Low Urine Specific Gravity Research Articles

Can Solid-Organ–Transplanted Patients Perform a Cycling Marathon? Trends in Kidney Function Parameters in Comparison With Healthy Subjects

BackgroundFew solid-organ–transplanted patients (TP) perform regular sport activity. Poor data are available on the safety of intense and prolonged physical exercise on this population. The aim of the study was to evaluate kidney function parameters in a group of TP in comparison with healthy volunteers (HV) involved in a long-distance road cycling race: length 130 km and total uphill gradient, 1871 m. MethodsNineteen TP were recruited: 10 renal, 8 liver, and 1 heart and compared with 35 HV. Renal function parameters, namely, creatinine, estimated glomerular filtration rate (eGFR), urea, uric acid, urine specific gravity, microalbuminuria, and proteinuria were collected and their values were compared the day before the race (T1), immediately after crossing the finish line (T2), and 18 to 24 hours after the competition (T3). ResultsNo adverse events were recorded. At baseline, TP showed lower values of eGFR (69 ± 22 versus 87 ± 13 mL/min/1.73 m2), lower urine specific gravity (1015 ± 4 versus 1019 ± 6), and higher microalbuminuria (56 ± 74 versus 8 ± 15) and proteinuria values (166 ± 99 versus 74 ± 44) (in mg/L). At T2 in both groups, renal function parameters showed the same trends: decline of eGFR (54 ± 19 versus 69 ± 15 mL/min/1.73 m2) and rise in protein excretion. At T3, functional parameters returned to baseline, except for urine specific gravity values remaining stable in TP (1018 ± 6) and growing higher in HV (1028 ± 4). ConclusionsSelected and well-trained organ-transplanted patients can perform an intensive exercise, displaying temporary modifications on kidney function parameters comparable to healthy subjects, despite differences related to baseline clinical conditions and pharmacological therapies.

Renal sonography in bipolar patients on long-term lithium treatment.

The aim of the study was to analyze sonographic (US) renal findings in lithium-treated bipolar patients and to correlate them with renal function. Renal US and renal function tests were performed on 120 patients with bipolar disorder. Ninety patients (30 males, 60 females), aged 36-82 years, had received lithium therapy for an average of 16 years, whereas 30 patients (10 males, 20 females), aged 35-85 years, who had never been exposed to lithium, served as controls. In the lithium-treated group, patients with macrocysts (22%) had poorer renal function with higher creatinine serum concentrations, lower estimated glomerular filtration rates, and lower urine specific gravity, compared with the patients without macrocysts. The US changes characteristic for lithium nephropathy (punctate hyperechoic foci, microcysts < 2 mm, and increased echogenicity) were seen in three patients. These patients had been treated with lithium for more than 20 years and had impaired renal function. Sixteen percent of patients in the control group had macrocysts; however, no correlation between their presence and impaired renal function was found. The presence of macrocysts in the kidneys of lithium-treated bipolar patients is associated with impaired renal function. The US changes characteristic for lithium nephropathy are rare, and in our study, were only found in patients treated with lithium for 20 years or more. © 2016 Wiley Periodicals, Inc. J Clin Ultrasound 44:354-359, 2016.

Cerebral Malaria: An Unusual Cause of Central Diabetes Insipidus.

Central diabetes insipidus is an uncommon feature of malaria. A previously healthy 72-year-old man presented with fever, rigors, and altered mental status after a recent trip to Liberia, a country known for endemic falciparum malaria. Investigations confirmed plasmodium falciparum parasitemia. Within one week after admission, the serum sodium rose to 166 mEq/L and the urine output increased to 7 liters/day. Other labs were notable for a high serum osmolality, low urine osmolality, and low urine specific gravity. The hypernatremia did not respond to hypotonic fluids. Diabetes insipidus was suspected and parenteral desmopressin was started with a prompt decrease in urinary output and improvement in mental status. Additional testing showed normal anterior pituitary hormones. The desmopressin was eventually tapered off with complete resolution of symptoms. Central diabetes insipidus occurred likely as a result of obstruction of the neurohypophyseal microvasculature. Other endocrinopathies that have been reported with malaria include hyponatremia, adrenal insufficiency, hypothyroidism, hypocalcemia, hypophosphatemia, hyper-, and hypoglycemia, but none manifested in our patient. Though diabetes insipidus is a rare complication of malaria, clinicians need to be aware of this manifestation, as failure to do so may lead to fatality particularly if the patient is dehydrated.

