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==Planning==
===Choice of modality===*Preferably '''[[ultrasonography of the urinary system]]'''. ==Evaluation=====Grading===The Society of Fetal Ultrasound has developed a grading system for hydronephrosis, initially intended for use in neonatal and infant hydronephrosis, but it is now used for grading hydronephrosis in adults as well:<ref>{{cite web|url=https://www.uptodate.com/contents/overviewHydronephrosis -choice of-fetal-hydronephrosis|title=Overview of fetal hydronephrosis. Version Version 29.0|author=Laurence S Baskin|website=UpToDate|accessdate=2017-04-25modality}} Last updated Apr 20, 2017</ref>* Grade 0 – No renal pelvis dilation. Cutoff values for different patient populations are::*Fetuses: An anteroposterior diameter of less than 4 mm in fetuses up to 32 weeks of gestational age and 7 mm afterwards.<ref name="D'Addario2014">[https://books.google.com/books?id=2PwlBgAAQBAJ&pg=PA189 Page 189] in: {{cite book|title=Donald School Basic Textbook of Ultrasound in Obstetrics & Gynecology|author=V. D'Addario|publisher=JP Medical Ltd|year=2014|isbn=9789351523376}}</ref> :*Adults, defineddifferently by different sources, with anteroposterior diameters ranging between 10 and 20 mm.<ref>[https://books.google.com/books?id=7YfQAQAAQBAJ&pg=PA78 Page 78] in: {{cite book|title=Emergency Ultrasound Made Easy, Edition 2|author=Justin Bowra, Russell E|publisher=Elsevier Health Sciences|year=2011|isbn=9780702048722}}</ref> About 13% of normal healthy adults have a transverse pelvic diameter of over 10 mm.<ref>{{cite journal |vauthors=Emamian SA, Nielsen MB, Pedersen JF, Ytte L |title=Sonographic evaluation of renal appearance in 665 adult volunteers. Correlation with age and obesity |journal=Acta Radiol |volume=34 |issue=5 |pages=482–5 |year=1993 |pmid=8369185 |doi= 10.3109/02841859309175388|url=}}</ref>:*Pregnant women in the last two trimesters: The maximum normal expected renal pelvic diameter (97.5 percent prediction interval) is 27 mm on the right and 18 mm on the left.<ref name="EricksonNicholson1979">{{cite journal|last1=Erickson|first1=L. M.|last2=Nicholson|first2=S. F.|last3=Lewall|first3=D. B.|last4=Frischke|first4=Lauraline|title=Ultrasound evaluation of hydronephrosis of pregnancy|journal=Journal of Clinical Ultrasound|volume=7|issue=2|year=1979|pages=128–132|issn=00912751|doi=10.1002/jcu.1870070211}}</ref> * Grade 1 (mild) – Mild renal pelvis dilation (anteroposterior diameter less than 10 mm in fetuses<ref name="D'Addario2014" />) without dilation of the calyces nor parenchymal atrophy* Grade 2 (mild) – Moderate renal pelvis dilation (between 10 and 15 mm in fetuses<ref name="D'Addario2014" />), including a few calyces * Grade 3 (moderate) – Renal pelvis dilation with all calyces uniformly dilated. Normal renal parenchyma* Grade 4 (severe) – As grade 3 but with thinning of the renal parenchyma
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