PAEDIATRIC RENAL & UROLOGY
URINARY SYSTEM EMBRYOLOGY
• Urogenital system derived from intermediate mesoderm ® forms a urogenital ridge on either side of the developing aorta.
• Kidneys develop through 3 successive sets of tubular nephric structures:
(1) Pronephros ® (2) Mesonephros ® (3) Metanephros (gonads)
Urine production in utero
Metanephros– primordia of permanent kidneys begin to produce urine early in week 9 ® mixed with the amniotic fluid ® continues
throughout foetal life +
• A mature foetus swallows several hundred millilitres of amniotic fluid each day ® then absorbed by intestine.
• Waste products eliminated by placental circulation into maternal blood for elimination by the kidneys.
The metanephros develops from an outgrowth of the:
Outgrowth Forms the Function Adult derivatives of
Secretes growth factors that induce • Podocytes and bowman’s capsule
Condensation growth of the ureteric bud
Metanephric • Proximal convoluted tubules
of intermediate
blastema • Loop of Henle
mesoderm
• Distal convoluted tubule
Caudal Ureteric bud responds and secretes • Collecting tubules and ducts
mesonephric Ureteric bud growth factors to induces growth and • Minor and major calyces
duct differentiation of metanephric blastema • Ureters
Positional changes of kidneys [ascending ® inferior ® superior inc. renal arteries]
• During ascent of the embryonic kidneys (from pelvis ® upper posterior abdominal wall
• New blood vessels arise from the aorta and supply the kidney, while the vessels at the lower level disappear.
Development of the urinary bladder and urethra
• Cloaca = terminal hindgut lined with endoderm + • Bladder (lined by mesoderm) ç vesical part of the urogenital sinus,
receives the allantois (finger-like diverticulum) on its • BUT Trigone region ç caudal ends of mesonephric ducts.
ventral side.
o Due to traction with kidney ascent + ureters needing to
• urorectal septum (mesenchyme) divides cloaca into: enter obliquely through the base of the bladder.
o Ventral (urogenital sinus) • Orifices of mesonephric ducts move close together and enter
o Dorsal parts (rectum and anal canal) prostatic part of the urethra to become the ejaculatory ducts.
, Types of embryological renal anomalies
Anomalies of number What embryological urinary tract abnormality will cause oligohydramnios
during pregnancy?
• Unilateral renal agenesis (absence of one
kidney) • If foetus kidneys are not
• Supernumerary right kidney (separate or producing urine (e.g. bilateral
partially fused extra kidney) renal agenesis)
• decrease in amount of the
amniotic fluid in pregnancy
(oligohydramnios) since urine
produced is usually mixed
with amniotic fluid
• No fluid to cushion umbilical
cord from uterine
compression
• baby cannot survive
Anomalies of ascent Anomalies of form and fusion
• Renal ectopia is a congenital renal anomaly • Crossed renal ectopia with or without fusion
characterized by the abnormal location of one or • Horseshoe kidney (arrested by IMA)
both kidneys
• e.g. diaphragmatic kidney, pelvic kidney,
cephalad renal ectopia, thoracic kidney
PELVIC KIDNEY DIAPHRAGMATIC KIDNEY
Anomalies of rotation Anomalies of renal vasculature
• Malrotation Accessory renal vessels
• Failure of lower vessels to degenerate
during embryonic kidney ascending =
persistent accessory renal arteries (end
arteries)
• Consequently, if damaged or ligated the
part of the kidney supplied by accessory
artery is likely to become ischemic è may
need transplant
Anomalies of collecting Patent Urachus
system • Opening between the bladder and the umbilicus ® closes before birth
• Duplicated collecting system • An open urachus typically occurs in infants è can lead to cysts or
umbilical polyps
URINARY SYSTEM EMBRYOLOGY
• Urogenital system derived from intermediate mesoderm ® forms a urogenital ridge on either side of the developing aorta.
• Kidneys develop through 3 successive sets of tubular nephric structures:
(1) Pronephros ® (2) Mesonephros ® (3) Metanephros (gonads)
Urine production in utero
Metanephros– primordia of permanent kidneys begin to produce urine early in week 9 ® mixed with the amniotic fluid ® continues
throughout foetal life +
• A mature foetus swallows several hundred millilitres of amniotic fluid each day ® then absorbed by intestine.
• Waste products eliminated by placental circulation into maternal blood for elimination by the kidneys.
The metanephros develops from an outgrowth of the:
Outgrowth Forms the Function Adult derivatives of
Secretes growth factors that induce • Podocytes and bowman’s capsule
Condensation growth of the ureteric bud
Metanephric • Proximal convoluted tubules
of intermediate
blastema • Loop of Henle
mesoderm
• Distal convoluted tubule
Caudal Ureteric bud responds and secretes • Collecting tubules and ducts
mesonephric Ureteric bud growth factors to induces growth and • Minor and major calyces
duct differentiation of metanephric blastema • Ureters
Positional changes of kidneys [ascending ® inferior ® superior inc. renal arteries]
• During ascent of the embryonic kidneys (from pelvis ® upper posterior abdominal wall
• New blood vessels arise from the aorta and supply the kidney, while the vessels at the lower level disappear.
Development of the urinary bladder and urethra
• Cloaca = terminal hindgut lined with endoderm + • Bladder (lined by mesoderm) ç vesical part of the urogenital sinus,
receives the allantois (finger-like diverticulum) on its • BUT Trigone region ç caudal ends of mesonephric ducts.
ventral side.
o Due to traction with kidney ascent + ureters needing to
• urorectal septum (mesenchyme) divides cloaca into: enter obliquely through the base of the bladder.
o Ventral (urogenital sinus) • Orifices of mesonephric ducts move close together and enter
o Dorsal parts (rectum and anal canal) prostatic part of the urethra to become the ejaculatory ducts.
, Types of embryological renal anomalies
Anomalies of number What embryological urinary tract abnormality will cause oligohydramnios
during pregnancy?
• Unilateral renal agenesis (absence of one
kidney) • If foetus kidneys are not
• Supernumerary right kidney (separate or producing urine (e.g. bilateral
partially fused extra kidney) renal agenesis)
• decrease in amount of the
amniotic fluid in pregnancy
(oligohydramnios) since urine
produced is usually mixed
with amniotic fluid
• No fluid to cushion umbilical
cord from uterine
compression
• baby cannot survive
Anomalies of ascent Anomalies of form and fusion
• Renal ectopia is a congenital renal anomaly • Crossed renal ectopia with or without fusion
characterized by the abnormal location of one or • Horseshoe kidney (arrested by IMA)
both kidneys
• e.g. diaphragmatic kidney, pelvic kidney,
cephalad renal ectopia, thoracic kidney
PELVIC KIDNEY DIAPHRAGMATIC KIDNEY
Anomalies of rotation Anomalies of renal vasculature
• Malrotation Accessory renal vessels
• Failure of lower vessels to degenerate
during embryonic kidney ascending =
persistent accessory renal arteries (end
arteries)
• Consequently, if damaged or ligated the
part of the kidney supplied by accessory
artery is likely to become ischemic è may
need transplant
Anomalies of collecting Patent Urachus
system • Opening between the bladder and the umbilicus ® closes before birth
• Duplicated collecting system • An open urachus typically occurs in infants è can lead to cysts or
umbilical polyps
