Pregnancy often predisposes to the development of urinary tract disorders even though some diseases of the kidney and urinary tract may be associated with pregnancy by chance. In certain instances, pregnancy may predispose to worsening of preexisting renal disease.
URINARY TRACT CHANGES DURING PREGNANCY
During pregnancy, certain changes in both structure and function take place in the urinary tract. Some of the important changes are:
1) Dilatation of the renal calyces, pelves as well as the ureters occurs. This along with the increased vesicoureteral reflux predispose to urinary tract infections.
2) Effective renal plasma flow and glomerular filtration are increased, on an average, by 40 and 65% respectively. These changes have clinical relevance while interpreting the renal function tests, for example, serum concentrations of creatinine and urea are decreased in normal pregnancy.
URINARY TRACT INFECTIONS
These are the most common infections encountered during pregnancy. In most of the cases, the organism found is E. coli. These could be grouped as asymptomatic bacteriuria, cystitis or pyelonephritis
Asymptomatic Bacteriuria
Asymptomatic bacteriuria occurs in approximately 5% of patients but is worth investigating because about 30% of these may subsequently develop acute symptomatic infection during pregnancy,
DIAGNOSIS OF ASYMPTOMATIC BACTERIURIA
A diagnosis of asymptomatic bacteriuria is made when a routine urine culture of a clean-voided specimen contains more than 100,000 organisms per ml. Less expensive tests such as the leukocyte esterase-nitrite dipstick can be used for screening if the prevalence is low in the population.
MANAGEMENT
It is essential to treat this condition even though the patients are asymptomatic. One of several anti-microbial agents can be given or the selection of anti-microbial may be selected on the basis of in vitro susceptibilities. Treatment with 100 mg of nitrofurantoin four times a day for 10 days has proved effective in most women. Other regimens include ampicillin, amoxicillin or cephalosporin.
EFFECT OF ASYMPTOMATIC BACTERIURIA SYMPTOMATIC ON MATERNAL AND FETAL OUTCOME
Asymptomatic bacteriuria is associated with and increased risk for maternal anemia, hypertension or preeclampsia as well as low birth weight and preterm delivery. Bacteriuria may also persist in these women after delivery and may need to be investigated in detail.
Cystitis
Cystitis occurs from bacterial infection of the bladder.
SYMPTOMS
Cystitis is characterised by dysuria, urgency and frequency. There are few associated systemic findings. Although cystitis is usually uncomplicated, the upper urinary tract may become involved by ascending infection.
MANAGEMENT
Nitrofurantoin, ampicillin or cephalosporin are all effective in the treatment of cystitis.
Acute Pyelonephritis
Acute pyelonephritis is one of the serious medical complications of pregnancy and occurs in about 2% of patients. Renal infection is more common after mid-pregnancy. It is usually unilateral and right sided in more than half of the cases and bilateral in one-fourth. The infection is caused by bacteria which ascend from the lower urinary tract. The causative microorganisms come from a wide spectrum; the most common isolate (in 90% of cases) is Escherichia coli.
SYMPTOMS
Pyelonephritis usually has a sudden onset with symptoms of fever with chills, anorexia, nausea and vomiting, and pain in one or both lumbar regions.
SIGNS:
The temperature is usually raised above 101°F.On palpation, tenderness is elicited in one or both loins in the regions of the kidney.
DIAGNOSIS:
Examination of the urine will clinch the diagnosis. On microscopic examination the urine contains pus cells and, on staining the sediment, numerous bacilli can be demonstrated. In the early stages, renal function is not impaired.
DIFFERENTIAL DIAGNOSIS
In the acute stage of the disease, pyelonephritis may have to be differentiated from malaria, acute appendicitis, enteric fever and abruptio placentae. The fever with rigor may simulate an attack of malaria in areas where malaria is endemic. Examination of blood and urine will aid in diagnosis. Enteric fever can be ruled out by blood culture in the early days and by Widal reaction later. The presence of pain and tenderness in the lower abdomen may simulate an attack of acute appendicitis. Careful physical examination and examination of the urine will help in differentiation.
MANAGEMENT
In serious cases when there is high fever, it may be better to hospitalise the patient. These infections usually respond quickly to intravenous hydration and anti-microbial therapy. Intravenous infusion may be required specially if the intake is low due to the associated symptoms. The choice of anti-microbial agent will depend on the sensitivity of the organism but it may take 48 hours to get the sensitivity results. Hence the choice of the drug may be empirical. Ampicillin plus gentamycin, cefazolin, or ceftriaxone have been shown to be 95% effective. Ampicillin resistance of E. coli has become common and only half of the strains are sensitive in vitro to ampicillin; hence it is preferable to give gentamicin or another aminoglycoside with ampicillin.
Most urinary infections respond readily to adequate anti-microbial therapy. Symptoms disappear in 48-72 hours and urine culture becomes sterile. However, therapy is recommended for 7- 10 days. The physiological changes in the urinary tract due to pregnancy are unaltered by treatment and so reinfection and recurrence of symptoms during pregnancy and puerperium are common. Pyelonephritis in pregnancy must not be considered as cured unless the urine remains sterile on repeated examination.
EFFECT ON PREGNANCY OUTCOME
Recurrent urinary tract infections during pregnancy is known to be associated with increased risk for preterm labour and low birth weight.
Chronic Pyelonephritis
This disease is chronic interstitial nephritis and is thought to be caused by bacterial infection. Chronic infection is frequently not symptomatic, and in advanced cases, symptoms are those of renal insufficiency.Maternal and fetal prognosis depends on the extent of renal destruction.