SAN FRANCISCO - Echogenicity is a better predictor of renal function than parenchymal thinning on postnatal ultrasound, according to a presenter at the American Academy of Pediatrics (AAP) meeting. This sonographic data can help clinicians prognosticate the outcome of further radiological testing, as well as counsel patients and their families.
"Hydronephrosis is the most commonly detected genitourinary anomaly found on fetal ultrasound," explained Dr. Thomas Chi in a talk on Monday. "Without further extensive radiological testing, it's difficult to predict which patients will go on to have impaired renal function. Prior studies have suggested that echogenicity and parenchymal thinning may be correlated with decreased renal function."
"The purpose of our study was to use these two parameters to predict which of these clinical scenarios would result in the impairment of renal function," added Chi, who is from the urology department at the University of California, San Francisco. His co-authors, Dr. Maria Nguyen and Dr. Vickie Feldstein, are from the UCSF department of radiology.
For this retrospective study, records of 177 patients, who presented with moderate to severe hydronephrosis, were reviewed. The patients underwent ultrasound exams, voiding cystourethrogram (VCUG), and MAG-3 diuretic renograms in order to determine split renal function.
According to the results, all patients with kidney function of less than 20% showed markedly increased echogenicity on initial postnatal ultrasound. For those with a kidney functioning at 40% or greater, 95% had normal echogenicity. However, no significant correlation could be found between parenchymal thinning and renal function, Chi said.
For the segment of the patients in whom ultrasound revealed a markedly thin parenchyma, 77% still had normal renal function. This is most likely because with a hydronephrotic kidney, functioning renal parenchyma may spread over a larger surface area and appear thinner on cross-sectional sonography, the group explained in their abstract.
"Our results suggest that echogenicity on the postnatal ultrasound can be used to predict impaired renal function," Chi concluded. "All of our patients who had significantly impaired function -- less than 10% -- showed markedly increased echogenicity. All of our patients with function of less than 20% had slightly or markedly increased echo. And all our patients with normal function showed no echogenicity."
In a related AAP poster presentation, a group from Albany Medical College in New York examined whether renal ultrasound is even necessary to assess febrile urinary tract infections (UTI). Current AAP guidelines recommend both VCUG and renal ultrasound after febrile UTI (American Family Physician, October 15, 2000, Vol. 62:8, pp. 1815-1822).
Dr. Louis Giorgi and colleagues reviewed the charts of 282 patients (ages 5 days to 6 months) who underwent the suggested full radiographic evaluation for febrile UTI. They found that of the 203 patients with normal VCUG results, ultrasound scans were abnormal in 32 cases (16%). Subsequent workup revealed one case each of the following:
- Significant ureteropelvic junction (UPJ) obstruction
- Ectopic ureter in a bilaterally duplicated system
- Renal duplication with and without calculus
- Ectopic ureter
- Renal cysts
- Multicystic dysplastic kidney
- Renal scarring
Finally, there were three cases of ureterovesical obstruction. Because ultrasound inspired further evaluation, patient management or parental counseling was altered in nine patients, with two having to undergo surgical intervention, the group said. For example, the patient with multicystic dyplastic kidney had a metabolic workup followed by surveillance. The patient with ectopic ureter in duplicated system underwent ureteroureterostomy.
"In our population, renal ultrasound does add information ... after febrile UTI. This information alters management ... in a significant number of patients," they said.
By Shalmali Pal
AuntMinnie.com staff writer
October 14, 2004
Related Reading
Embryo and Fetal Pathology: Color Atlas with Ultrasound Correlation, October 13, 2004
To boldly go: Genitourinary ultrasound blasts into orbit, July 30, 2004
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