Spina bifida occulta
Most common Neural tube defect - failure of bony spinal canal to close, but no herniation - usually seen at lower vertebral levels - dura is intact - associated with tuft of hair or skin dimple at level of bony defect - normal AFP
Meningocele
Neural tube defect - meninges (but no neural tissue) herniate through bony defect - skin defect/thinning
Meningomyelocele
Neural tube defect - Meninges and neural tissue (e.g. cauda equina) herniate through bony defect - skin thin or absent
Anencephaly
Forebrain anomaly - malformation of the anterior neural tube --> no forebrain, open calvarium - ↑AFP, polydydramnios (no swallowing center in brain) - associated with maternal type 1 diabetes - maternal folate supplementation decreases risk
Holoprosencephaly
Forebrain anomaly - failure of left and right hemisphere to separate - moderate form has cleft lip/palate, most severe form results in cyclopia - seen in Patau syndrom (Trisomy 13) and fetal alcohol syndrom
Potter sequence
Oligohydramnios --> compression of developing fetus --> limb deformities, facial anomalies (e.g. low-set ears and retrognathia, flattened nose--> compression of chest and lack of amniotic fluid aspiration into fetal lungs --> pulmonary hypoplasia Causes include ARPKD, obstructive uropathy, bilateral renal agenesis, chronic placental insufficiency "Babies who cant Pee in utero develop Potter sequence"
Horseshoe kidney
- inferior poles of both kidneys fuse abnormally - as they ascend from pelvis during fetal development, horseshoe kidneys get trapped under inferior mesenteric artery and remain low in the abdomen - kidneys function normally - associated with hydronephrosis, renal stones, infection, chromosomal aneuploidy syndroms
Unilateral renal agenesis
Uretic bud fails to develop and induce differentiation of metanephric mesenchyme--> complete absence of kidney and ureter
Multicystic dysplastic kidney
Uretic bud fails to induce differentiation of metanephric mesenchyme--> nonfunctional kidney consisting of cysts and connective tissue
Duplex collecting system
Bifurcation of uretic bud before it enters the metanephric blastema creates a Y-shaped bifid ureter - strongly associated with vesicoureteral reflux and/or uretal obstruction, ↑ risk for UTIs
Kidney embryology
Pronephros - degenerates Mesonephros - functions as intermin kidney, later contributes to male genital system Metanephros - permanent- Ureteric bud: derived from caudal end of mesonephric duct, gives rise to ureter, pelvises, calyces, collecting ducts- Metanephric mesenchyme: ureteric bud interacts with this tissue; interaction induces differentiation and formation of glomerulus through to distal convoluted tubule- Aberrant interaction between these 2 tissues may result in congenital malformations Ureteropelvic junction - last to canalize --> most common site of obstruction (hydronephrosis) in fetus
