32 - Pregnancy

Authors: Macfarlane, Michael T.

Title: Urology, 4th Edition

Copyright 2006 Lippincott Williams & Wilkins

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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.

Physiologic Changes

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.

Urologic Changes

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

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of right-sided involvement (~75%) has been noted. Mechanical compression at the pelvic brim by the gravid uterus is the major cause. The left ureter appears to be somewhat protected from this compression by the sigmoid colon. Significant resolution of the condition can be expected within 24 to 48 hours after delivery. Urinary stasis is the most common adverse consequence of this partial obstruction; however, spontaneous rupture of the kidney has been known to occur. The bladder tends to be displaced anteriorly and superiorly by the growing uterus, producing more of an abdominal than pelvic location during pregnancy.

Urologic Complications

Infections

Asymptomatic Bacteriuria

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.

Vaginitis

The high levels of estrogens that are present during pregnancy are associated with increased vulvovaginal candidiasis. Trichomonas

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vaginitis during pregnancy should be treated with clotrimazole vaginal suppositories. Metronidazole has been demonstrated to be carcinogenic in animal studies, and it diffuses readily across the placenta.

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.

Antibiotic Choices

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.

Stones

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,

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is sometimes warranted. A nuclear renogram is an alternative to intravenous urogram. It limits maternal and fetal radiation exposure at the expense of anatomic definition.

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.