THE URINARY TRACT
THE KIDNEY.
The kidneys, ureters, bladder and urethra remain comparable in all
mammals excepting the monotremes where there is no urinary passage
through genital openings, the urine being ejected through the vesicoanal
pouch, a sort of cloaca. In the bird the first two parts remain as in
mammals while the ureters terminate in a hernia-like pouch of the rear
wall of the cloaca. It would seem from this arrangement that ureteral
transmission of infection from the anal area to the kidneys would be
facilitated in the lowest mammals and in the Aves. Variations in size,
shape and position exist to a minor extent in the higher orders but in
all forms, the system remains a post-peritoneal structure.
Differences in construction are to be seen for example, in the single
pyramidal kidneys of marsupials and certain rodents, in the lobulated
organ of bears, cattle and seals, in the twisted viscus of horses, but
these gross appearances do not destroy the uniform scheme upon which the
functionating unit is built. The single-lobed kidney discharges all its
collecting tubules into one calyx while the multiple pyramids of the
lobulated organ are fitted with individual calices which in turn empty
into the pelvis proper; this is true whether the lobulations are
retained, as in the bear, or are smoothed out in the course of
development as in man. The secretory tubule remains in essentially the
same form in all kidneys; the modern idea of its anatomy may be found in
the work of Huber[32].
The most decided example of the lobulated kidney is to be found in the
class Aves, wherein the organ consists of two or three large lobes lying
in concavities of the sacrum, each lobe being made up of tiny lobules.
The latter appear to the unaided eye as fairly distinct divisions
whether viewed on the exterior or by cross section. There is a cortex
and a medulla to each, the separation being clear in a large specimen,
vague in a small one. These lobulations are quite well observed when the
kidney is full of urates, a common finding in birds. Magnification of
the avian kidney reveals an apparently simpler tubular arrangement than
is found for mammals[33][34], yet the relation of vascular plexuses and
secreting tubules remains similar.
From the standpoint of comparative pathology attention can be drawn to
the glomerulus, to the interstitial tissue, and to the character of the
epithelium. The tuft of intricately wound capillaries called the
glomerulus has always been viewed as the part of the secretory unit
chiefly concerned in urine production whether one accept the older idea
that it excretes only fluid or the modern belief of many observers that
all parts of the urine go out through it. In the mammal the tuft is
closely wound, is surrounded by a distinct space and a limiting membrane
of appreciable width called Bowman’s capsule; all this so-called
Malpighian body has a breadth varying from 120 to 300 micra. There is
however great variation in the size of this body when seen in the
peripheral and deeper zones of the same organ, amounting at times to
seventy per cent. of the diameter. The capillary congeries forming the
avian tuft is by no means so delicate and one can see individual
capillaries with more ease. It may be impossible to discover a space
between the tuft and its exceedingly delicate capsule, the latter being
usually applied closely to the vascular corpuscle. The whole breadth
varies from 70 to 140 micra with an average of 110. There is more
uniformity in size than in the mammalian organ.
Supporting tissues between the tubules seem less definitely nuclear in
the bird than in the mammal, at least in so far as connective tissue is
concerned, there being in the former only a few groups of mononuclears
to be seen in the cortex. Perivascular tissues are reasonably rich. The
epithelium of proximal and distal tubules is not easily fixed by our
customary laboratory techniques, the best results being obtained by
Zenker’s fluid. As seen in a routine specimen of a normal organ it is
vacuolated or very palely stained. The individual cells stand out
clearly and many present a pointed end to the tubular lumen.
KIDNEY WEIGHTS.
According to the work of Mangan[35] and of Alezais[36], the bird has an
average kidney-to-body weight of 6.9 grams per kilo while man has a
ratio of 4.3 grams, dog 5.9 grams and guinea-pig 8.5 grams. The first
author would show that the fish-eating birds have the heaviest and
vegetarian birds the lightest organ. Our own figures are limited to the
weights of apparently normal organs in thirty-one mammals and five
birds; they are as follows:
│per kilo of body weight
Primates (5)│ 7.7 grams│
Carnivora (6)│ 7.6 grams│
Rodentia (2)│ 15. grams│
Hyracoidea (1)│ 7.5 grams│
Ungulata (9)│ 3.5 grams│
Edentata (1)│ 5.6 grams│
Marsupialia (7)│ 7.6 grams│
Monotremata (1)│ 11.2 grams│
│ │Average 7.
Steganopodes (1)│ 9.1 grams│
Anseres (1)│ 3.9 grams│
Struthiones (3)│ 7. grams│
│ │Average 6.7
────────────────┴───────────┴───────────
This to be sure is not a very exhaustive list but is the result of our
routine observations and subject to all limitations of such work.
Grossly diseased organs are naturally excluded. More avian weights are
not available because of the difficulty of removing the organ from its
bed, in a manner assuring us of completeness. I am inclined to view our
mammalian records as fairly representative. Figures to be found in text-
books of human and veterinary anatomy correspond to those given by the
authors just quoted and in our own list. The values for rodents,
hyraces, edentates and monotremes may be modified by more figures.
