Clinical, clinicopathologic, radiographic, and ultrasonographic abnormalities in cats with ureteral calculi: 163 cases (1984-2002)

OBJECTIVE: To determine clinical, clinicopathologic, radiographic, and ultrasonographic abnormalities in cats with ureteral calculi. DESIGN: Retrospective study. ANIMALS: 163 client-owned cats. PROCEDURE: Medical records were reviewed, and information on signalment, history, clinical signs, and results of clinicopathologic testing and diagnostic imaging was obtained. RESULTS: The number of cats in which ureterolithiasis was diagnosed each year increased progressively during the study period. Clinical signs tended to be non-specific and included inappetence, vomiting, lethargy, and weight loss. A combination of survey radiography and abdominal ultrasonography revealed ureteral calculi in 66 of 73 (90%) cats in which the diagnosis was confirmed at surgery or necropsy. Ultrasonography revealed that ureteral calculi were causing ureteral obstruction in 143 of 155 (92%) cats. One hundred thirty-four of 162 (83%) cats had azotemia, 84 of 156 (54%) had hyperphosphatemia, and 22 of 152 (14%) had hypercalcemia. Urinary tract infection was documented in 10 of 119 (8%). Fifty-eight of 76 (76%) cats with unilateral ureterolithiasis had azotemia and 33 (43%) had hyperphosphatemia, indicating impairment of renal function in the contralateral kidney or prerenal azotemia. Ultrasonographic imaging of the contralateral kidney in cats with unilateral ureteral calculi suggested that preexisting renal parenchymal disease was common in cats with ureterolithiasis. Ninety-one of 93 (98%) ureteral calculi contained calcium oxalate. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that abdominal imaging should be performed in all cats with chronic nonspecific signs or with acute or chronic renal failure to rule out ureterolithiasis. Preexisting renal disease may be common in cats with ureteral calculi.     

Diagnosis and surgical management of ureteral calculi in dogs: 16 cases (1990-2003)

AIMS: To examine the clinical signs, laboratory and radiographic findings, surgical technique, ureterolith composition, and post-operative outcomes in dogs managed surgically for ureterolithiasis to determine whether surgical removal of ureteroliths in dogs resulted in a positive clinical outcome. METHODS: The medical record database of a university veterinary hospital in Pennsylvania, USA, was searched for dogs that underwent surgery to remove obstructive ureteral calculi between 1990 and 2003. Records were reviewed for signalment, clinical history and examination findings, radiographic and laboratory test results, surgical technique, and ureterolith analysis. Follow-up information was obtained from telephone interviews with owners or referring veterinarians, or by reviewing the medical record of subsequent hospital visits. RESULTS: Sixteen dogs were included in this study; ten were neutered females, two intact females and four castrated males. Abdominal radiography revealed ureteral calculi in 14/16 dogs, renal calculi in 8/16, cystic calculi in 8/16, urethral calculi in 1/16, renomegaly in 6/16 and renal mineralisation in 5/16. Ureterolith type included struvite in six dogs, calcium oxalate in five, calcium phosphate in one, and a mix of struvite, calcium phosphate and calcium oxalate in another. Compared to dogs with non-struvite ureteroliths, those with struvite ureteroliths had a higher pre-operative white blood cell (WBC) count (25.6, SD 7 vs 17.6, SD 6 x 103 cells/mul; p=0.046), and were more likely to have a purulent discharge from the ureteral incision noted at the time of surgery (p=0.015). Following discharge, 14/16 dogs were re-evaluated. Median survival time was 904 days (range 2-1,876). Two dogs required additional surgery on the urinary tract. Four dogs died or were euthanised because of azotaemia and clinical signs related to the urinary system or non-specific signs of illness (vomiting, lethargy) at 8, 90, 333 and 904 days post-operatively. CONCLUSIONS: Surgical management of ureteroliths was successful and resulted in good long-term survival in the majority of dogs examined in this small study population. Similar proportions of calcium oxalate and struvite ureteroliths were identified. CLINICAL RELEVANCE: The use of the ureteral surgery may increase as the frequency of diagnosis of ureteroliths in dogs increases.     

