Kidneys with a complete parenchymal bridge in the sinus, which is diagnostic for a duplex collecting system, were also excluded from the study. The children were between 1 month and 18 years old (mean age, 6.1 Â± 5.9 years).he objective of our study was to develop, by use of ultrasound, nomograms of renal parenchymal thickness, medullary pyramid thickness (height), renal length, and the ratio of medullary pyramid thickness to parenchymal thickness in healthy children.
erythropoietin. a glycoprotein hormone secreted by the kidney in the adult and by the liver in the fetus, which acts on stem cells of the bone marrow to stimulate red blood cell production (erythropoiesis).
The main regulator of the red cell production is the hormone erythropoietin (EPO). This hormone is largely secreted by the kidneys, although, about 10% may be produced and secreted by the liver. Erythropoietin secretion is up-regulated in response to low oxygen levels (hypoxia) in the blood. More oxygen can be carried to tissues when erythropoietin stimulates red blood cell production in the bone marrow to compensate for the hypoxia. Neonatal (newborn) polycythemia can be seen in 1% to 5% of newborns. The most common causes may be related to transfusion of blood, transfer of placental blood to the infant after delivery, or chronic inadequate oxygenation of the fetus (intrauterine hypoxia) due to placental insufficiency.