Neonatal Jaundice: Causes by Day of Life

Key Principle

Day-by-Day Classification

🔴 Day 1 (< 24 hours of life) — Always Pathological

🟡 Day 2–3 — Physiological + Pathological

🟡 Day 4–7 — Pathological Causes More Prominent

🟠 > Day 7 (Prolonged Jaundice) — Beyond 2 Weeks (Term) / 3 Weeks (Preterm)

Unconjugated Causes

Conjugated Causes (Direct bilirubin > 1 mg/dL or > 20% of total) — Always Pathological

Summary Table

Key Clinical Pearls

• Any jaundice in the first 24 hours = hemolysis until proven otherwise; send urgent bilirubin + Coombs test.
• Conjugated (direct) hyperbilirubinemia at any age = always pathological; never physiological.
• Physiological jaundice peaks at day 3–4 in term infants, day 5–7 in preterm; resolves by 2 weeks (term) and 3 weeks (preterm). (Harrison's, p. 9341)
• Breast milk jaundice (late form) peaks at week 2–3 and can persist up to 12 weeks; it is a diagnosis of exclusion.
• Biliary atresia is a surgical emergency — the window for Kasai hepatoportoenterostomy closes by ~8 weeks of age.

Reticulocyte Count

What Are Reticulocytes?

• Normal reticulocyte count: 1–2%
• Reflects daily replacement of 0.8–1.0% of the circulating RBC population

Calculations

1. Raw (Uncorrected) Reticulocyte Percentage

2. Corrected Reticulocyte Count (CRC)

• Normal CRC: 1–2%
• CRC > 2% → adequate marrow response (hemolysis/blood loss)
• CRC < 2% → inadequate marrow response

3. Reticulocyte Production Index (RPI)

• RPI > 2.5 → Hyperproliferative (adequate marrow response) → think hemolysis or blood loss
• RPI < 2.0 → Hypoproliferative or maturation defect

4. Absolute Reticulocyte Count (ARC)

• Normal: 25,000–75,000 cells/µL (some sources: 50,000–100,000/µL)
• Most straightforward and increasingly preferred in modern automated analyzers

Clinical Interpretation: Anemia Classification

RPI ≥ 2.5 — Hyperproliferative (Marrow Responding)

RPI < 2.0 — Hypoproliferative or Maturation Disorder (Marrow Failing to Respond)

A. Normocytic Normochromic → Hypoproliferative

B. Microcytic Hypochromic → Maturation Disorder (Iron/Heme defect)

C. Macrocytic → Maturation Disorder (Nuclear/DNA defect)

Quick Reference Summary

Clinical Pearls

• Always use RPI or ARC rather than raw reticulocyte percentage — the raw percentage is misleading in anemia.
• A high RPI with a falling Hb means the marrow is responding but can't keep up — look for ongoing hemolysis or blood loss.
• A low RPI despite severe anemia is a marrow failure signal — consider bone marrow examination.
• In post-treatment monitoring (e.g., iron, B12 therapy), a rising reticulocyte count ("reticulocyte crisis") at 5–10 days confirms the diagnosis and treatment response.
• Reticulocytosis is also expected after EPO therapy, recovery from aplastic anemia, or after stopping a marrow-suppressive agent.

Clinical Examination of a Newborn with CTEV

The Four Core Deformity Components (CAVE mnemonic)

All four components are present in true CTEV. The deformity is fixed, unlike postural talipes which is fully correctable.

Step-by-Step Examination

1. Look (Inspection)

• Overall posture of foot: plantarflexed, inverted, adducted
• Hindfoot: small, underdeveloped heel; varus position of calcaneus
• Calf: may show calf muscle hypoplasia (thinner calf compared to normal side — especially in unilateral cases)
• Skin creases:
  • Deep medial crease at the midfoot (due to adductus/cavus)
  • Deep posterior crease at the ankle (due to equinus)
  • These creases indicate severity — deeper creases = more rigid deformity
• Foot size: the affected foot is often shorter and smaller
• Bilateral vs. unilateral: note if one or both feet are involved (bilateral in ~50%)

2. Feel (Palpation)

• Head of talus: prominently palpable on the dorsolateral aspect of the foot (as navicular is displaced medially)
• Calcaneus: small, difficult to palpate in severe cases; positioned in varus and equinus
• Medial structures: tight — tibialis posterior, flexor digitorum longus, flexor hallucis longus tendons
• Posterior structures: tight — tendo-Achilles, posterior capsule
• Muscle bulk: assess calf bulk bilaterally

3. Move (Mobility — Most Important Step)

• True CTEV: deformity is fixed/rigid — cannot be passively corrected to neutral
• Postural talipes: deformity is fully correctable to neutral or beyond — benign, resolves with physiotherapy

• Dorsiflexion at ankle (equinus correction)
• Eversion at subtalar joint (varus correction)
• Abduction of forefoot (adductus correction)

4. Severity Scoring

Pirani Scoring System (0–6)

• Score 0 = normal foot
• Score 6 = most severe
• Predicts number of Ponseti casts needed and likelihood of tenotomy

Diméglio Classification (0–20)

5. Associated Findings to Look For

6. Differentiate True CTEV from Postural Talipes

Key Clinical Pearls

• First step in management after diagnosis: refer early for Ponseti method (serial casting) — ideally started within the first 1–2 weeks of life when ligaments are most pliable.
• The lateral border of a normal foot is straight — a curved lateral border on inspection is a reliable sign of forefoot adductus.
• Calf wasting in unilateral cases is a clue to an underlying neurological cause (e.g., spina bifida, polio).
• Always palpate the head of the talus — in CTEV it is uncovered laterally and is the key landmark for Ponseti casting correction.
• A deep posterior crease + rigid equinus = higher likelihood of needing Achilles tenotomy.