Additional information about Renal Pyelectasis

The following studies show that depending on the definition used, the type of patients studies, and the gestational age at which the ultrasound examination was done there are considerable differences in the outcome of mild renal pyelectasis.

Natural history of fetal hydronephrosis diagnosed on mid-trimester
ultrasound.

Sairam S, Al-Habib A, Sasson S, Thilaganathan B.
Feto-Maternal Medicine Unit, Homerton Hospital, Academic Unit of
Obstetrics and Gynaecology, St Bartholomew's and The Royal London School of Medicine and Dentistry, London, UK.

OBJECTIVES: Renal tract dilatation is a common finding in routine prenatal ultrasound. However, there is no consensus as to the criteria used for differentiating pathological from physiological dilatation. The aim of this study was to evaluate the natural history and postnatal
outcome of fetal hydronephrosis in an unselected obstetric population.
DESIGN: This was a prospective study of fetal hydronephrosis, detected at 18-23 weeks' gestation, in a routine obstetric population. Fetal hydronephrosis was diagnosed as 'mild' if the antero-posterior renal pelvic diameter (APRPD) measured >or = 4 mm and as 'moderate/severe' if the APRPD measured > or = 7 mm or if there was associated calyceal dilatation. The postnatal outcome of fetuses with persistent hydronephrosis (> or = 10 mm in the third trimester) was determined from a postal questionnaire.
RESULTS: During the study period, 11 465 women underwent an anomaly scan at 18-23 weeks of gestation. Fetal hydronephrosis was identified in 2.3% (268/11 465) of women. Mild hydronephrosis was present in 80.6% (216/268) and moderate/severe hydronephrosis in 19.4% (52/268). The hydronephrosis resolved in the antenatal or early neonatal period in 88% of fetuses. None of the fetuses with mild hydronephrosis and approximately one in three fetuses with persistent moderate/severe hydronephrosis required postnatal surgery. Overall, only one in every 1000 total births in the study population required postnatal urological surgery. CONCLUSIONS: The current study highlights the natural history of antenatally detected hydronephrosis. Mild fetal hydronephrosis appears to be associated with an excellent prognosis and probably represents the group with physiological renal pelvic dilatation. Moderate/severe fetal hydronephrosis is associated with poorer outcome and is perhaps the group that will need more intense follow up both antenatally and postnatally.

The increase of renal pelvis dilatation in the fetus and its
significance.

Aviram R, Pomeran A, Sharony R, Beyth Y, Rathaus V, Tepper R.
Ultrasound Unit, Sapir Medical Center, Kfar Saba, Israel.

OBJECTIVE: To determine the effects of the changes in fetal renal pelvis dilatation on post-natal diagnosis and outcome.
METHODS: Prenatal sonographic fetal renal anteroposterior diameters of > or = 4 mm in the second trimester, which persisted to > or = 7 mm in the third trimester, were the inclusion criteria. Fifty-six fetuses and 73 renal units with normal karotypes and a solitary sonographic finding of renal pyelectasis, which met the inclusion criteria, were followed, post-natally, until the age of 30 months. The neonates were categorized into three groups, according to their final diagnosis: No hydronephrosis, pelvi-ureteric junction obstruction and hydronephrosis from other causes. The neonates were also categorized according to their outcome: no treatment, follow-up only and surgical treatment.
RESULTS: In 17 neonates (30.4%), and 19 renal units, the diagnosis of hydronephrosis was excluded post-natally. In 39 neonates (69.6%), and 54 renal units, an urinary tract pathology was confirmed. The dynamics of pyelectasis in the second and third trimesters of pregnancy differed
significantly among the neonates when categorized according to the final diagnosis (P < 0.05), or according to outcome (P < 0.05).
CONCLUSION: It is possible to predict, and distinguish between, long-term conservative and surgical treatments of renal pelvis dilatation in the third trimester of pregnancy.

Isolated mild fetal pyelectasis detected by transvaginal sonography in advanced maternal age.

Guariglia L, Rosati P.
Department of Obstetrics and Gynecology, Catholic University of the
Sacred Heart, Rome, Italy.

OBJECTIVE: To evaluate the importance and evolution of isolated, mild fetal pyelectasis, detected in early pregnancy by high-resolution transvaginal sonography, and to determine its association with abnormal fetal karyotypes.
METHODS: Transvaginal scan at 11-16 weeks' gestation and transabdominal ultrasound examinations at the time of amniocentesis (16-18 weeks) were performed in 1093 pregnant women undergoing genetic amniocentesis because of advanced maternal age. In 795 cases,
transabdominal scans were repeated at 22-24 weeks. Women were excluded if they had a spontaneous abortion, chose to terminate their pregnancy, or declined amniocentesis. Each patient was screened for fetal pyelectasis, defined as an increase in anteroposterior renal pelvic
diameter, using cutoff values related to various stages of pregnancy.
RESULTS: Isolated fetal pyelectasis was detected at the first ultrasound examination in 56 women (5.1%) in early pregnancy, in 32 (2.9%) at the time of amniocentesis, and in 23 (2.9%) at 22-24 weeks' gestation. Two fetuses with diagnoses of mild pyelectasis at the first transvaginal
ultrasound demonstrated abnormal karyotypes at amniocentesis. In one case, the pyelectasis disappeared at 22-24 weeks' gestation.
CONCLUSION: This retrospective study shows that pyelectasis is more frequently detectable by high-resolution transvaginal sonography in the first half of pregnancy than in the second half. When detected in early pregnancy, the finding is frequently transient and not associated with an increased risk of abnormal fetal karyotypes.