Dr Abdullah Ansari MBBS, MD Medicine Aligarh Muslim University Physiological changes during pregnancy Systemic changes Renal changes Renal function Tubular function Plasma osmolality Anatomical changes AKI during pregnancy Pre-renal causes Renal causes Post-renal causes Investigations Management

1. Pregnancy Physiology
&
Acute Kidney Injury
Dr Abdullah Ansari
MBBS, MD Medicine
Aligarh Muslim University

3. Systemic changes
• Increased cardiac output ~ 50%
• Increased plasma volume ~ 30–40%
• Increased peripheral vasodilatation (NO,
prostaglandins, relaxin)
• Decreased systemic vascular resistance
• Modest fall in BP and widening of pulse pressure
in 1st & 2nd trimesters, normalizes in 3rd trimester

4. Renal changes
• Increased renal blood flow ~ 70–80% in 2nd
trimester
• Transglomerular pressure remains same, with
matching dilatation of afferent & efferent
arterioles
• Marked stimulation of RAAS
• Increased GFR ~ 40% by end of 1st trimester
• Increase in proteinuria (≤300 mg/24h not
significant in pregnancy)

5. Renal function
• eGFR not validated in pregnancy
• MDRD underestimates & Cockcroft – Gault
overestimates
• SCr >0.9mg/dL or Urea >14mg/dL may indicate
renal impairment
• 24hr urinary creatinine clearance remains the
gold standard (NR: 125 – 50mL/min; 30% above
range for non-pregnant women)

6. Tubular function
• Glycosuria during pregnancy not necessarily
indicate impaired glucose tolerance. If persistent
measure blood glucose
• Hyperventilation decreases pCO2, causes mild
respiratory alkalosis (pH 7.4 to 7.43)
• HCO3
– excretion increases to compensate and
serum HCO3
– falls to 18-22mEq/L
• Urinary calcium excretion increased
• Serum urate falls in early pregnancy

7. Plasma osmolality reduced
• Women gain 9–14kg during pregnancy, with up to
8L body water
• ADH release threshold lowered, sustained release
decreases plasma osmolality ~10mOsmol/kg
• Serum Na+ falls to 132–140mEq/L (Na+>140mEq/L
may indicate hypernatraemia in pregnancy)
• Rare transient diabetes insipidus of pregnancy in
3rdtrimester (cranial or increased ADH degradation)

8. Anatomical changes
• Increased kidney volume, size, and weight
• Renal length increases by 1cm
• Collecting system dilatation begins at 8 weeks
and apparent by 20 weeks gestation (~2cm)
• Collecting system dilatation resolves within 48hr
of delivery in 50% cases but may persist up to 12
weeks post-partum

10. Introduction
• A significant problem in developing world,
accounts for up to 20% of all AKI (usual in
inaccessible safe and sterile termination)
• In developed world, pre-eclampsia is the
commonest cause

11. Pre-renal causes
• Volume depletion: Hyperemesis gravidarum
in 1st trimester
• Placental abruption: presents with
abdominal pain and PV bleeding in 2nd or 3rd
trimester, classical cause of cortical necrosis
• Post-partum hemorrhage: cortical necrosis
• Septic abortion: presents with abdominal
pain, fever, and shock

12. Renal causes
• Pre-eclampsia
• Acute fatty liver of pregnancy: presents in 3rd
trimester as fulminant hepatic failure, AKI common
• HUS/TTP: present either antenatal or postpartum
• Exacerbation of existing renal disease: SLE
• Acute interstitial nephritis: Often drug-related,
NSAIDs, antibiotics
• Nephrotoxic drugs

13. Post-renal causes
• Acute urinary retention: 3rd trimester,
relates to bulk of expanding uterus

14. Investigations
• S Cr >0.9mg/dL may indicate renal impairment
in pregnancy
• Complete blood counts, renal functions &
electrolytes, liver functions, calcium, clotting,
urate, hemolysis screen, infection screen (MSU,
blood cultures, vaginal swabs)

15. Management
• Assess fluid status, and correct volume depletion
• Check for complications
▫ Hyperkalemia
▫ Volume overload and pulmonary edema
▫ Acidosis
• Treat underlying cause
• Dialysis if indicated