[The utility of gammagraphy with Tc 99-labelled dimercaptosuccinic acid (DMSA) in the protocol for studying urinary infection in a 2nd-level hospital].

OBJECTIVE

Not all hospitals in our country have their own nuclear medicine laboratory. Most small and medium size hospitals must arrange their radioisotope studies with private clinics. The objective of this study was to assess if a single DMSA scan performed after an acute infection in a group of patients chosen according to certain risk criteria would allow the selection of those who run the risk of progressive renal damage.

PATIENTS AND METHODS

A descriptive and retrospective study of the clinical records of 65 patients under 14 years of age with urinary tract infection (UTI) seen at our institution between 1994 and 1995 and on whom a DMSA scan had been performed was carried out. The study groups was formed by the fifteen children with scintigraphic findings compatible with renal scarring. The fifty children with normal DMSA scans were used as controls.

RESULTS

Renal scarring was found more often in patients over one year of age (p < 0.05), in those with reinfections (p < 0.001) and in those kidneys with grade III vesicoureteral reflux (VUR, p < 0.05). The most severe lesions, with reduction of renal size, shape abnormalities and diminished uptake of the tracer were found together with VUR. The renal sonogram performed during the acute stage of the UTI was able to detect only four of the six children most severely affected.

CONCLUSIONS

Delaying the practice of the DMSA scan until 6 months after the last episode of bacteriuria would allow selection of those patients at the highest risk of progressive renal damage. This guideline would reduce scintigraphic studies 30 to 90%, since it would avoid repeated studies in those children with abnormal findings in the acute stage. The practice of the radioisotope study only in a reduced subset of patients selected on the basis of risk criteria such as recurrent UTI, VUR or suspected pyelonephritis does not allow detection of all scars.