Hardened _in situ_. Left renal vein (not marked) is seen curving round
posterior end of left adrenal.
]
The =left kidney= (Ren sinister) is bean-shaped. It is considerably
longer and narrower than the right one, and is situated nearer the
median plane and further back, so that the hilus of the left kidney is
about opposite to the posterior extremity of the right one. It lies
usually under the upper part of the last rib and the first two or three
lumbar transverse processes. The =dorsal surface= is convex, and is
related to the left crus of the diaphragm, the psoas muscles, and the
base of the spleen. The =ventral surface= is convex and irregular; the
greater part of it is covered by the peritoneum. It is in relation with
the origin of the small colon, the terminal part of the duodenum, the
left adrenal, and the left extremity of the pancreas. The =internal
border= is longer, straighter, and thicker than that of the rightkidney.
It is related to the posterior aorta, the adrenal, and the ureter. The
=external border= is related chiefly to the base of the spleen. The
=anterior extremity= extends almost to the saccus cæcus of the stomach;
it is related to the left end of the pancreas, and the splenic vessels.
The =posterior extremity= is usually larger than the anterior one.
The form of the left kidney is variable. In some cases its outline is
similar to that of the right kidney, but its ventral surface is convex
and is often marked by several furrows which diverge from the hilus.
In well hardened specimens the three areas of the dorsal surface are
often distinct. The psoas area is flat, parallel with the inner
border, and widens behind. The diaphragmatic area is small and convex;
it is crescentic and is confined to the anterior pole. The splenic
area, convex and external, is often so extensive and distinct as
really to constitute a third surface.
=Fixation.=—The kidneys are held in position chiefly by the pressure of
adjacent organs and by the renal fascia. The latter is a special
development of the subperitoneal tissue, which splits into two layers to
inclose the kidney, together with the perirenal fat or capsula adiposa.
On account of its relations with the liver, pancreas, and the base of
the cæcum, the right kidney is much more strongly attached than the left
one. It is, therefore, not surprising that the latter varies somewhat in
position; its posterior pole may be found ventral to the third or fourth
lumbar transverse process. The position of the right kidney seems to be
very constant, excluding its movements during respiration.
[Illustration: