Is there a link between hyperbilirubinemia and elevated urine nitrite

OBJECTIVE

The aim of this study was to determine whether hyperbilirubinemia affects the association between a positive urine nitrite test and a positive urine culture.

METHODS

We conducted an institutional review board-approved, retrospective review of 12 months of patient data, compiling information for patients having urinalysis, urine culture, and total serum bilirubin. Patients were divided into 3 groups according to total serum bilirubin: less than 1.5 mg/dL, 1.5 to 3.0 mg/dL, and greater than 3.0 mg/dL. The point estimates and 95% confidence intervals of the sensitivity, specificity, false-positive proportion (proportion of false positive to all positive tests), and other test characteristics of urine nitrite as an indicator of urinary tract infection were calculated and tested for trend as a function of the 3 total serum bilirubin ranges.

RESULTS

Three thousand one hundred seventy-four patients met our study criteria. Specificity of the nitrite test decreased as a function of increasing total serum bilirubin (0.974, 0.966, and 0.855 for the 3 total bilirubin levels, respectively) with a significant trend (P < .0001). There was no significant trend in comparable sensitivity values (0.380, 0.417, and 0.241, respectively) with P = .55. The false-positive proportion also increased as a function of total serum bilirubin (17.5%, 17.3%, and 72.0%) with P < .0001. Thus, if a patient's total serum bilirubin was elevated to the point of jaundice (>3.0 mg/dL), it was approximately 4 times more likely that a positive urine nitrite test would be a "false positive" (ie, nitrite-positive/culture-negative) compared with those with normal serum bilirubin levels.

CONCLUSIONS

Specificity of the urine nitrite test for urinary tract infection decreases as a function of increasing serum bilirubin. Most patients with hyperbilirubinemia and a positive nitrite test in our sample did not have an associated urinary tract infection.

Comparison of urinary excretion of pravastatin and temocapril in bile duct-ligated rats and Eisai hyperbilirubinemic rats (EHBR)

BACKGROUND/PURPOSE

In patients with complete bile duct obstruction, the only pathway for the elimination of cholephilic compounds is through the urine. Although changes in various transporters in the liver and kidney in cholestasis have been elucidated, little is known about how effectively the elimination of these compounds is compensated for by urinary excretion.

METHODS

In the present study, the urinary excretion of pravastatin and temocapril was studied in bile-duct-ligated rats (BDLR) for 3 days and in Eisai hyperbilirubinemic rats (EHBR). After urinary bladder cannulation, radiolabeled pravastatin and temocapril were injected intravenously. Urine samples were collected every 1 h for 4 h, and the radioactivity was counted.

RESULTS

Urinary excretion of pravastatin was markedly increased in BDLR (85.9% of the dose after 4 h) and moderately increased in EHBR (35.9% of the dose after 4 h) compared with that in control rats (5.5% of the dose after 4 h). Similar but less prominent differences were observed with temocapril after it was administered (50.7%, 38.2%, and 22.0% of the dose after 4 h in BDLR, EHBR, and the controls, respectively).

CONCLUSIONS

The absence of biliary excretion of anionic drugs was compensated for by urinary excretion in BDLR and EHBR, and the compensation was more efficient with pravastatin than with temocapril. In patients with complete bile duct obstruction, the only pathway for the elimination of cholephilic compounds is through the urine. Although changes in various transporters in the liver and kidney in cholestasis have been elucidated, little is known about how effectively the elimination of these compounds is compensated for by urinary excretion.

Monitoring of cytochrome P-450 1A activity by determination of the urinary pattern of caffeine metabolites in Wistar and hyperbilirubinemic Gunn rats

Various studies suggest that induction of cytochrome P-450 1A (CYP1A) might be a valuable therapeutic modality for reducing the hyperbilirubinemia of infants with Crigler-Najjar syndrome type I (CNS-I), a severe form of congenital jaundice. To evaluate inducers of CYP1A as possible tools in the treatment of hyperbilirubinemia, a novel assay was established, based on the analysis of the urinary pattern of caffeine metabolites in rats. Wistar rats received [1-Me-(14)C]-caffeine (10 mg/kg i.p.), before and 48h after administration of the potent CYP1A inducer 5,6-benzoflavone (BNF) (80 mg/kg, i.p.). A substantial increase in the fractions of the terminal caffeine metabolites 1-methyluric acid (1-U), 1-methylxanthine (1-X), and a concomitant decrease in the caffeine demethylation product 1,7-dimethylxanthine (1,7-X) was observed after application of BNF. The ratio of the caffeine metabolites (1-U+1-X)/1,7-X may serve as an index of CYP1A activity in rats in vivo. Hyperbilirubinemic, homozygous (jj) Gunn rats are an accepted model for human CNS-I. In male jj Gunn rats treated with BNF or with indole-3-carbinol (I3C, 80 mg/kg, oral gavage), the inducing effect of BNF and 13C on CYP1A activity was confirmed by the urinary pattern of caffeine metabolites, and was parallelled by a decrease in plasma bilirubin levels. These data demonstrate the usefulness of the established caffeine assay for the evaluation of inducers of CYP1A as tools for reducing hyperbilirubinemia and further confirm the potential value of I3C in the treatment of CNS-I.

Alteration in bilirubin excretion in individuals chronically exposed to arsenic in Mexico

We have studied hepatic function in individuals chronically exposed to arsenic (As) via drinking water in Region Lagunera, Mexico. We studied 51 individuals living in three villages exposed to As in water. Nazareno (0.014 mgAs/l), Santa Ana (0.1 mgAs/l) and Benito Juárez (0.3 mgAs/l). We determined the serum activity of aspartate aminotransferase (SAT) and alanine aminotransferase (ALT) as indicators of hepatocellular injury and that of gamma-glutamyl-transpeptidase (GGT) and alkaline phosphatase (ALP) as indicators of cholestasic injury. Serum bilirubin was used as an indicator of organic conjugated anion transport. Total proteins, albumin and globulin fraction in serum were used as indicators of biosynthetic liver capacity. The main findings of this study were the predominantly conjugated hyperbilirubinemia and increased serum ALP activity which were related to the concentration of total arsenic (TAs) in urine, suggesting the presence of cholestasis in As-exposed individuals. No significant changes were observed in the other parameters studied.

Chromatographic fractionation and analysis by mass spectrometry of conjugated metabolites of bis(2-ethylhexyl)phthalate in urine

Mono(2-ethylhexyl)phthalate (MEHP), the primary metabolite of the plasticizer bis(2-ethylhexyl)phthalate (DEHP), was given to guinea pigs and mice and the methods for the isolation, separation and analysis of its metabolites in urine were developed. Following solid-phase extraction with octadecylsilane-bonded silica, individual metabolites were purified and separated using a combination of ion-exchange chromatography on lipophilic gels and reversed-phase high-performance liquid chromatography. Analysis of intact conjugates, as well as nonconjugated metabolites, was performed by fast atom bombardment mass spectrometry (FAB-MS) and, after derivatization, by gas chromatography-mass spectrometry. Enzymatic methods were used for further characterization. The study confirms glucuronidation as the major conjugation pathway for MEHP in the investigated species. Although less important quantitatively, glucosidation is shown to be an alternative conjugation pathway in mice. The methods developed were applied to a sample of urine from a hyperbilirubinemic newborn infant subjected to DEHP-exposure in conjunction with an exchange transfusion. It was demonstrated that metabolites of DEHP were excreted in amounts which could be analyzed by FAB-MS.

Severe renal hypouricemia secondary to hyperbilirubinemia

A 64-year-old man with alcoholic liver cirrhosis had a progressive decrease in the serum uric acid (UA) until it became undetectable, an increase renal UA clearance, mild glycosuria with normal serum glucose and a decrease in the tubular reabsorption of phosphate in association with cholestasis secondary to a gallbladder carcinoma. All these abnormalities returned to normal when the serum bilirubin levels decreased following surgical treatment. This clinical observation suggests that the reversible renal tubular transport defect was secondary to high levels of serum bilirubin.

