For years, it has been the belief of the scientific community that gestational hypertension and pre-eclampsia were relatively unique to humans, although there has been some recent evidence that other primates can also develop similar conditions, albeit due to different underlying mechanisms. The underlying cause of gestational hypertension in humans is commonly believed to be an improperly implanted placenta. Humans have evolved to have a very invasive placenta to facilitate better oxygen transfer from the mother to the fetus, to support the growth of its large brain. Origins of the placenta
The origins of gestational hypertension may lie with the development of humans hemochorial placenta. A hemochorial placenta optimizes the amount of oxygen and nutrients that can be absorbed into the fetal blood supply, while at the same time ensuring rapid diffusion of wastes away from the fetus. This hemochorial placenta differs from lower primates epitheliochorial placentae in the way that it allows the fetal tissues to interact directly with the mothers blood. The hemochorial placenta thereby promotes more rapid diffusion to and from the fetal blood supply.In animals with epitheliochorial placentae such as horses and pigs, the greatest resistance to maternal blood flow in the vascular system was found within the placenta. However, in animals with hemochorial placental structures such as rodents and primates, the vascular resistance in the placenta was low, leading scientists to the conclusion that the greatest resistance to maternal blood flow is found elsewhere in the maternal vascular system.
Causes
Dietary exposure to aristolochic acid is the cause of BEN and its attendant transitional cell cancers. Former hypotheses that included roles for ochratoxin, poisoning by organic compounds leached from lignite or by heavy metals, viruses, and trace-element deficiencies, are not supported by current evidence. Genetic factors may be involved in determining which persons exposed to aristolochic acid suffer from BEN and which do not.In the Balkan region, dietary aristolochic acid exposure may come from the consumption of the seeds of Aristolochia clematitis (European birthwort), a plant native to the endemic region, which grows among wheat plants and whose seeds mingle with the wheat used for bread. Aristolochic-acid-containing herbal remedies used in traditional Chinese medicine are associated with a related—possibly identical—condition known as "Chinese herbs nephropathy".Exposure to aristolochic acid is associated with a high incidence of uroepithelial tumorigenesis. Diagnosis
History
The first official published description of the disease was made by the Bulgarian nephrologist Dr.Yoto Tanchev (1917–2000) and his team in 1956 in the Bulgarian Journal Savremenna Medizina, a priority generally acknowledged by the international nephrological community. Their study was based on a wide screening of inhabitants of the villages around the town of Vratsa, Bulgaria.