KIDNEY OF ELEPHANTS

Background: Elephants are an important and isolated order. Their kidne ys need substantial investigation and hitherto have not been portrayed even by a pyelogram. Methods: Pyelograms and injection of vessels wit h colored acrylic emulsions were done initially. Dissection was under fiberoptics using a dissecting microscope with frequent measurements. Special areas were cut for microscopy (light and electron) and photogr aphy. Glomerular counts were done by macerating weighed pieces of cort ex and later finding the cortical fraction of the renal parenchyma. Re sult: The elephant kidney is devoid of dorsoventral symmetry. It is co mposed of 8 +/- 2 lobes separated by fine interlobar septa. There is n o reduction of lobes with maturity. The pelvis bifurcates at the sinus into primary branches or infundibula which dispatch a secondary branc h or infundibulum into every lobe. Interlobar arteries and veins, nerv es, fat, and connective tissue generally accompany every secondary inf undibulum into its lobe, A major branch of the renal artery may perfor ate the renal capsule and course to the cortico-medullary (C-M) border independently of the secondary infundibulum to that lobe. The number of glomeruli per kidney is approximately 15 x 10(6). In adults the glo merular mass is 4.9 +/- 0.5% of the renal parenchyma and 6.7 +/- 0.3% of the cortex. Areae cribrosae occur generally at low papillae. They a re the outlets of numerous terminal collecting ducts which may be acco mpanied by a tubus maximus (T.M.) A T.M. of diameter 1.6 mm and length 10 mm may act as the only substitute for an area cribrosa. Wide anast omoses between the two main renal veins occur within the renal sinus. Intralobar arteries and veins often course right through the outer med ulla to and from, respectively, the C-M border. Conclusions: Anatomica lly, an elephant's kidneys appear to be able to concentrate urine only moderately, Their kidneys tend to resemble those of the manatee but n ot of the dugong. (C) 1995 Wiley-Liss, Inc.