Note
Values considered normal when not pregnant may reflect decreased renal function in pregnancy. Creatinine >75mol/L and urea >4.5mmol/L merit further investigation. See p 15. Glycosuria in pregnancy may reflect altered renal physiology and not necessarily imply hyperglycaemia.
Asymptomatic bacteriuria
Found in 2% of sexually active women it is commoner (up to 7%) during pregnancyespecially in diabetics and in those with renal transplants. With the dilatation of the calyces and ureters that occurs in pregnancy, 25% will go on to develop pyelonephritis, which can cause fetal growth restriction, fetal death, and premature labour. This is the argument for screening all women for bacteriuria at booking. If present on 2 MSUs treatment is given (eg amoxicillin 250mg/8h PO with a high fluid intake). Test for cure after 1 and 2 weeks. If the organism is not sensitive to amoxicillin, consider nitrofurantoin 50mg/6h PO with food.
Pyelonephritis
This may present as malaise with urinary frequency or as a more florid picture with raised temperature, tachycardia, vomiting, and loin pain. It is common at around 20 weeks and in the puerperium. Urinary infections should always be carefully excluded in those with hyperemesis gravidarum and in those admitted with premature labour. Treatment is with bed rest and plenty of fluids. After blood and urine culture give IV antibiotics (eg ampicillin 500mg/6h IV, according to sensitivities) if oral drugs cannot be used (eg if vomiting). Treat for 23 weeks. MSUs should be checked every fortnight for the rest of the pregnancy. 20% of women having pyelonephritis in pregnancy have underlying renal tract abnormalities and an IVU or ultrasound at 16 weeks' postpartum should be considered. In those who suffer repeated infection, nitrofurantoin (100mg/24h PO with food) may prevent recurrences. Avoid if the glomerular filtration rate is <50mL/min. SE: vomiting, peripheral neuropathy, pulmonary infiltration, and liver damage.
Chronic renal disease
With mild renal impairment (pre-pregnancy creatinine <125mmol/L) without hypertension there is little evidence that pregnancy accelerates renal disorders. Patients with marked anaemia, hypertension, retinopathy, or heavy proteinuria should avoid pregnancy as further deterioration in renal function may be expected. Close collaboration between physicians and obstetricians during pregnancy in those with renal disease is the aim. Induction of labour may become advisable in those with hypertension and proteinuria, or if fetal growth is retarded.
Pregnancy for those on dialysis is fraught with problems (fluid overload, hypertension, pre-eclampsia, polyhydramnios). A 50% increase in dialysis is needed. Live birth outcome is 5070%. Outcome is better for those with renal transplants; but 10% of mothers die within 7 years from birth.
Obstetric causes of acute tubular necrosis
Acute tubular necrosis may be a complication of any of the following situations:
Septicaemia (eg from septic abortion or pyelonephritis).
Haemolysis (eg sickling crisis, malaria).
Hypovolaemia, eg in pre-eclampsia; haemorrhage (APH, eg abruption, PPH, or intrapartum); DIC; abortionor adrenal failure in those on steroids not receiving booster doses to cover labour.
Whenever these situations occur, monitor urine output carefully (catheterize the bladder). Aim for >30mL/h output. Monitor renal function (U&E, creatinine). Dialysis may be needed.
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