Does lower urine-specific gravity predict decline in renal function and hypernatremia in older adults exposed to psychotropic medications? An exploratory analysis.

BackgroundExposure to psychotropic agents, including lithium, antipsychotics and antidepressants, has been associated with nephrogenic diabetes insipidus (NDI). This is especially concerning in older adults already at risk of developing chronic kidney disease (CKD) and hypernatremia with advanced aging. This study investigates whether commonly performed random urine-specific gravity (USG) tests can predict adverse NDI outcomes (CKD and hypernatremia) in psychotropic-exposed older adults.MethodsThis was a retrospective longitudinal study of 173 geriatric psychiatry patients (age ≥65 years) exposed to psychotropic medications. Our main continuous outcome was ‘decrease in estimated glomerular filtration rate (eGFR) >10 mL/min/1.73 m2’ over 5-year follow-up. Hypernatremia and acute kidney injury (AKI) were secondary outcomes. Whether baseline USG <1.010 predicted outcomes was assessed in bivariate and multivariate analyses.ResultsUSG <1.010 predicted hypernatremia episodes (sodium concentration ≥150 mmol/L—28.1 versus 12%, χ2 = 4.7, P = 0.03). USG <1.010 [odds ratio 2.36 (95% confidence interval 0.93–6.0), P = 0.07], baseline eGFR and typical antipsychotic use independently predicted decrease in eGFR >10 mL/min/1.73 m2. Patients with a single baseline sodium concentration of ≥140 mmol/L and USG <1.010 have a 26.3% incidence of AKI and a 57.9% incidence of hypernatremia over the ensuing 5 years.ConclusionsIn psychotropic-exposed older adults, there appears to be a clinically important association between low USG and developing both hypernatremia and CKD. USG may be a useful surrogate measure for NDI-related outcomes in large administrative database studies, where ideal measures such as 24-h urine volume may not be available.

Diagnostic Accuracy of Urine Protein/Creatinine Ratio Is Influenced by Urine Concentration

BackgroundThe usage of urine protein/creatinine ratio to estimate daily urine protein excretion is prevalent, but relatively little attention has been paid to the influence of urine concentration and its impact on test accuracy. We took advantage of 24-hour urine collection to examine both urine protein/creatinine ratio (UPCR) and daily urine protein excretion, with the latter as the reference standard. Specific gravity from a concomitant urinalysis of the same urine sample was used to indicate the urine concentration.MethodsDuring 2010 to 2014, there were 540 adequately collected 24h urine samples with protein concentration, creatinine concentration, total volume, and a concomitant urinalysis of the same sample. Variables associated with an accurate UPCR estimation were determined by multivariate linear regression analysis. Receiver operating characteristic (ROC) curves were generated to determine the discriminant cut-off values of urine creatinine concentration for predicting an accurate UPCR estimation in either dilute or concentrated urine samples.ResultsOur findings indicated that for dilute urine, as indicated by a low urine specific gravity, UPCR is more likely to overestimate the actual daily urine protein excretion. On the contrary, UPCR of concentrated urine is more likely to result in an underestimation. By ROC curve analysis, the best cut-off value of urine creatinine concentration for predicting overestimation by UPCR of dilute urine (specific gravity ≦ 1.005) was ≦ 38.8 mg/dL, whereas the best cut-off values of urine creatinine for predicting underestimation by UPCR of thick urine were ≧ 63.6 mg/dL (specific gravity ≧ 1.015), ≧ 62.1 mg/dL (specific gravity ≧ 1.020), ≧ 61.5 mg/dL (specific gravity ≧ 1.025), respectively. We also compared distribution patterns of urine creatinine concentration of 24h urine cohort with a concurrent spot urine cohort and found that the underestimation might be more profound in single voided samples.ConclusionsThe UPCR in samples with low or high specific gravity is more likely to overestimate or underestimate actual daily urine protein amount, respectively, especially in a dilute urine sample with its creatinine below 38.8 mg/dL or a concentrated sample with its creatinine above 61.5 mg/dL. In particular, UPCR results should be interpreted with caution in cases that involve dilute urine samples because its overestimation may lead to an erroneous diagnosis of proteinuric renal disease or an incorrect staging of chronic kidney disease.

