Prenatal sonographic diagnosis of horseshoe kidney

Prenatal diagnosis of horseshoe kidney by measurement of the renal pelvic angle

OBJECTIVE

The aim of this study was to evaluate the usefulness of measurement of the angle between bilateral renal pelves on axial views in the prenatal ultrasonographic diagnosis of horseshoe kidney.

METHODS

We retrospectively measured the renal pelvic angle in 19 fetuses with horseshoe and 20 fetuses with normal kidneys in the second and third trimesters. Renal pelvic angle was defined as the angle between the long axis of the renal pelves on the axial view of the abdomen. We compared the renal pelvic angles of horseshoe and normal kidneys with unpaired t-test. Taking 140 degrees as a cut-off value, we calculated the sensitivity, specificity and accuracy of pelvic angle measurement for the prenatal diagnosis of horseshoe kidney.

RESULTS

The mean pelvic angles in the fetuses with horseshoe kidney were 116 degrees and 110 degrees in the second and third trimester, respectively. In the normal fetuses, the equivalent angles were 172 degrees and 161 degrees. The difference between the two groups was statistically significant (P < 0.01). Using 140 degrees as the discriminating criterion, the sensitivity, specificity and accuracy of renal pelvic angle measurement for the prenatal diagnosis of horseshoe kidney were all 100%. Fifteen of 19 fetuses with horseshoe kidney had no other abnormality. Four (21%) fetuses had severe complex abnormalities which were associated with trisomy 18 in three cases.

CONCLUSION

Observation and measurement of the renal pelvic angle is a simple and useful method in the prenatal diagnosis of the horseshoe kidney.

Sonographic findings of fetuses with an empty renal fossa and normal amniotic fluid volume

OBJECTIVE

To review the antenatal sonographic findings and postnatal follow-up of fetuses with empty renal fossa (ERF) and normal amniotic fluid volume.

METHODS

Sonographic examinations of 13,705 fetuses were retrospectively analyzed and all fetuses with at least one ERF and normal antenatal amniotic fluid volume were included in this study.

RESULTS

Forty cases with antenatal ERF were diagnosed. Prenatal diagnosis consisted of pelvic kidney (n = 24), unilateral renal agenesis (n = 13), horseshoe kidney (n = 2) and crossed fused renal ectopia (n = 1). The prevalence of ERF in the low-risk population approximated 3.2 per thousand. There was no serious renal complication during a mean follow-up period of 30 months except one case of crossed fused renal ectopia requiring hemodialysis.

CONCLUSION

The underlying cause of ERF in the majority of cases with normal amniotic fluid volume is renal ectopia. Prenatal ultrasonography seems to be highly reliable in diagnosing these anomalies. Prognosis is favorable in the absence of additional extraurinary malformations.

Determining the incidence of horseshoe kidney from radiographic data at a single institution

PURPOSE

An estimated 150,000 children are born with birth defects each year. One of the most frequent genitourinary abnormalities is horseshoe kidney (HSK). The incidence of HSK in the population is estimated to be 1/400 to 1,600 births based on autopsy data from the 1940s and 1950s. We prospectively evaluated the incidence of HSK based on radiographic studies to determine the contemporary incidence of HSK.

MATERIALS AND METHODS

In a 6-month period patients undergoing abdominal computerized tomography, renal ultrasonography and excretory urography were screened for HSK. After identification medical charts were reviewed for demographics, history, study indication and findings. A literature review of 12 studies of 825 patients with HSK was compared with the current series with regard to common associated findings.

RESULTS

From 15,320 radiographs 23 patients were identified with HSK for an overall incidence of 1/666. Computerized tomography, excretory urography and ultrasound identified 16, 5 and 2 patients, respectively, while 16 were male, 7 were female, 20 were adults and 3 were children. The most common concomitant urological disorder was nephrolithiasis in 9 patients (39%), prompting operative intervention in 4. The radiographic incidence of HSK closely matched data from autopsy series and yet it differed from that in current radiographic series using ultrasound in the perinatal period.

CONCLUSIONS

Our radiographic evaluation of the HSK incidence closely matches past autopsy series. This finding suggests that the incidence of HSK remains stable despite an increasing number of birth defects. Moreover, it appears that radiographic studies can accurately estimate the incidence of congenital anatomical disorders. Our data suggest that HSK is a relatively benign condition with a low requirement for operative intervention in these incidentally identified patients.