Canine calcium oxalate urolithiasis: Frequency of Whewellite and Weddellite stones from 1979 to 2015

This study reports on a retrospective evaluation of epidemiological data from calcium oxalate stones in dogs differentiated into calcium oxalate monohydrate (Whewellite, Wh) and calcium oxalate dihydrate (Weddellite, Wd). Of the 22 456 uroliths submitted from 1979 to 2015, 6690 (29.8%) were composed of > 70% calcium oxalate. During the observation period, the proportion of calcium oxalate stones rose from 4% (1979) to 46% (2015). Of all the calcium oxalate stones, 31.0% were Wh and 49.4% Wd, while 19.6% were a mixture of Wh and Wd. The dogs with Wh stones were significantly older than the dogs with Wd stones. Several breeds have increased odds ratios (OR) for either Wh (5 highest OR: Norwich terrier, keeshond, Norfolk terrier, fox terrier, sheltie) or Wd (Pomeranian, borzoi, Japanese spitz, Finnish lapphund, bichon frise). Analytical differentiation of the calcium oxalate stones into Wh and Wd is important for understanding the cause and possible treatment and prevention of the uroliths.

Dietary cation-anion difference may explain why ammonium urate nephrolithiasis occurs more frequently in common bottlenose dolphins () under human care than in free-ranging common bottlenose dolphins

Ammonium urate nephrolithiasis frequently develops in common bottlenose dolphins () managed under human care but is rare in free-ranging common bottlenose dolphins. In other species, the dietary cation-anion difference (DCAD) can affect ammonium urate urolith formation by increasing proton excretion as ammonium ions. Therefore, differences in diet between the 2 dolphin populations could affect urolith formation, but the DCAD of most species consumed by free-ranging and managed dolphins is unknown. To compare the nutrient composition of diets consumed by free-ranging and managed bottlenose dolphins, samples ( = 5) of the 8 species of fish commonly consumed by free-ranging bottlenose dolphins in Sarasota Bay, FL, and the 7 species of fish and squid commonly fed to managed bottlenose dolphins were analyzed for nutrient content. Metabolizable energy was calculated using Atwater factors; the DCAD was calculated using 4 equations commonly used in people and animals that use different absorption coefficients. The nutrient composition of individual species was used to predict the DCAD of 2 model diets typically fed to managed common bottlenose dolphins and a model diet typically consumed by common bottlenose dolphins in Sarasota Bay. To mimic differences in postmortem handling of fish for the 2 populations of bottlenose dolphins, "free-ranging" samples were immediately frozen at -80°C and minimally thawed before analysis, whereas "managed" samples were frozen for 6 to 9 mo at -18°C and completely thawed. "Free-ranging" species contained more Ca and P and less Na and Cl than "managed" fish and squid species. As a consequence, the DCAD of both model managed dolphin diets obtained using 3 of the 4 equations was much more negative than the DCAD of the model free-ranging bottlenose dolphin diet ( < 0.05). The results imply that managed bottlenose dolphins must excrete more protons in urine than free-ranging bottlenose dolphins, which will promote nephrolith formation. The nutrient composition of the free-ranging bottlenose dolphin diet, determined for the first time here, can be used as a guide for feeding managed bottlenose dolphins, but research in vivo is warranted to determine whether adding more cations to the diet will prevent urolith formation in managed dolphins.

Pathophysiological and physicochemical basis of ammonium urate stone formation in dolphins

PURPOSE

Nephrolithiasis is increasingly reported in bottle-nosed dolphins. All cases to date have been ammonium urate nephrolithiasis.

MATERIALS AND METHODS

A case-control study was performed in dolphins with and without evidence of nephrolithiasis to identify biomarkers and risk factors associated with stone formation in a managed population. Dolphins were sampled in fasting and postprandial states to study the effect of dietary factors on serum and urinary biochemistry. Urine was continuously collected for 6 hours via catheter and divided into 3, 2-hour collections with a bolus fish meal given after completing the first collection. Blood was sampled at the beginning of the fasting period and the end of the postprandial period.

RESULTS

There were no significant differences in serum and urine chemistry or acid-base profiles between dolphins with vs without stones at baseline or postprandially. This suggests that cases and controls represent a continuum of stone risk. On analysis combining cases and controls in a single cohort we noted significant postprandial increases in urinary uric acid, sulfate and net acid excretion accompanied by increased urinary ammonium excretion and a commensurate increase in urine pH. The supersaturation index of ammonium urate increased more than twofold postprandially.

CONCLUSIONS

These findings suggest that dolphins are susceptible to ammonium urate nephrolithiasis at least in part because a high dietary load of acid and purines results in a transient but marked increase in the urinary supersaturation of the sparingly soluble ammonium urate salt.

