Diseases of urinary system in pregnancy

Diseases Of Urinary System In Pregnancy

Dr Shaimaa Kadhim Al-Khafajy

Urinary tract infection

UTI is defined as the presence of at least 100,000 organisms per milliliter of urine in an asymptomatic patient, or as more than 100 organisms/mL of urine with accompanying pyuria (> 7 white blood cells [WBCs]/mL) in asymptomatic patient. A diagnosis of UTI should be supported by a positive culture for a uropathogen, particularly in patients with vague symptoms

Pathophysiology

Infections result from ascending colonization of the urinary tract, primarily by existing vaginal, perineal, and fecal flora. Various maternal physiologic and anatomic factors predispose to ascending infection. Such factors include urinary retention caused by the weight of the enlarging uterus and urinary stasis due to progesterone-induced ureteral smooth muscle relaxation. Blood-volume expansion is accompanied by increases in the glomerular filtration rate and urinary output.

Loss of ureteral tone combined with increased urinary tract volume results in urinary stasis, which can lead to dilatation of the ureters, renal pelvis, and calyces. Urinary stasis and the presence of vesicoureteral reflux predispose some women to upper urinary tract infections (UTIs) and acute pyelonephritis.

Calyceal and ureteral dilatation are more common on the right side; in 86% of cases, the dilatation is localized to the right. The degree of calyceal dilatation is also more pronounced on the right than the left (average 15 mm vs 5 mm). This dilatation appears to begin by about 10 weeks’ gestation and worsens throughout pregnancy.

Glycosuria and an increase in levels of urinary amino acids (aminoaciduria) during pregnancy are additional factors that lead to UTI.

Etiology

E coli is the most common cause of urinary tract infection (UTI), accounting for approximately 80-90% of cases. It originates from fecal flora colonizing the periurethral area, causing an ascending infection. Other pathogens include the following:
Klebsiella pneumoniae (5%)
Proteus mirabilis (5%)
Enterobacter species (3%)
Staphylococcus saprophyticus (2%)
Group B beta-hemolytic Streptococcus (GBS; 1%)
Proteus species (2%)


Classification of UTI’s
• Clinical:
• Anatomical:
Lower tract dis: asymptomatic bacteriuria and acute cystitis
Upper tract dis: acute pyelonephritis

Asymptomatic bacteriuria

IT is commonly defined as the presence of more than 100,000 organisms/mL in 2 consecutive urine samples in the absence of declared symptoms. Untreated asymptomatic bacteriuria is a risk factor for acute cystitis (40%) and pyelonephritis (25-30%) in pregnancy.

Acute cystitis

Acute cystitis involves only the lower urinary tract; it is characterized by inflammation of the bladder as a result of bacterial or nonbacterial causes (eg, radiation or viral infection). Acute cystitis develops in approximately 1% of pregnant patients, of whom 60% have a negative result on initial screening. Signs and symptoms include hematuria, dysuria, suprapubic discomfort, frequency, urgency, and nocturia. These symptoms are often difficult to distinguish from those due to pregnancy itself.

Acute pyelonephritis

Pyelonephritis is the most common urinary tract complication in pregnant women, occurring in approximately 2% of all pregnancies. Acute pyelonephritis is characterized by fever, flank pain, and tenderness in addition to significant bacteriuria. Other symptoms may include nausea, vomiting, frequency, urgency, and dysuria. Furthermore, women with additional risk factors (eg, immunosuppression, diabetes, sickle cell anemia, neurogenic bladder, recurrent or persistent UTIs before pregnancy) are at an increased risk for a complicated UTI.

Complications

The primary complication of bacteriuria during pregnancy is cystitis,. Other complications may include the following:
Perinephric cellulitis and abscess
Septic shock (rare)
Renal dysfunction (usually transient, but as many as 25% of pregnant women with pyelonephritis have a decreased glomerular filtration rate)
Hematologic dysfunction
Hypoxic fetal events due to maternal complications of infection that lead to hypoperfusion of the placenta
Premature delivery leading to increased infant morbidity and mortality
acute respiratory distress syndrome


Diagnosis
Laboratory studies can include blood studies and urine studies, including culture, urinalysis, dipstick testing.
Imaging tests can include ultrasonography and intravenous pyelography.

Complete blood count (CBC)

Serum electrolytes
Blood urea nitrogen (BUN)
Serum creatinine

Treatment of asymptomatic bacteruria & acute cystitis

Antibiotic therapy
Oral antibiotics are the treatment of choice for asymptomatic bacteriuria and cystitis. Appropriate oral regimens include the following:
Cephalexin 500 mg 4 times daily
Ampicillin 500 mg 4 times daily
Nitrofurantoin 100 mg twice daily
Sulfisoxazole 1 g 4 times daily

10-14 days of treatment is usually recommended to eradicate the offending bacteria.

Treatment of pyelonephritis
Hospital admission and intravenous (IV) administration of cephalosporins or penicillins. IV fluids must be administered with caution. Patients with pyelonephritis can become dehydrated because of nausea and vomiting and need IV hydration. However, they are at high risk for the development of pulmonary edema and acute respiratory distress syndrome (ARDS).


Fever should be managed with antipyretics (preferably, acetaminophen) and nausea and vomiting with antiemetics.

Chronic Renal disease

Women with chronic kidney disease are less able to make the renal adaptations necessary for a healthy pregnancy and pregnancy in women with renal disease therefore requires increased maternal and fetal surveillance.