There is however one point which does not appear in the list. Small
animals have relatively larger kidneys than large animals. This is
perhaps most strikingly illustrated among the ungulates which have the
lowest value quoted. A small deer had a kidney-to-body index of 5.9
grams per kilo while a camel had only 2.8. Judging by the work of Magnan
the avian kidney should be larger than the mammalian, a conclusion with
which I am inclined to coincide, even though the weights cited do not
bear this out.
In so far as the function and chemistry of the kidney and its excretion
are concerned this study can supply little. The general metabolism is
known for most animals, it being dependent upon diet and
gastrointestinal discharge of excrement. What lessons can be learned
will be discussed by Dr. Corson-White in the section on diet. Our
observations upon the ability of the kidney to excrete normal urine are
limited to the examination of vesical contents at death or of the
occasional specimen obtained in cages in the quarantine room. Renal
disease was formerly considered of little or no importance in veterinary
medicine or at least was studied only as a specific separate and
occasional occurrence. Kitt[37] systematized the knowledge of the
subject at the time he wrote but it remained for Hutyra and Marek in
their text-book to emphasize its general importance and to clarify
diagnostic measures. Breindl[38] pointed out that nephritis occurs more
often in acute general diseases, notably the specific infections, than
was customarily thought, thus placing the subject for the lower animal
where it is in human medicine.
Renal disease is quite common among wild animals albeit there are
certain orders in which the lesions are less conspicuous. Clinical
diagnoses of nephritis, and this is the only diagnosis attempted, have
been made on monkeys by examination of urine which shows the same
characters as in the human disease. In ungulates more attention is to be
placed upon the cellular contents of the urine since renal epithelium is
apparently shed more readily and casts less often formed. Signs and
symptoms of renal disease are limited to edema and uremia; cases of the
latter are rare enough to discuss separately at the proper place.
ABSENCE OF ABNORMALITIES.
Abnormalities of size, shape and position of the kidney are frequently
reported in literature of veterinary medicine and aplasia has been
described. Our material has failed to present cases of horse-shoe kidney
well known to occur in horses, cows, sheep and dogs. Wandering kidneys
are also known but have not been seen in our wild animals. Shall these
abnormalities be considered as due to degenerative changes in cross bred
animals or as the result of the strain of domestication? To such a
speculative question our material affords no answer.
HYPERTROPHY.
That the kidney has the power of hypertrophy in a compensatory manner is
illustrated by two cases. A Japanese Macaque (_Macacus fuscatus_) ♂
apparently had suffered with a unilateral nephritis which had gone into
a contracted stage. At all events much functionating tissue was gone,
the organ irregular and small, being half or less of the size of the
other organ which was larger than is considered normal for the species.
Histologically the large organ was practically normal. A common opossum
(_Didelphys virginiana_) suffered with a complete suppurative nephritis
of the right side which completely destroyed the organ; the origin of
this is not clear as no ascending disease could be determined and no
certain acute infection had existed; decomposition precluded
satisfactory bacteriology. The left kidney was nearly twice its normal
size and involved in an early diffuse nephritis, with miliary abscesses,
in which the glomeruli did not participate. There were in these sections
evidences of regeneration, swollen reduplicated epithelial coverings
presenting a picture similar to those seen in so-called chronic
nephritis secondary to interstitial change.
INFILTRATIONS.
Pathological infiltrations of the renal structures are exceedingly
uncommon. Early in our experience we were often perplexed at the
appearance of certain organs, notably in carnivores and marsupials to
which we were inclined to apply the term fat infiltration. However the
absence of reasons for considering this picture pathological seemed
sufficient cause to ignore the finding, and later Pfeiffer[39] called
attention to the apparent inability of these kidneys to emulsify fat or
at least to combine it in an invisible form, an ability possessed by the
herbivorous organ. A monkey and a passerine bird only showed sufficient
fat visible in the renal epithelium to warrant a denomination of fatty
infiltration; these were both obese specimens. Amyloid infiltration
occurred in four mammals and six birds, being a sequel of its usual
causes, tuberculosis, chronic suppuration and osseous system disease. It
is perhaps well to emphasize the fact that every organ the seat of
amyloid deposit need not be enlarged. This teaching is common but I have
seen human cases without enlargement and only two of the ten cases in
these animals are noted as bulkier than normal.
DEGENERATIONS.
Degenerations represent the reaction of the kidney to toxic or
infectious agents and might be considered as indicating the
vulnerability of the organ. Their incidence does not coincide with that
of nephritis as we shall see later. Any discussion of degenerative
phenomena, and especially in the kidney, should be limited by a
definition of what they are believed to be and their separation from
inflammations. Degenerations are swellings, granularities,
vacuolizations or infiltrations of tubular epithelium, changes which
destroy the outline and internal structure, perhaps including the
nucleus. No changes of the glomerular tuft or interstitial tissue are
necessary for this conception since when these occur the picture becomes
that of nephritis. In border-line cases it is safer to include the case
under the latter heading since then the physiology is apt to be
disturbed, albumen and casts appearing in the urine. Degenerations
appear in various pathological states—toxemia, infection, prolonged
congestion and others. The first named cause seems to be the most
important in our records and the seat of the toxine production seems to
be the intestine. Enteritis stands very high in the list of accompanying
factors, especially in Carnivora, Primates and in Aves. Perhaps the most
instructive cases are to be found in the Ungulata with toxic duodenitis.