Effects of protein addition to carbohydrate–electrolyte solutions on postexercise rehydration

Background/ObjectiveThis study aimed to examine the effects of the addition of whey or casein protein, the two major proteins in milk, to carbohydrate–electrolyte (CE) solutions on postexercise rehydration. MethodsTen young men aged 20.7 ± 1.4 years with an average VO2max of 60.7 mL/kg/min ran for 60 minutes at 65% VO2max on three occasions followed by 4 hours' recovery. During recovery, the participants consumed either CE solution with 66 g/L carbohydrate (CHO), or CE plus whey protein solution (CW trial, 44 g/L CHO, 22 g/L whey), or CE plus casein protein solution (CC trial, 44 g/L CHO, 22 g/L casein); the solutions were matched for energy and electrolyte content. ResultsThe participants lost 2.36 ± 0.32% of their pre-exercise body weight after the exercise. Total urine output after recovery was greater in the CE and CC trials than CW trial (CE vs. CW vs. CC: 1184 ± 378 mL vs. 1005 ± 214 mL vs. 1256 ± 413 mL; p < 0.05). Fluid retention after ingestion of CW solution was greater than CE and CC solutions (CE vs. CW vs. CC: 46.9 ± 16.5% vs. 54.9 ± 9.2% vs. 45.8 ± 17.3%; p < 0.05). Lower urine specific gravity and urine osmolality were observed by the end of recovery in the CE trial compared with CW trial (p < 0.05). No difference was found in the changes in plasma volume in all trials. ConclusionThese results suggest that during the 4 hours' recovery after a 60-minute run, the CW solution was more effective for rehydration compared with the CE or CC solution.

Tubulointerstitial nephritis antigen expression in chronic kidney disease and its clinical significance

To explore tubulointerstitial nephritis antigen (TIN-ag) expression of chronic kidney disease (CKD) patients' renal tissue and the correlation to clinical phenotype. Through digital drawing lots, a total of 77 CKD patients from October 2012 to February 2013 at our department were randomly selected. All of them underwent biopsy. Based upon their pathological findings, they were divided into 2 groups of minimal change disease (MCD) and non-minimal change disease (NMCD). The stains of hematoxylin and eosin and Masson were used to observe renal pathological changes and immunofluorescence for detecting the TIN-ag expression of kidney tissue. The serum levels of creatinine, blood urea nitrogen, estimated glomerular filtration rate (eGFR), 24-hour urine output, 24-hour urine protein, α1-microglobulin, β2-microglobulin, pathological casts, N-acetyl-beta-glucosaminidase (NAG), specific gravity and other clinical parameters were monitored to examine their relationship between renal tissue TIN-ag expression. TIN-ag expression was distinct in renal tubular basement membrane of MCD patients while weak in primary focal segmental glomerulosclerosis (FSGS)(n = 16), IgA nephropathy (n = 23), MN (n = 14) and LN (n = 15) renal tissue. Immunofluorescence quantitative analysis showed that tubular TIN-ag fluorescence intensity of NMCD group was significantly lower than that of MCD group (4.84(3.02, 10.73) vs 20.79(8.19, 37.00), P < 0.01). In addition, TIN-ag expression in renal interstitial collagen area deposition of 0 grade group was higher than that of collagen area deposition 1-3 grades group (all P < 0.05). Serum α1-microglobulin and pathological urine cast, 24-hour urine protein of CKD patients were negatively correlated with kidney tubules TIN-ag expression (r = -0.312, -0.298, -0.214, all P < 0.05). Serum creatinine, blood urea nitrogen, serum β2-microglobulin and eGFR of CKD patients had no significant correlations with TIN-ag expression (P > 0.05). TIN-ag expression of CKD patients with lower expression levels of NAG was significantly higher than that of normal levels of NAG expression. TIN-ag expression of low urine specific gravity group was lower than that of normal urine specific gravity group (P < 0.05). TIN-ag expression of renal tissue tubule basement membrane in NMCD group is significantly lower than that in MCD group. TIN-ag expression is negatively correlated with renal tissue fibrosis. Expression of serum α1-microglobulin and concentrations of urinary pathology tube, 24-hour urine protein, NAG expression and urine specific gravity are negatively correlated with renal tissue TIN-ag expression in CKD patients.

