Citation, DOI, disclosures and article data
At the time the article was created Yuranga Weerakkody had no recorded disclosures.View Yuranga Weerakkody's current disclosures
Fetal pyelectasis refers to the prominence of the renal pelvis in utero that is a relatively common finding, which in the majority of cases resolves spontaneously.
Please refer to the article on fetal hydronephrosis for a continued discussion on this matter.
Although there is an overlap of definition between pyelectasis and hydronephrosis, the former has been widely used instead of mild hydronephrosis given that the vast majority of the cases represent only a physiological incidental finding that resolves spontaneously, while the latter tends to be reserved for cases where a pathological obstruction is suspected.
Fetal pyelectasis can be a relatively common finding on antenatal ultrasounds, often detected at the routine 2nd trimester morphology scan. There is a recognized male predilection. The estimated prevalence is at ~2% of routine second trimester scans 13.
trisomy 21: isolated fetal renal pyelectasis is not considered to increase the risk of aneuploidies, however, in combination with other soft markers, the risk will increase 14 (see antenatal features of Down syndrome)
Pyelectasis can result from a number of factors. In the majority of cases, it is physiological and resolves spontaneously. However, it may also herald the presence or evolution of renal tract pathology, such as:
urethral obstruction, e.g. posterior urethral valves
Fetal pyelectasis is assessed as an AP measurement of the renal pelves on an axial plane ultrasound image.
According to the Society of Fetal Urology (SFU) consensus15, fetal pyelectasis is considered present if the anterior to posterior diameter of the renal pelvis measures:
>4 mm up to 28 weeks
>7 mm at or after 28 weeks gestation
Note should also be made of any renal calyceal dilatation, ureteric dilatation, renal parenchymal appearance, bladder appearance and any unexplained oligohydramnios.
Fetal pyelectasis can also be affected by maternal hydration, i.e. physiological fetal pyelectasis 5.
Treatment and prognosis
The vast majority of cases (~96%) with mild pyelectasis in the second trimester resolve, either during pregnancy or in the early postpartum period. The risk of postnatal renal pathology is increased with:
increasing degree of pelvic dilatation
in utero progression
Antenatally detected renal pelvic dilatation, especially in isolation, is considered a weak predictor of vesicoureteric reflux 7 although postnatal sonographic evaluation is often recommended.
The finding of pyelectasis in the second trimester is typically monitored with a repeat prenatal scan in the third trimester, with further postnatal follow-up recommended in cases of persistent pyelectasis 10.
Postnatally, most cases with pyelectasis resolve spontaneously in the first year of life, and invasive procedures are not required.
- 1. Thornburg LL, Pressman EK, Chelamkuri S et-al. Third trimester ultrasound of fetal pyelectasis: predictor for postnatal surgery. J Pediatr Urol. 2008;4 (1): 51-4. doi:10.1016/j.jpurol.2007.04.005 - Pubmed citation
- 2. Allen KS, Arger PH, Mennuti M et-al. Effects of maternal hydration on fetal renal pyelectasis. Radiology. 1987;163 (3): 807-9. Radiology (abstract) - Pubmed citation
- 3. Yamamura Y, Swartout JP, Anderson EA et-al. Management of mild fetal pyelectasis: a comparative analysis. J Ultrasound Med. 2007;26 (11): 1539-43. J Ultrasound Med (full text) - Pubmed citation
- 4. Nyberg DA, Souter VL. Sonographic markers of fetal trisomies: second trimester. J Ultrasound Med. 2001;20 (6): 655-74. J Ultrasound Med (abstract) - Pubmed citation
- 5. Babcook CJ, Silvera M, Drake C et-al. Effect of maternal hydration on mild fetal pyelectasis. J Ultrasound Med. 1998;17 (9): 539-44. J Ultrasound Med (abstract) - Pubmed citation
- 6. Anderson N, Clautice-engle T, Allan R et-al. Detection of obstructive uropathy in the fetus: predictive value of sonographic measurements of renal pelvic diameter at various gestational ages. AJR Am J Roentgenol. 1995;164 (3): 719-23. AJR Am J Roentgenol (abstract) - Pubmed citation
- 7. Walsh G, Dubbins PA. Antenatal renal pelvis dilatation: a predictor of vesicoureteral reflux? AJR Am J Roentgenol. 1996;167 (4): 897-900. AJR Am J Roentgenol (abstract) - Pubmed citation
- 8. Ahmad G, Green P. Outcome of fetal pyelectasis diagnosed antenatally. J Obstet Gynaecol. 2005;25 (2): 119-22. doi:10.1080/01443610500041446 - Pubmed citation
- 9. Chudleigh T. Mild pyelectasis. Prenat. Diagn. 2001;21 (11): 936-41. Prenat. Diagn. (link) - Pubmed citation
- 10. Wilson RD, Lynch S, Lessoway VA. Fetal pyelectasis: comparison of postnatal renal pathology with unilateral and bilateral pyelectasis. Prenat. Diagn. 1997;17 (5): 451-5. Prenat. Diagn. (link) - Pubmed citation
- 11. Corteville JE, Dicke JM, Crane JP. Fetal pyelectasis and Down syndrome: is genetic amniocentesis warranted? Obstet Gynecol. 1992;79 (5 ( Pt 1)): 770-2. - Pubmed citation
- 12. Wickstrom EA, Thangavelu M, Parilla BV et-al. A prospective study of the association between isolated fetal pyelectasis and chromosomal abnormality. Obstet Gynecol. 1996;88 (3): 379-82. doi:10.1016/0029-7844(96)00211-6 - Pubmed citation
- 13. Entezami M, Albig M, Knoll U et-al. Ultrasound Diagnosis of Fetal Anomalies. Thieme. (2003) ISBN:1588902129. Read it at Google Books - Find it at Amazon
- 14. Agathokleous M, Chaveeva P, Poon LC et-al. Meta-analysis of second-trimester markers for trisomy 21. Ultrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology. 41 (3): 247-61. doi:10.1002/uog.12364 - Pubmed
- 15. Nguyen HT, Benson CB, Bromley B et-al. Multidisciplinary consensus on the classification of prenatal and postnatal urinary tract dilation (UTD classification system). (2014) Journal of pediatric urology. 10 (6): 982-98. doi:10.1016/j.jpurol.2014.10.002 - Pubmed