SECTION VIII. The Urinary Tract

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.

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, 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 and of Alezais, 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 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 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 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.

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.