Renal pathology of the fowl--a review

Mesotocin receptor binding of cortical and medullary kidney tissues of the hen

[125I]Mesotocin (MT) binding of membrane fractions of the cortical tissue and the medullary tissue (medullary cone) of the kidney of nonlaying hens was measured by the use of radioligand binding assays to determine the distribution of two distinct MT receptors within the hen kidney. The binding to [125I]MT in the medullary tissue was found to be highly competitive with unlabeled MT. In the cortical tissue, the binding was competitive with both unlabeled MT and arginine vasotocin. Kinetic and Scatchard analyses of specific binding revealed that the binding affinity was higher in the cortical tissue than in the medullary tissue, but the binding capacity was less in the cortical tissue. The localization of two distinct MT receptor having different binding properties may be related to the biphasic action of MT within the tissue of the kidney of the hen.

Comparative pathology of a chicken-origin and two duck-origin influenza virus isolates in chickens: the effect of route of inoculation

Forty-nine 5-week-old chickens were inoculated by the intravenous (i.v.), intratracheal (IT), or intranasal (IN) routes with either a chicken-origin or one of two duck-origin type A influenza virus isolates. Twelve control chickens were inoculated with sterile chorioallantoic fluid. For all viruses, i.v. inoculation produced predominate lesions of renal tubule necrosis (nephrosis) and nephritis, and influenza virus nucleoprotein was localized in nuclei and cytoplasm of necrotic renal tubule epithelium. Chickens inoculated by the IT route, and to a lesser extent the IN route, had mild to severe tracheitis, bronchitis, and ventromedial pneumonia associated with secondary bronchi but lacked renal tubule necrosis and nephritis. These data indicate low-virulence avian-origin influenza viruses were nephrotropic during simulated systemic infection (i.v. inoculation) and pneumotropic during simulated local infection (IT and IN inoculation). Gross and histologic kidney lesions produced by i.v. inoculation of the chicken-origin influenza virus were similar to changes reported in outbreaks of low-virulence influenza virus in laying chickens.

Susceptibility of two commercial single comb White Leghorn strains to calcium-induced urolithiasis: efficacy of dietary supplementation with DL-methionine and ammonium sulphate

1. Susceptibility to calcium-induced urolithiasis was assessed in pullets of two commercial SCWL strains (A and B) reared together from 5 to 18 weeks of age on diets containing 10 g/kg calcium (normal calcium: NC) or 35 g/kg calcium (high calcium: HC). 2. Kidney damage was not observed in pullets reared on NC diets. For pullets fed on HC diets, strain A developed significantly greater kidney asymmetry, a higher incidence of gross kidney damage and a higher incidence of uroliths than strain B. 3. Supplementing the HC diet with 6 g/kg DL-methionine significantly reduced the incidence of calcium-induced gross kidney damage and urolith formation in both strains. Ammonium sulphate (5.3 g/kg) was significantly more effective than DL-methionine in reducing calcium-induced kidney damage. 4. Neither DL-methionine nor ammonium sulphate caused a measurable metabolic acidosis. Neither supplement consistently affected water consumption or manure moisture.

Liquid methionine hydroxy analog (free acid) and DL-methionine attenuate calcium-induced kidney damage in domestic fowl

To evaluate the possibility that kidney damage may be induced by the commercial practice of feeding high-Ca (HCa) prelayer rations, and to evaluate the protective efficacy of supplementing HCa diets with liquid methionine hydroxy analog free acid or DL-methionine, 12-wk-old female Single Comb White Leghorn pullets were fed one of the following corn-soybean meal-based diets until they reached 22 wk of age: normal-Ca (NC, 1% Ca); HCa (HC, 3.5% Ca); HCa supplemented with .34 or .68% liquid methionine hydroxy analog free acid (HC3A or HC6A); or HCa supplemented with .3 or .6% DL-methionine (HC3DL or HC6DL). The unsupplemented HC diet caused a significant reduction in kidney mass and a significant increase in the incidence of gross kidney damage and urolithiasis in pullets necropsied at 22 wk of age. Calcium-induced kidney damage was attenuated in a dose-response fashion by supplementing the HC diet with liquid methionine hydroxy analog and DL-methionine. None of the diets caused a significant metabolic acidosis. Plasma uric acid concentrations were not predictive of the extent of Ca-induced kidney damage. Analyses of glomerular size distributions indicated that subclinical or "hidden" kidney damage may not progressively develop into urolithiasis as hens mature. When compared with hens reared on the NC diet, rearing hens on the HC, HC3A, HC3DL, HC6A, or HC6DL diets did not consistently affect hen-day egg production, egg mass, eggshell mass, percentage eggshell, or bone mineralization.

