Pediatric Pathology Flashcards
What is the fetal period and its two subsections?
9 weeks until birth - where differentiation and maturation of the organ systems occurs
9-20 weeks: Previable period
20-38 weeks: Viable period
What is a neonate vs infant?
Neonate = first 4 weeks, as in psychiatry the time when perinatal depression occurs.
Infant = 4 weeks - 1 year of life
What is meant by AGA, SGA, and LGA birth weights?
SGA = small for gestational age, <10th percentile
AGA = appropriate for gestational age, 10-90th percentile
LGA = large for gestational age, >90th percentile
What are the categories of things which can cause small birth weights?
- Appropriate for gestational age, but low birth weight -> due to prematurity
- Small for gestational age, but low birth weight -> normal small (low percentile)
- Small for gestational age, but low birth weight -> pathologically small fetus
Why are babies typically very low birthweight (less than 1500g)?
Due to extreme prematurity -> accounts for half of all neonatal deaths
What is meant by intrauterine growth retardation?
Being born small for gestational age, i.e. fetal growth retardation. Includes weight, height, and head circumference <10th percentile
-> Infnants are born at <2500gm and are simply small despite making it to full gestation based on number of weeks
What are the two types of intrauterine growth retardation? When in the pregnancy do these onset?
Type 1: Symmetric Growth Retardation - early onset in pregnancy. Body and organs, including the brain, are proportionate.
Type 2: Asymmetric Growth Retardation - late onset in pregnancy. Body and organs are disproportionately small relative to the brain.
What causes symmetric growth retardation?
Chromosomal disorders, congenital anomalies / malformation syndrome, early intrauterine infections (i.e. TORCH infections)
-> fetal causes, early onset
What causes asymmetric growth retardation?
> uteroplacental causes, later onset
Due to maternal conditions, i.e. vascular insufficiency, nutrition, toxin / drug, infection
Is Large for Gestation Age (LGA) a problem? What causes it?
Yes, it is associated with increased morbidity and mortality
Caused by maternal diabetes mellitus, or a postmaturity syndrome (baby is born late)
What are the three categories of factors which influence fetal growth, and which one is most commonly aberrant?
- Fetal - intrinsic fetal conditions (genetic or infection), reducing growth potential of fetus despite an adequate supply of nutrients
- Maternal - most common cause of IUGR - decreased placental blood flow, due to maternal CVD, preeclampsia, renal disease, smoking, infections, narcotics, alcohol, etc.
- Placental - Inadequate uteroplacental function
What are things that can cause uteroplacental insufficiency?
Vascular anomalies (i.e. single umbilical artery), placental abruption (tearing of placenta from uterine wall), infarction, infection, multiple gestations
What is the clinical definition of abortion? What is early vs late?
Abortion: spontaneous or induced termination of pregnancy prior to fetal viability (~22 weeks)
Early - embryonic period, up to 8 weeks
Late - fetal period, 9-22 weeks (viability)
What are the leading causes of death in children under 1 year?
- Congenital anomalies
- Prematurity, low birth weight
- SIDS
What are the leading causes of death in children 1-4 years?
- Accidents
- Cancer
- Congenital anomalies
Define the following clinical categories of abortion: threatened, inevitable, incomplete, missed, recurrrent.
Threatened: Blood discharge without cervical dilation
Inevitable: Prolonged bleeding with cervical dilation
Incomplete: Retention in the uterus of portions of conceptus (fetus or placenta)
Missed: Retention of dead fetus in uterus for >4 weeks
Recurrent: 3 or more consecutive spontaneous abortions
Is spontaneous abortion common?
Yes, up to 15-25% of recognized pregnancies abort in the first two trimsters
What is the definition of stillbirth and its two types?
Death prior to delivery of a potentially viable fetus (>22 weeks)
- Intrauterine death - occurring more than 24 hours prior to delivery
- Intrapartum death - occurring within 24 hours before or during or 24 hours after delivery
How are intrauterine vs intrapartum stillbirths told apart?
