Inguinal Hernia in Premature Infants

I was interested to read the article by Harper et al. in the July 1975 issue on the incidence of hernias in premature infants weighing 1000 gm or less at birth. According to these
authors, no one thus far has recognized the remarkably high incidence of inguinal hernias (30%) in premature infants weighing less than 1000gm. I should like to point out, however, that a high incidence of such hernias in very-low-birth-weight preiiiature infants was reported by Knox in 1959 and Walsh in 1962. In the latter study, 82 healthy premature infants weighing less than 2000 gm at birth were divided into two groups according to birth weight. Group 1 included 28 infants weighing less than 1500 gm and group 2 included those weighing more than 1500 gm. The two groups were not comparable in regard to race and sex. All the infants were examined during the first week of life. Regular follow-up observations were made whenever possible at the following ages: 1 week to 1 month, 1 to 3 months, 3 to 6 months, 6 to 12 months, and over 12 months. Thirty of the 82 infants were sen on five or more occasions. Two were seen only twice.

Seventeen of the 82 infants has external henias, an overall incidence of 20%. The frequency of inguinal hernia in infants weighing less than 1500 gm (25%) greatly exceeded that in infants weighing more than 1500 gm, (5.4%). Five of the seven infants with hernia in group 1 infants with a hernia in group 1 had inguinal hernia only (in one instance, inguinal hernias were bilateral; in two instances, both inguinal and umbilical hernias were present). None of the infants in group 1 had only an umbilical hernia. Umbilical hernias alone, on the other hand, occurred in six of the ten infants with a hernia in group 2, and this type of hernia was twice as common as inguinal hernia.

All the inguinal hernias were detected before the age of 6 months. None became incarcerated: all were repaired without incident, along with one of the umbilical hernias as well.

In this study, the incidence of umbilical hernia was significantlv less than that found by Hess and Lundeen in premature infants (70%), and was the same as that reported by Wood in full-term infants (20%). On the other hand, the incidence of inguimial hernias was much greater than that reported in full-term infants (1 to 4%) and was particularly high in infants of very low birth weight. This also appeared to be the case in Knox’s study. As inguinal hernias in infants result not from muscular weakness but from incomplete obliteration of the processus vaginalis, this was not an unxpected finding. Unlike the infants studied by -larper et al., none of these infants had problems that might have contributed to the developuient of a hernia, such as gastrointestinal and/or respiratory symptoms.

The data of Harper et al. support the conclusion arrived at. i .e., that low-birth-weight infants born prematurely have a significantly higher incidence of inguinal hernias than term infants and that the lower the birth weight, the higher the incidence of inguinal hernia.

Department of Pediatrics,
Karolinska Hospital