Renal System

Renal System

Renal blood flow increases by 80% during pregnancy, causing the kidney to swell and increase in size, appearing 1cm longer on ultra sound. The renal pelvis and ureters dilate under the influence of progress throne, which is enhanced by the enlarging uterus producing partial obstruction of the ureters. There is a large increase in glomerular filtration rate (GFR) by the end of the first trimester leading to increased clearance of urea and creatinine. During pregnancy, urea and creatinine levels are 40% lower than non-pregnant values. The normal values therefore need to be adjusted as values within the normal range for the non-pregnant state may indicate significant renal function impairment during pregnancy. Proteinuria increases during pregnancy, but levels above 0.3 g in 24 hours should be considered abnormal.

Rental Disease

Pregnant women are at increased risk of urinary tract infections (UTI) which if untreated will develop into acute pyelonephritis in 20% of cases, sympotoms of acute pyelonephritis include: fever chills, flank pain and other symptoms of lower UTI. The caysative organisms are usually E, coil, Klebsiella, and proteus. Useful antibiotics for the treatment of UTI's include nitrofurantoin (not in first trimester), trimethoprim, amplicillin and cephalosporins. Pregnancy may predispose to the formation of renal stones in some susceptible women, which can be extremely painful, difficult to manage and may lead to acute renal failure (ARF).

The classification and some causes of ARF in pregnancy are:

• Pre-renal: hypovolaemia caused by haemorrhage, hyperemesis gravidarum and dehydration, and low cardiac output states.
• Fenal: pre-eclampsia, eclampsia, HELLP syndrome, septic abortion, amniotic fluid embolus, pyelonephritis, acute tubular necrosis, and glomerulonephritis.
• Post-renal: Renal stones, ureteral obstruction.

ARF is characterized by a rapid rise in serum creatinine (>73 mmol/L) and urea leavels (>4.3 mmol/L), and urine output may fall to <400mL/day. ARF is not common in pregnancy and usually reflects severe underlying disease that requires urgent diagnosis and treatment. In women with chronic renal failure (CRF), the chances of becoming pregnant decrease with declining renal function and pregnancy is rare if the kidneys are functioning at high risk of developing pre-eclampsia and LUGR, with a high perinatal mortality. The increase in GFR during pregnancy will cause further damage to kidneys which are already impaired, and the woman's own condition is likely to deteriorate. Chronic renal impairment leads to activation of the rennin-angiorate. Chronic renal impairment leads to activation of the rennin-angiotorate system result in salt and water retention, and hypertension. The outcome of pregnancy depends on the degree of renal impairment, the blood pressure and episodes of infection. Termination of pregnancy of early induction of labour may be offered if the mother's condition is deteriorating. Women with CRF prior to pregnancy may never recover pre-pregnancy renal function if renal function deteriorates.