The kidney in these animals is deep red or purple, with a spanned
capsule. The section surface bulges slightly, is of an opaque, dull
purple color and shows a congested zone between cortex and medulla.
Tubular epithelium may be found, under the microscope, sufficiently
swollen to fill the lumina, in places being like ground glass, in others
distinctly vacuolated. It cannot be stated absolutely which part of the
tubule is usually affected; it seems more often the distal convoluted
portions than other subdivisions. Glomeruli may be full of blood but
there is no increase in cells nor any material in the capsular space.
The urine is dark and may or may not show albumen. The kidney of
kangaroos with streptothricosis is similar to the picture just given.
Mammals have shown a percentage incidence of renal degenerations of 4.8
per cent. while Aves show only 3. per cent. In order of incidence the
carnivores head the list followed by Lemures, Accipitres, Rodentia,
Primates and Marsupialia; the remaining groups show but a few cases. A
form of degeneration is sometimes seen in the avian kidney the seat of
excess urate collections, especially when these are arranged as so-
called uratic infarcts. This last term has been applied to the streaking
and mottling of human kidneys by the accumulations of these salts in a
manner believed by some to be related to the formation of uratic
calculi. The epithelium of such a kidney may show granularity and
collections of acids and salts have been found in the lumina. In the
bird on the other hand one frequently sees masses of urates in one
lobule, or a part thereof, arranged to simulate closely the common
infarct shape. Secretory cells in the affected area are hydropic, with
absent or dislocated nucleus, or again they present a densely basic
staining protoplasm. This form of kidney is well seen in what has been
called here an uratic serositis, a coating of all somatic free membranes
with a thin, white, granular film. We have tried with many techniques to
preserve one of these cases but the deposit either dissolves or the
whole specimen becomes opaque. Although the term infarct is applied to
these lesions, they are of course not infarcts in the customary use of
the term. True infarcts are exceedingly uncommon and, with the exception
of one case which became infected and suppurated, have been negligible
in our material.
HEMORRHAGES.
Hemorrhages into the kidney are found in acute infections and certain
diseases like leucemia; they are of little moment. Perirenal hemorrhage
is a somewhat striking and unusual affair. Recently I saw at a human
autopsy of a young subject a subcapsular hemorrhage from the renal
substance probably due to vascular rupture in an acute nephritis; there
was no history of injury. There have been three cases of subcapsular
hemorrhage in our records and as two of them represented the immediate
cause of death, are interesting enough to record. An armadillo suffered
an acute diffuse nephritis with much congestion but not enough to call
it hemorrhagic. There was a large hemorrhage around the left organ,
probably from a vessel near the hilum, sufficient to compress the kidney
and cause it to atrophy. A lion presented an acute vegetative
endocarditis with all its usual complications. The right renal capsule
was distended with recent clot to a size which reached to the pelvic
brim. Presumably an embolism caused thrombosis, ulceration and rupture
of some middle size vessel. A dormouse suffering with an acute general
infection probably emanating from the intestine, had several small
recent clots separating the kidney from its capsule.
NEPHRITIS.
Nephritis, whether one begin its conception with the clinicopathological
picture originally given by Bright, with the purely pathological
classification of Weigert and Virchow or the modern tendency to
subordinate all physical changes to clinical phenomena, is nevertheless
a process of degeneration and inflammation affecting the secreting and
supporting structures of the kidney and leading to some degree of
impaired function. The disease is bilateral in so nearly every case that
for practical purposes unilateral cases may be ignored. This implies
that for some reason the renal tissues are generally susceptible to
etiological agents so that when one side is affected its fellow seems
always to participate or to follow. It seems desirable in studying
nephritis to evaluate fully the mutual relations of functionating and
supporting tissues and of the various sections of the first named. It is
taught in many places that inflammations of one or another of these
parts may occur independently, as for example a tubular nephritis, a
glomerulonephritis and an interstitial nephritis. If however one reflect
upon the dependence of the tubular function upon the glomerulus and
_vice versa_ or upon the effect of inflammatory exudates in the
supporting tissues upon the blood supply of the tubule, it becomes
evident that only the most trivial or evanescent pathological changes in
one can be without effect upon the others. It is difficult to see how,
for examples, a glomerulus could remain normal if its associated tubule
were destroyed or how if round cell infiltration or pus surround a
capsule for any length of time, this structure could fail to be doomed.
All this is by way of directing attention to the progress of physical
damage in a kidney which has received injury sufficient to cause
nephritis, but of course it does not explain the cause.
In classification of nephritis different commentators have employed
different standards according as they viewed the acuteness or chronicity
of the process, or as the principal functionating structures,
glomerulus, tubular epithelium, blood vessels, or supporting connective
tissues, presented the most conspicuous changes. To these, clinicians
have added phenomena of constitutional complication or of direct renal
insufficiency. These latter being unavailable for us, we must fall back
upon a classification based upon physical changes and to this end we
have always used a slight modification of the Weigert method. This
classification offers little in the direction of etiology except that
toxins are believed to cause tubular changes, bacteria to produce
glomerular lesions and vascular deficiencies to lie at the root of
chronic interstitial nephritis.