The effects of D-penicillamine on the renal and liver functions in neonates and the in vitro influence on granulocytes

D-Penicillamine (DPA) was introduced to treat neonatal hyperbilirubinemia in 1973 and to prevent retinopathy of prematurity in 1980. In this study we investigated the renal and liver functions of neonates treated with DPA and the in vitro effect of the drug on superoxide anion generation and beta-glucuronidase release as well as phagocytic and intracellular killing activation of human peripheral blood granulocytes. Our data concerning the renal and liver functions before and after 3 to 4 days DPA treatment reveal that the drug does not produce any pathological change during short-term administration in the neonatal period. Furthermore, it was found that superoxide anion generation was slightly increased, and beta-glucuronidase release markedly increased by preincubation with DPA at concentrations of 0.5-5 mM. The rise was directly proportional to the concentration in the examined range. On the other hand, none of the examined DPA concentrations influenced the phagocytic or killing activity of neutrophils.

Plasma-amino acid profiles in sepsis and stress

Sepsis has been associated with specific plasma amino acid patterns. Sixty-five patients were prospectively investigated as to whether these patterns are indeed sepsis specific, or specific for metabolic stress without concomitant sepsis, or associated with the presence of organ failure. Virtually all aminoacid levels were decreased by 10-30% (p less than 0.05), whereas cystine and phenylalanine were significantly elevated. These changes were more pronounced in severe sepsis. Organ failure was not associated with significantly altered amino acid profiles. No differences were found between sepsis and stress without signs of sepsis. In addition, imminent death was not associated with aberrant amino acid profiles. We conclude that sepsis and metabolic stress are associated with changes in plasma amino acid profiles, but that such changes are aspecific and therefore poor indicators of disease severity.

Urinary porphyrins in liver disease

By use of quantitative thin-layer chromatography, urinary porphyrins were examined in 40 healthy volunteers, 38 patients with prophyria cutanea tarda (PCT), and 139 patients with various liver diseases. Significant elevations not only of coproporphyrin but also of some other porphyrins were found in many patients with liver disease. However, there was no evident relationship between porphyrin disturbances and functional or clinical findings, and all of these non-PCT patients who initially demonstrated intense uroporphyrinuria, when re-studied apparently had more normal porphyrin excretion. It seems, therefore, that whereas porphyrin estimations are useful in porphyrias, no clinically important conclusions can be drawn from urinary findings in patients with liver disease. The origin of defective haem biosynthesis in liver disease remains obscure. It can only be speculated that transient and reversible urocoproporphyrinuria may occur in patients with defective hepatic uroporphyrinogen decarboxylase activity who clinically and biochemically are not porphyric.

Urinary polyamines in preterm infants

Polyamines were determined in urine of 22 preterm infants (mean 30.0 weeks gestation) from birth to 22 weeks of age, and in full-term infants in the first week of life. A significant decline in urine putrescine and spermidine levels occurred with increased postnatal age in preterm infants. At expected term preterm infants had significantly higher levels of polyamines in urine than full-term infants at the same postconceptional age. No constant correlations between weight or linear growth velocity and urinary polyamine excretion could be established in this group of infants. Altered urine polyamine values were detected in two clinical situations: hyperbilirubinemia was associated with increased urine spermidine (and with increased spermidine/putrescine ratio), and liver disease was associated with increased levels of both putrescine and spermidine in urine.

Urinary estrogen assays and maternal hyperbilirubinemia

Urinary estrogen determinations have simplified the care of pregnant patients with certain metabolic disorders known to adversely affect the fetus. This report demonstrates that erroneously low values for urinary estrogens may be obtained if colorimetric assay methods are used for patients with congenital hemolytic anemias during an acute hemolytic crisis. This appears to be due to the interference of the large amounts of urobilin present in the urine of these patients.