Anatomical distribution of meconium detected by focused abdominal ultrasound in hospitalized healthy and sick neonatal foals.

Overview

• This study investigated the presence and location of meconium in newborn foals using a focused abdominal ultrasound protocol to better understand its appearance and distribution, especially concerning meconium impaction, a common cause of neonatal colic.

Background and Purpose

• Meconium impaction is a frequent issue causing abdominal pain (colic) in foals shortly after birth.
• The ultrasonographic characteristics and specific anatomical locations of meconium within the intestines were not well documented prior to this study.
• The study’s primary aim was to describe how often meconium is detected, where it is located within the intestines, and what it looks like on ultrasound in both healthy and sick hospitalized neonatal foals.

Methods

• A focused ultrasound (FUS) protocol was developed that included nine specific acoustic windows on the foal’s abdomen: three on the left side, three ventral (underside), and three on the right side.
• Ultrasound exams were performed once per foal during hospitalization by one operator using a curvilinear transducer.
• Thirty-six foals aged 7 days or younger were evaluated, including 16 healthy and 20 sick foals.

Key Findings

• Meconium was detected in 19 out of 36 foals (approximately 53%):
  • 9 of 16 healthy foals (7 were younger than 36 hours old, 2 were older than 36 hours).
  • 10 of 20 sick foals (4 younger than 36 hours, 6 older than 36 hours).
  • None of the healthy foals required treatment for impaction.
  • Three sick foals with meconium received treatment for impaction.
• Meconium was visualized in six out of the nine ultrasound windows most commonly in:
  • Retrosternal window (located near the breastbone area).
  • Ventrolateral windows (areas on the lower sides of the abdomen).
• The intestinal segment most frequently containing meconium was the sternal flexure in 12 of the 19 foals with meconium, followed by:
  • Right ventral colon/cecum in 9 foals.
  • Left ventral colon in 9 foals.
• Sick foals more commonly showed involvement of multiple acoustic windows, indicating more widespread meconium presence.
• All foals that were treated for impaction had meconium specifically located in the small colon, detected via the hypogastric ultrasound window (lower midline below the navel).

Ultrasonographic Appearance of Meconium

• Meconium appeared as a ball-shaped mass within the intestinal lumen.
• In the large colon, it appeared either hypoechoic (darker on ultrasound) or with mixed echogenicity.
• In the small colon, it appeared hyperechoic (brighter on ultrasound) or mixed echogenicity.

Limitations

• Ultrasound examinations were performed by a single operator, which may limit generalizability.
• The sample size was relatively small and based on convenience sampling, possibly introducing selection bias.
• The study used a focused ultrasound protocol rather than a full comprehensive abdominal ultrasound, thus some findings might be missed.

Conclusions and Clinical Implications

• In foals older than 36 hours, detecting meconium may often be incidental and not necessarily indicative of a problem needing treatment.
• The hypogastric (lower abdominal) ultrasound window is critical when impaction is suspected because it allows visualization of the small colon where impactions requiring treatment often occur.
• The focused ultrasound protocol used in this study shows promise as a useful, standardized method for:
  • Identifying meconium distribution in neonatal foals.
  • Monitoring changes over time during hospitalization.
  • Evaluating response to treatment for meconium impaction.