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T3.2 Duplex Kidneys & Recurrent UTIs in Pregnancy

Duplex Kidneys

  • Definition & Anatomy

    • A “duplex kidney” (also called duplicated collecting system) has two separate pelvicalyceal systems draining a single renal parenchyma.
    • May present as:
    • Two distinct ureters exiting the kidney and joining the main ureter lower down.
    • Partial duplication where the accessory ureter fuses with the primary ureter close to the renal pelvis.
    • Either one or both kidneys can be affected.

  • Epidemiology

    • Uncommon in the general population, but midwives/obstetric teams may encounter it sporadically.

  • Obstetric Significance

    • Pregnancy-induced physiological changes (dilated ureters, ↑ renal blood flow, ↑ urinary stasis) compound the workload of a duplex system.
    • Higher likelihood of recurrent UTIs → pyelonephritis → possible pre-term labour.
    • Midwives should maintain heightened vigilance, even if previous pregnancies were uncomplicated.

  • “Rule of Thirds” (Practical Risk Stratification)

    • \frac{1}{3} experience no complications (e.g. first pregnancy case).
    • \frac{1}{3} develop moderate issues (sporadic UTIs, occasional admission).
    • \frac{1}{3} may face significant morbidity (frequent pyelonephritis, earlier pre-term birth).

  • Illustrative Case

    • First pregnancy: patient with duplex kidney had a completely normal antenatal course and term birth.
    • Second pregnancy: same patient developed pyelonephritis from 32 wks, required ∼3 hospital admissions, IV antibiotics, delivered at 35 wks.
    • Take-home: Past success ≠ future guarantee; always counsel on potential pre-term labour.

Recurrent & Symptomatic UTIs in Pregnancy

  • Core Symptoms to Elicit

    • Dysuria ("painful stinging")
    • Frequency with low volume (“can only pass a dribble”)
    • Suprapubic pain / flank pain
    • Fever ≥ 38^\circ\text{C}

  • Assessment Checklist

    • Full history (previous UTIs, renal anomalies, antibiotic allergies, gestation).
    • Vital signs: Temp, HR, BP.
    • Abdominal palpation for uterine activity (pre-term labour?) and renal angle tenderness.
    • Collect clean-catch MSU before first antibiotic dose.

  • Empiric Treatment Algorithm (NZ context; adjust locally)

    • Symptomatic UTI → treat immediately while awaiting culture.
    • First-line choices (avoid amoxicillin):
    • Trimethoprim 300\,\text{mg} nocte × 3 days (avoid in 1st trimester)
    • Nitrofurantoin 100\,\text{mg} QID × 5–7 days (stop at ≥ 36 wks)
    • Augmentin 500/125\,\text{mg} TDS × 7 days
    • Cefaclor 500\,\text{mg} TDS × 7 days (kept in reserve)
    • Document prescription clearly; verify allergy status.

  • Follow-Up

    • Contact patient at 48–72 h or sooner if symptoms worsen.
    • Review culture/sensitivity:
    • If sensitive → continue course.
    • If resistant → switch per lab guidance.
    • Always arrange a test-of-cure (TOC) MSU 7 days after finishing antibiotics.

Interpreting MSU / Lab Reports

  • Microscopy Flags

    • Leukocytes > 10 per hpf → pyuria.
    • Erythrocytes: haematuria may signal renal involvement.
    • Epithelial cells > 10 per hpf → likely contamination.

  • Culture Results

    • "Heavy growth E. coli" with valid sensitivities → treat.
    • "Mixed growth / doubtful significance" → repeat MSU (contaminated specimen).
    • Always cross-check microscopy + culture + clinical picture.

  • Example Interpretations

    1. Leukocytes 49, epithelial 48, heavy E. coli growth.
    • Despite epithelial contamination, lab deemed result significant; proceed with therapy.
    1. Mixed growth + high leukocytes.
    • Probable contamination; repeat specimen with clean-catch instructions.

Special Pathogens & Scenarios

  • Group B Streptococcus (GBS) Bacteriuria

    • Any growth of GBS in urine at any gestation = marker of heavy maternal colonisation.
    • Requires immediate treatment (even if asymptomatic) and mandates intrapartum IV prophylaxis.
    • First trimester: avoid trimethoprim; choose alternatives (e.g. amoxicillin, cephalexin). If penicillin-allergic, phone lab for susceptibilities and involve obstetric team.

  • Third UTI in Current Pregnancy

    • Triggers obstetric consultation.
    • Consider monthly MSU surveillance.
    • Prophylactic low-dose nitrofurantoin 50\,\text{mg} 1–2×/day until 3rd trimester (team decision).
    • Respect informed refusal; emphasise prompt self-reporting of new symptoms.

Clean-Catch Technique (Patient Education)

  • Wash hands → separate labia → mid-stream catch → avoid contact with skin/container rim.
  • Explain why contamination blurs results and causes repeat tests.
  • Provide written/visual aids; acknowledge difficulty in late pregnancy.

Practical Communication & Documentation

  • Lab Forms / e-Ordering

    • Offer options: hand form over, post, or send electronically.
    • Duplicate if lost; forms are cheap—patient adherence is priceless.

  • Safety-Netting Statements

    • "If stinging, fever or contractions worsen before results return, ring immediately—don’t wait the full 48–72 h."

Ethical & Workload Considerations (Midwife Perspective)

  • Balancing caseload vs complexity: teams may decline high-risk bookings without adequate cover.
  • Transparent dialogue with women about service availability and risk.
  • Importance of collegial support when primary LMC is on leave.

Antimicrobial Stewardship (Preview)

  • Rational empiric choice → de-escalate after sensitivities.
  • Avoid unnecessary broad-spectrum antibiotics to slow resistance.
  • Patient-centred discussion ensures adherence and reduces repeat courses.