Acute renal failure (ARF) can present in multiple complicated medical conditions but is predominantly acquired in hospitalized patients. This is not a rare medical condition, with as many as 5% of all hospitalized patients having some degree of ARF. With respect to the obstetric patient, however, ARF has become an uncommon complication of pregnancy in developed countries. It is estimated that the current incidence of ARF complicating pregnancy approximates 1 per 10,000 pregnant women. In 3 successive periods of 10 years between 1958 and 1987, Stratta and colleagues have reported a continued decrease in ARF requiring emergency renal dialysis from a rate of 1 in 3000 in 1958 to 1 in 15,000 pregnancies in 1987. They documented 81 cases of ARF in pregnancy of which 11.6% experienced irreversible renal damage. The majority of these cases resulted from complications of either severe preeclampsia or eclampsia. Possible explanations for this dramatic trend in this subset of patients includes ready availability of prenatal care and the legalization of medical abortions as main factors responsible for this reduction in the incidence of ARF requiring dialytic support. However, in underdeveloped countries of the world, ARF remains a frequent complication of pregnancy and has an attendant maternal mortality surpassing 50%. In these countries, ARF has a bimodal distribution with peaks in the first and third trimester, presumably reflective of the continued practice of illegal abortions, the lack of access to quality prenatal care, and the occurrence of preeclampsia or eclampsia. Whatever the explanation, ARF in pregnancy can be the result of any of the disorders, which lead to severe renal dysfunction in nonpregnant patients or may result from disorders that are unique to the pregnant condition.
RENAL ANATOMY AND FUNCTION DURING PREGNANCY
An understanding of the dramatic changes that occur normally in renal architecture, function, and blood flow is essential to the correct diagnosis and management of renal disease in the pregnant patient (Table 13-1).
TABLE 13-1.Renal Changes in Normal Pregnancy |Favorite Table|Download (.pdf) TABLE 13-1. Renal Changes in Normal Pregnancy
|Alteration ||Change ||Clinical relevance |
|Increased renal size ||Renal length about 1 cm greater ||Postpartum decrease in size should not be mistaken for parenchymal loss |
|Dilation of pelves, calyces, and ureters ||Resembles hydronephrosis on ultrasound or IVP ||Not to be mistaken for obstructive uropathy, increased rates of upper tract infections |
|Increased renal hemodynamics ||Increased GFR and renal plasma flow ||Decreased serum creatinine and BUN; increased excretion of amino acids, protein, and glucose |
|Changes in acid-base metabolism ||Renal bicarbonate threshold decreases ||Serum bicarbonate level lower by 4-5 mEq/L |
|Renal water handling ||Osmoregulation altered with decreased osmotic thresholds for AVP release, and thirst ||Serum osmolality decreases 10 mOsm/L during normal gestation |
There is a marked increase in kidney size during pregnancy. This increase in size is primarily due to the ...