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Introduction: 16 year old female with history of depression was brought to our hospital after an intentional overdose of carbamazepine. The patient was found lying by the side of the bed in an unresponsive state. Patient's mother found approximately twenty (200 mg each) carbamazepine pills missing from her step-brother's medication bottle. EMS brought the girl to the emergency department. Enroute to the hospital, a dose of diphenhydramine was given for dystonic posturing. Carbamazepine level upon admission was 24.1mcg/ml and a CT scan of the brain was reported normal. EKG shows borderline QRS widening with possible right bundle branch block. Echocardiogram and cardiac enzymes were normal. She was started on activated charcoal and received multiple doses during her hospital stay. Two hours following the admission the child was intubated and placed on a mechanical ventilator for decreased sensorium. Sodium bicarbonate was added to intravenous fluids to correct metabolic acidosis. The carbamazepine levels were monitored every six hours and at six hours after the admission the level was 34.5 mcg/ml and decreased to 4.2 mcg/ml in three days. Urine toxicology screen was negative. On day two of admission, the patient was polyuric with urine output at 7ml/kg/hr with negative fluid balance of 3398 ml over a 12-hour period. Possibility of diabetes insipidus considered and work up was sent. Laboratory data showed hypernatremia (160 mEq/L) and serum hyperosmolality (329 mosm/kg) with a urine osmolality of 459 mosm/kg and a urine specific gravity of 1.000. Appropriate fluid therapy was initiated and hypernatremia corrected over next 48 hours and urine output normalized. Child was discharged from the PICU with normal electrolyte and acid-base balance, cardiovascular and neurologic condition. Although the fluid balance was positive for first 24 hours she never developed hyponatremia. The lowest sodium concentration during her stay was 141 mEq/L. Discussion Carbamazepine is a commonly used medication in children with seizure disorders. It shares structural similarity with tricyclic antidepressants. Carbamazepine toxicity mainly manifests with neurological and cardiac side effects. Rare but life threatening adverse reactions includes agranulocytosis, bone marrow suppression, multiorgan hypersensitivity reactions (DRESS- Drug rash with eosinophilia and systemic symptoms). Among the other uncommon side effects include hyponatremia due to inappropriately excess anti diuretic hormone secretion (SIADH) and abnormal thyroid function. SIADH characterized by hyponatremia, low serum osmolality and oliguria. SIADH state due to carbamazepine was thought to be by two mechanisms by increasing endogenous antidiuretic hormone (ADH) release and by increasing the sensitivity of renal tubules to the ADH. Carbamazepine is used to treat patients with central or lithium induced diabetes insipidus. However, our index patient developed transient diabetes insipidus (DI). High urine output, hypernatremia, low urine osmolality compared to plasma and low urine specific gravity suggest DI in our patient. Urine output decreased to normal range within 24 hours after the onset of diuresis without the use of vasopressin. The mechanism of development of DI is not known. Whether the DI was of central or peripheral in origin could not be determined in our patient. Conclusion SIADH is a commonly reported endocrine complication of carbamazepine toxicity. To our knowledge we are presenting the first case of transient diabetes insipidus with carbamazepine toxicity. The mechanism of development of DI with carbamazepine is not known.

