Polymelous Layer Chick Displaying Additional Malformations of the Hind Gut: Case Report and In‐Depth Review of Related Literature

Abstract

A case report of a male 6-day-old male layer chick featuring incomplete polymelia of the hind limbs and hindgut malformations is presented. The chick was submitted to computed tomography (CT) examination and subsequent anatomical dissection. Apart from the two supernumerary hind limbs, the anatomical dissection revealed additional hindgut alterations: three uniform-sized caeca flanked the ileum, and the rectum branched into paired cloacae. The supernumerary hind limbs were localized caudal to the normal hind limbs in an inverted position and were attached to pelvic girdle elements and to a curtate pygostyle. They featured a prominent unpaired femur besides paired tibiotarsi, tarsometatarsi and species-specific phalanges of the toes. Additionally, two separate bones attached to the caudoventral aspect of the regular hip bones were developed. The supernumerary limbs were in part mobile and received nerve and vascular supply. Digital 3D-reconstruction based on the CT datasets revealed the osseous components of the malformed body parts. The possible morphogenesis including an in-depth literature review and the clinical implications of the reported malformations are discussed.

Amputation of Polymelia in a Layer Chicken

“…Although clinical and radiographic examinations revealed no other obvious malformations in the present case, an MRI or CT scan was essential to document the complete absence of any other defects. In this respect, CT findings of a previous case of polymelia revealed additional hindgut alterations including three uniform-sized ceca flanking the ileum and a rectum that branched into paired cloacae (6).…”

“…According to the available literature, two case reports recorded this defect in a 6-day-old male layer chick featuring incomplete polymelia of the hind limbs and hindgut malformations (6) and in a 7-wk-old slaughterhouse chicken (2). This report records-for the first time-the surgical treatment and outcome of polymelia in a 7-mo-old layer chicken.…”

Polymelia and duplication of the descending colon in a Poodle dog - a case report

“…the causes for the occurrence of these embryological disorders could be genetic, environmental (infectious agents, toxic plants, chemical substances, physical damage and nutritional deficiencies) or multifactorial (FELIPE, 2003;McGEADY et al, 2006;raDOStItS et al, 2007;hIrSChBerG et al, 2012), varying according to the type of agent and gestational period, and may occur in any anatomical region (ahMaDY and LISEY, 2009). However, malformations can occur in a sporadic way with no specific cause (FeLIPe, 2003;McGeaDY et al, 2006;raDOStItS et al, 2007) which could be the case with the animal in this study, since there were no accidents reported with the progenitors and no medications were administered during gestation.…”

“…they may be related to the erratic spread of germ cells in the embryo, or to the abnormal duplication of those cells at the beginning of the embryo development (CeBrIÁN et al, 2006;ahMaDY and LISeY, 2009;McGeaDY et al, 2006). extra limbs have no function (FeLIPe, 2003;hIrSChBerG et al, 2012). However, walking difficulties can cause distress to the animal.…”

“…There is no classification or data regarding its frequency of occurrence, the location of the extra limbs or its association with other congenital abnormalities (VerMa et al, 2013;MONtaLVO et al, 2014). In animals, there are reports of polymelia in calves (BehreNS et al, 1993;CeBrIÁN et al, 2006;MONteS et al, 2012), sheep (ahMaDY and LISeY, 2009), amphibians (MahaPatra et al, 2001, reptiles (CUPUL-MaGaÑa et al, 2014), poultry (hIrSChBerG et al, 2012), wild birds (rOGerS et al, 2016), and one case report in dogs (ZUCker et al, 1993).…”