Excess sodium bicarbonate in the diet and its effect on Leghorn chickens

1. A commercial 62-week-old layer flock experienced an acute drop in egg production and an increase in shell-less egg production within 2 days of consuming feed erroneously formulated to contain over 30 g/kg instead of 3 g/kg sodium bicarbonate (NaHCO3). Other symptoms included increased water consumption, diarrhoea and increased mortality associated with visceral gout. 2. An experiment was conducted to assess the responses of hens under controlled conditions. Twenty Dekalb XL Single Comb White Leghorn hens (50 weeks old) were placed in individual cages, having ad libitum access to water from trough waterers. Ten hens were fed the TEST (High NaHCO3) feed for one week (Test group), and ten hens remained on normal commercial layer ration (Control group). 3. Hens in the Test group had high water consumption and watery droppings, but egg production and mortality were not affected. Physiological evaluations indicated the Test feed caused metabolic alkalosis. Plasma sodium, urine pH and urinary sodium excretion were increased, and glomerular filtration rates were decreased in the Test group. 4. These physiological effects are consistent with known responses to excess sodium intake in domestic fowl. The reduced egg production and increased mortality caused by the Test feed under commercial conditions may be related to more severe dehydration experienced by hens in multi-bird cages supplied by cup-type watering systems.

Proviral rearrangements and overexpression of a new cellular gene (nov) in myeloblastosis-associated virus type 1-induced nephroblastomas

Histological and anatomopathological studies performed on 152 independent myeloblastosis-associated virus type 1 (MAV1)-induced nephroblastomas allowed us to precisely define the chronology of tumor development in chickens. Three tumors representing increasing developmental stages were used to construct genomic libraries and to study both the state of proviral genomes and the sites of MAV1 integration in genomic DNA. We established that increasing levels of proviral rearrangement, eventually leading to the elimination of infectious MAV genomes, were associated with tumor progression and that 22 individual tumors, representative of different developmental stages, did not contain any common MAV1 integration site. Cloning of cellular fragments flanking the MAV1-related proviruses in tumor DNA showed that each one of eight nephroblastomas tested expressed a high level of an as yet unidentified cellular gene (nov) whose transcription is normally arrested in adult kidney cells. Cloning of the normal nov gene established that in one tumor, fused long terminal repeat-truncated nov mRNA species were expressed, indicating that at least in that case, the high level of nov expression was under the control of the MAV long terminal repeat promoter. The normal nov gene encodes a putative 32-kDa secreted polypeptide, which is a member of a new family of proteins likely to be involved in cell growth regulation. We also showed that the expression of an amino-terminal-truncated nov product in chicken embryo fibroblasts was sufficient to induce their transformation.

Proviral rearrangements and overexpression of a new cellular gene (nov) in myeloblastosis-associated virus type 1-induced nephroblastomas

Histological and anatomopathological studies performed on 152 independent myeloblastosis-associated virus type 1 (MAV1)-induced nephroblastomas allowed us to precisely define the chronology of tumor development in chickens. Three tumors representing increasing developmental stages were used to construct genomic libraries and to study both the state of proviral genomes and the sites of MAV1 integration in genomic DNA. We established that increasing levels of proviral rearrangement, eventually leading to the elimination of infectious MAV genomes, were associated with tumor progression and that 22 individual tumors, representative of different developmental stages, did not contain any common MAV1 integration site. Cloning of cellular fragments flanking the MAV1-related proviruses in tumor DNA showed that each one of eight nephroblastomas tested expressed a high level of an as yet unidentified cellular gene (nov) whose transcription is normally arrested in adult kidney cells. Cloning of the normal nov gene established that in one tumor, fused long terminal repeat-truncated nov mRNA species were expressed, indicating that at least in that case, the high level of nov expression was under the control of the MAV long terminal repeat promoter. The normal nov gene encodes a putative 32-kDa secreted polypeptide, which is a member of a new family of proteins likely to be involved in cell growth regulation. We also showed that the expression of an amino-terminal-truncated nov product in chicken embryo fibroblasts was sufficient to induce their transformation.