Evaluation of the Clinical and Histologic Features of Renal Allograft Rejection in Cats

OBJECTIVES: To describe the clinical signs and histopathologic features of renal allograft rejection in cats, and to provide a historical, untreated control group for use in future studies of feline renal allograft rejection. ANIMALS: Fourteen adult research cats. METHODS: Renal transplantation and bilateral nephrectomy were performed in pairs of immunogenically mismatched cats. A physical examination was performed, and packed cell volume, total protein, and plasma creatinine concentrations were measured each day after surgery. The cats were euthanatized when plasma creatinine concentration exceeded 7 mg/dL or when weight loss exceeded 20%. Renal histopathology was scored according to the Banff 97 criteria by 3 pathologists. RESULTS: Nine cats completed the study. Plasma creatinine exceeded 7 mg/dL in 5 cats, weight loss exceeded 20% in 3 cats, and 1 cat was found dead. Clinical signs in cats with rejection were nonspecific or absent. Rectal temperature decreased by 0.8 +/- 0.5 degrees C in the 24 hours before euthanasia. The pathologists agreed on the allograft histopathologic category in 6 of 9 cats. The histologic consensus was acute/active rejection in 8 cats and normal in 1 cat. Median survival time of the 8 cats with histologically confirmed allograft rejection was 23 days (range, 8-34 days). CONCLUSIONS AND CLINICAL RELEVANCE: Renal allograft rejection is associated with minimal clinical signs. Therefore, plasma creatinine concentration should be measured routinely in patients with a functioning allograft. An increase in plasma creatinine concentration is highly suspicious for allograft rejection, although a biopsy of the renal allograft is needed for definitive diagnosis.     

Hypercalcemia in cats: a retrospective study of 71 cases (1991-1997)

A retrospective study was conducted to characterize the diseases, clinical findings, and clinicopathologic and ultrasonographic findings associated with hypercalcemia (serum calcium concentration >11 mg/dL) in 71 cats presented to North Carolina State University Veterinary Teaching Hospital. The 3 most common diagnoses were neoplasia (n = 21), renal failure (n = 18), and urolithiasis (n = 11). Primary hyperparathyroidism was diagnosed in 4 cats. Lymphoma and squamous cell carcinoma were the most frequently diagnosed tumors. Calcium oxalate uroliths were diagnosed in 8 of 11 cats with urolithiasis. Cats with neoplasia had a higher serum calcium concentration (13.5 ± 2.5 mg/dL) than cats with renal failure or urolithiasis and renal failure (11.5 ± 0.4 mg/dL; P <.03). Serum phosphorus concentration was higher in cats with renal failure than in cats with neoplasia ( P < .004). Despite the fact that the majority of cats with uroliths were azotemic, their serum urea nitrogen and creatinine concentrations and urine specific gravity differed from that of cats with renal failure. Additional studies are warranted to determine the underlying disease mechanism in the cats we identified with hypercalcemia and urolithiasis. We also identified a small number of cats with diseases that are not commonly reported with hypercalcemia. Further studies are needed to determine whether an association exists between these diseases and hypercalcemia, as well as to characterize the underlying pathophysiologic mechanism for each disease process.     

Acute toxoplasmosis following renal transplantation in three cats and a dog.

Three cats and 1 dog that had undergone renal transplantation because of end-stage renal disease were examined because of complications 3 to 6 weeks after surgery. One cat died prior to treatment of the complications; Toxoplasma cysts were found in sections of the renal allograft, and Toxoplasma tachyzoites were found in other organs. The other 2 cats and the dog died despite treatment, and protozoal cysts, as well as tachyzoites, were identified in other organs but not within the allografts, suggesting that reactivation of latent infection following immunosuppression was the most likely cause of disseminated toxoplasmosis. These cases illustrate that toxoplasmosis can be a fatal complication in renal transplant recipients. We currently recommend that feline and canine donors and recipients undergo serologic testing for toxoplasmosis prior to surgery. In addition, we suggest that seropositive donors not be used for seronegative recipients and that seropositive recipients and that seropositive recipients be monitored closely after surgery for clinical signs of toxoplasmosis.     

