Diuretic Renal Imaging

This portion of the study is acquired with the patient ideally in an upright position if possible, if not patient may be supine.

Administer diuretic 15-20 minutes after radiopharmaceutical slowly over 2-3 minutes

1mg/kg (up to 40mg) for children 40mg for adults **max of 80mg may be required for patients with impaired renal function

Diuretic response usually begins 2 to 5 minutes after injection; however, maximal diuresis is frequently not reached until 15 minutes after injection.

As with standard functional assesment, a 20 minute acquisition, 20 seconds/frame usually compressed into 2-minute static images, is performed

Subtopic

Tc-99m MAG3

agent of choice for renographyof patients with suspected collectiong system obstruction

Tc-99m DTPA

may also be acceptable in more acute and less severe obstruction

Normal

A half-time of less than 10-15 minutes from time of diuretic effect constitutes a normal response

Abnormal

In the case of significant mechanical obstruction, there is very little decrease in renal collecting system activity after furosemide administration, owing to the narrow fixed lumen of the ureter

Factors that produce false-positive impression of mechanical obstruction or that contribute to indeterminate resuls

poor hydration, resulting in poor diuretic response

poor underlying renal function, resulting in diminished diuretic response

a noncompliant or rigid renal pelvis, producing increasing resistance to urine flow as diuresis increases urine volume

high filling pressure of the bladder due to a distended or noncompliant bladder, which may impair washout from the upper urinary track

an overcompliant or patuluos renal pelvis. During diuretic response, increased urine flow may be sufficient to fill this large reservoir without being sufficient enough to washout the tracer, producing a rising renogram curve

a large hydronephrotic volume, especially in the presence of diminished function. With a larger volume in the system, a larger diuretic response is needed to clear that system of accumulated activity. This is also known as the reservoir effect

Renogram curves using a ROI over only the collecting systems or over the entire kidneys are obtained

collecting systems are preferred which could also include the ureters if they appear to retain the rph

Calculating the half-time excretion is often performed either from the injection of diuretic or at the beginning of diuretic response.

Patient should be well hydrated

bladder should be emptied before administration of Furosimide

In adults and children that can not empty their bladder a catheter may be used

To distinguish between

Obstructive hydronephosis

Nonobstructive collecting system dilation due to

Vesicouretal reflux

Urinary tract infection

Congenital malformations

Previous obstruction

a noncompliant bladder

evaluation of

renal function

urodynamics

Recent studies with contrast

medications that block tubular secretion