The relationships between dietary crude protein, body weight, and fertility in naturally mated broiler breeder males

1. Naturally mated male broiler breeders were fed to achieve five levels of body weight gain on a high (160 g crude protein (CP)/kg) or low (110 g CP/kg) protein diet. Males were separately fed in 9 of the experimental treatments and fed with the females in the other. 2. There was an optimum body weight for maximum fertility which changed with age. The best fertility was shown by males weighing 3.2 kg at 26 weeks rising to 4.0 kg at 60 weeks of age. 3. The low protein diet was associated with higher fertility, particularly during the latter part of the breeding period (49-60 weeks). 4. Head width reached a plateau after 26 weeks of age and was 1 mm greater in males weighing more than 5 kg compared with males weighing 3 to 4 kg at 60 weeks of age.

Maturation of glomerular size distribution profiles in domestic fowl (Gallus gallus)

Previous histological evaluations of chick kidneys indicated nephrons continue to develop from embryonic foci for up to 6 weeks after hatching. The present study was conducted using an in vivo alcian blue staining technique to quantify posthatch changes in glomerular numbers and sizes in female domestic fowl at 1, 3, 5, 9, 12, 21, and 30 weeks of age. Changes in glomerular size distributions reflect changes in the heterogeneous nephron populations of avian kidneys. Foci of embryonic tissue were observed at the periphery of renal lobules up to 12 weeks of age. Glomerular numbers increased from 69,800/kidney at 1 week to 586,000/kidney at 12 weeks, with no further significant increase up to 30 weeks (599,000/kidney). The increase in glomerular number per gram kidney weight remained constant as kidney mass increased up to 12 weeks of age, after which the number of glomeruli per gram kidney weight declined significantly as kidney size increased without further addition of new nephrons. Glomerular size distribution profiles were constructed using eleven circumference categories. The peak number of glomeruli fell within the 0.11-0.14 mm category at 1 and 3 weeks; within the 0.15-0.18 mm category at 5, 9, and 12 weeks; and within the 0.19-0.22 mm category at 21 and 30 weeks. One and 3-week-old chicks had no glomeruli within the largest (greater than or equal to 0.35 mm circumference) size categories, and 9-12-week-old birds had significantly fewer glomeruli in these categories than 21-30-week-old birds. These results demonstrate that posthatch renal maturation in domestic fowl involves the ongoing formation of new nephrons up to 12 weeks of age, with subsequent kidney growth (12-30 weeks of age) accomplished by enlargement of existing nephrons (nephron hypertrophy). The cumulative evidence indicates that nephrons destined to develop loops of Henle (mammalian-type) develop first, with shorter (reptilian-type) nephrons developing later as the kidneys enlarge.

Effect of Gray strain infectious bronchitis virus and high dietary calcium on renal function of Single Comb White Leghorn pullets at 6, 10, and 18 weeks of age

Experiments were designed to evaluate the effects of Gray strain infectious bronchitis virus (IBV) and high dietary calcium (Ca), alone and in combination, on renal function in pullets. Eight hundred female Single Comb White Leghorn chicks were raised on starter ration. Five hundred chicks were inoculated intravenously with Gray strain IBV at 4 wk of age; the remaining chicks were not exposed to IBV. At 6 wk of age, IBV-inoculated and uninoculated chicks were randomly divided into two diet treatment groups. Half the chicks were fed commercial grower ration (approximately 1.0% Ca, .6% available P) and half were fed commercial layer ration (approximately 3.25% Ca, .5% available P). Birds remained on their respective diets until 18 wk of age. Kidney function studies were conducted on anesthetized birds at 6 wk of age prior to initiation of the diet treatments, at 10 wk of age, and at 18 wk of age. The layer ration increased Ca excretion, decreased inorganic phosphate excretion, and decreased urine hydrogen ion concentration in 10-wk-old pullets in comparison with the grower ration. These diet effects on kidney function were attenuated when the pullets reached 18 wk of age. The layer ration also caused an 11.5% incidence of urolithiasis, and significantly increased kidney asymmetry in 18-wk-old pullets relative to the effects of the grower ration. Gray strain IBV exposure significantly increased kidney asymmetry in 18-wk-old pullets, but had no gross effect on kidney function clearly related to the etiology of urolithiasis. Gray strain IBV did not enhance the incidence of urolithiasis in any of the age groups.