Intrauterine= macerated stillborn = baby will be macerated due to autolytic change in utero. Will also have been decreased body movements and stoppage of maternal weight gain
Intrapartum = fresh stillborn = baby will not be macerated, but will instead have meconium passed. Baby dies within 24 hours prior, during, or after delivery. If dead during delivery, will exhibit deceleration of heartbeat, acidosis, and cessation of movements
What is meconium? Why is it associated with intrapartum death?
Dark greenish material accumulating in bowel during fetal life which is normally discharged shortly after birth.
Distress in utero may cause fetus to defecate meconium prior to delivery -> meconium will be present as they come out.
How do you calculate gestational age?
Weeks since last menstrual period - 2 = GA
LMP - 2 = GA, since ovulation + fertilization happens 2 weeks after LMP
How are the causes of spontaneous abortion / stillbirth similar to those causing intrauterine growth retardation (IUGR)
- Fetal / placental causes like chromosomal abnormalities, malformations no associated with genetics (i.e. NTD, limb development), and placental factors like abruption, multiple births and umbilical cord accidents can cause death.
- Maternal causes also cause this.
- Obstetrical difficulties -> unique to abortion / stillbirth
What are the maternal causes of spontaneous abortion / stillbirth? Specify:
- Maternal age
- Infections
- Uterine abnormalities
- Maternal diseases
- Nutrition status
- Exposure to toxins / drugs
- Maternal age - increased risk in young or old mothers
- Infections - Commonly ascending genital infections like Mycoplasma hominis, Chlamydia, TORCH
- Uterine abnormalities - IUD, uterine alformations
- Maternal diseases - HTN, diabetes vascular insufficiency, antibodies from previous pregnancy
- Nutrition status - decreased folate, zinc
- Exposure to toxins / drugs - cigarettes, teratogens
Why might a congenital malformation leading to an abortion / stillbirth not become apparent until after fetal death?
Heart, lungs, kidneys, and other internal organs may not have their faulty functioning exposed util after birth, when the placental unit is no longer there.
This is why we count babies that die within 24 hours as fresh stillborns
What are the three primary changes that occur during maceration and how do they allow us to identify the intrauterine time of death of the baby?
- Skin changes - skin slippage / bulla formation within 24 hours
- Color change - from normal to purple to yellow to gray over a 1-2 week period
- Fluid - fluid accumulates in body cavities
What happens in the placenta during maceration?
Fibrin deposition and fibrosis with calcification, due to long-lived fibroblasts even after the death of the placental unit.
What do necrosis / inflammation of the fetus or placenta indicate?
A non-autolytic tissue change (not maceration) which is likely a pathologic process which may have contributed to fetal death
What is the defining characteristic of hydrops fetalis?
Generalized edema - interstitial, subcutaneous, body cavities
What is immune hydrops fetalis called and what are its two causes?
Erythroblastosis fetalis -> hemolytic disease of the fetus or newborn via passage across placenta of maternal antibodies against fetal erythrocytes
- Rh incompatability - maternal antibodies to D antigen
- ABO incompatibility - most common in type A infants. Significant disease is uncommon.
Why does erythoblastosis fetalis lead to edema / hydrops?
Resultant anemia from binding of Rh antigens or ABO antigens will lead to decreased O2 carrying capacity of the blood, making the baby’s heart work harder.
-> eventual cardiac decompensation and heart failure leads to systemic congestion / edema
What are the three basic mechanisms by which hydrops fetalis can be caused?
- Increased capillary / venous pressure
- Decreased oncotic pressure
- Decreased capillary integrity
(basically all the causes of transudative / exudative edema)
What types of things can lead to increased capillary / venous pressure -> hydrops fetalis?
High cardiac output state (i.e. AV malformation)
Vascular obstruction
Cardiac failure
What types of things can lead to decreased oncotic pressure in the fetus?
Decreased albumin synthesis (hepatic disease) or increased loss of albumin (renal disease)
What types of things can damage capillary integrity?
Sepsis
Drugs or toxins
Hypoxia of tissues
How will the bone marrow, liver, and spleen respond to hydrops fetalis?