Novel markers of kidney injury in bipolar patients on long‐term lithium treatment

We assessed kidney function in long-term lithium-treated bipolar patients compared with age-matched patients not taking lithium, including novel markers of kidney injury such as plasma neutrophil gelatinase-associated lipocalin (NGAL) and urinary beta-2 microglobulin (β2-MG) METHODS: The study comprised 120 patients with bipolar disorder of which 90 (30 males and 60 females) have been receiving lithium for 5-38 (mean 16) years, and 30 (10 males and 20 females) have never been exposed to lithium. Lithium-treated patients, both men and women, showed significantly higher plasma NGAL and urinary β2-MG and lower urine specific gravity and estimated glomerular filtration rate (eGFR), compared with patients not taking lithium. In these patients, serum NGAL did not correlate with any clinical feature or other parameter of kidney function. Urinary β2-MG correlated with serum creatinine and eGFR in the whole group of lithium-treated patients and in addition, in males, with duration of illness, duration of lithium treatment, and urine specific gravity. Lithium treatment causes an impairment of kidney function reflected also by abnormal levels of novel markers of kidney injury. Of these, urinary β2-MG, as a marker of tubular function seems to be better predictor than serum NGAL in lithium-treated patients because it shows multiple clinical and biochemical correlations, especially in men.

Suspected carprofen toxicosis caused by coprophagia in a dog

A 1-year-old spayed female mixed-breed dog was evaluated because of urinary incontinence, polyuria, polydipsia, and minimally concentrated urine. Markedly high circulating alanine transaminase activity, mildly high circulating alkaline phosphatase activity, and low urine specific gravity were detected for the dog. Results of ultrasonographic examination of the abdomen and cytologic examination of liver samples were unremarkable. Carprofen was detected in serum and plasma samples obtained from the dog. Exposure to carprofen was attributed to ingestion of feces of another dog in the household that was receiving the drug daily. Access to feces of other dogs in the household was prevented; no other treatment was initiated. Urinary incontinence, polyuria, and polydipsia resolved, and urine specific gravity increased within 7 days following discontinuation of consumption of feces. Alanine transaminase activity was substantially lower than the value determined during the initial examination, and alkaline phosphatase activity was within the reference range 5 weeks after discontinuation of consumption of feces by the dog. Findings for the dog of this report suggested that carprofen toxicosis can be caused by consumption of feces of another dog receiving the drug. This cause of adverse effects should be a differential diagnosis for dogs with clinical signs and clinicopathologic abnormalities consistent with carprofen toxicosis.

A Rare Case of MRI Negative Pituitary Germinoma

To the Editor: Magnetic resonance imaging (MRI) is the preferred imaging modality to evaluate pituitary tumors; however a normal MRI scan has to be interpreted with caution. We present a case of pituitary germinoma with a normal MRI at presentation. A 15-y-old boy was evaluated for short stature, polyuria and polydipsia in our clinic. Family history was unremarkable. Patient’s height at 6 y was 105.6 cm (5th percentile), at 13 y 128.75 cm (3rd percentile) and, at 15 y was 133.1 cm (<3rd percentile). Physical exam showed sparse pubic hair and small testes (Tanner stage 2). Laboratory evaluation revealed low IGF-1, normal thyroid function tests, elevated sodium and low urine specific gravity. Bone agewas delayed by 4 y.MRI of the brain and pituitary was normal (Fig. 1a). Patient was diagnosed with diabetes insipidus (DI) and growth failure and started on desmopressin acetate (DDAVP) and growth hormone therapy. The patient’s symptoms resolved and he grew 13 cm. Three years later he presented with fatigue and declining school performance. Physical exam showed small testes (Tanner stage 3). Hormonal evaluation showed a low free T4 and mildly elevated TSH. Thyroid hormone replacement and short duration (3-mo) testosterone therapy were started. Repeat MRI of the brain and pituitary (Fig. 1b) showed pineal gland enlargement, pituitary stalk thickening (PST) and hyperintense lesions in the basal ganglia, internal capsule and corpus callosum. Biopsy revealed pituitary germinoma. Following 6 wk of external beam radiotherapy, repeat MRI showed near complete resolution of lesions. About 32 % of childhood DI cases are idiopathic however growth failure, presentation after age five and anterior pituitary deficiencies suggest an organic etiology of DI [1]. MRI findings in pituitary germinomas include PST, loss of posterior pituitary enhancement, and pituitary gland enlargement; however these are not sensitive or specific [2]. Mootha et al. recommended that patients presenting with apparent idiopathic DI receive pituitary MRIs every 3–6 mo for 1–2 y, then every 6 mo for 5 y to rule out a structural pituitary lesion [3]. Pituitary germinomas can be occult and nonspecific, therefore a comprehensive pituitary evaluation and follow up neuroimaging is essential for an accurate diagnosis.