The origin of acute nephritis of chiefly degenerative character seems
best explained by reference to some form of toxemia, whereas exudative
processes, be they in glomerulus or supporting structures, seem to
depend upon the direct action of bacteria. The origin of a chronic
nephritis cannot be explained quite so readily. No one has answered with
complete satisfaction whether a chronic process always begins with and
proceeds from a single attack of acute disease, whether many acute
attacks succeed upon one another or whether many small crops of agents
successively attack the organ over a long time. Nor has an adequate
explanation of the rôle of damaged blood vessels been given. It is
reasonably easy in man to discover the existence of nephritis and of a
possible cause; this is only true of acute cases in wild animals. Focal
infections, those which might be the point of mobilization for bacteria
sent to the kidneys, are frequently found in man but with exception of
an occasional carious tooth, or a chronic osteitis are to be localized
with difficulty in lower animals. In so far as the rôle of a single
acute attack in the causation of chronic disease is concerned our
material offers nothing, but some collateral or presumptive evidence may
be mustered in regard to multiple infections.
Wild animals do not give evidence of repeated attacks of acute disease
and indeed it would seem that they more often die of an acute infection
than live to have it repeated. Evidences of chronic infection, not
focal, are reasonably definite in forty-eight per cent. of the cases of
chronic nephritis encountered here. This suggests strongly that in this
material protracted infectious states offer opportunities for renal
damage of progressive character. Vascular disease has been found twenty-
eight times (see also section on arteries), in twenty-six of which the
nephritis seemed due to or advanced by the damage to the vessels. This
means further that only 14.3 per cent. of the chronic forms and 4 per
cent. of the total seem closely related to disease of blood vessels.
Nephritis has been found in 12.2 per cent. of our total autopsies.
Mammals show an incidence of 20.6 per cent., birds 7.7 per cent. Only
the orders upon which more than one hundred autopsies have been held are
subjected to separate analysis. Some of the remaining orders give very
high figures which may indicate great renal vulnerability but it is
deemed unfair to make statements upon them. Carnivorous mammals and
birds lead their respective classes, the succeeding order of renal
vulnerability being marsupials, ungulates, rodents, Primates, Galli,
Striges, anserine birds, parrots, and doves. The leaders of this list,
Carnivora and Accipitres, occupy a definite position in the analysis of
acute and chronic lesions. Their kidneys show the smallest percentages
of acute lesions and the highest percentages of chronic lesions. This
would seem to indicate a resistance to acute injuries but susceptibility
to prolongated or repeated infections or intoxications. The relation of
chronic infection of some sort to chronic renal disease is not as clear
as the influence of acute infection to acute nephritis. Taking Carnivora
for example with 34.2 per cent. of chronic nephritis we find 22.4 per
cent. with evident chronic inflammation while in the 55 per cent. of
acute forms 40 per cent. are of acute infectious origin—the relation is
as 64 is to 74.
While the relation of infection to nephritis is a consistent and
perfectly acceptable one, the frequency of this disease in the
carnivorous orders obliges one to think of high protein diet as a
favoring factor. Renal disease is common enough in other orders, some
strictly herbivorous, and it is fair only to emphasize which are the
leaders in incidence. In so far as anatomy or habits are concerned no
generalizations seem permissible. There is no relation of nephritis to
the size of the kidney as given on a previous page, to the length of the
alimentary tract, or to the expected longevity.
Toxic nephritis is a term applied when the kidney is the seat of
epithelial degeneration, much congestion, perhaps leading to tiny
hemorrhages, and definite swelling of the tuft without exudation into
the capsular space. It is a severe grade of the degenerations already
mentioned and is exemplified by the organ in cases of acute duodenitis
of ungulates and in some monkeys dying after tuberculin injection. It
seems especially to follow gastrointestinal diseases believed to be due
to food intoxications. It seems important in monkeys and wild rodents.
No adequate explanation is at hand for the latter.
As has already been stated vascular disease was present in twenty-six
cases in a manner suggesting some relation to the cardiorenal complex
but the only organ to which the term renal sclerosis of arteriosclerotic
origin could be applied is that of an eagle; the autopsy is cited.
Bald Eagle (_Haliæetus leucocephalus_). ♀ General obliterating
endoarteritis. Chronic interstitial nephritis. Passive congestion of
liver. Chronic localized myocarditis. Near the apex of the heart the
muscle shows a slight opacity. The kidney is enlarged, firm, section
surface glistening. Both section and surface show a mottled brown and
white appearance, following particularly on section the division into
cortices and medullæ. Digestive system apparently normal. Microscopic
section of heart muscle from the wall of the ventricle shows well
preserved muscle fibres with a slightly unusual degree of
pigmentation. Section from valve base shows a definite interfascicular
and intrafascicular fibrosis which is co-extensive with a similar
thickening of the endo- and pericardium. The new tissue under the
latter is edematous. The valve itself is thickened the fibres swollen
and hyaline. There is no reduplication of the endothelium. One artery
in the muscle is obliterated. This is not associated with any
degeneration of the muscle in the section. Section of kidney shows the
pale areas noted grossly to be made up of groups of arteries with
their extensive coalescing adventitiæ. The changes in the arteries are
precisely the same as those seen in the liver but are more extensive.