Idiopathic hypercalcemia in cats

Unexplained hypercalcemia has been increasingly recognized in cats since 1990. In some instances, hypercalcemia has been associated with calcium oxalate urolithiasis, and some affected cats have been fed acidifying diets. We studied the laboratory findings, clinical course, and treatment of 20 cats with idiopathic hypercalcemia. Eight (40%) of the cats were longhaired and all 14 cats for which adequate dietary history was available had been fed acidifying diets. Clinical signs included vomiting (6 cats), weight loss (4 cats), dysuria (4 cats), anorexia (3 cats), and inappropriate urinations (3 cats). Hypercalcemia was mild to moderate in severity. and serum parathyroid hormone concentrations were normal or low. Serum concentrations of phosphorus, parathyroid hormone-related peptide, 25-hydroxycholecalciferol, and calcitriol were within the reference range in most cats. Diseases commonly associated with hypercalcemia (eg, neoplasia, primary hyperparathyroidism) were not identified despite thorough medical evaluations and long-term clinical follow-up. Azotemia either did not develop (10 cats) or developed after the onset of hypercalcemia (3 cats), suggesting that renal failure was not the cause of hypercalcemia in affected cats. Seven of 20 cats (35%) had urolithiasis, and in 2 cats uroliths were composed of calcium oxalate. Subtotal parathyroidectomy in 2 cats and dietary modification in 11 cats did not result in resolution of hypercalcemia. Treatment with prednisone resulted in complete resolution of hypercalcemia in 4 cats.     

Evaluation of erythropoiesis and changes in serum erythropoietin concentration in cats after renal transplantation

OBJECTIVE: To investigate the clinicopathologic patterns of the erythropoietic response after renal transplantation in cats with chronic renal failure (CRF). ANIMALS: 14 cats with CRF undergoing renal transplantation. PROCEDURE: Before and at intervals during a 6-month period after transplantation, serum creatinine and erythropoietin concentrations, Hct, erythrocyte indices, aggregate reticulocyte percentage, and iron variables were measured. Additionally, the number of transfusions administered to and any complications that developed in each cat were recorded. RESULTS: In all cats, preoperative azotemia resolved within 6 days after renal transplantation. Two cats had a temporary increase in serum creatinine concentration secondary to an acute graft rejection episode. Anemia (defined as Hct < 28%) resolved in 10 cats 3 to 49 days after surgery. Resolution of anemia was delayed in 2 cats that had acute rejection episodes. Serum erythropoietin concentration and reticulocyte percentage were low preoperatively; values after surgery were highly variable. Compared with preoperative values, serum erythropoietin concentration increased 1 to 4 days after surgery in 11 cats; between days 5 and 58, another increase was detected in 9 cats. Serum iron concentrations were generally low before and 14 days after transplantation. CONCLUSION AND CLINICAL RELEVANCE: The erythropoietic response was highly variable in cats after renal transplantation, but anemia typically resolved within 1 month after surgery. A delay in resolution of anemia in cats may indicate poor graft function and inadequate iron stores, suggesting the need for further evaluation for concurrent illness.     

Effects of diet on urine composition of cats with calcium oxalate urolithiasis

Ten client-owned cats with calcium oxalate (CaOx) urolithiasis were evaluated to determine the effect of diet on urine CaOx saturation. Two dietary treatments were evaluated in each cat: the diet consumed just prior to urolith detection and a canned diet formulated to prevent CaOx uroliths. This study revealed that hypercalciuria is a consistent abnormality in cats with CaOx urolith formation. When urolith-forming cats consumed a diet formulated to prevent urolith formation, activity product ratios for CaOx (which estimate the degree to which urine is saturated with CaOx) were significantly lower. These results suggest that consumption of an appropriately formulated urolith-prevention diet will reduce recurrence of CaOx urolithiasis.     

Renal transplantation for treatment of end-stage renal failure in cats.

Renal transplantation was performed as treatment of end-stage renal failure in 23 cats. Twenty-two cats had chronic renal disease and 1 cat had acute renal disease associated with ethylene glycol-induced toxicosis. Sixteen cats were discharged from the hospital. Nine survived a mean of 8.4 +/- 6.5 months, and 7 cats continue to survive at the time of this report (mean 12.6 months). Seven cats died within 2 weeks of surgery. All renal allografts were obtained from unrelated blood-crossmatch-compatible donors. No deaths were attributable to acute renal allograft rejection, demonstrating the successful maintenance of renal allografts by use of cyclosporine and prednisolone immunosuppression in cats.     

