الفهرس 
Renal physiological changes during pregnancyOnly 14 pages are availabe for public view
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Abstract
The kidneys have essential role in excretion of waste products including ammonia, urea, creatinine, from protein & uric acid from nucleic acid, drugs & toxins. They regulate fluid & electrolyte balance by making large volume of an ultra-filtrate of plasma (170 L/day) at glomerulus & selectively reabsorbing component of this ultra-filtrate at points along the nephron. Rate of filtration & reabsorption are controlled by many hormonal & hemodynamic signals. Kidney regulates acid-base hemostasis, calcium hemostasis, vitamin D metabolism & production of red blood cells. Kidney regulate blood pressure as renin secreted from juxtaglomerular apparatus in response to reduced afferent arteriolar pressure, stimulation of sympathetic nerves & changes in sodium content of fluid in distal convoluted tubules at macula densa and it is the first step in generation of aldosterone release, which in turn regulate systemic vasoconstriction & extracellular volume.
Pregnancy is characterized by significant physiological change that begins shortly after conception. The length of both kidneys increases approximately by 1 cm during gestation due to dilation of calicyal system, renal pelvis and ureters, right kidney increase in size more than the left one. The smooth muscles and connective tissue in renal system show hypertrophy and hyperplasia as well as increase in tone of tissues. The increase 1 cm in kidney till 16th week postpartum is an accepted physiological norm and should not be considered as Pathological.
Acute kidney injury (AKI) during pregnancy occurs with a bimodal distribution, one peak occurring during the 7th and 8th weeks of pregnancy and a second peak occurring during the 32nd and 36th weeks of pregnancy. Based on the trimester of pregnancy, AKI during pregnancy is divided into three groups. First half, second half and postpartum AKI. Septic abortion is the most common cause of AKI during the first half of pregnancy; pre-eclampsia, abruptio placenta, post-partum hemorrhage and acute fatty liver are the causes in the second half of pregnancy while hemolytic uremic syndrome occurs in the postpartum period.
P-AKI in developed countries is estimated around 1 in 20,000 pregnancies. The decrease in the incidence of pregnancy AKI mainly because of the near disappearance of post abortion sepsis after legalization of abortion in most developed countries and the improved management of hypertensive complication of pregnancy. In contrast, the incidence of P-AKI remains unacceptably high in developing countries. It was associated with a high incidence of fetal/neonatal (39%) and maternal (20%) mortality.The specific factors leading to persistent high incidence of P-AKI in developing countries include septic abortion usually performed in the absence of adequate medical monitoring, overall poor follow up of pregnancy with limited screening of hypertensive complication of pregnancy, and relatively late referral of patients with these disorders.
Renal changes unique to the pregnant state must be considered during diagnosis, treatment and management of pregnant woman with renal disorders. Diagnostic criteria used for AKI in the non-pregnant state may not be valid or useful during pregnancy, so practitioners unfamiliar with renal physiology of pregnancy may be slow to recognize AKI. Prompt recognition may theoretically reduce permanent injury. Some important general measures to minimize renal injury (such as etiology treatment, suspension of nephrotoxic drugs or treatment of an infectious disease) should be started as soon as possible. The second step is administration of intravenous fluids to restore or maintain renal perfusion this procedure also prevents hypovolemia and ensures an adequate utero-placental perfusion and fetal well-being.