A hernia umbilicalis is the protrusion of intestines through a rupture gate in the umbilical region, lined with an outer hernial sac formed from the skin and subcutis and an inner hernial sac dressed by the peritoneum. The hernia gate often has a round to oval shape. The aim of this report was to investigate whether umbilical hernias are always congenital or may arise later. In addition, factors as gender, course of birth, colic up to 7d p.n., meconium obstipation, umbilical hematoma, omphalitis were evaluated in connection to umbilical hernias. On a large Warmblood stud, data of 1440 foals from birth to weaning were collected during the 2020 breeding season. The foals were examined as part of a routine clinical examination carried out once weekly by a veterinarian during which the abdominal wall in the navel region was routinely palpated. An umbilical hernia was diagnosed in 201 foals. In only three of these 201 foals an umbilical hernia was detected immediately after birth while in 20 foals (10 %) the hernia was diagnosed between the 15th and 30th day of life. Most umbilical hernias (56.2 %, n = 113 of 201) occurred between the 30th and 90th day of life and in the 4th month of life 31 (15.4 %) foals developed a hernia. In 34 foals (16,9 %) an umbilical hernia was first diagnosed after the fourth month of life. Altogether 14 % of all foals (201 of 1440) showed an umbilical hernia up to the age of 6 months. 37.8 % (76 of 201) of these required surgical closure under general anesthesia while 8,5 % foals (17 of 201) showed spontaneous closure of the hernial orifice up to 6 months of age. The parturition was analyzed regarding a possible association with the development of umbilical hernias. Medium to strong traction aid was needed on 56 foals and 33,9 % of these foals (19 of 56) were diagnosed with an umbilical hernia. Of these 19, two foals developed an umbilical hernia within the first 30 days of life. One of them had to be treated surgically. The umbilical hernia of the second foal closed spontaneously after two months. Five (of 19) foals developed an umbilical hernia between the 30th and 60th day of life, all others after the 60th day of life. A statistical analysis showed that there is no increased risk of developing an umbilical hernia within the first 30 days following a difficult parturition (p < 0.0001). In addition, the foals were compared in terms of their sex in association with umbilical hernia. A total of 712 fillies (49.4 %) and 728 colts (50.6 %) were born in the year examined. Of the foals that survived to weaning age, 121 fillies (8,4 %) and 80 colts (6 %) developed an umbilical hernia. There are significantly more umbilical hernias in fillies than in colts (p < 0.0001). Furthermore, occurrence of meconium obstipation in association with umbilical hernia was investigated. Meconium obstipation was treated in ten of 1440 foals. One of these ten foals developed an umbilical hernia when it was four months old, therefore no association was shown between meconium obstipation and umbilical hernia. The occurrence of colic in the first days of life was also evaluated. Eleven foals showed colic at this stage of life and one of these foals had an umbilical hernia by the age of six months. In addition, pathological findings of the umbilicus were also examined. An omphalitis or a hematoma of the umbilicus were diagnosed in 203 of the foals (14.1 %; 203 of 1440). Of these 203 animals, 13 (6.4 %) developed an umbilical hernia, four of these required surgical treatment. The chi-square-test showed that foals with umbilical inflammation do not develop an umbilical hernia more often than other foals (p < 0.0001). A total of 105 foals with an umbilical hernia were weaned from their mare. Foals weaned with umbilical hernia were examined three more times after weaning. In total, the data from 105 foals were available. In 67 % (70 of 105) of the foals weaned with an umbilical hernia, the hernial orifice had decreased progressively in size by the age of 10 months. Spontaneous occlusion was observed in 55 % (58 of 105) of the animals. 5 % (5 of 105) of the foals showed an increasingly larger hernial orifice after weaning. Therefore, surgical closure of the umbilical hernia is not necessary in all cases. However, it is important to check these foals regularly in order to be able to identify the risk of incarceration in time.
