Indicaciones de la cistografía en niños. Anomalías morfológicas y defectos funcionales

Until the introduction of ultrasound in clinical practice, routine performance of a cystography and urethrography was the standard of care following a first urinary tract infection (UTI). Current indications for this technique are based on clinical features, age or sex. This study aims to assess the importance of basic kidney function tests in determining the indication for cystography in the pediatric population.

We conducted a cross-sectional observational and analytical, diagnostic accuracy study in 175 children who underwent ultrasound examinations for assessment of morphological abnormalities or with a history of one or more UTIs. We applied the term "significant morphological abnormalities" (SMAs) excluding cases with an anteroposterior diameter of the pelvis of less than 2 cm. The basic kidney function tests used in the assessment were the maximum urinary osmolality (UOsm) and urinary albumin/creatinine and NAG/creatinine ratios.

The number of patients with normal cystography was 118; the remaining 57 had vesicoureteral reflux (VUR). We found a statistically significant association between UTI and VUR. Significant morphological abnormalities were present in 32/57 cases of VUR (56.1%) and the maximum UOsm was abnormal in 75% of cases with VUR (43/57). The association of "UTI + significant SMA" offered a negative predictive value (NPV) of 89% and a positive predictive value of 49%, leaving two cases of grade IV VUR undiagnosed. The association of UTI with "SMAs or reduced maximum UOsm" predicted all severe cases of VUR (grades IV-V).

In children who have had UTI, in the presence of SMAs, prior determination of the maximum UOsm does not seem necessary to indicate a cystography. In patients who have not suffered from UTI, determining the maximum UOsm is useful for ruling out the presence of severe VUR. Renal tubular function tests, combined with other clinical, laboratory and sonographic variables, can guide decision-making to avoid unnecessary cystography.