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Conjoined twin piglets

REPORTS of conjoined or identical twins have been found exclusively in cattle (Arthur 1956). To the authors’ knowledge, identical twins have not yet been recorded in sheep, pigs, dogs or cats. This short communication describes a rare case of conjoined twins in newborn piglets in which the component parts were diplopagus (equal and symmetrical). Conjoined female piglets were born, together with eight normal piglets, to a sow approximately four years old. After 24 hours they were admitted to the Surgery Clinic, Faculty of Veterinary Medicine, Makerere University, Kampala, Uganda, but they were weak and died 30 minutes after arrival. Postmortem examination revealed the two piglets to be identical and symmetrical. The body length of each was 20·5 cm. The skin was covered with black and white hair, with patches of black hair on the head, withers and rump. Both heads and necks were completely separated; there were four ears, four eyes, four nostrils and two mouths. All four limbs were duplicated and were fully developed (Fig 1). Dissections of the abdominal and thoracic cavities showed that each piglet had a separate abdominal and thoracic cavity. The abdominal cavities were fused at the cranial third of the abdomen. The skin, abdominal muscles and peritoneum were shared and covered both abdominal cavities. The thoracic cavities appeared cylindrical in shape, were completely fused at the sternum, and had pairs of ribs. The anatomical structures in one piglet were a mirror image of the other. The internal organs of both were similar and well developed. The small intestines were arranged in small coils, chiefly on the left side and floor of the abdomen. The liver of each piglet appeared triangular in outline. The livers were fused together, but each had a separate gall bladder (Fig 2). There was a common umbilical cord for both piglets, and the cord had three branches. A pair of vessels (urachi) connected the umbilicus to both urinary bladders, and the third branch (the umbilical vein) was attached to the common livers. Getty (1975) and Reef and Collatos (1988) reported that there are four internal umbilical structures in the fetus and in the clinically normal equine neonate; the urachus, the umbilical vein and two umbilical arteries. At birth, the umbilicus separates and the urachus retracts, then closes and atrophies. When the umbilical cord ruptures, the umbilical arteries atrophy and form the round ligaments of the bladder, and the umbilical vein atrophies and forms the round ligament of the liver. Therefore, these structures were considered to be postnatal umbilical remnants. Unfortunately, it was not possible to detect the umbilical arteries. Each twin had a separate long, narrow spleen and stomach, two normal kidneys and ureters, and a urinary bladder. Each piglet also had a heart and pair of lungs but there was a common pericardial membrane (Fig 3). The heart and lungs of one piglet were comparatively less well developed than those of other twin (Fig 4). Conjoined or identical twins are rare in cattle, with conjoined twins occurring approximately once in every 100,000 births (Leipold and others 1972), but the incidence of congenital inherited defects in pigs is low, at approximately 1·25 per cent (Roberts 1986). Omran (1996) reported the incidence of congenital inherited defects in cattle to be 5·4 per cent of animals examined. In the present study, the newborn female piglets were identical, completely symmetrical, and fused together at the thoracic cavity and the cranial third of the abdominal cavity. Short Communications