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Radiology
Immune Hydrops Fetalis
Built from Obstetric Imaging
What’s inside
11 sections · 86 slides
Overview
- Scope of this presentation
Defining immune hydrops
What counts as hydrops, and what makes it immune
- Definition of fetal hydrops
- The four fetal compartments involved
- Definition of immune hydrops
- Hemolytic disease of the fetus and newborn as the working term
Prevalence and epidemiology
How often alloimmunization happens, and which antibodies matter now
- 6.8:1000
- Incidence of Rh(D) alloimmunization
- Findings from a Canadian prenatal population
- Antibodies most often responsible
- Single antibodies found in a Canadian prenatal cohort
- Red cell antigens that cause severe disease
Etiology and pathogenesis
From a few fetal cells in maternal blood to fluid in the fetal abdomen
- Fetal red cells in the maternal circulation
- Events that carry a risk of fetomaternal transfer
- Mechanism of immune hydrops
- The maternal immune response to a foreign antigen
- Time course of maternal sensitization
- Volume of blood required to sensitize
- Factors thought to influence sensitization
- Degree of anemia that produces hydrops
- Kell alloimmunization as a special case
- Proposed mechanisms of fluid accumulation
- Gestational age and the appearance of hydrops
Clinical presentation
How the disease reaches the clinician, in the mother and in the fetus
- Antibody screening at the first prenatal visit
- Presentation when screening has not happened
- Mirror syndrome
- Mirror syndrome compared with preeclampsia
Ultrasound findings
The six findings, their look-alikes, and the measurements that separate them
- Making the diagnosis on ultrasound
- Abdominal ascites
- Scalp edema, ascites and raised cerebral artery velocity at 18 weeks
- Free fluid outlining the fetal bowel and liver
- Alloimmunization in a twin pregnancy
- Ascites, scalp edema and anemia in the affected twin
- Pleural effusion
- Fetal pleural effusions in two planes
- Pericardial effusion
- Pathologic pericardial effusion at 22 weeks
- Skin edema
- Generalized fetal skin edema with severe anemia
- Polyhydramnios and placental thickening
- Classic sonographic signs of hydrops
- Scope of the scan in a hydropic fetus
Middle cerebral artery Doppler
The test that detects fetal anemia before any fluid appears
- Principle of MCA-PSV in fetal anemia
- From fetal anemia to a raised Doppler velocity
- Accuracy of MCA-PSV for moderate to severe anemia
- Technique for obtaining the MCA-PSV
- Middle cerebral artery Doppler waveform in anti-Kell disease
- Quality of Doppler images in routine practice
- Interpreting the measured value
Other modalities and differential diagnosis
What has no role, what is obsolete, and what else looks the same
- Magnetic resonance imaging and delta OD 450
- Differential diagnosis from imaging findings
Prenatal management
Screening, titers, fetal genotyping, Doppler surveillance and transfusion
- When to test for maternal antibodies
- The indirect Coombs test and how titers are reported
- Laboratory variation in titer results
- First affected pregnancy compared with a later one
- Paternal zygosity testing
- Decision from paternal zygosity
- Fetal genotyping with cell-free DNA
- Fetal blood typing by amniocentesis
- Serial titers once the fetus is at risk
- The critical titer
- When to begin MCA-PSV surveillance
- Scan interval and reporting of results
- Antenatal testing and timing of delivery
- Titer pathway and fetal antigen testing
- Doppler surveillance, cordocentesis and delivery
- Management algorithm for the at-risk gestation
- Reading the titer arm of the algorithm
- Reading the Doppler arm of the algorithm
- Pregnancies with a severe past history
- Immunomodulation before transfusion is feasible
- Intraperitoneal transfusion before 18 weeks
- 94%
- Indications and limits for intrauterine transfusion
Postnatal care
Why the disease continues for weeks after the baby is born
- Suppressed erythropoiesis after serial transfusions
- Continuing hemolysis after birth
- Newborn treatment and handover to the pediatrician
Summary
What to carry away from this topic
- What the referring physician needs to know
- Key points on definition and cause
- Key points on diagnosis and treatment
- References
- References (continued)
- References (continued)
- References (continued)
- References (continued)
- References (continued)
- Obstetric Imaging: Fetal Diagnosis and Care, 2nd Edition