Hypokalemic paralysis in a girl with dental and renal calculi: Questions

A 15-year-old Chinese girl presented to the emergency department with muscle paralysis of bilateral lower extremities over the course of 1 day. She had a 2-year history of polyuria, nocturia, and rampant dental caries and calculi. She denied vomiting, diarrhea, or use of alcohol, laxatives, or diuretics, and her family history was unremarkable. Her pulse rate was 90/min, blood pressure 112/72 mmHg, and body temperature 36.4 °C. Physical examination revealed severe dental caries and calculi (Fig. 1a) with dry oral mucosa. Her thyroid gland was not enlarged. Neurologic examination disclosed symmetric flaccid paralysis with areflexia of both lower extremities. The remainder of the physical examination was unremarkable. The most striking biochemical abnormalities were profound hypokalemia (1.8 mEq/l) and hyperchloremic metabolic acidosis (pH 7.28, HCO3 – 16.6, Na 141 and Cl 114 mEq/l). Her renal, liver, and thyroid function were all normal (creatinine 0.9 mg/dl). Urinalysis revealed proteinuria (1+), low urine specific gravity (1.010), high K excretion (transtubular K gradient 5, 24-h urine K 38 mEq/day), positive urine anion gap (Na 43, K 16 and Cl 39 mEq/l) and persistent alkaline urine (pH 7–7.5). Electrocardiogram revealed prolonged PR interval with flattened T wave. Abdominal ultrasonography showed bilaterally medullary nephrocalcinosis (Fig. 1b). Questions:

Evaluation of factors that affect analytic variability of urine protein-to-creatinine ratio determination in dogs

To determine whether preanalytic and analytic factors affect evaluation of the urinary protein-to-creatinine (UPC) ratio in dogs. 50 canine urine samples. The UPC ratio was measured to assess the intra-assay imprecision (20 measurements within a single session), the influence of predilution (1:10, 1:20, and 1:100) for urine creatinine concentration measurement, and the effect of storage at room temperature (approx 20°C), 4°C, and -20°C. The coefficient of variation at room temperature determined with the 1:20 predilution was < 10.0%, with the highest coefficients of variation found in samples with a low protein concentration or low urine specific gravity. This variability could result in misclassification of samples with UPC ratios close to the thresholds defined by the International Renal Interest Society to classify dogs as nonproteinuric (0.2), borderline proteinuric (0.21 to 0.50), or proteinuric (> 0.51). A proportional bias was found in samples prediluted 1:10, compared with samples prediluted 1:20 or 1:100. At room temperature, the UPC ratio did not significantly increase after 2 and 4 hours. After 12 hours at room temperature and at 4°C, the UPC ratio significantly increased. The UPC ratio did not significantly change during 3 months of storage at -20°C. The intra-assay precision of the UPC ratio was sufficiently low to avoid misclassification of samples, except for values close to 0.2 or 0.5. The optimal predilution ratio for urine creatinine concentration measurement was 1:20. A 1:100 predilution is recommended in samples with a urine specific gravity > 1.030. The UPC ratio must be measured as soon as samples are collected. Alternatively, samples should be immediately frozen to increase their stability and minimize the risk of misclassification of proteinuria.

Apparent Dexmedetomidine-Induced Polyuric Syndrome in an Achondroplastic Patient Undergoing Posterior Spinal Fusion

A 40-year-old achondroplastic patient underwent posterior spinal fusion under general endotracheal anesthesia. Anesthesia was maintained with isoflurane, and sufentanil, dexmedetomidine, and lidocaine infusions. Urine output increased from 150 mL/hr to 950 mL/hr the fourth hour. An increasing serum sodium, low urine-specific gravity, and increased serum osmolarity occurred simultaneously with the polyuria. Within 2 hours of discontinuing the dexmedetomidine infusion urine output greatly decreased. Within 24 hours all signs of the polyuric syndrome resolved spontaneously. Alpha(2) agonists block arginine-vasopressin release and action; however, a polyuric syndrome has not been reported in the human literature.

