow Pattern Y‐shaped CD Signals. (c) Bowel Colour Doppler Study Image in a 27‐week Infant Diagnosed to have NEC Requiring Surgical Intervention on day 33 of Life Showing Increased Bowel Wall Perfusion. (d) Bowel Colour Doppler Study Image in the Same 27‐week Infant Diagnosed to have NEC Requiring Surgical Intervention on Day 33 of Life Showing Increased Bowel Wall Thickening and Increased Vascularity. (e) Normal Bowel Wall Perfusion on Colour Doppler.

Figure 6

(a, b) Demonstration of Intramural Gas (Pneumatosis Intestinalis) on Bowel Ultrasound. Intramural Gas Seen as Multiple Echogenic Dots Varies Between a Few Foci to Involvement of the Whole Circumference of the Bowel Wall known as the ‘circle sign’.

Figure 7

(a) Plain Abdominal Film Showing Portal Venous Gas. (b) Normal Hepatic Echotexture on Ultrasound. (c) Extended Portal Venous Gas in the Smaller Branches of the Portal Vein Appearing as Dendriform Granular Echogenicities in the Liver Parenchyma ‘Trapped Microbubbles’. This Gas can be Impressively Visualised Rapidly Tracking Upwards through the Portal Vein On Real‐time Ultrasound, Trapping of this Gas Produces the Echogenic Dots within the Liver Parenchyma.

Figure 8

BUS Image in the Same 27‐week Infant Diagnosed to have NEC Requiring Surgical Intervention on Day 33 of Life Showing Increased Bowel Wall Thickening (Bowel Wall Thickness Measured 3.2 mm).

Figure 9

(a) Plain X‐Ray Showing Paucity of Gas with no Evidence of Pneumatosis Intestinalis in 24‐week Infant Diagnosed to have NEC Requiring Surgical Intervention on Day 24 of Life. (b, c) BUS Performed at the Time of Plain Radiograph Assessment as Shown in Figure a Detected Significant Dilatation of the Intestinal Loops with no Visible Peristalsis and Absent Bowel Wall Perfusion.

Figure 10

(a) Plain Abdominal Radiograph Showing a Distended Gastric Bubble with Paucity of Gas Beyond the Gastric Bubble in a 36‐week Infant Diagnosed with Malrotation on Laparotomy. (b) Normal Anatomical Orientation of the Superior Mesenteric Vessels. The Superior Mesenteric Vein Seen at 11o'clock Position to the Superior Mesenteric Artery. (c) Colour Doppler Study Showing the Superior Mesenteric Vein Swirling Around the Superior Mesenteric Artery, the ‘Whirlpool Sign᾽ Diagnostic of Malrotation.

Figure 11

(a) Plain Abdominal Radiograph Showing Dilated Bowel Loops in the Right Upper Quadrant. This Infant was Diagnosed to have Volvulus on Day 2 of Life. (b) Concurrent BUS Image of the Same Distended Bowel Loop in Real‐time Showed Dilated, Thinned Bowel Segment with no Visible Peristalsis.