Chapter 44: Transillumination and Point-of-Care Ultrasound

INTRODUCTION

Transillumination and point-of-care ultrasound (POCUS) are techniques that can be used as an aid in performing procedures, to diagnose specific conditions, and to help in clinical decision making. Both transillumination and POCUS can be performed at the bedside, require no sedation, and have no significant complications. Although transillumination has been around since 1831 (Richard Bright’s first description using a candlelight to shine through the head of a macrocephalic adult and diagnose hydrocephalus), it has only been used in neonatology since the 1970s. The first ultrasound studies can be traced back to 1794, but diagnostic ultrasound did not enter medicine until the 1950s. The first portable ultrasound unit was initially developed in 1988 to help identify and diagnose serious injuries in troops in the field. POCUS was used in the late 1990s by emergency room physicians as a trauma screening tool and is now gaining popularity in other medical disciplines.

I. TRANSILLUMINATION

1. Indications. Transillumination is the use of a strong light source as a noninvasive tool for bedside diagnosis and to aid in procedures. By shining a bright light through an area of the body or an organ, abnormal air, fluid, or a nonsolid mass can be potentially diagnosed. One of the best uses of transillumination in the neonatal care unit is that it can provide a rapid diagnosis in an unstable infant with a tension pneumothorax, pneumopericardium, or abdominal perforation and allow for immediate intervention if necessary. Individuals with deutan color vision (red-green blindness) may have difficulty with transillumination techniques.

   1. Procedures

      1. Localize an artery or vein for vessel cannulation or blood sampling.

      2. Bladder aspiration. Verify the presence of urine in the bladder and show the size and location of the bladder.

      3. Cannulation of umbilical vessels. Identify the path of vessels and identify a false passage of an umbilical catheter.

      4. Aid in oro-/nasoduodenal feeding tube insertion by gauging distension of stomach with air.

      5. Thoracentesis, chest tube thoracostomy, or pericardiocentesis. Document the success of air removal in a pneumothorax or in a pneumopericardium.

   2. Diagnosis. Air, fluid, or nonsolid masses light up brightly when transilluminated, whereas solid masses appear dark. Normally there is a 2-cm area of lucency around the probe. If there is >2 cm lucency, it is considered abnormal, and further testing may have to be done.

      1. Chest abnormalities. Air leaks (eg, pneumothorax, pneumomediastinum, and pneumopericardium) can be suspected and some diagnosed with transillumination. The thin wall of the infant’s chest makes it easy to transilluminate, and as little as 10 mL of free air can be detected. Obtain a baseline on any infant at high risk for an air leak.

      2. Abnormalities in the head such as hydrocephalus, intracranial hemorrhage, subdural effusion or hematoma, skull fractures, hydranencephaly, anencephaly, porencephaly, encephalocele, and large cerebral cysts. Transillumination of the skull is known as skull diaphanoscopy.

      3. Differentiate cystic from solid masses such as cystic hygroma, a congenital macrocystic lymphatic malformation commonly found in the left base ...