Pre-pregnancy counselling

Pre-pregnancy counselling is recommended in all women with chronic kidney disease and they should be made aware of the risks to the fetus and to their long-term renal function before conception.
Pre-pregnancy counselling discussion should include:

Safe contraception until pregnancy advised

Fertility issues if indicated
Genetic counselling if inherited disorder
Risks to mother and fetus during pregnancy
Avoid known teratogens and contraindicated drugs

Management of antihypertensives

Low-dose aspirin for most pregnancies
Need for anticoagulation once pregnant in some conditions
Need for compliance with strict surveillance
Likelihood of prolonged admission or early delivery
Possibility of accelerated decline in maternal renal function
Need for postpartum follow up.


Chronic kidney disease
Chronic kidney disease (CKD) is classified into five stages based on the level of renal function. Stages 1 and 2 affect around 3 per cent of women of childbearing age (20–39), and while stages 3–5 affect 1 in 150 women in this age group, pregnancy in these women is less common. Some women are found to have CKD for the first time in their pregnancy, and pregnancy can unmask previously unrecognized renal disease.

Stages of chronic kidney disease

stage
Description
• Estimated GFR (mL/min/1.73m2)

1
• Kidney damage with normal/raised GFR

• >90

2
Kidney damage with mildly low GFR
60-89
3
• Moderately low GFR

30-59

4
Severely low GFR
15-29
5
Kidney failure


• <15 or dialysis

Effect of pregnancy on CKD

Women with CKD stages 1–2 have mild renal dysfunction and usually have an uneventful pregnancy and good renal outcome. Pregnancy with a serum creatinine < 110 mmol/L, minimal proteinuria (<1 g/24 hours), and absent or well-controlled hypertension pre-pregnancy has been shown to have little or no adverse effect on long-term maternal renal function.

Women with moderate to severe disease (stages 3–5) are at highest risk of complications during pregnancy and of an accelerated decline in their renal function. Pre-existing hypertension and proteinuria greatly increase the risk. If pre-eclampsia develops, maternal renal function often deteriorates further, but any other additional complications, such as postpartum haemorrhage or use of non-steroidal anti-inflammatory drugs, can critically threaten maternal renal function.

Effect of CKD on pregnancy outcome

Pregnancies in mothers with CKD have increased risks of preterm delivery, delivery by Caesarean section (40 per cent) and FGR (increased two-fold). Diastolic blood pressure has been suggested as the greatest risk factor for fetal death, but overall fetal survival is reported at around 95 per cent. The risk of adverse pregnancy outcome correlates with the degree of renal dysfunction.

Estimated effects of renal function on pregnancy outcome and maternal renal function

• Mean pre-pregnancy value
• serum creatinine

• <125

• 125–180

• >180

• Fetal growth restriction (%)
25
40
65
Preterm delivery (%)
30
60
>90
Pre-eclampsia (%)
22
40
60
• Loss of <25% renal function
0
20
50
• End-stage renal failure after 1 year (%)
0
2
35


Monitoring of patients with CKD during pregnancy

Blood pressure

Renal function
creatinine
Urine
infection
proteinuria

Full blood count

haemoglobin
ferritin
Renal ultrasound
Fetal ultrasound
• anatomy
• uterine artery Doppler 20–24 weeks
• growth.

Dialysis

The incidence of pregnancy on dialysis (stage 5 CKD) is increasing. Dialysis must be adjusted to allow for the physiological changes of pregnancy (plasma volume, fluid retention, electrolytes), and haemodialysis is usually more effective then peritoneal dialysis in achieving this.


Complications include preterm delivery, polyhydramnios (30–60 per cent), pre-eclampsia (40–80 per cent) and Caesarean delivery (50 per cent). If conceived on dialysis, 50 per cent of infants survive, but pregnancy before dialysis has a better outcome.

Pregnancy in women with renal transplants

Women with end-stage kidney disease have hypothalamic-gonadal dysfunction and infertility, so conception is rare. Female fertility returns rapidly after renal transplantation and it is estimated that 2–10 per cent of female recipients conceive.

Of pregnancies progressing beyond the third trimester, the vast majority (>90 per cent) result in a successful pregnancy outcome. Most transplantation centres advise that conception is safe after the second post-transplantation year, provided the graft is functioning well and no rejection episodes occur in the year before conception.

All pregnancies in transplant recipients are high risk and should be managed by a multidisciplinary team. Lower immunosuppressive steroid dosage, longer time since transplantation and better graft function with absence of chronic rejection, are all associated with better maternal outcomes.

Complications of pregnancy in renal transplant patients include high rates of pregnancy-induced hypertension (30–50 per cent), preterm delivery (40–60 per cent), pre-eclampsia (10–40 per cent) and urinary tract infection (20–40 per cent). Diagnosing pre-eclampsia can be difficult due to the normal rise in blood pressure after 20 weeks and the presence of pre-existing proteinuria.

The risk of acute rejection in pregnancy is estimated at 2–10 per cent, and allograft dysfunction may also be difficult to detect during pregnancy. Vaginal delivery is safe, with Caesarean section considered for the usual obstetric indications. From 5 to 15 per cent of women have worse graft function after pregnancy.

Monitoring of renal transplant patients during pregnancy

Renal function
blood pressure
creatinine
proteinuria
Drug levels
Fetal growth


If renal function declines, exclude:
Obstruction.
Infection. Rejection.

Predictors of fetal outcome include pre-pregnancy maternal hypertension, diabetes mellitus and maternal drug treatment. Many women have concerns about the immunosuppressive drugs used post-transplantation,

and since immunosuppressive medications must be continued throughout pregnancy, the fetus is inevitably exposed to potential fetotoxic and teratogenic agents throughout development.

The actual effects of medications on growth and development are difficult to determine

and may not be obvious at birth. It is also difficult to assess the relative effect of immunosuppressive agents. Prednisolone, azathioprine, cyclosporin and tacrolimus are considered safe.