Poster Presentation - SOMANZ ASM Society of Obstetric Medicine of Australia and New Zealand ASM 2023

Hypersulfataemia in a pregnant patient requiring haemodialysis during pregnancy (#53)

Julia Jefferis 1 2 , Isabel Scalia 1 , Avis McWhinney 3 , Ann-Maree Craven 4 , Dharmenaan Palamuthusingam 1 , Paul Dawson 5
  1. Kidney Health Service, Royal Brisbane and Women’s Hospital, Brisbane, Australia
  2. Faculty of Medicine, University of Queensland, Brisbane, Australia
  3. Mater Pathology, Mater Health Services, Queensland, Brisbane, QLD, Australia
  4. Department of Obstetric Medicine, Royal Brisbane and Women's Hospital, Herston, QLD, Australia
  5. Mater Research Institute, University of Queensland, Woolloongabba, QLD, Australia

Introduction

Sulfate (SO42-) is an important anion utilised in many metabolic and developmental processes and is essential for healthy fetal development, with serum levels upregulated during pregnancy to support fetal requirements. During pregnancy, sulfate reabsorption in the maternal kidneys increases which bolsters circulating levels by ≈ 2-fold (non-pregnant 300 μmol/L, compared to 452 and 502 μmol/L at 10-20 and 30-37 weeks gestation, respectively), providing a source of sulfate for fetal growth and development. Circulating sulfate levels are increased in chronic kidney disease (CKD) as a result of reduced glomerular filtration rate. The kidney is key in maintaining sulfate homeostasis during pregnancy, yet there are currently no studies of how sulfate levels vary in pregnant patients with CKD on chronic dialysis. In view of this, we measured serum and urine sulfate levels in a patient with end-stage kidney failure requiring haemodialysis through pregnancy.

 

Case report

A 19-year-old female was diagnosed with end stage kidney failure secondary to nephronophthisis at week 17 of first pregnancy (G1P0), after presenting with a urinary tract infection. The patient had no previous nephrology follow-up. Family history was significant for nephronophthisis with CKD also diagnosed in a sibling, determined as Senior Loken syndrome. Initial biochemistry showed a creatinine of 413mmol/L, eGFR 13ml/min/1.73m2 and haemoglobin of 80g/L. Haemodiafiltration was commenced via tunnelled central line for six hours a day, six times a week, with variable compliance. The patient maintained residual urine output of approximately 2 litres per day. Medications through pregnancy included heparin sodium intravenous on dialysis, darbepoetin alfa 200mcg subcutaneous weekly, iron polymaltose 100mg IV, folic acid 5mg, pregnancy multivitamin, phosphate effervescent 1g daily and sodium phosphate supplementation in the dialysate. Obstetric scan at 26+6 weeks were within expected range. Anaemia was persistent (haemoglobin 80g/L), despite intensive epoetin treatment. The pregnancy progressed well with a healthy baby delivered  by spontaneous vaginal delivery at 39 weeks, weighing 3.41kg, with no maternal or fetal complications, and no concerns for congenital anomalies.

 

Results

We found pre-dialysis sulfate levels in this patient were elevated at 831mmol/L and reduced by 70% after haemodialfiltration. Interestingly, the urinary fractional excretion of sulfate was 0.34, higher than seen in a healthy population at this stage of pregnancy.

 

Conclusion

This case suggests that sulfate metabolism is altered in pregnant patients with kidney disease, with sufficient sulfate levels to support development of the fetus.