Hypophosphatemia in Cats After Renal Transplantation

Objective— To report the prevalence of hypophosphatemia after renal transplantation in a historical cohort of cats. Design— Case series. Animals— Cats (n=86) that received a renal allograft. Methods— Medical records (January 200–June 2006) were reviewed. Signalment, clinical signs, pre‐ and postoperative diet, pre‐ and postoperative clinicopathologic variables, renal histopathology, and outcome were retrieved. Prevalence, onset, duration, treatment and associated clinical signs of hypophosphatemia were recorded. A χ² test was used to compare hemolysis frequency between cats with normal serum phosphorus concentration or a single spurious low serum phosphorus concentration for <24 hours duration (group 1) and confirmed hypophosphatemia for >24 hours (group 2). A Cox proportional hazards model was used to evaluate the effects of hypophosphatemia on survival while controlling for other potentially confounding variables (age, sex, weight, body condition score, and pre‐ and 24 hours postoperative clinicopathologic variables). Results— Eighty‐six cats (mean age, 7.7 years) were identified. Hypophosphatemia occurred in 32 cats (37%), with a median onset of 2 days and median duration of 4 days. Treatment was initiated in 48 (56%) of hypophosphatemic cats. Survival and hemolysis frequency was not significantly different between groups, and no risk factors were identified. Conclusion— Hypophosphatemia occurs in cats after renal transplantation and does not affect survival. Clinical Relevance— The clinical importance of hypophosphatemia in renal transplant recipients remains unknown.     

Management of hypertension controls postoperative neurologic disorders after renal transplantation in cats

OBJECTIVES: To determine the prevalence and describe the management of hypertension and central nervous system (CNS) complications after renal transplantation in cats. We also compared the prevalence of CNS complications between cats monitored and treated for postoperative hypertension and a previously described, historical control group of cats not monitored or treated for postoperative hypertension. STUDY DESIGN: Retrospective clinical study. ANIMALS OR SAMPLE POPULATION: A total of 34 client-owned cats that received renal allografts for the treatment of end-stage renal failure. METHODS: Medical records were reviewed. Data obtained included preoperative and postoperative systolic blood pressures, antihypertensive therapy, response to treatment, neurologic signs, and clinical outcome. The results were compared with a historical control group of feline renal allograft recipients that were neither monitored nor treated for postoperative hypertension. RESULTS: Severe postoperative hypertension occurred in 21 of 34 of cats. Hypertension was treated in all 21 cats with subcutaneously administered hydralazine which reduced systolic blood pressure to less than 170 mm Hg in 15 minutes in 20 of 21 cats; hydralazine produced hypotension in one cat and failed to control hypertension in 1 cat. After transplantation, seizures were observed in one cat and other neurologic complications (stupor, ataxia, and central blindness) were observed in three cats. The prevalence of seizures and neurologic complication-related deaths after transplantation was significantly reduced with treatment of postoperative hypertension. CONCLUSIONS AND CLINICAL RELEVANCE: Hypertension is a major contributing factor to postoperative seizure activity after renal transplantation in cats; treatment of hypertension reduces the frequency of neurologic complications.     

Renal Calculi in Dogs and Cats: Prevalence, Mineral Type, Breed, Age, and Gender Interrelationships (1981–1993)