Connective tissue goes out from the arteries into the parenchyma
distorting the tubules and enclosing the glomeruli so that the capsule
of the latter is much thickened. Epithelium is granular, in some
places absent, nearly always low. Section of liver shows general
parenchyma practically normal with slight granularity in places and
moderate passive congestion. Veins are negative but arteries show a
general arteritis. The picture varies somewhat in different arteries
ranging from a simple thickening of the adventitia to a change
involving all three layers. There is hyaline change in the media in
many sections. Lumen is in all cases reduced and in some there is
active intimal proliferation in excess of what would be expected in
connection with the medial change. A few of the arteries have their
lumen completely obliterated.
This is meant to illustrate the picture of vascular disease in the
kidney in the absence of satisfactory evidence that nephritis _per se_
antedated or accompanied changes in the vessels. In such cases vascular
disease dominates, renal parenchymatous damage being relatively
inconspicuous. Two old carnivores, a paradoxure and a skunk, presented
shrunken kidneys with prominent wide-walled vessels but in these some
definite evidence of old nephritis was at hand.
In so far as the relation of senility to nephritis is concerned the data
at hand are not conclusive. In many old animals some degree of fibrosis
is present without the existence of truly destructive changes in the
parenchyma. Plimmer of London writes that there is increased nephritis
in old age but from our material I would be inclined to put in that in
many cases the nephritis was the reason for old age rather than that old
age brought on a nephritis. However the exact length of life and of
captivity is known in too few specimens to make a conclusion justified.
ASCENDING NEPHRITIS.
There is some difference of opinion as to the definition of the term
ascending nephritis, a confusion arising partly from the intended
meaning of the participial adjective, partly from the frequency with
which infections or obstructions of the urinary outlets antedate or
accompany suppurative nephritis. Perhaps our records may help to
straighten out this matter.
Ascending nephritis means for our study an infection which passes from
the pelvic surfaces of the pyramids outward toward the renal capsule.
Thus it is immaterial whether there be or be not an obstruction lower
down. Such forms of nephritis are infiltrative, frequently purulent and
are dependent upon pyelitis or the settling of bacteria in the deepest
parts of the medulla.
Three explanations are given in human medicine for the origin of this
lesion. Some observers assume a direct transmission of bacteria up the
ureter from an infected bladder or urethra, in a direction contrary to
the urinary current. This, it is believed by some can occur only in the
presence of physical obstruction, stone, kink, or pressure of adjacent
masses upon the ureter, whereby its blood supply is damaged and
infection facilitated. Others would explain the path of infection as the
lymphatics of the ureteral wall which are infected at the opening in the
bladder by a deep seated cystitis or by infection from a periproctitis
or from the female genitalia. Still another explanation is offered by
those who do not credit ascending infections. They would have it that
pyelitis arises from bacteria in the blood stream and only in the
presence of injury (_calculus_), ureteral dilation (slowly progressive
stenosis, or kinks, floating kidney, pressure by pregnant uterus) and
similarly operative factors. There should be excluded from this category
cases of chronic nephrolithiasis, and of stone only in the pelvis. Under
such conditions it is inevitable that a low grade of fibrosis with
damage to the secretory structures should exist, even in the absence of
active bacterial invasion. The cases are only important for our present
subject when active bacterial infection is implanted upon them.
Among our autopsies there have been found fourteen cases of ascending
nephritis and seven cases of pyelitis; the most instructive examples are
mentioned briefly as follows: Five of this twenty-one were associated
with general infectious diseases (three septicemias) and presented no
evidence of ascending obstruction. Two of this five were a bear and a
fox, the former suffering with streptothricosis septicemia, the latter
with distemper; one was a fox whose pelvic and renal lesion seemed
entirely primary for no apparent focus was detected; two were birds with
acute general infection. These cases seem therefore to be instances of
primary pyelitis. The following group includes cases with inflammation
low in the urinary tract. A fox had a cystitis, urethritis and colitis,
a distinct edema and congestion being found in the pelvis around the
rectum. Two opossums had cystitis, one due to a traumatic urethritis,
the other secondary to a prostatitis of undetermined causation. A
raccoon had a chronic cystitis with swelling and edema of the first
parts of ureter. A parrakeet showed ureteritis, pyelitis and nephritis
from simple cloacitis.
Where obstruction was more definite the following cases were observed.
Suppurative nephritis succeeded upon gangrenous cystitis after uterine
prolapse in a deer. The following cases of pyelitis and nephritis were
associated with calculus, only in the renal pelvis—an armadillo,
Tasmanian devil, a deer and a goose. A cockatoo had a stone in the
cloaca which seemed to cause a definite obstruction to both ureters and
a catarrhal inflammation of the wall. Pyelitis and interstitial
nephritis can also follow excessive urate collections in birds. At a
later time this will be discussed more fully, but at this place two
cases of distinct abscess formation in a renal lobule based upon urate
collections may be mentioned since in a measure the lesions were
dependent upon obstruction.
