Dear Ms Ultrasound,
Our doctor requested that we get a 33-week ultrasound because our 24-week ultrasound showed abnormal amounts of fluid in the babies kidneys. What is this, what causes it, and how is it treated?
Thank you for your time.
Hi. What your doctor would like to rule out is an obstruction of the babies urinary tract (kidneys). First off, because your doctor waited almost 10 weeks in between ultrasounds, it makes me think that the first findings of fluid in the kidneys, was borderline and did not concern anyone too much.
It is not uncommon to see a 'fullness' of what is called the renal pelvis, in a fetus (59% of fetal kidneys examined will show this). The renal pelvis is the point where the urine empties into the ureter(the tube that goes down to the bladder). A measurement of 5 mm or less is considered normal. 6-9 mm is probably normal and anything over 10 mm would be called significant and should be monitored closely and the baby should be scanned after birth. It is best to perform the postnatal ultrasound a few days after birth and not immediately to get accurate results.
My guess is that your baby falls into the 59% of kidney ultrasounds and that everything is normal.
-- Jane, RDMS
Jane Foley has worked as a Sonographer (Ultrasound Technologist) since 1979. Jane has lived and worked in many parts of the world including Saudi Arabia. She is a Registered Diagnostic Medical Sonographer or RDMS. She pulls a wealth of information from her experience in the field of Radiology and her interactions with such a broad cross-section of cultures she has visited. She now makes her home on the island of Maui with her English husband, Michael.