Strain differences in the number and size of glomeruli in domestic fowl

1. An investigation was made into strain differences and the effect of the type of drinker on the number and size of glomeruli of Single Comb White Leghorn pullets. 2. The Dekalb XL strain had more glomeruli per kidney and per g of kidney than the Hyline W-36. The glomeruli of the Dekalb XL were smaller in circumference. There were no significant differences in the absolute or relative weights of the kidney. 3. The type of drinker, bell or trigger-cups, had no effect on the body weight or those kidney variables studied.

Comparative nephropathogenicity of different strains of infectious bronchitis virus in chickens

Two-week-old White Leghorn chickens were injected intravenously with Australian T, Holte, Gray, and M 41 strains of infectious bronchitis virus. A total of 100, 90, 85, and 20% of the chickens infected with Australian T, Holte, Gray, and M 41, respectively, had variable degrees of nephritis. The Australian T strain induced the most rapid and the most severe kidney lesions followed by Holte, Gray, and M 41 in descending order.

Effect of dietary acidification on kidney damage induced in immature chickens by excess calcium and infectious bronchitis virus

Experiments were designed to evaluate the effect of dietary acidification on the development of kidney lesions induced by excess dietary calcium (Ca) and Gray strain infectious bronchitis virus (IBV). Specific pathogen-free (SPF) chicks and SPF chicks inoculated with Gray strain IBV were fed one of three diets: a commercial pullet grower ration (1% Ca); a commercial layer ration (3.25% Ca); or layer ration plus .5% ammonium chloride (acidified layer ration). Gray strain IBV significantly reduced total kidney weights in males, reduced total kidney weight as a percentage of body weight in males, increased the number of gross kidney lesions, and decreased the number of filtering nephrons when compared with uninoculated birds when both groups were fed the grower ration. The layer ration induced a 60% incidence of kidney lesions, caused a significant increase in kidney weight asymmetry ratios, and caused a 25% reduction in the number of filtering nephrons. Acidifying the layer ration significantly reduced the incidence of gross kidney lesions and reduced kidney weight asymmetry ratios, but did not prevent Ca-induced reductions in filtering nephrons.

Kidney function in domestic fowl with chronic occlusion of the ureter and caudal renal vein

A previously published technique for producing renal insufficiency in chicks involves ligating the caudal renal vein together with the ureter near the midpoint of the kidney. This ligation occludes the normal route (caudal renal vein) by which blood exits the medial and posterior kidney divisions. The present study was conducted to evaluate kidney function following chronic caudal renal vein and ureter occlusion. The ureters and caudal renal veins of 2 to 3-week-old chicks were clamped with hemostatic clips (Clamp Group), and kidney function evaluations were conducted when the birds reached 14 weeks of age. Plasma values [osmolality, Na, K, Ca, inorganic P (Pi)] of control, sham, and clamp groups did not differ significantly. Plasma uric acid concentrations did not differ when the control and clamp groups were compared. Clamping the ureter near the midpoint of the kidney caused a significant reduction in the number of filtering glomeruli per kidney, but due to compensatory hypertrophy the kidney weights of the groups did not differ significantly. Kidney function comparisons (urine flow rates, glomerular filtration rates, renal plasma flow rates, urine pH, fractional excretion of Na, K, Ca, Pi, and uric acid) revealed a significant reduction in Na and K excretion by the clamp group, but other renal function parameters did not differ significantly. These experiments demonstrate that chickens have a remarkable capacity to survive significant reductions in renal mass and to adapt to major disruptions of blood flow patterns.

Distribution and form of uranium-containing deposits in chickens treated with uranyl nitrate

The kidneys of chicks treated with uranyl nitrate were examined by electron microscopy. Most deposits of electron-dense material containing uranium were found in the lumina of distal tubules and collecting ducts of kidneys collected 12-24 hours post-treatment. Some deposits were present in extracellular spaces between adjacent cells. Only occasionally were deposits found intracellularly where they were associated with localized cellular degeneration. A generalized cellular degeneration over the whole kidney was seen 72-96 hours post-treatment, but this was not directly associated with the deposits of electron-dense material.

Characterization and composition of uroliths from domestic fowl

Urolithiasis (kidney stone formation) is an acquired degenerative kidney lesion affecting sexually mature and immature domestic fowl. For the present study, uroliths were collected from three commercial flocks during outbreaks of urolithiasis. Uroliths also were collected from a research flock in which urolithiasis was induced by feeding immature chickens a diet formulated to contain excess calcium (3.25% Ca) and .4% available phosphorus. All uroliths were tested by x-ray diffractometry, infrared spectrophotometry, and emission spectrography. With one exception, the stones were composed of compact masses of microcrystalline to fine pleomorphic crystals of calcium sodium urate, with random substitution of magnesium for calcium, and potassium for sodium. No initiating nidus was evident. One of four stones from one laying hen flock was positively identified as an ammonium acid (hydrogen) urate. The unique calcium-sodium-urate stone composition in all but one of the stones tested suggests that similar processes were involved in stone formation in the four different flocks.