It is therefore evident that all the theories of the causation of
pyelitis with resultant nephritis seem acceptable. It has been claimed
that bacteria may be found in the blood stream before evidences of
pyelitis present themselves. Concerning this our records offer no
information, but it is worthy of note that five of twenty-one instances
gave a picture of septicemia. It is, however, fair to state that, while
mild cases of pyelitis occurred where there was, judging from the
protocol and histological sections, obvious opportunity for its ascent,
in ten other cases of cystitis and urethritis no pelvic or renal disease
is recorded; two of these were acute exudative cystitis and one was a
tumor. It seems that wild animals seldom live long enough to have
obstructions exert back pressure of urine to the extent which one is
accustomed to see in human medicine. Hydroureter and hydronephrosis have
not been seen.
Abscess of the kidney has occurred occasionally in the metastatic form
and only twice as the large destructive process such as is seen in the
human being (surgical kidney). One massive abscess was seen involving
about one-third of the organ, and this seems to have had a tuberculous
basis. Another destructive purulent nephritis was quoted on page 268
when illustrating compensatory hypertrophy.
Examination of records and preserved specimens of nephritis reveals few
striking differences which might be considered characteristic for the
various orders. This is possibly due to the fact that the lesions have
been classified under the same system, a method which has proven
convenient and consistent. In support of this one might refer to that
form of nephritis which gives the most definite clinical and
pathological picture of renal disease, namely the chronic
parenchymatous. This is fairly well represented in Primates, Carnivora
and Ungulata. In one-fourth of the cases one finds distinct edema,
especially in the body cavities, cervical and mediastinal tissues, and
in one-fifth an appreciable grade of anemia; uremia was the terminal
picture in one animal of each order.
HISTOLOGY OF NEPHRITIS.
An attempt to discover minute lesions peculiar to the various groups
gives results that are far from satisfactory. With reserve it may be
said that carnivorous animals show a tendency to greater interstitial
and glomerular lesions than do herbivorous ones, and that casts are more
often found, in all kinds of nephritis, in the former varieties. Rodents
are conspicuous exceptions to this statement, since they frequently have
glomerular lesions and casts in abundance; this exception exemplifies
the unwisdom of drawing definite conclusions in this respect.
Birds as contrasted with mammals show very prominent tubular and
inconspicuous glomerular lesions. The principal alterations seen in the
avian kidney are round cell infiltrations of the deep cortical and outer
medullary zones, and cloudy or hydropic swelling of the convoluted
tubules. In chronic cases intertubular fibrosis is clear but not so
definite as the perivascular, while the glomerular tufts are
occasionally wholly normal. When these are destroyed it seems to have
occurred by compression rather than by inflammation. A form of nephritis
peculiar to birds might be termed local necrotizing. It seems to be due
to local urate deposits and to have its origin like that form already
mentioned under acute interstitial nephritis. It has been seen in avian
gout, a condition in which the kidneys may or may not have visible
masses of hardened urates in them. The gross picture is of a spotty pale
organ of a gray-brown color. Minutely studied the medulla, adjacent
cortical tubules and perhaps the pelvic tissues will present an opaque
condition taking a diffuse basic dye. Crystals have not been seen. This
form is especially common in Columbæ, Psittaci and Herodiones.
GENERAL EFFECTS OF NEPHRITIS.
The results of nephritis generally speaking are edema, anemia, cardiac
hypertrophy, inflammations of the serous surfaces and uremia. Aside from
the cases of chronic parenchymatous nephritis cited above, edema has
been decidedly inconspicuous. It may be found in avian cases of acute
and subacute nephritis, about the flanks and in the thoracic areolar
tissues, but is only exceptionally perceptible before the body is
opened. Anemia is almost never extreme. The bone marrow although
mentioned in but few histories, seems unchanged. Cardiac hypertrophy was
observed ten times in 652 cases of nephritis, twice in 460 acute and
subacute cases, eight in 192 chronic cases. In the former no myocarditis
was found, in six of the latter it was found. Clinical and pathological
experience teaches that serous surfaces are frequently inflamed during a
nephritis. Observations on our material coincide with this statement,
but do not offer an explanation of it. The figures should be examined
for mammals and for birds separately, since the serous cavities of the
former are closed, separated, and protected, whereas a close apposition
exists between the serous membranes and the lungs in birds, an
arrangement facilitating infection from without. Nevertheless the bird
has definitely less serositis accompanying nephritis than does the
mammal—4.4 per cent., _versus_ 8.6 per cent. In the former class 70 per
cent. of these accompany acute nephritis associated with acute general
disease while only 45 per cent. of the 8.6 per cent. of mammals had
serositis, acute nephritis and general infection. This indicates clearly
that mammalian renal disease has some effect upon serous membranes other
than the simple participating coincidence of the two types of changes
during an acute general infectious disease. No one kind of nephritis was
especially characterized by this complication.
