The Abnormal Urinalysis

Tubulointerstitial nephritis (TIN) and uveitis (TINU) syndrome is a rare disease. The renal prognosis is generally thought to be better in children with TINU syndrome than in adults. However, data are scarce. We aimed to investigate the long-term renal prognosis in a French cohort of children with TINU syndrome.

We performed a national retrospective study including 23 French pediatric nephrology centers enrolling patients with TINU syndrome diagnosed between January 2000 and December 2018.

A total of 46 patients were included (52% female, median age 13.8 years). At diagnosis of TIN, the median estimated glomerular filtration rate (eGFR) was 30.6 ml/min per 1.73 m² (4.9–62.8). The median time between diagnosis of uveitis and TIN was 0.4 months (−4.1; +17.1). All patients had anterior uveitis, but 12 (29%) were asymptomatic. Nearly all patients (44 of 46) received steroid treatment, and 12 patients (26%) received a second-line therapy. At last follow-up (median 2.8 years), the median eGFR was 87.5 ml/min per 1.73 m² (60.3–152.7) and <90 ml/min per 1.73 m² in 20 patients.

In our study, nearly half of the patients had renal sequelae at last follow-up. Given the possible progression to chronic kidney disease, long-term monitoring of children with TINU syndrome is mandatory. Approximately a quarter of the children had asymptomatic uveitis suggesting all children presenting with TIN should undergo systematic ophthalmologic screening even in the absence of ocular signs.

This chapter describes the physiology and selected disorders related to urinary tract, kidneys, blood pressure, fluids, and electrolytes.

Haematuria and proteinuria are common findings on urinalysis in childhood. They usually occur in either children with specific symptoms e.g. macroscopic haematuria or nephrotic syndrome, or in those who have non-specific symptoms (usually when looking to exclude urinary tract infection) and sometimes in asymptomatic children. The majority of children fall into the latter two groups, the finding is temporary and not associated with long term renal disease. If the finding is persistent or patients have specific clinical features then renal abnormalities are more frequent and appropriate investigation is required. This review provides a rationale for an approach that allows reassurance to be given to children and their families in whom the finding is transient and benign, whilst identifying those in whom renal abnormalities are present and treatment required. It describes algorithms for macroscopic haematuria (MaH), asymptomatic microscopic haematuria (MiH) and proteinuria.

Urine contains an enormous amount of information. Well-standardized procedures for collection, transport, sample preparation and analysis should become the basis of an effective diagnostic strategy for urinalysis. As reproducibility of urinalysis has been greatly improved due to recent technological progress, preanalytical requirements of urinalysis have gained importance and have become stricter. Since the patients themselves often collect urine specimens, urinalysis is very susceptible to preanalytical issues. Various collection methods and inappropriate specimen transport can cause important preanalytical errors. In addition to the insurance of correct collection, the clinical laboratory should optimize transport and sample preservation. Errors due to variation in diuresis may be corrected by recalculating the results using dilution parameters (e.g. osmolality, creatinine, conductivity, urine density). Next to the use of a primary urine container, it is recommended to split the original urine sample into various smaller aliquots for morphological, microbiological and chemical analyses, decreasing the risk of contamination. The use of preservatives may be helpful for particular analytes. A universal urine preservative however does not exist. Preanalytical aspects are also of major importance for newer urinalysis applications (e.g. metabolomics).