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Ask Dr. Arun Phophalia Your Own Question
Dr. Arun Phophalia
Dr. Arun Phophalia, Doctor
Category: Pediatrics
Satisfied Customers: 31648
Experience:  MBBS, MS, Fellowship in sports medicine. Deals with general pediatric surgical disorders.
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1 month-old infant with grade IV hidronephrosis in left

Customer Question

1 month-old infant with grade IV hidronephrosis in left kidney (obstructive primary megaureter). Right kidney is normal. After diuretic renogram the right kidney shows good response to diruetic (T1/2=5min) but delayed Tmax (14min). Does this suggest a dilated non obstructive patttern in the right kidney, although it has always appeared normal in ultrasound? I can upload a picture of the renogram.
Submitted: 12 days ago.
Category: Pediatrics
Customer: replied 12 days ago.
I have attached a picture of the renogram
Customer: replied 12 days ago.
By the way, when asked that question, our pediatric nephrologist told us that for pediatric patients they don't care about time to peak, only T1/2 to evaluate partial/full obstruction, but I'm still concerned about the delayed tmax in both kidneys.
Expert:  Dr. Arun Phophalia replied 12 days ago.

Hello! My name is***** to JustAnswer. I'm reviewing your question now, and will post back with the reply momentarily.

Expert:  Dr. Arun Phophalia replied 12 days ago.

This is normal and not worrisome. physiologic retention of the tracer in the renal calyces or pelvis can alter the shape of the renogram curve and lead to prolonged values for the time to peak, 20 min/max ratio and half-life.

Thus please do not get anxious.

Anatomically and physiologically the right kidney is normal.

It is privilege assisting you.

Please let me know if you have further queries or unanswered questions.

Please consider a positive rating if this interaction has been satisfactory, as this is the only way we experts are credited and compensated for the time and work. You are not charged again for giving a rating.

Thank you.

Wishing you all the very best in life.

Customer: replied 12 days ago.
Hello,Thanks, ***** ***** see that your reply is copied/pasted from http://interactive.snm.org/docs/cg_ch03.pdf"1. Tmax is the time to peak height of the renogram curve. MAG3, DTPA and OIH
renograms normally peak by 5 min after injection and reach half peak height by
about 15 min after injection; however, physiologic retention of the tracer in the
renal calyces or pelvis can alter the shape of the renogram curve and lead to prolonged
values for the time to peak, 20 min/max ratio and half-life (T1/2)."I'm not looking for an answer copied from the internet, which I can myself look up, but from an experienced urologist/nephrologist that has seen these kind of curves in his daily practice. If this is not the case, I would like an answer from a different expert.Thank you.
Expert:  Dr. Arun Phophalia replied 12 days ago.

You are welcome.

I have done 13 kidney transplants. As a general surgeon, my 25% of practice is related to urology.

This is not copy pasted but is in all of our medical literature about the renal nuclear scans and if you see at other places, this is the explanation. A physiological retention is a common phenomenon and renal scan is interpreted by anatomical detail and physiological function. If there is no anatomical obstruction; tracer retention is not an issue.

Here the issues are two for renal scan to decide for the right kidney;

1) Is the right kidney normal in anatomy and physiology?

2) If the renal scan is showing an abnormality (which is an aberration from what we had decided as abnormal for tracer to outflow from the kidneys filtration system to the collecting system); is this physiological or outflow obstruction.

This is the reason, I mentioned that it is considered as normal physiological aberration.

I would be open to answer your further questions and if you wish, I will opt out for the other experts.

Expert:  Dr. Arun Phophalia replied 12 days ago.

Just wanted to add about the physiological retention of the tracer. This occurs in kidneys which have the counter part having problem. As it has to function more than the normal and there is not usual 50-50% split of the function. Thus the retention.

Expert:  Dr. Arun Phophalia replied 12 days ago.

Urologists use only decreased differential renal function as a sign of obstruction, and would not take consideration of the half-life and the washout curve.