Urolithiasis in pullets and laying hens: role of dietary calcium and phosphorus

A study was conducted to test the independent and combined effects of high dietary calcium and low available phosphorus on the incidence of urolithiasis in pullets and laying hens. One thousand Single Comb White Leghorn pullets were divided into four diet treatment groups beginning at 50 days of age. A normal calcium (1%), normal available phosphorus (.6%) diet (NCNP) was fed to control pullets. Other pullet groups were fed a high calcium (3.25%), normal available phosphorus (.6%) diet (HCNP), a normal calcium (1%), low available phosphorus (.4%) diet (NCLP), or a high calcium (3.25%), low available phosphorus (.4%) diet (HCLP). At 18 weeks of age, 368 pullets were necropsied. One percent of the HCNP group and 14% of the HCLP group developed urolithiasis. Urolithiasis was not found in pullets raised on the NCNP and NCLP diets. The remaining pullets were transferred to laying cages and were fed a commercial layer ration until they were 51 weeks old. None of the hens raised on the NCNP diet, 12% of the hens raised on the HCNP diet, 2% of the hens raised on the NCLP diet, and 14% of the hens raised on the HCLP diet had urolithiasis. Renal function studies were performed on 18-week-old pullets and 51-week-old hens. Pullets raised on the HCLP diet had significantly higher urine pH, significantly lower fractional inorganic phosphate excretion, and significantly higher fractional calcium excretion when compared with pullets raised on the other diet treatments. The profound effect of the HCLP diet on renal calcium and phosphorus excretion in pullets was not retained in the hens.(ABSTRACT TRUNCATED AT 250 WORDS)

Induction of urolithiasis in single comb white Leghorn pullets: effect on glomerular number

Urolithiasis was induced in an experimental group of Single Comb White Leghorn pullets by feeding them layer ration and exposing them to nephrotrophic Gray strain infectious bronchitis virus (IBV). Gray strain IBV was recovered from kidney and cloacal swabs for up to 26 days after exposure to the virus. Control pullets fed pullet grower ration and not exposed to Gray strain IBV did not develop urolithiasis. The experimental design did not allow differentiation between the roles of layer ration and IBV in triggering urolithiasis. Urolithiasis was associated with asymmetry in left vs. right kidney weight comparisons for individual pullets. Pullets from the urolithiasis group had 43,800 +/- 4,500 glomeruli/gram kidney weight, whereas control pullets had 68,770 +/- 3,500 glomeruli/gram kidney weight. This difference was significant (P less than .01). Total kidney weights did not differ significantly when the experimental and control pullets were compared. Comparisons of glomeruli size distributions indicated that the number of intermediate sized glomeruli (.15 to .22 mm in circumference) was significantly reduced in pullets from the urolithiasis treatment group. These observations indicate that a significant reduction in nephron number can be masked by compensatory hypertrophy of the remaining kidney tissue in pullets with urolithiasis.

A comparison of two techniques for determining glomerular size distributions in domestic fowl

Nephrons in the avian kidney have an extremely heterogeneous size distribution. The shortest nephrons have very small glomeruli, and the larger nephrons have very large glomeruli. Physiological, nutritional, and disease factors may be correlated with the functioning of different sized nephrons. The present study was conducted to compare two techniques for measuring glomerular size distributions. A postmortem India ink infusion technique gave results that were highly comparable to an in vivo alcian blue infusion technique. Single Comb White Leghorn pullets were found to have approximately 270,000 glomeruli per kidney; glomerular circumferences and diameters ranged between .07 to .42 mm and .02 to.14 mm, respectively. A unimodal size distribution was found, with most glomeruli falling within the circumference range of .15 to .26 mm. The alcian blue technique should provide a quantitative in vivo method for evaluating selective tubular damage or physiological glomerular intermittency.