Three hundred seventeen specimens of urinary calculi of renal origin from 214 female dogs and 103 male dogs, and 71 specimens of urinary calculi of renal origin from 38 female cats and 33 male cats were submitted for mineral analysis between July 1, 1981, and December 31, 1993. Among dogs, 45 breeds were affected with renal calculi. Thirty-three breeds and a crossbred group were represented among females, but 8 breeds and the crossbred group accounted for 81% of the total. Among male dogs, 30 breeds and a crossbred group were represented, but 7 breeds and the crossbred group accounted for 69% of the total. Among cats, 10 breeds and a crossbred group were represented. Dogs and cats with renal calculi were older than those of 2 comparison population groups. More than one-half of the renal calculi in both dogs and cats were from the 1st known episode of urolithiasis. The risk of formation of renal calculi was found to be higher for cats than for dogs, when compared to other stone-forming cats and dogs (approximately 4.95 per 100 stone-forming cats and 2.88 per 100 stone-forming dogs). Among dogs, breeds at highest risk of developing renal calculi were Miniature Schnauzers, Shih Tzus, Lhasa Apsos, Yorkshire Terriers, and female Pugs. Also at high risk were male Dalmatians and male Basset Hounds. Among small dogs, females generally were at higher risk of developing renal calculi than were males. Regardless of size, terrier breed males generally were at higher risk of developing renal calculi. Breeds of dogs at low risk for development of renal calculi included crossbreds, German Shepherd Dogs, Labrador Retrievers, Golden Retrievers, and female Dachshunds. When only 1 kidney was involved, the risk of left renal calculus was greatest for both dogs and cats, but bilateral renal involvement was relatively common in both species (19% and 9%, respectively). Among dogs, specimens composed of 1 mineral substance (eg, struvite) occurred more often in males (58.3%) than in females (37.9%). Female dogs formed renal calculi containing struvite or oxalate more often than did males; males formed calculi containing urate more often than did females. Calculi containing oxalate, apatite, or some combination of these minerals predominated among cats; only 1 specimen from 38 female cats and only 4 specimens from 33 male cats contained neither oxalate nor apatite. Crossbred cats were significantly less likely to have renal calculi than were other breeds. A single renal calculus specimen was identified in several uncommon breeds including Tonkinese and Birman cats, and Affenpinscher, Clumber Spaniel, English Shepherd, and Field Spaniel dogs. No significant differences were observed between male and female dogs or between male and female cats with regard to mineral type of the specimen and the presence of urinary tract infection.     

Medical dissolution of feline struvite urocystoliths

The efficacy of a diet designed to facilitate dissolution of feline magnesium ammonium phosphate (struvite) uroliths was evaluated in 30 cases of urolithiasis, sterile struvite uroliths dissolved in a mean of 36 days after initiation of dietary treatment. In 5 cases of urolithiasis, struvite urocystoliths associated with urease-negative bacterial urinary tract infection dissolved in a mean of 23 days after initiation of dietary and antimicrobial treatment. In 3 cases of urolithiasis, struvite urocystoliths associated with urease-positive staphylococcal urinary tract infection dissolved in a mean of 79 days after initiation of dietary and antimicrobial treatment. Dissolution of uroliths in cats fed the treatment diet was associated with concomitant remission of dysuria, hematuria, and pyuria, and reduction in urine pH and struvite crystalluria. In one case, a urocystolith composed of 100% ammonium urate, and in another case, a urolith composed of 60% calcium phosphate, 20% calcium oxalate, and 20% magnesium ammonium phosphate did not dissolve.     

Pharmacokinetics of tacrolimus after multidose oral administration and efficacy in the prevention of allograft rejection in cats with renal transplants

OBJECTIVE: To describe pharmacokinetics of multi-dose oral administration of tacrolimus in healthy cats and evaluate the efficacy of tacrolimus in the prevention of allograft rejection in cats with renal transplants. ANIMALS: 6 healthy research cats. PROCEDURE: Cats received tacrolimus (0.375 mg/kg, PO, q 12 h) for 14 days. Blood tacrolimus concentrations were measured by a high performance liquid chromatography-mass spectrometry assay. Each cat received an immunogenically mismatched renal allograft and native kidney nephrectomy. Tacrolimus dosage was modified to maintain a target blood concentration of 5 to 10 ng/mL. Cats were euthanatized if plasma creatinine concentration exceeded 7 mg/dL, body weight loss exceeded 20%, or on day 50 after surgery. Kaplan-Meier survival curves were plotted for 6 cats treated with tacrolimus and for 8 cats with renal transplants that did not receive immunosuppressive treatment. RESULTS: Mean (+/- SD) values of elimination half-life, time to maximum concentration, maximum blood concentration, and area under the concentration versus time curve from the last dose of tacrolimus to 12 hours later were 20.5 +/- 9.8 hours, 0.77 +/- 0.37 hours, 27.5 +/- 31.8 ng/mL, and 161 +/- 168 hours x ng/mL, respectively. Tacrolimus treated cats survived longer (median, 44 days; range, 24 to 52 days) than untreated cats (median, 23 days; range, 8 to 34 days). On histologic evaluation, 3 cats had evidence of acute-active rejection, 1 cat had necrotizing vasculitis, and 2 cats euthanatized at study termination had normal appearing allografts. CONCLUSIONS AND CLINICAL RELEVANCE: Tacrolimus may be an effective immunosuppressive agent for renal transplantation in cats.     

