Horseshoe kidney: A new theory on lts embrogenesis based on the study of a 16‐mm human embryo

Abstract

We studied a human embryo of 16 mm crown-rump (CR) length in excellent condition with a horseshoe kidney malformation. An exhaustive study of this specimen and a review of published material on the human embryo brings us to propose a new theory on the embryogenesis of this malformation. The most commonly accepted theory consists of a mechanical interpretation based on the relation between the metanephroi and the umbilical arteries during the development of the latter. Nevertheless, in those cases where renal parenchyma constitutes the isthmic region, we believe that these arise from nephrogenic cells that have migrated across the primitive streak in the final phase of gastrulation and thus arise from the posterior nephrogenic area of the epiblast.

Incidence of Tumoural Pathology in Horseshoe Kidneys

“…Presently, the studies by Domenech-Mateu et al [17] validate this theory solely in the presence of a fibrous isthmus, which in our series occurred only in 2 cases. The same authors propose the abnormal migration of the cells of the rear nephrogenic area as the embryopathogenic mechanism responsible for HKs with parenchymatous isthmus (8 out of our 10 cases), resulting from the cranial traction of the lateral areas of the metanephric masses due to trunk growth, whilst the isthmus is hindered by the lower mesenteric artery.…”

Horseshoe kidney - a case report

“…The polar fusion results in an isthmus of tissue (parenchymal or fibrous between the 2 kidneys). The kidneys fuse in the pelvic cavity prior to ascending, this leads to a large U-shaped kidney 3 which is unable to ascend to the level of L1 because it's ascent is arrested by the origin of the inferior mesenteric artery from the aorta at the level of L3 vertebra. This leaves the kidney in the hypogastric region.…”

“…Upper pole and mid fusion are rare. 3 Even though the horse shoe kidney produces no symptoms, it is frequently concomitant with other vascular or genitourinary anomalies. [5][6][7][8] Therefore, it is important to be aware of these anomalies in clinical practice.…”

Optimal Scintigraphic Evaluation of a Hydronephrotic Horseshoe Kidney

“…The anomaly consists of 2 renal masses connected at their lower poles by a parenchymal or fibrous isthmus. Several hypotheses have attempted to explain the malformation, including attribution of the fusion anomaly to a converging course of the ureteric buds, a medial position of the metanephric ducts relative to the umbilical arteries, or some combination thereof (2). Though one third of patients remain asymptomatic, nonspecific abdominal pain radiating to the lower back is a common complaint (1).…”