infant showing pneumatosis intestinalis and branching radiolucencies (arrowheads ) within the liver representing air within the portovenous system D: US of another infant with perforation following necrotizing enterocolitis shows free intraperitoneal fluid (F) containing echogenic debris and punctated areas of high echogenicity within the intestinal wall (arrows ), consistent with pneumatosis intestinalis E: Left lateral decubitus radiograph shows free intraperitoneal air (arrow ) indicating perforation in an infant with necrotizing enterocolitis (Reprinted with permission from Brant WE, Helms C Fundamentals of Diagnostic Radiology Philadelphia, PA: Lippincott Williams & Wilkins; 2012.) CLINICAL PEARLS AND PITFALLS Reduction of an incarcerated hernia may require sedation to facilitate adequate muscle relaxation; sedation in the neonate requires additional post-sedation monitoring Patients with abdominal wall defects, connective tissue disorders, or chronically increased intra-abdominal pressure (ascites, dialysis, ventriculoperitoneal shunting, etc.) are at increased risk for umbilical or inguinal hernias In females, inguinal hernias may contain the ovary and may present with labial swelling Inguinal Hernia Inguinal hernias result when abdominal contents pass through the inguinal canal The overall incidence is between 1% and 4% but can be as high as 30% in preterm infants Similarly, the rates of incarceration increase with decreasing gestational age Hernias often will present with an intermittent bulge in the groin, or swelling of the testes (boys) or labia (girls) that can be exacerbated during crying or Valsalva maneuvers While most inguinal hernias are painless, an incarcerated hernia will present with a bulge that does not reduce spontaneously and may be associated with irritability, pain, and/or vomiting The differential diagnosis of an inguinal mass includes hydrocele, testicular torsion, or lymphadenopathy Distinguishing between inguinal hernias and hydroceles may be difficult at this age, and transillumination of the scrotal sac may not be a reliable test In general, hydroceles rarely cause pain and typically not fully reduce In testicular torsion the testes is palpable and hard, and may or may not be tender on examination While most hernias, hydroceles, and torsions can be differentiated on examination, US can be a helpful adjuvant Given the high rate of incarceration, surgical repair is recommended once an inguinal hernia is identified, and can be done as an elective outpatient procedure If the hernia was difficult to reduce, surgical intervention should be performed