Hypothermic Storage of Feline Kidneys for Transplantation: Successful Ex Vivo Storage Up to 7 Hours

Objective—To describe the effect of hypothermic storage on transplanted feline kidneys.
Study Design—Kidneys were stored in University of Wisconsin (UW) sodium gluconate (n = 3) or phosphate-buffered sucrose (n = 5) solutions before transplantation.
Animal Population—Eight cats with renal failure and seven normal cats as kidney donors.
Methods—Kidneys were perfused through the renal artery with cold (10°C) storage solution and immersed in the solution on ice until transplantation.
Results—Mean ex vivo storage time was 4.8 ± 0.36 hours (range, 3.5 to 7 hours). Seven recipient cats survived surgery. Five of the cats had decreased serum creatinine concentrations from a mean of 8.2 mg/dL (range, 4.0 to 15.8 mg/dL) preoperatively to 1.7 mg/dL (range, 1.3 to 2.2 mg/dL) within 4 days of surgery. In one cat, serum creatinine concentration dropped from 15.1 to 3.7 mg/dL in 3 days, but the cat developed a ureteral stricture that required revision. One graft did not function, and the cat died on day 19. The mean postoperative survival time of cats that were discharged from the hospital (n = 6) was 254 days (range, 49 to 717 days) at the time of this report. Long-term renal function (>60 days postoperatively; n = 5) was excellent with mean serum creatinine concentrations of 1.6 ± 0.15 mg/dL.
Conclusions—Hypothermic storage is feasible for short-term preservation of feline kidneys.
The maximal length of feasible storage remains unknown.
Clinical Relevance—Hypothermia protects against ischemia-induced nephron loss during ex vivo manipulation of the allograft and allows longer safe vascular anastomosis times. Short-term hypothermic storage also provides time to accommodate modifications in scheduling or anesthetic management of the recipient operation.     

Urolithiasis in 68 Horses

Medical records of 68 horses with urolithiasis were examined. Calculi were in the bladder in 47 horses, urethra in 11 horses, kidneys in 15 horses, and ureter in two horses. They occurred at several sites in six horses. Common clinical signs included hematuria, altered micturition (pollakiuria, dysuria, urinary incontinence), and tenesmus. Weight loss, possibly attributable to chronic renal failure and colic, was associated more commonly with renal and ureteral calculi. Weight loss also occurred in 13% of horses with cystic calculi only. In male horses, most cystic calculi were removed by perineal (ischial) urethrotomy under epidural anesthesia. Although there were few surgical complications with urethrotomy, seven of 15 horses with follow-up suffered recurrent urolithiasis.     

Evaluation of the prevalence of infections in cats after renal transplantation: 169 cases (1987-2003)

OBJECTIVE: To determine the prevalence of infections developing postoperatively, document the contribution of infection to increased risk of death, and identify risk factors associated with the development of infectious complications in cats after renal transplantation. DESIGN: Retrospective study. ANIMALS: 169 cats that received renal allograft transplants. PROCEDURES: Medical records of cats receiving renal transplants at the University of California from January 1987 through December 2003 were reviewed. RESULTS: 47 infections developed in 43 of 169 cats. Bacterial infections were most common (25/47 cats), followed by viral (13/47), fungal (6/47), and protozoal (3/47) infections. The median duration from transplant surgery to development of infection was 2.5 months. Infection was the second most common cause of death after acute rejection of the transplant, accounting for 14% of deaths overall. Cats with concurrent diabetes mellitus had a significantly increased risk of developing an infection after renal transplantation. Sex, increasing age, concurrent neoplasia, and previous treatment for transplant rejection were not associated with development of infection. CONCLUSIONS AND CLINICAL RELEVANCE: Infection was a common complication and an important cause of death or euthanasia in cats after renal transplantation. Development of diabetes mellitus after transplantation significantly increased the risk of infection.     

