Intrathoracic Kidney Associated with Congenital Diaphragmatic Hernia – A Causal Relationship?

Introduction

Renal ectopias are found in less than 1 % of autopsies performed [9]. In a series of 16 000 autopsies, only 22 ectopic kidneys were found and only 1 intrathoracic ectopia. The intrathoracic kidney is a rare and special form representing in less than 5 % of all renal ectopias. Boys are more frequently affected than girls. The misplaced kidney is found more frequently on the left than on the right side [5], [12], [13]. Conclusions regarding the embryogenesis of this malformation cannot be made on the basis of associated anomalies, which are extremely rare. So far only the following anomalies associated with an intrathoracic renal ectopia have been found: thoracic ectopic spleen, adrenal ectopia, congenital diaphragmatic hernia, ureteropelvic junction stenosis, renal cysts, renal duplication, double-sided renal ectopia, cloacal malformations, myelomeningocele, pulmonary sequestrum, omphalocele, vertebral or costal malformations and dextrocardia [8].

According to the current standard of knowledge, a thoracic ectopia is either due to a malformation during renal embryogenesis or can be seen as a secondary phenomenon resulting from diaphragmatic anomaly. Further ascension of the kidney is stopped during the 9th week of pregnancy, apparently by involution of the mesonephric duct [1]. The diaphragm, which could be an anatomical barrier for further ascension of the kidney, develops at approximately the same time. A causal relationship between the formation of an intrathoracic renal ectopia and possibly late or incomplete diaphragmatic development has been excluded at present, as the combination with a congenital diaphragmatic hernia is extremely rare [12]. A delayed involution of the mesonephric duct could cause the excessive renal ascension, which leads to intrathoracic ectopia [1], [6], [12]. In the following we shall discuss the embryogenesis of the intrathoracic ectopia based on the literature and a case report.

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