A STUDY IN RENAL SENESCENCE* 
JOSEPH WALSH, M.D. 
PHILADELPHIA 
In a study of the kidneys four years ago I thought I 
noticed a fact which I had never heard mentioned, 
namely, that as age advanced there was a thickening of 
the interstitial tissue at the apex or papillary end of the 
pyramids and that this thickening was reasonably uni- 
form. Further study on one hundred and fifty kidneys 
from individuals of all ages dying from many different 
diseases (though the majority died from tuberculosis of 
the lungs) added confirmation. I then showed a num- 
ber of unselected specimens, the identification of which 
was withheld, to Dr. McFarland, who was so successful 
in determining the ages of the patients by the criterion 
mentioned that I have thought it worth while to prepare 
the following notes for publication. 
The condition is practically one for demonstration 
Tather than for description, yet the specimens shown at 
the time of the reading of the paper might be described 
as follows: The specimen from the child one month 
old showed through a % lens the tubules at the apex 
of the pyramids practically in juxtaposition with so lit- 
tle interstitial tissue between them that it was practic- 
ally invisible; in the 9-year old specimen there were one 
or two fine lines of interstitial tissue between the tubules; 
in the 27-year-old specimen three or four lines; in the 
35-year-old specimen five or six; in the G9-year-o!d 
♦ From the Laboratory of the Henry Phipps Institute; read 
before the Philadelphia Pathological Society, Feb. 24, 1910. 2 
specimen eight to ten lines and in the 99-year-old speci- 
men ten to twenty lines.. 
Moreover, the study revealed that this thickening of 
the interstitial tissue was not dependent on the accom- 
panying pathologic condition of the kidney, but occurred 
apparently only as a result of age. All kinds of patho- 
logic conditions were found in the one hundred and 
fifty kidneys studied, namely, cloudy swelling, acute 
parenchymatous nephritis, chronic parenchymatous ne- 
phritis, focal interstitial nephritis, the various kinds of 
general interstitial nephritis, amyloid degeneration, 
pyelonephritis, etc. It was found that pyelonephritis 
and hydronephrosis injured the pyramids and increased 
the interstitial tissue in them to such an extent as defi- 
nitely to obscure the comparatively slight increase due to 
age; in these cases, therefore, the age could not be told 
from the appearance. 
In addition it was found that a general or a marked 
focal interstitial condition which is commonly only 
studied and described from the appearances in the cor- 
tex affected also the pyramids and hence increased the 
interstitial condition at the apex of the pyramids so 
that the thickening at this point did not correspond ex- 
actly with the age. Comparison of many such kidneys, 
however, showed that it was not difficult to learn from 
the condition in the cortex how much of the thickening 
at the apex of the pyramids was to be attributed to the 
pathologic condition and how much to age. In other 
words though interstitial nephritis modifies the amount 
of interstitial thickening at the apex of the pyramids, 
this modification can be recognized and taken into ac- 
count. In regard to the question which naturally arises 
as to how reliable is the differentiation of age from this 
thickening of the interstitial tissue, I would say that it 
is almost as reliable as the appearance of the face; 
though we can generally give a pretty good idea of the 
age of an individual by looking at him we are sometimes 
mistaken in middle life to the extent of ten or even fif- 3 
teen years and in old age rarely even to the extent of 
twenty years. 
In deciding the age of the individual from the thick- 
ening of the interstitial tissue at the apex of the pyra- 
mids the following precautions should he taken: First, 
the apex of the pyramid should be in view. Sometimes 
a cross-section of the kidney is made in such a way that 
we see a long stretch of pyramid but instead of one we 
are looking at two pyramids end to end; in other words, 
a specimen may be cut across two pyramids in such a 
way that the apical portion of one pyramid will run into 
the apical portion of the other so as to make the end of 
the specimen actually near the second cortex though the 
second cortex is not in view. Second, edema must be 
differentiated from thickening of the interstitial tissue. 
Third, the amount of interstitial tissue should be esti- 
mated, not from one single location, but from several 
fields of a % lens. Fourth, interstitial nephritis in- 
creases the amount of interstitial tissue at the apex of 
the pyramid* and must be accounted for. Fifth, pye- 
lonephritis and hydronephrosis obscure completely the 
thickening due to age. 
SUMMARY 
1. There is a gradual increase in the amount of in- 
terstitial tissue at the apex of the renal pyramids so uni- 
form with advancing age that the age of the individual 
is evident from the amount of interstitial tissue found. 
2. This relation of the amount of interstitial tissue 
to the age is lost in cases of pyelonephritis and hydrone- 
phrosis; and modified by interstitial nephritis, though 
this modification can be accounted for, so that the age 
remains evident. 
732 Pine Street. Reprinted from The Journal of the American Medical Association 
June 4, 1910, Vol. LIV, pp. 1851 and 1852 
Copyright, 1910 
American Medical Association, 535 Dearhorn Ave., Chicago