When is red urine not hematuria?: A case report

Pitfalls in the diagnosis of hematuria

Detection of hemoglobin (Hb) and red blood cells in urine (hematuria) is characterized by a large number of pitfalls. Clinicians and laboratory specialists must be aware of these pitfalls since they often lead to medical overconsumption or incorrect diagnosis. Pre-analytical issues (use of vacuum tubes or urine tubes containing preservatives) can affect test results. In routine clinical laboratories, hematuria can be assayed using either chemical (test strips) or particle-counting techniques. In cases of doubtful results, Munchausen syndrome or adulteration of the urine specimen should be excluded. Pigmenturia (caused by the presence of dyes, urinary metabolites such as porphyrins and homogentisic acid, and certain drugs in the urine) can be easily confused with hematuria. The peroxidase activity (test strip) can be positively affected by the presence of non-Hb peroxidases (e.g. myoglobin, semen peroxidases, bacterial, and vegetable peroxidases). Urinary pH, haptoglobin concentration, and urine osmolality may affect specific peroxidase activity. The implementation of expert systems may be helpful in detecting preanalytical and analytical errors in the assessment of hematuria. Correcting for dilution using osmolality, density, or conductivity may be useful for heavily concentrated or diluted urine samples.

Urine bag as a modern day matula

Since time immemorial uroscopic analysis has been a staple of diagnostic medicine. It received prominence during the middle ages with the introduction of the matula. Urinary discoloration is generally due to changes in urochrome concentration associated with the presence of other endogenous or exogenous pigments. Observation of urine colors has received less attention due to the advances made in urinalysis. A gamut of urine colors can be seen in urine bags of hospitalized patients that may give clue to presence of infections, medications, poisons, and hemolysis. Although worrisome to the patient, urine discoloration is mostly benign and resolves with removal of the offending agent. Twelve urine bags with discolored urine (and their predisposing causes) have been shown as examples. Urine colors (blue-green, yellow, orange, pink, red, brown, black, white, and purple) and their etiologies have been reviewed following a literature search in these databases: Pubmed, EBSCO, Science Direct, Proquest, Google Scholar, Springer, and Ovid.

Highlights for the management of a child with proteinuria and hematuria

The identification of hematuria or proteinuria in an otherwise healthy child can cause anxiety to both the family and the pediatrician. The etiology of hematuria and proteinuria includes a long list of conditions, and detailed workup can be exhaustive, expensive and not essential in most of the patients. As will be described in this paper, most of the children with proteinuria or hematuria have a benign etiology. The primary role of the pediatrician is to identify hematuria/proteinuria, recognize the common causes of hematuria/proteinuria, and more importantly identify children with serious conditions that need referral to the nephrologist in a timely manner.

Evaluation of hematuria and proteinuria: how should a pediatrician proceed?

PURPOSE OF REVIEW

Finding blood or protein in the urine of a patient can be the source of immense anxiety. The list of diseases that result in these findings is quite long. Thus, many pediatricians believe that an exhaustive investigation is necessary to be certain of the cause. The review will discuss the major causes of hematuria and proteinuria in the pediatric population, and discuss a rational approach to the evaluation of these conditions.

RECENT FINDINGS

A number of recent studies have examined the results of mass screenings of school-age children and the final outcome of examination of children with hematuria and/or proteinuria. Most children with either isolated hematuria or isolated proteinuria had benign disease processes. Children with combined hematuria and proteinuria had a higher prevalence of significant kidney disease.

SUMMARY

The urinalysis combined with the history and physical examination should indicate the cause of hematuria and proteinuria in most cases. Significant renal disease can be ruled out with a minimal amount of work-up in most patients. The presence of hematuria and proteinuria together significantly increases the likelihood of significant renal disease and should prompt a referral to a specialist.