Outside my Comfort Zone: The Overlap Between Nephrology and Obstetric Medicine

As a current Nephrology trainee I recently decided to do a side step and rotate through obstetric medicine (looking after medical problems in pregnant women). I was interested in this for a few reasons. Throughout my medical training I had encountered pregnant or postnatal women with various problems e.g. severe pneumonia, fever of unknown origin, chest pain. Although these were common medical presentations, in a pregnant patient it was always accompanied by a heightened degree of angst, being more challenging than typical day-to-day cases- extra differentials, changes to normal parameters and two patients to think of.

In nephrolgoy training I then came across a new problem – being asked to consult on patients with complicated preeclampsia. Barn door preeclampsia is easily handled by the obstetric teams, without our input. We were generally only consulted when there was something not quite fitting in e.g. refractory hypertension, severe AKI, oliguria, nephrotic range proteinuria, superimposed preeclampsia. In the early days, my lack of experience with even ‘simple’ preeclampsia made it pretty challenging to deal with these more difficult cases!

My interest was really piqued during my first renal advanced training rotation, when we looked after a patient who came to our attention at 20 weeks gestation with CKD stage 5. She was started on 6 days per week haemodialysis and we looked after her throughout her pregnancy. In fact I went to see her to review her target weight while she was in the dialysis unit to find out she was in labour! We quickly arranged a transfer to the labour ward.

Given the overlap with nephrology, the relative frequency with which I encountered pregnant patients and the added challenges I decided first to do a rotation and then to also train in obstetric medicine. 

Excited about my new books =)

This blog post focuses on hypertension and pregnancy using some brief illustrative cases which are intended to highlight some important areas in this field. The guideline that I use, which I have also used to inform this blog is the SOMANZ (Society of Obstetric Medicine of Australia and New Zealand) Guideline for the Management of Hypertensive Disorders of Pregnancy. This guideline has the advantages of being both relatively recent (2014) and local (I practice in Auckland, New Zealand). *The below Case are not real cases but based on my experiences.

Case 1: 25 year old patient G1P0 (1st pregnancy- I had to remind myself when I started) with blood pressure 140/90 mm Hg at 30 weeks. No other symptoms or lab abnormalites and normally grown fetus. Mild oedema. No proteinuria.

What is her diagnosis? 

Diagnosis: Gestational hypertension. This is the onset of hypertension after 20 weeks of gestation without any maternal or fetal features of preeclampsia. This should return to normal within 3 months of delivery. Some people initially diagnosed with gestational hypertension are in the process of developing preeclampsia. Development of preeclampsia is more likely with more severe and early hypertension.

Case 2: 22 year old G1P0 presents with blood pressure 172/90 mm Hg at 33 weeks gestation. No other symptoms or lab abnormalities and normally grown fetus. Mild edema. No proteinuria.

How should she be treated? 

This patient has severe hypertension defined as a systolic blood pressure ≥ 170 ± diastolic blood pressure ≥ 110 mm Hg requiring urgent treatment. Treatment should be started in all women with a systolic blood pressure ≥160 mm Hg or a diastolic blood pressure ≥100 mm Hg.

Treatment of mild-moderate hypertension is not clear. Antihypertensive therapy does not prevent eclampsia or adverse perinatal outcomes. It does significantly decrease the development of severe hypertension. Arguments against treatment include worries about decreased fetal perfusion with low blood pressure.

The antihypertensives used during pregnancy are different than those we use day to day. Our local practice is to use labetalol (100-400mg q8h) or nifedipine (20mg -60 mg slow release bd) as our first line agents with methyldopa (250-750mg tds) added if required. Which medication to choose is individualised to the patient and their comorbidities.

Case 3: 40 year old woman G1P0 presents at 36 weeks gestation with blood pressure 150/100 mm Hg and right upper quadrant pain. Investigations revealed a raised ALT and AST. There was no proteinuria. Ultrasound revealed fetal growth restriction (FGR).

What is the diagnosis?

Diagnosis: preeclampsia Preeclampsia is a multisystem disease unique to human pregnancy. Diagnosis requires hypertension (>140/90 mm Hg after 20 weeks) and involvement of another organ system (see below) ± the fetus. Proteinuria is not required to diagnose preeclampsia.

Kidney involvement

• Significant proteinuria –a spot urine protein/creatinine ratio ≥ 30mg/mmol 
• Serum or plasma creatinine greater than 90 μmol/L
• Oliguria: less than 80mL/4 hr 

Haematological involvement

• Thrombocytopenia less than100,000 /μL
• Hemolysis
• Disseminated intravascular coagulation 

Liver involvement

• Raised serum transaminases
• Severe epigastric ± right upper quadrant pain

Neurological involvement

• Convulsions (eclampsia)
• Hypereflexia with sustained clonus
• Persistent, new headache
• Persistent visual disturbances
• Stroke 

Pulmonary

• edema 
• Fetal growth restriction (FGR) 

Case 4: 35 year old with IgA Nephropathy. Has hypertension and stable proteinuria (PCR 100 mg/mmol). Antihypertensives stopped in early pregnancy due to hypotension. At 32 weeks, blood pressure 145/90 mm Hg, PCR 220 mg/mmol. No other symptoms, signs or laboratory abnormalities. No FGR.

What is the diagnosis?

Diagnosis: This is a challenging case but most likely she just has pre-existing hypertension that, due to physiological drop in blood pressure in the first half of pregnancy, was not present earlier in pregnancy. After a nadir at 20 weeks her blood pressure will have started to increase back to preconception levels. Her proteinuria is likely exacerbated by pregnancy. She has no other features to suggest preeclampsia. However she is a high risk patient who should be monitored closely. The differential is superimposed preeclampsia. Substantial increases in proteinuria and hypertension should raise suspicion of preeclampsia but the diagnosis cannot be made without developing other maternal systemic features or fetal adverse effects.

Given our familiarity with hypertension and its treatment, proteinuria and renal impairment, a renal consult is often sought for gestational hypertension or preeclampsia. Importantly the thresholds for diagnosing severe hypertension requiring urgent treatment, significant proteinuria and a high creatinine are much lower than we would usually use, meaning we have to take extra care not to overlook them. As the theme for World Kidney Day this year is “Kidneys and Womens’ Health” this area is currently getting a lot of attention.

Sarah Gleeson
Nephrology Fellow (and Obstetrics)
Auckland, New Zealand
NSMC Intern, Class of 2018

Here is a post from Silvi Shah RE Pregnancy and Kidney Transplant when she was a NSMC intern. You can also review the entire Obstetrics region of NephMadness 2015