The Kidney
Clinical anatomy
Clinical skills
The kidney is difficult to palpate because of its position high up on the posterior abdominal wall.
In thin individuals however palpation is possible. The position of the kidneys is different by about
2.5cm standing up and lying down. There is a slight rising and falling with respiration. The
surface projection of the kidneys
anteriorly can be related to the costal margin. The hilum of the
right kidney is slightly medial and inferior to the apex of the ninth costal cartilage (transpyloric
plane), while the hilum of the left kidney is slightly medial and superior to the apex of the left
ninth costal cartilage. Posteriorly
the hilum is about 5cm lateral from the first lumbar spine's lower
edge, with the left being slightly above and the right slightly below this point.
Posterior surgical approach
Since the kidneys lie in part above the twelfth rib, a direct posterior approach might pass first into
the thorax, perforating the pleural cavity. A posterior approach to the kidney also puts at risk the
subcostal and iliohypogastric nerves which pass laterally behind the kidney.
The transversalis fascia
Since the kidney and ureter are within a compartment formed by the transversalis fascia, any
blood, urine or infection can pass from the source in the kidney, to lie in the pelvis around the
bladder. Infection within this fascial compartment (Girota's fascia) may occur following
percutaneous procedures on the kidney.
Aberrant or accessory renal artery
Since the blood supply of the kidney changes during development, it is common for early arteries
arising from the common iliac arteries or lower abdominal aorta to
persist. These arteries are not
extra, in that they are the sole supply of part of the kidney. Such arteries may take anoblique
course, constricting the ureter as they pass upwards and laterally from the lower aorta to the
kidney.
Congenital anomalies
Renal agenesis may occur if the metanephric bud does not come into contact with the metanephric
mesoderm. Either one or both kidneys may fail to develop.
The kidney may reach an ectopic position or may be rotated in an unusual fashion. Neither of
these cases is a significant problem as long as there is no interference with blood supply, venous
drainage or with the ureter.
A horseshoe kidney results
from a lack of separation of the metanephric mass into two kidneys.
The kidney will ascend until it gets caught on the root of the inferior mesenteric artery.
Congenital polycystic disease can occur as a problem of tubule development. Instead of making
proper contact with the collecting ducts the metanephric tubules swell up into cysts and are not
functional.
Diseases of the renal corpuscle
Most of the problems of the kidney can be related to the components of the renal corpuscle.
These include :
renal failure due to thickened glomerular capillaries
Mesangial disease in which there is excess mesangial matrix and deposition of immune complexes
Basement membrane abnormalities as in nephrotic syndrome. In diabetes there is thickening of
the basement membrane but it is more permeable than normal
Podocyte changes in which the foot processes are reduced as in 'minimal change nephropathy'
Obstruction of outflow
The left renal vein passes between the root of the superior mesenteric artery and the aorta and
may be occluded at this site. The ureter may be occluded at many sites with resulting infection
and kidney damage.
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