Authors: Macfarlane, Michael T.
Title: Urology, 4th Edition
Copyright 2006 Lippincott Williams & Wilkins
> Table of Contents > Part Two - Selected Topics > Chapter 32 - Pregnancy
It is not surprising, with the intimate anatomic and physiologic relationship between the reproductive and urinary systems, that pregnancy should have significant effects on urinary function. These changes are generally the normal consequences of pregnancy. This appreciation is helpful when called on to evaluate a urologic problem in a pregnant patient.
Total blood volume increases during pregnancy because of a 50% increase in plasma volume and a lesser increase in red cell volume. This results in hemodilution and decreased hematocrit. With the increased blood volume, cardiac output increases early in pregnancy by 1 to 2 L/minute and is maintained until delivery. Despite the increased blood volume and cardiac output, systolic blood pressure remains essentially unchanged. This is probably due in part to the increased blood flow to the uterus (80% to the choriodecidua) and lowered peripheral vascular resistance.
During pregnancy, the mother's serum creatinine generally decreases because of a 30% to 50% increase in both renal blood flow and glomerular filtration rate (GFR). Mean serum creatinine levels of 0.46 are common. Retention of sodium and water and renal wasting of glucose and amino acids also are noted during pregnancy. These changes are generally maintained up to term. By approximately 8 postpartum weeks, most physiologic changes of pregnancy can be expected to have returned to normal.
Pyeloureteral dilatation occurs commonly during pregnancy and is most prominent by weeks 22 to 24. The muscle-relaxing effects of increased progesterone during pregnancy is thought to play a major role in addition to mechanical factors related to the fetus. A preponderance
Asymptomatic bacteriuria occurs in 2% to 7% of pregnancies. Escherichia coli is the infecting organism in more than 80% of cases. Complications of these asymptomatic infections include pyelonephritis, prematurity, low birth weight, anemia, hypertension, and preeclampsia. Treatment of asymptomatic bacteriuria with a 10- to 14-day course of antimicrobials has been shown to decrease the risk of developing complications. Ampicillin or cephalosporins are generally safe and effective during any phase of pregnancy. Patients with persistent bacteriuria should be treated with suppressive therapy for the remainder of the pregnancy.
Symptomatic Urinary Tract Infections
Symptomatic urinary tract infections can result in significant maternal morbidity. Upper-tract obstruction and stasis are not uncommon during pregnancy and are believed to be an important predisposing factor. Pyelonephritis is a common complication of pregnancy, generally during the last two trimesters. Pyuria alone is not considered a reliable indicator of the presence or absence of infection during pregnancy. Cultures must be obtained. Treatment should be aggressive. Bacterial surveillance with frequent cultures or prolonged urinary suppression for the remainder of the pregnancy should be conducted because of the high incidence of recurrent infections.
The high levels of estrogens that are present during pregnancy are associated with increased vulvovaginal candidiasis. Trichomonas
Sexually Transmitted Disease
Chlamydial infection can cause cervicitis and pelvic inflammatory disease (PID). Fetal conjunctivitis is a common sequela if left untreated. Erythromycin is the drug of choice during pregnancy because of less fetal toxicity. Gonorrhea also is common in pregnancy. Diagnosis is made by smear and culture of cervical and urethral discharge. Treatment is aqueous procaine penicillin G, 4.8 million units intramuscularly, with oral probenecid.
All antibiotics cross the placental barrier to various degrees. Penicillin derivatives and cephalosporins have been shown to have minimal toxic effects to both mother and fetus and are therefore commonly used. Nitrofurantoins also are highly effective for simple urinary tract infections of pregnancy but can cause nausea and vomiting. Aminoglycosides can be used for pyelonephritis in pregnancy when other less toxic choices are unsuitable. However, because of their potential side effects of nephrotoxicity and ototoxicity, they must be used with caution in patients with renal insufficiency. Tetracyclines have numerous side effects, such as teratogenic potential and staining of the teeth, and should be avoided. Trimethoprim-sulfamethoxazole combinations are effective but should be avoided near term.
Pregnant patients who present with renal colic and microscopic hematuria should undergo renal ultrasound. If hydronephrosis is present, presumption of a ureteral calculus can be made. Fifty percent of these stones can be expected to pass spontaneously. If renal colic fails to resolve with hydration and analgesics or in the setting of severe obstruction or sepsis, then retrograde placement of a silicone double-J ureteral stent under local anesthesia may be attempted. Retrograde internal stent passage may be difficult during the third trimester, making a percutaneous approach advantageous. Radiographic studies may be necessary. A plain abdominal film [kidney, ureter, and bladder (KUB)] exposes the fetus to only 200 mrad. A limited excretory urogram, consisting of one plain film and a 30-minute film to determine obstruction,
Complications of Cesarean Section
Unrecognized injury to the urinary tract can occur during a cesarean section. The bladder is most commonly involved, resulting in a vesicovaginal fistula. These patients will present with urinary incontinence after surgery. If the injury is recognized within 2 to 3 days of surgery, repair should be attempted promptly; otherwise, definitive treatment should be delayed for 2 to 3 months. Ureteral injury, more commonly on the left, can result in a fistulous communication between the ureter and the vagina or uterine corpus. Alternatively, the ureter may be inadvertently ligated in the course of controlling bleeding.
Pregnancy in Transplantation
Pregnancy in the transplant recipient is a high-risk situation with increased perinatal morbidity and maternal complications, including graft rejection. Fetal complications also are high, with as many as 50% of these infants being born prematurely. However, because many successful pregnancies have been reported in transplant recipients, most centers will cautiously sanction pregnancy in selected patients with good physical and psychological health and who are at least 2 years after transplant.