B30. Pyelitis in pregnancy

Pyelonephritis, bacterial infection of the renal pelvis, is more common in pregnancy due to physiological changes of the urinary tract. Most cases occur in the second and third trimester. It most frequently occurs on the right side.

Pregnancy predisposes to higher risk of complications from pyelonephritis, both medical and obstetrical.

Etiology

Pyelonephritis is a result of untreated or unnoticed lower urinary tract infection which ascends into the upper urinary tract. E. coli accounts for the majority of UTIs.

Risk factors:

• Asymptomatic bacteriuria
• Diabetes mellitus
• History of UTI

Pathomechanism

During pregnancy, the ureters and renal pelvis dilate, and the ureteral peristalsis is decreased. This predisposes to urinary stasis.

The right side is more frequently affected because the right ureter crosses the common iliac artery at a right angle while the left ureter crosses the left common iliac artery at an acute angle, and because of rotation of the uterus to the right (dextro-rotation).

Clinical features

Clinical features of pyelonephritis in pregnancy are no different from those outside pregnancy, other than that they mostly occur on the right side. Fever, chills, nausea/vomiting, low back or abdominal pain, and tenderness to percussion over the costovertebral angle are typical features of pregnant pyelonephritis. Features of the lower UTI may also be present, which causes dysuria.

Diagnosis and evaluation

The diagnosis is made when there is pyuria in a patient with typical clinical features. Urine culture should be obtained to guide antibiotic therapy. If sepsis is suspected, blood culture should be obtained as well.

Differential diagnosis

• Chorioamnionitis – may cause fever and abdominal pain
• Placental abruption – may cause acute back pain

Treatment

Hospital admission for i.v. antibiotic therapy is required. The choice of empiric antibiotic depends on local recommendations and severity. Sensible choices include cefuroxime or cefotaxime.

Prevention

Screening for and treating asymptomatic bacteriuria with antibiotics decreases the risk of pyelonephritis. In many countries, all pregnant women are screened for asymptomatic bacteriuria during prenatal visits in week 12 – 16. It is treated as a lower UTI. In Norway, only those at high risk for asymptomatic bacteriuria are screened.

Complications

• Medical complications
  • Anaemia
  • Bacteraemia
  • Acute respiratory distress syndrome
  • Acute kidney injury
  • Sepsis
  • Renal abscess
• Obstetric complications
  • Intrauterine growth restriction
  • Preeclampsia
  • C-section
  • Preterm delivery