Bone marrow - hyperplasia of erythroid precursors to make more RBCs
Liver - extramedullary hematopoiesis + hepatomegaly
Spleen - extramedullary hematopoiesis + splenomegaly
What is the most serious long-term threat of sequelae in hydrops fetalis?
Permanent CNS damage due to hyperbilirubinemia -> easily cross BBB in fetus -> kernicterus, causing selective necrosis of neurons
Where does unconjugated bilirubin tend to accumulate in kernicterus?
Basal ganglia and thalamus
What are the two categories of intrapartum birth injury and some major risk factors?
- Traumatic birth injury
- Perinatal asphyxia
Risk factors: Maternal poor health, placental abnormalities, fetal conditions (especially LGA), and obstetrical problems like forceps delivery
What is caput succedaneum and what does it cause?
A type of traumatic birth injury -> cranial trauma
Interstitial fluid in soft tissues of the scalp - not clinically significant
What do you call a hemorrhage under the periosteum of the skull which can lead to the thickening of the skull in traumatic birth injury?
Cephalhematoma
What is the most common important birth injury?
Intracranial hemorrhage
When does a skull fracture typically happen?
Occurs in deliveries with inappropriate use of forceps, with large fetal head size in comparison to birth control
What is osteodiathesis? Where does it commonly occur?
Separation of cranial bone sutures, happens especially with occipital sutures.
What other traumatic injuries can occur in birth?
Laceration of brain, other soft tissue
Bone fractures / dislocations (shoulder is tough), peripheral nerve injures (especially brachial plexus), cervical spinal cord injuries
Organ injuries
What is some nonspecific evidence of fetal distress / birth asphyxia?
Skin / placental staining with meconium
Aspiration of meconium in lungs
Vascular congestion
Hemorrhages on organ surfaces like thymus and lungs
What are some specific patterns of acute organ injury due to asphyxia?
- Hypoxic-ischemic brain damage -> especially in Purkinje cells
- Neonatal respiratory distress syndrome
- Acute tubular necrosis in kidneys
- Lymphocyte depletion in thymus (starry sky appearance)
- Adrenal hemorrhages
What is being assessed on APGAR score and what is the highest score possible? List the best possible state in each category
APGAR
Appearance - Completely pink (vs blue body, or blue extremities)
Pulse - >100 bpm
Grimace - Cough / Sneeze to nasal catheter
Activity - Active motion (vs just some flexion)
Respirations - Good / crying is best
All scores are 0, 1, or 2
Highest score is 10, >7 is normal, <3 = poor prognosis
What is static encephalopathy?
Cerebral palsy - permanent, nonprogressive brain dysfunction due to intrauterine or perinatal brain damage
How is prematurity defined? What is the lowest weight which can survive typically?
Spontaneous or induced birth prior to 37 weeks gestation
500g+ can survive with extensive care
What are the anatomical stages of lung development?
Lung bud = 4-6 weeks
Pseudoglandular period = 6-16 weeks
Canalicular period = 16-26 weeks
Alveolar period = 26 weeks to term
End of canalicular period you start having some respiratory epithelium and can potentially survive (around 22 weeks)
How is maturity of the lungs measured in utero?
Lecithin:sphingomyelin ratio in amniotic fluid. If >2, very low chance of neonatal respiratory distress syndrome. (Lecithin is produced more later, and sphingomyelin gets filtered out)
When do Type 2 pneumocytes first appear and then produce adequate surfactant?
First appear around 22 weeks gestation -> beginning of viability
Produce adequate surfactant (lecithins, DPPC) by around 36 weeks
What happens to connective tissue in the lung during development?
It decreases, as the alveolar septae get thinner and thinner
How does nervous system immaturity affect premature infants?
Poor respiratory, vasomotor control, regulation of temperature, and feeding (lack of moro reflex)
What are premature infants at increased risk of kernicterus?
Liver may be physiologically immature and unable to conjugate bilirubin -> hyperbilirubinemia
Very bad because they have immature BBB
What is the leading cause of morbidity and mortality in premature infants, and what is it also called?
Respiratory distress syndrome, also called hyaline membrane disease (HMD)