New alternatives for minimally invasive management of uroliths: nephroliths

Urolithiasis is a common clinical problem in small animal veterinary patients. Management of upper urinary tract calculi can be particularly challenging in small animals, as traditional surgical removal can be associated with significant morbidity. In humans, minimally invasive treatment options have replaced traditional surgical removal in many cases. This article reviews the current literature on the various types of lithotripsy and some of the newer minimally invasive options available for management of nephrolithiasis in small animal veterinary patients. An article in the January 2013 issue addressed management of lower urinary tract uroliths; a future article will discuss current management strategies for ureteroliths.

(99m)Tc-DTPA diuretic renal scintigraphy in dogs with nephroureterolithiasis

This study evaluated the results of diuretic renal scintigraphy in dogs with urolithiasis. Eighty-three kidneys with nephroureterolithiasis +/- renal pelvis/ureteral dilation were included in the study. Sixty-three kidneys showed a non-obstructive pattern, with a steep drop or gradual downward slope of renal time-activity curve (TAC). Excretion half-time of radiopharmaceutical (T(1/2)) was 3.99 (2.99 to 7.95) min. Three kidneys showed an obstructive pattern, with continuous rise of the TAC and median T(1/2) of -10.71 (-5.20 to -17.56) min. Fifteen kidneys had non-diagnostic studies characterized by flat TAC. Individual kidney glomerular filtration rate was <0.5 mL/min/kg body weight in most non-diagnostic studies. Diuretic renal scintigraphy appears to be a useful adjunct modality to rule out or confirm ureteral obstruction in dogs. Additional diagnostic procedures may be necessary to achieve a definitive diagnosis in cases of severely impaired renal function.

Hypocitraturia in common bottlenose dolphins (Tursiops truncatus): assessing a potential risk factor for urate nephrolithiasis

Numerous cases of urate nephrolithiasis in managed collections of common bottlenose dolphins (Tursiops truncatus) have been reported, but nephrolithiasis is believed to be uncommon in wild dolphins. Risk factors for urate nephrolithiasis in humans include low urinary pH and hypocitraturia. Urine samples from 94 dolphins were collected during April 2006 through June 2009 from 4 wild populations (n = 62) and 4 managed collections (n = 32). In addition, urine uric acid and pH were tested in a subset of these animals. Our null hypothesis was that wild and managed collection dolphins would have no significant differences in urinary creatinine, citrate, and uric acid concentrations and pH. Among urine samples from all 94 dolphins, the urinary levels (mean +/- SEM) for creatinine, citrate, uric acid, and pH were 139 +/- 7.6 mg/dL, 100 +/- 20 mg citrate/g creatinine, 305 +/- 32 mg uric acid/g creatinine, and 6.2 +/- 0.05, respectively. Of the 4 urinary variables, only citrate concentration varied significantly between the 2 primary study groups; compared with wild dolphins, managed collection dolphins were more likely to have undetectable levels of citrate in the urine (21.0% and 81.3%, respectively). Mean urinary citrate concentrations for managed collection and wild dolphin populations were 2 and 150 mg citrate/g creatinine, respectively. We conclude that some managed collections of dolphins, like humans, may be predisposed to urate nephrolithiasis due to the presence of hypocitraturia. Subsequent investigations can include associations between metabolic syndrome, hypocitraturia, and urate nephrolithiasis in humans and dolphins; and the impact of varying levels of seawater ingestion on citrate excretion.

Clinical relevance of urate nephrolithiasis in bottlenose dolphins Tursiops truncatus

Few cases of nephrolithiasis (renal calculi) have been reported in bottlenose dolphins Tursiops truncatus. A case-control study was conducted to compare ultrasonographic images and clinicopathologic serum and urine values among 14 dolphins with nephrolithiasis (mild cases: 1 to 19 nephroliths, n = 8; advanced cases: > or = 20 nephroliths, n = 6) to 6 controls over an 18 mo period. Archived nephroliths collected postmortem from 7 additional bottlenose dolphins were characterized using quantitative analysis. All advanced cases had bilateral nephroliths, and 67% had visible collecting ducts. During the study, 2 of the advanced cases developed hydronephrosis, and 1 of these cases had ureteral obstruction due to a nephrolith. Compared to controls, cases (mild and advanced) were significantly more likely to have anemia (hematocrit [HCT] < 38%), high blood urea nitrogen (>59 mg dl(-1)), high creatinine (>1.9 mg dl(-1)), and low estimated glomerular filtration rate (<150 ml min(-1) 2.78 m(-2)). Advanced-case urine samples were more likely to have erythrocytes, occult blood, and lower pH compared to mild cases and controls. Mean serum uric acid among all study groups was low (0.15 to 0.27 mg dl(-1)). Urinary uric acid concentrations were highest among mild cases (272 mg g(-1) creatinine), but advanced cases had levels lower than that of controls (40 and 127 mg g(-1) creatinine, respectively). All nephroliths were characterized as 100% ammonium acid urate. We conclude that nephrolithiasis is clinically relevant in dolphins and can decrease renal function and HCT. The presence of nephrolithiasis, presumably ammonium acid urate nephrolithiasis, in the face of low serum uric and relatively low urinary uric acid in advanced cases may indicate a metabolic syndrome similar to that reported in humans.