Structure of the avian kidney

The kidneys from 6 domestic fowl were fixed in situ by perfusion from the left ventricle. In the bird there are two types of nephrons. One reptilian-type without Henle's loop and medullary tissue, and one mammalian-type with Henle's loop lying in medullary tissue. Serial sections from kidney tissue embedded in plexiglass or in paraffin were used to study the architecture of eight reconstructed reptilian-type nephrons from different cortical levels. All reconstructed nephrons had four major bends, but particularly in the subcapsular nephrons additional bends parallel to the kidney surface were found. There was no loop of Henle, but before entering the collecting duct the distal tubule usually had a very thin-walled segment. No proximal convoluted part was found in the reptilian-type nephrons. The length of the tubules varied between 3,000 microns and 6,000 microns. In the distal tubule a macula densa segment was found in all nephrons of the reptilian and mammalian type. The capillary network between the inter- and intralobular veins was composed of increasingly larger capillaries towards the intralobular vein. Segments of the distal tubule were indented into these capillaries and completely surrounded by them. In the nephrons of the mammalian type the proximal tubule was found to be convoluted as is usual for mammalian species.

Nephropathogenicity of infectious bronchitis virus

Four strains of infectious bronchitis virus (IBV) were compared in chickens as to nephropathogenicity. Two of the viruses were from the United States, one was from Australia, and one from Italy. Each has been described as nephropathogenic. The Australian strain proved to be most pathogenic and was then followed by the Italian strain and, finally, the two viruses from the United States. With an increase in the age of the chickens there was an apparent decrease in pathogenic effect. All of the viruses were highly pathogenic in the respiratory tract regardless of the age of the test birds. Kidney damage, or nephritis, was detected more readily on histological study rather than by gross examination. Each of the viruses was unrelated to the others when the sera were assayed by virus neutralization. Massachusetts and Connecticut IBV vaccines gave erratic, or only, partial protection against challenge form the respective viruses which confirmed their aberrant nature. Lesions of IBV infection in the respiratory tract did not necessarily correlate with the results from challenge virus recovery attempts. One Massachusetts-type IB vaccine strain, Holland IBV, proved capable of inciting nephritis under the conditions of this study and from inoculating specific-pathogen-free chickens at 2 days of age. The lower embryo passage of this strain proved more nephropathogenic than the higher ones. Other Massachusetts-type vaccine viruses and the Connecticut-type did not induce nephritis. The nephropathogenic potential for certain vaccine strains is discussed.

Hematological changes in nephritis in poultry induced by diets high in protein, high in calcium, containing urea, or deficient in vitamin A

Nephritis was induced in 300, 18-day-old male Arbor Acre broiler chicks by feeding diets high (42.28%) in protein, high (3.27%) in calcium, containing urea (5%), or deficient in vitamin A. Various hematological parameters were studied at weekly intervals. Normocytic-normochromic anemia, characterized by a decrease in total erythrocyte counts, hemoglobin, packed cell volume, and an increase in erythrocyte sedimentation rate, was evident in the birds kept on diets high in protein, high in calcium, or deficient in vitamin A. Increased total erythrocytes, hemoglobin packed cell volume, and erythrocyte sedimentation rate was observed in birds fed urea. Differential leucocyte counts revealed lymphopenia, heterophilia and monocytosis in birds kept on diets high in protein, containing urea, or deficient in vitamin A. However, lymphocytosis, heteropenia , and monocytosis were recorded in birds fed the high calcium diet.

Kidney function of pullets and laying hens during outbreaks of urolithiasis

Renal function evaluations were conducted on pullets and laying hens during outbreaks of urolithiasis. The following parameters were measured: kidney weights; hematocrits; plasma concentrations of uric acid, calcium, inorganic phosphate, magnesium, sodium, and potassium; urine flow rates; glomerular filtration rates; renal plasma flow rates; urine pH; and relative clearances of inorganic phosphate, calcium, magnesium, sodium, potassium, and para-amino hippuric acid. The adequacy of renal portal perfusion was estimated by timed phenol red extraction. Considerable interindividual variability was noted, presumably due to differences in age and reproductive status. Intraindividual left versus right kidney comparisons also were made, since urolithiasis often is associated with macroscopic lesions of one kidney but not the other. The results indicate that even when gross lesions of only one kidney were present, specific tubular transport processes were similar in both kidneys. Urolithiasis did cause significant alterations in urine flow rates, glomerular filtration rates and renal plasma flow rates. it was concluded that the changes associated with urolithiasis reflect the expected compensatory hypertrophic responses of surviving kidney tissue to a reduction of renal mass. The physiological impact of this form of kidney damage appears to arise from reduced renal mass rather than from inappropriate renal handling of minerals or electrolytes.