A Multicenter Retrospective Study of 151 Renal Biopsies in Horses

Renal biopsies are uncommonly performed in horses and little is known about their diagnostic utility and associated complication rate. To describe the techniques, the complication rate, risk factors, and histopathology results; as well as evaluate the safety and diagnostic utility of renal biopsy in the horse. One hundred and forty-six horses from which 151 renal biopsies were obtained. Animals ranged in age from 48 hours to 30 years. Multicenter retrospective study, with participation of 14 institutions (1983-2009). Renal biopsy in horses was associated with a similar rate of complications (11.3%) to that occurring in humans and companion animals. Complications were generally associated with hemorrhage or signs of colic, and required treatment in 3% of cases. Fatality rate was low (1/151; 0.7%). Biopsy specimens yielded sufficient tissue for a histopathologic diagnosis in most cases (94%) but diagnoses had only fair (72%) agreement with postmortem findings. Risk factors for complications included biopsy specimens of the left kidney (P = .030), a diagnosis of neoplasia (P = .004), and low urine specific gravity (P = .030). No association with complications was found for age, sex, breed, institution, presenting complaint, other initial clinicopathologic data, biopsy instrument, needle size, or use of ultrasonographic guidance. Renal biopsy in horses has low morbidity and results in a morphological histopathologic diagnosis in 94% of cases. However, this procedure might result in serious complications and should only be used when information obtained would be likely to impact decisions regarding patient management and prognosis.

Diagnostic utility and cost‐effectiveness of reflex bacterial culture for the detection of urinary tract infection in dogs with low urine specific gravity

Urinary tract infections (UTIs) may be subclinical or difficult to detect in dilute urine as sediment abnormalities may not be observed. In our laboratory, bacterial culture is automatically performed (reflex culture) on samples with urine specific gravity (USG)< or =1.013 to increase the likelihood of detecting infection. The value of routine culture of dilute urine, however, has not been fully assessed. The purpose of this retrospective study was to evaluate the frequency of positive bacterial cultures and analyze the diagnostic utility and cost-effectiveness of culture compared with routine sediment examination for detecting UTI in dilute urine specimens from dogs. Urinalysis and concurrent aerobic bacterial culture results were obtained from the electronic medical record system at the University of California-Davis Veterinary Medical Teaching Hospital for samples with USG< or =1.013 analyzed from July 1998 through January 2005. Urine collection method, presence of leukocytes and bacteria, bacterial culture results, and clinical diagnosis were recorded. Cost-effectiveness of reflex culture, based on low USG as the sole criterion, was evaluated. Of 1264 urine specimens, 106 (8.4%) had positive bacterial cultures. Using culture as the gold standard, sediment evaluation had a diagnostic sensitivity of 58.5% and specificity of 98.3% (diagnostic accuracy 94.9%). An additional cost of $60 per patient was incurred, leading to average annual costs of $11,668 for reflex bacterial cultures of all samples with low USG, regardless of collection method. Within our study population, 10 urine samples needed to be cultured for each true positive result. The sensitivity of urine sediment evaluation is low for UTI in dilute urine samples; however, reflex bacterial culture does not appear to be cost-effective in dogs with USG< or =1.013 in the absence of active urine sediment or high clinical suspicion for UTI.

Evaluation of serum cardiac troponin I concentration in dogs with renal failure

To determine whether dogs with renal failure have higher serum cardiac troponin I (cTnI) concentrations than healthy dogs. Case-control study. 31 dogs with renal failure and 51 healthy dogs. Serum concentrations of creatinine and cardiac troponin I, urine specific gravity, and systolic arterial blood pressure were measured for all dogs. Dogs underwent a standardized physical examination, and any dog with evidence of cardiovascular disease or other nonrenal disease was excluded from final analyses. Dogs were considered to be in renal failure when the serum creatinine concentration was >or= 3.0 mg/dL, urine specific gravity was between 1.007 and 1.030, and renal failure had been clinically diagnosed. Dogs with renal failure had significantly higher serum cTnI concentrations (median, 0.35 ng/mL) than did healthy dogs (0.20 ng/mL). The renal failure group also had a significantly higher median systolic blood pressure (156 mm Hg) than did healthy dogs (138 mm Hg), although serum cTnI concentration was not correlated with systolic blood pressure in dogs with renal failure. There was no significant difference in age between dogs with renal failure and healthy dogs, but dogs with renal failure had significantly higher serum creatinine concentration and lower urine specific gravity. Although dogs with renal failure did not have overt clinical signs of cardiac disease, they had high serum cTnI concentrations, which may have been associated with subclinical cardiovascular disease. The cause of the high serum cTnI concentration in these dogs requires additional investigation.

