Further studies on the kidney of the hook‐lipped African rhinoceros, Diceros bicornis

Abstract

A healthy, pregnant Diceros bicornis (No. 29455), with histologically normal but relatively large kidneys containing a correspondingly large number of nephrons, died suddenly from an injury. Renal lobation was studied partly from serial transverse cuts across the kidney. The fibromuscular pelvic conduits, which are a craniocaudal bifurcation of the ureter, are associated with prominent longitudinally disposed paraconduital veins which anastomose with the interlobar veins. The arcuate veins open widely into the paraconduital veins. The latter drain into the major tributaries of the renal vein at the renal sinus. The interlobar arteries enter the parenchyma through the interlobar septa. These arteries release internal perforator branches, through the septa, which pass to the corticomedullary border, branch along that border as arcuate arteries, and release cortical branches centrifugally. All these branches give off twigs to the glomeruli. Relative renal mass of mammals is inversely proportional to their adult body mass. This is indicated by a regression line which includes rhinoceroses. D. bicornis No. 29455, accordingly, has exceptionally large kidneys. The mesonephros of the 75 mm fetus of D. bicornis has mature glomeruli and tubules. The metanephros has pelvic conduits, paraconduital veins, but, as yet, no medullary loops.

Kidney of elephants

“…The number of glomeruli per kidney of the elephants is 14,957,798 * 2,820,139 (n = 4). This slightly exceeds that in the rhinoceroses which is 14,135,865 +-2,009,736 (n = 8 ) (data in Table 1 of Maluf, 1994a). The average diameter of the glomerular capsule of adult elephants (311 +-40.6 pm, n = 114) is, however, considerably larger than that of the adult and subadult rhinoceroses (237 t 50 pm, n = 140) so that the mass of glomeruli per gram of cortex of the adults is essentially equal: 6.7 5 0.3% (n = 3), in elephants and 7.3 ?…”

“…Renal mass per area cribrosa of adult elephants may exceed 285 g. This implies that every medullary outlet drains a large mass of kidney. Renal mass per lobe in adults of five species of rhinoceros is much less than in elephants, namely, 50 t 14g (data from Maluf, 1987Maluf, , 1991aMaluf, , 1994a. In man with a standard of 14 lobes per 150 g kidney, the mass per lobe is only 10.7 g.…”

“…Interlobar septa preclude interlobar venous anastomoses, as they do in rhinoceroses (Maluf, 1991a(Maluf, , 1994a. Even when interlobar septa are non-existent, as in man, prominent venous anastomoses occur in the renal sinus at the level of the calyces rather than across lobes (von Lenhoss6ks, 1876;Hauch, 1903;von Mollendorff, 1930).…”

“…In elephants the fibromuscular partitions between adjacent lobes are well defined, relatively thin, and contain no vessels larger than capillaries. In contrast the interlobar arteries of rhinoceroses course through the interlobar septa and supply internal perforating arteries to the adjacent cortices (Maluf, 1989c(Maluf, , 1991a(Maluf, , 1994a. Sperber (1944) noted cortical hairpin loops in Elephas maximus and stated that "kidneys that contain numerous cortical nephrons seem to have a very large cortex in proportion to the medulla.…”

The giraffe kidney tolerates high arterial blood pressure by high renal interstitial pressure and low glomerular filtration rate

“…Interspecific analyses reveal that GFR scales similarly to metabolism with body mass, whereas snGFR is relatively independent of body size (Singer ). The mass of the giraffe kidney relative to body mass is no different than other mammals (Maluf , ), which implies that they have either a high GFR (i.e. high snGFR with a normal number of glomeruli), or a functional adaption that normalizes the Starling forces across the glomerulus despite the high renal arterial pressure.…”