Type:
Educational Exhibit
Keywords:
Education and training, Developmental disease, Congenital, Normal variants, Education, Ultrasound, Fluoroscopy, CT, Urinary Tract / Bladder, Kidney, Anatomy
Authors:
M. Osman1, M. Skalski2, I. Bickle3, H. Knipe4, F. Gaillard5; 1MEADOWBROOK/AU, 2LOS ANGELES/US, 3BANDAR SERI BEGAWAN/BN, 4MELBOURNE/AU, 5Parkville/AU
DOI:
10.1594/ranzcr2014/R-0202
Background
Congenital renal parenchymal anomalies occur in approximately 1% of the population [1].
The importance of these anomalies is two-fold.
First,
these anomalies should not be mistaken for pathology themselves.
Second,
it is important to recognise that pathology,
such as infection or calculus formation,
can occur more frequently in these anomalies.
Embryological development of the kidney and collecting system represents the complex interplay between two embryological structures: the metanephros and ureteric bud.
Congenital renal anomalies are the result of abnormal development,
abnormal migration and/or abnormal fusion.
The collecting system arises from the ureteric bud,
which arises from the mesonephric duct in the fourth week of gestation.
The renal parenchyma arises from the metanephros, a derivative of the intermediate mesoderm, which appears in the fifth week.
The ureteric bud penetrates the metanephric mesoderm,
which forms as a cup-shaped tissue cap.
The ureteric bud dilates and subdivides to form twelve or so generations of tubules,
with the first generations fusing to form the renal pelvis,
major and minor calyces,
and renal pyramids,
and the later generations forming approximately a million renal tubules.
Early division of the ureteric bud can result in a duplex kidney or other anomalies of the ureter.
Under complex signalling pathways the ureteric bud incites the metanephric tissue to form small renal vesicles that eventually form primitive S-nephrons that are invaginated by endothelial cells from nearby angioblasts,
and go on to form the definitive nephron.
Errors in the signalling pathway or formation of the metanephric tissue cap can result in renal agenesis or other renal parenchymal abnormalities.
The kidney develops in the pelvis,
but rises to its normal abdominal location in adults due to disproportionate growth of the body in the lumbar and sacral regions.
During the relative ascent of the kidney,
as they pass through a fork formed by the umbilical arteries,
errors may result in an abnormal position or fusion.