Occult bacterial lower urinary tract infections in cats—Urinalysis and culture findings

Bacterial urinary tract infections (UTIs) can be detected in feline urine submitted for urinalysis and culture as part of the diagnostic workup for a variety of conditions. Our aim was to investigate urinalysis and culture findings in urine specimens from cats with no history of lower urinary tract signs. Study inclusion criteria required cystocentesis specimens from cats with no history of lower urinary tract signs, inappropriate urination, or previous UTI (including pyelonephritis). Of 132 specimens, 38 were culture positive and 94 were culture negative. Culture positive urine specimens were more likely to come from older female cats ( p = 0.03, p < 0.001, respectively) and they had higher pH ( p = 0.001), erythrocyte ( p = 0.013) and leukocyte counts ( p = 0.003) than culture negative urine specimens. Gram-negative infected specimens ( n = 15) had lower urine specific gravity and higher leukocyte counts than Gram-positive infected specimens ( n = 21; p = 0.0012, p = 0.005, respectively) and culture negative specimens ( p = 0.003, p < 0.0001, respectively). Urine protein:creatinine ratio was higher in Gram-negative infected urine than in culture negative urine ( p = 0.013). Enterococcus faecalis was the most commonly isolated bacteria (19 of a total of 44 isolates; 43.2%) and E. coli phylogenetic group B2 was the most common Gram-negative isolate (14 of a total of 44 isolates; 31.8%). We conclude that feline bacterial urinary tract infections can occur in cats without lower urinary tract signs, particularly older females and that they are associated with high urine erythrocyte and leukocyte counts.

Central diabetes insipidus misdiagnosed as acute gastroenteritis in a pediatric patient

This case report describes an unusual presentation of nausea, vomiting and diarrhea, which was misdiagnosed as acute gastroenteritis in a 6-year-old girl. The patient later returned to the emergency department (ED) with severe dehydration from idiopathic central diabetes insipidus (DI). At her first visit, this previously healthy patient presented with mild dehydration, signs of acute gastroenteritis and normal urine output. Her brother had experienced similar symptoms a few days earlier. She tolerated an oral fluid challenge and was discharged from the ED with stable vital signs. Two days later, the patient returned with severe dehydration, resolving diarrhea and persistent vomiting. She was admitted to the pediatric intensive care unit. Magnetic resonance imaging illustrated an absent posterior pituitary enhancing signal, which demonstrated a loss of function in that region. There were no other abnormalities. The patient subsequently received desmopressin with improving clinical status and was discharged on the eighth hospital day. DI is a rare disease, but can be fatal if left undiagnosed. It should, therefore, be considered in the differential diagnosis of a dehydrated patient with an unexpectedly low urine specific gravity.

The value of urine specific gravity in detecting diabetes insipidus in a patient with uncontrolled diabetes mellitus

When a patient with diabetes mellitus presents with worsening polyuria and polydipsia, what is a sensible, cost-effective approach? We report the unique coincidence of type 2 diabetes mellitus and diabetes insipidus. A 46-year-old woman with poorly controlled type 2 diabetes complained of polyuria with a daily output of 5 L. Although urinalysis demonstrated significant glucosuria, diabetes insipidus was suspected owing to a low urine specific gravity (1.008). The low specific gravity persisted during a water deprivation test. Ultimately, diabetes insipidus was confirmed when urine specific gravity and urine osmolaity normalized following desmopressin administration. This case emphasizes the importance of accurately interpreting the urine specific gravity in patients with polyuria and diabetes mellitus to detect diabetes insipidus.