Uremia, except under the best clinical conditions, is a term to use with
caution. I have seen several monkeys, a few marsupials and carnivores
and an occasional bird in a dazed ataxic condition, sometimes exhibiting
an atypical clonic or tonic convulsion, with fixed, rather small pupils.
To this picture I have applied the name uremia, and upon several
occasions have found a severe grade of nephritis. I must admit having
failed to find renal change, however, with this clinical picture,
especially in the carnivores and parrots, animals which “throw fits” at
times without apparent good reason. In so far as the monkey is
concerned, I am satisfied that the picture is similar to that seen in
the human being. The London Garden reports in 1917 the occurrence of
uremia in a Mandrill (_Papio maimon_).
CALCULI.
Calculi are well known in the renal system of the domesticated animals
so that it is not surprising to find them well represented all through
the lower orders. Their structure, composition and effects do not
differ, however, and it remains only to point out their distribution.
One of the frequent results of renal and pelvic lithiasis is, however,
missing in our records, namely hydronephrosis, and indeed a pressure
dilatation of the ureter and pelvis has not been observed in all our
experience. This would seem to be explained first upon the infrequency
of stone, of obstructive new growths and inflammatory strictures and
second by the fact that lower animals do not long survive conditions
which would occasion back pressure upon the kidneys.
Definite renal and pelvic calculi have occurred in five Ungulata, one
each in Edentata and Steganopodes. To these might be added cases of
uratic sand in one Carnivora, one Marsupialia, and uratic stones of
large size in the cloaca of two Passeres and one Accipitres. Uratic
collections within the avian kidney have been mentioned and will be
discussed later.
According to written descriptions and three preserved examples the
calculi in four of the ungulates are mixed urates and carbonates,
although one in a deer was said to be “mulberry” in surface. The
specimens at hand are moderately hard with rough irregularly
crystallized outer shells like carbonate deposits. Incomplete moulding
to the calyx is found. The pelvic cavity while seeming to be enlarged is
not distended nor do the stones assume the “antler” character and
distort the pyramid. All the animals showing these stones have but a
single pyramid in the kidney. The fifth example in the ungulate had
early stones forming in the apex of the pyramid and not yet discharged
into the pelvis. Four of these cases showed stones on both sides, one
only in the left kidney.
The case among the Edentata concerned an Armadillo (_Tatu
novemcinctus_), in the kidney of which there were definite smooth,
round, hard pebbles in the right pyramid and several fine grains in the
pelvis. There was a recent hemorrhage in the pelvis which, from local
appearances and autopsy survey, was due to the lithiasis.
A Gannet (_Sula bassana_) represents the only avian true calculus. In
this case many small, hard, yellow stones occupied the right pelves,
which contained also loose urates. The lobules were much distorted and
showed a mild interstitial change. This accumulation was confined to the
left side. These well developed cases having been mentioned the next
most important may be quoted:
Tasmanian Devil (_Sarcophilus ursinus_). Inactive and rather on the
decline for several months. Chronic diffuse nephritis with acute
interstitial exacerbation. Calculi in kidney pelvis. The kidney size
is normal, shape irregular, capsule smooth, strips easily leaving a
rough mottled green-brown surface. Consistency is soft, tough,
resilient. Cortex slightly wide, medulla normal. On removal of capsule
the surface is found very irregular and elevations from the surface
are pale red gray-green color. These elevations do not correspond with
any change in cortex on section. Section is smooth, solid, markings
not clear but glomeruli are distincter than striæ. Line between cortex
and medulla obscure. The left kidney contains sand-like calculi,
possibly uratic, as there are some pale areas near point of pyramid
which are firmer than rest of tissue and rather gritty. Microscopic
section of kidney shows the architecture much disturbed by connective
tissue overgrowth in outer layers of medulla and inner layers of
cortex and following the medullary rays to the capsule. Tubules are
compressed and distorted in the vicinity mentioned. Epithelium is
elsewhere low, opaque and granular. The connective tissue about the
glomeruli is thickened and hyaline as it is in most other places.
Tufts are not yet compressed. Following medullary rays there is a
recent round and polynuclear infiltrate both around and in tubules.
A Golden Cat (_Felis temminicki_) presented sand in the urethra, which
had caused a traumatic urethritis and distention of the bladder. There
was no evidence of renal urate collections, but a low grade prostatitis
existed so that the bladder might have been distended before the urethra
became inflamed, thereby giving opportunity for sand to form or to have
arisen in the prostatic ducts.
Three birds, a Bunting (_Passerina ciris_), a Bulbul (_Chloropsis
aurifrons_), and a Buzzard (_Buteo albicaudatus_), had large cloacal
urate calculi which could obstruct the ureter but had failed to do so;
one had an acute ascending pyelonephritis, however.
Excessive urate collections in ureters and kidneys occur all through the
avian orders and in about the same percentages; meat and fish-eating
birds have practically no cases, however. The condition seems at times
the only finding at autopsy, or it may be associated with uratic
serositis. Gout of birds is commonly accompanied by it, but need not be
since two of the best examples of this disease had practically normal
kidneys.