Ultrastructure of selected calcium oxalate-containing urinary calculi from dogs

OBJECTIVE: To elucidate the ultrastructural details of calcium oxalate-containing urinary calculi from dogs. Sample Population-38 specimens selected from a collection of 8,297 oxalate-containing urinary calculi from dogs: 22 specimens composed of calcium oxalate (calcium oxalate monohydrate [COM], calcium oxalate dihydrate [COD], or COM and COD) and 16 specimens composed of calcium oxalate with amorphous calcium phosphate. PROCEDURE: Analyses of specimens included use of plain, reflected, and polarized light microscopy, X-ray diffractometry, scanning electron microscopy (SEM) with backscattered electron (BSE) imagery, and electron microprobe analysis. RESULTS: Four texture types were observed in calcium oxalate calculi; 4 texture types of calcium oxalate-calcium phosphate-mixed calculi were recognized. Texture types were delineated through differences in calcium oxalate crystal sizes, which were affected by urine supersaturation and abundance of crystal nucleation sites. Segregation of calcium oxalate from calcium phosphate indicated they do not precipitate under the same conditions. Deposition of calcium phosphate between calcium oxalate crystals decreased the volume of pore spaces within calculi. Porosity was observed along boundaries between COM and COD. Minute pores increased the surface area of calculi exposed to urine, and this increase in liquid-solid interface promotes interaction of crystals with the surrounding urine. CONCLUSIONS AND CLINICAL RELEVANCE: Calcium oxalate urolithiasis is of major concern, because it is often a recurrent disease among dogs, principally treated by surgical removal of calculi, with few effective dissolution strategies. Understanding the ultrastructure and mineralogic content of calcium oxalate and its association with amorphous calcium phosphate is a step toward the solution of this increasingly important medical problem.     

Comparison of two surgical techniques for renal transplantation in cats

OBJECTIVE: To compare two surgical techniques for renal transplantation in cats with respect to graft warm ischemia time, total surgical time, operative and postoperative complications, and return to normal renal function based on measurement of plasma creatinine concentrations. STUDY DESIGN: Research study using normal cats. ANIMALS OR SAMPLE POPULATION: Fourteen adult, feline leukemia virus and feline immunodeficiency virus (FELV/FIV) negative, neutered male and spayed female cats. MATERIALS AND METHODS: Fourteen cats underwent heterotopic renal isograft transplantation with nephrectomy of the contralateral kidney. Renal arterial end-to-end anastomosis to the external iliac artery was performed in eight cats and renal arterial end-to-side anastomosis to the aorta was performed in six cats. Cats were monitored for 14 days after surgery. Renal function was evaluated by daily measurement of plasma creatinine concentrations. The cats' health was assessed by the daily recording of body weight, rectal temperature, postoperative complications, urine production, appetite, packed red blood cell volume, and total serum protein. Ultrasonographic assessment of the isograft was performed every third day. Animals were euthanatized or adopted 14 days after surgery and histopathologic analysis of biopsies or whole isograft tissues was performed. RESULTS: Nine of fourteen cats survived the 14-day study period. Although not statistically significant, mean total surgical time and graft warm ischemia time was shorter for the arterial end-to-side anastomosis. Mean daily plasma creatinine concentrations were not significantly different between the two groups. Five of eight cats (62%) undergoing the arterial end-to-end technique developed neuropraxia and lameness of the ipsilateral pelvic limb. Five cats died or were euthanatized because of other complications. CONCLUSIONS AND CLINICAL RELEVANCE: The arterial end-to-side technique appears to be the better method for renal transplantation in cats. Shorter graft warm ischemia and total surgical times, absence of pelvic limb complications, and an adequate return to normal renal function were associated with this technique.     

Hypercalcemia and calcium oxalate urolithiasis in cats: a report of five cases.

Five cats that presented for signs of lower urinary tract disease (i.e., pollakiuria and hematuria) secondary to a calcium oxalate urolithiasis are presented. On evaluation, all five cats had elevations of both serum ionized as well as total serum calcium. The hypercalcemia resolved after discontinuation of urinary acidifying therapy or a dietary change, or both.