Calcium oxalate urolithiasis

Calcium oxalate (CaOx) uroliths are one of the most common urolith types in dogs, cats, and humans. Many factors predispose animals to CaOx uroliths, including breed, old age, obesity, male sex, being neutered, and certain diseases. Because there are no effective strategies for medical dissolution of these uroliths, management should focus on physical removal (by surgical or nonsurgical methods) and prevention, especially in patients with recurring uroliths, high-risk breeds, and animals with predisposing diseases. Prevention focuses on diet modification, primarily to increase water intake, and the appropriate use or avoidance of specific medications.

Obstructive urolithiasis, unilateral hydronephrosis, and probable nephrolithiasis in a 12-year-old Clydesdale gelding

A 12-year-old Clydesdale gelding was presented for colic and dysuria. Obstructive urolithiasis and chronic renal disease were diagnosed via transurethral endoscopy and percutaneous ultrasonography. Nephroliths, hydronephrosis, and peri-ureteral fibrosis were present. Surgical intervention was declined and the gelding was managed medically with antibiotics and dietary modification.

Urate nephrolithiasis in a northern elephant seal (Mirounga angustirostris) and a California sea lion (Zalophus californianus)

Nephrolithiasis has rarely been reported in marine mammals. During 2004 and 2005, two cases of nephrolithiasis were diagnosed during routine necropsy examination, one in a northern elephant seal (Mirounga angustirostris) and one in a California sea lion (Zalophus californianus). Nephroliths were found throughout both kidneys during necropsy examination, varying in size from 1-10 mm in diameter in the northern elephant seal and from 1-15 mm in diameter in the California sea lion. Necropsy and histopathology revealed nephroliths in association with renal pelvic dilation and pyelonephritis in both animals. In addition, hydronephrosis was noted in the sea lion. Nephroliths were composed of uric acid and ammonium urate in the northern elephant seal and of ammonium urate in the California sea lion. The underlying disease leading to nephrolith formation was not determined; however, it is hypothesized that unknown metabolic derangements due to morphologic or physiologic differences may have played a role. This is the first report of urate nephrolithiasis in the California sea lion and northern elephant seal.

A case-control study of the effects of nephrolithiasis in cats with chronic kidney disease

OBJECTIVE

To determine whether nephrolithiasis was associated with an increase in mortality rate or in the rate of disease progression in cats with naturally occurring stage 2 (mild) or 3 (moderate) chronic kidney disease.

DESIGN

Retrospective case-control study.

ANIMALS

14 cats with stage 2 (mild) or 3 (moderate) chronic kidney disease (7 with nephroliths and 7 without).

PROCEDURES

All cats were evaluated every 3 months for up to 24 months. Possible associations between nephrolithiasis and clinicopathologic abnormalities, incidence of uremic crises, death secondary to renal causes, and death secondary to any cause were evaluated.

RESULTS

There were no clinically important differences in biochemical, hematologic, or urinalysis variables between cats with and without nephroliths at baseline or after 12 and 24 months of monitoring. No associations were detected between nephrolithiasis and rate of disease progression, incidence of uremic crises, or death.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that in cats with mild or moderate chronic kidney disease, nephrolithiasis was not associated with an increase in mortality rate or in the rate of disease progression. Findings support recommendations that cats with severe kidney disease and nephrolithiasis be managed without surgery.

Renal cysts, nephrolithiasis, and ovarian cysts in a donkey suspected of having been sexually abused

A female donkey was thought by its owner to have been sexually abused because it had severe perineal swelling. Besides the perineal swelling and a very small vaginal erosion, there were no other abnormalities at clinical examination. Haematology and blood biochemistry revealed an increased leukocyte count, an elevated blood lactate concentration, and a low ionized calcium concentration. During night the donkey's condition deteriorated and it was euthanized in the morning. At necropsy severe haemorrhages were found within the subserosa of the caudal abdomen. Both kidneys were polycystic, and multiple calculi were found in the right kidney. Both ovaries had multiple cysts. Lesions (fibrosis and mineralization) were found in the liver, lungs, and mesenteric artery and were suggestive of an earlier parasitic infection. There was no evidence of sexual abuse.