From these records it would seem that renal and pelvic calculi occur
almost exclusively in herbivorous animals. At least true stones forming
in the renal pyramid and pelvis are found most characteristically
developed in the Ungulata, the typically herbivorous mammal. Judging by
the bilateral distribution of stones and uratic collections, local
processes, inflammation especially, have less to do with their
production than the availability of precipitable inorganic salts in the
urine.
TUMORS.
Tumors of the kidney have been observed sixteen times, fourteen of which
were primary and two secondary. The latter two concerned an
epitheliomatous metastasis from a malignant papilloma in the stomach of
a Kangaroo (_Macropus rufus_) and a sarcoma growing like an infarct
secondary to a mediastinal tumor in a Dorcas Goat (_Capra hircus_). The
only important primary tumor of the kidney in a mammal was found in a
Gray Squirrel (_Sciurus carolinensis pennsylvanicus_), a solid gray
nodule composed histologically of large and small deeply staining cells,
many containing large vacuoles and fitted with a small dark nucleus. The
arrangement of the elements was in irregular acini or bundles and
thereby suggested the tumor known as hypernephroma. A small nodular
adenoma was found at the upper end of the right kidney in a common
opossum (_Didelphys virginiana_) and seemed to be purely of renal
construction in that an attempt to retain tubular arrangement was
evident.
[Illustration:
FIG. 21.—CALCULI FROM RENAL PELVIS TO END OF URETHRA. COMMON RACCOON
(PROCYON LOTOR). THESE STONES WERE PALE YELLOW-GRAY. THEY CONSISTED
OF A URATIC BASE, BUT SOME PHOSPHATES AND CARBONATES WERE FOUND. THE
RIGHT KIDNEY WAS NOT AFFECTED. THERE WAS ONE IRREGULAR CALCULUS AND
THIRTY-SEVEN SMOOTH MASSES FROM BLADDER TO END OF PENIS. THIS CASE
IS NOT INCLUDED IN STATISTICS. OCCURRING AFTER THEIR COLLECTION HAD
CEASED.
]
Twelve primary tumors occurred in birds, and of these five were found
among parrakeets, they being curiously enough all of the same type.
These cases were all discovered in the undulated grass variety
(_Melopsittacus undulatus_ ♂ ♂ ♂ ♂ ♂ ) and, because of this fact and
their histological similarity, have excited interest. Grossly they are
irregularly nodular or lobulated tumors usually springing distinctly
from one lobe, but sometimes destroying the whole organ; they are soft,
resilient and hold their place well during manipulation. Sometimes one
may detect the topography of the renal lobes on cross section while at
other times the mass is homogeneous. Microscopically one finds the
structure of papillary adenoma with cystic formations or the production
of atypical solid nests of epithelia which would have to be called
cancerous, for they certainly make no attempts to retain acinus or duct
groupings. Carcinomatous areas have been discovered in two of these
cases, not in the other three, which have been called papillary adenoma.
One of the tumors was subjected to many sectionings and different
stainings techniques to discover, if possible, animal and vegetable
parasites; this search failed. One of these tumors produced hemorrhage
by rupture of a pyramid but extension to adjacent tissue and metastases
have not been seen. Pathologically these must be classified with the
tumors but because of the number of closely similar growths in the same
avian species housed in the same enclosure, the possibility of a
parasitic cause will not be forgotten.
The remaining seven renal neoplasms are made up of two adenomata in a
Jungle Babbler, (_Crateropus canorus_) and a red headed duck (_Fulligula
ferina americana_), two adenocarcinomata in a saffron finch ♀ (_Sycalis
flaveola_), and a chestnut-eared finch, ♂ (_Amadina castanotis_), two
hypernephromata in an American robin, ♀ (_Planesticus migratorius_) and
a European blackbird, ♀ (_Merula merula_), and a spindle celled sarcoma
on a scaly ground dove ♀ (_Scardapella squamosa_). One adenocarcinoma
sent out metastases to the lung, one hypernephroma had secondary growths
in the lungs, the other in the liver. The sarcoma case presented a
metastasis in the tibia.
Diseases of the lower parts of the urinary tract are not numerous and of
incidental interest only; many are associated with or due to lesions in
the genital organs, and will be referred to later. Cystitis is uncommon,
only being observed some four times unrelated to prostatitis and
vesiculitis. Two of these cases were secondary to a traumatic
urethritis. No stones have been seen. A mixed cell sarcoma was found
springing from the bladder wall in a Richardson’s Kangaroo Rat
(_Perodipus richardsoni_). The written record has unfortunately been
lost, but the preserved slide confirms the original diagnosis. Rupture
of the bladder occurred in a Gray Fox with stenosis of the end of the
penile urethra causing retention and secondary cystitis. Another
stricture of the urethra in an Ocelot (_Felis chibigonazon_) caused
great dilatation of the bladder. This animal is thought to have chewed
off all the external genitalia because of lice, with the result that the
stump of the urethra became involved in a contracting cicatrix.
Opossums, raccoons and wild dogs have shown light cases of urethritis
seemingly traumatic in origin, and two dogs had cystitis and urethritis
associated with what was believed to be distemper.