This procedure in normally indicated to know whether there is significant obstruction or not which requires intervention in hydronephrotic kidneys (sometimes with associated hydroureters).

Information sought:
1. Functional status of the kidneys.
2. Tubular Transit Status
3. Adequacy of PUJ

Patient scheduling:
Normally there are no constraints for scheduling a renogram procedure.
Study can be scheduled any day and at any time of the day since Tc99m DTPA is easily available. If Tc99m EC is to be used then some labs might prefer to group such patients for a particular day by prior appointment.
Since 1 to 2 hours delayed image will be required often, patient is taken up accordingly so as to complete the delayed image before closing the lab.

Patient Preparation:
Adequate hydration is essential before diuretic renogram. Patients who are kept fasting for other reasons should receive IV fluids accordingly in consultation with the referring physician. For others ensuring that the patient drinks water or other beverages while waiting for the procedure (about 30 minutes before injection) will be more reliable.

Patient Information:
Other relevant investigation reports:
Ultrasound scan report, IVU, MCUG reports if any.
Details on previous surgery if any and Previous renogram images if any.
Reports on Serum Creatinine and Urea levels also if available.
Height, weight, age and sex to be recorded.

Dose preparation:
Tc99m DTPA or Tc99m EC
20 MBq to 370 MBq (0.5 mCi to 10 mCi) depending on the patient.
Activity of the dose for injection should be measured accurately with isotope calibrator and recorded for Clearance Quantitation. In some systems, static acquisition of pre-inj syringe activity may be required .

Patient should be asked to empty the bladder before taken up for scan.
In patients with associated bladder outflow abnormalities and hydroureterosis, continuous bladder drainage via a catheter may be ideal and should be arranged in consultation with the referring physician.

Patient positioning:
Supine in relaxed comfortable position with camera kept beneath.
Patient should be explained on the need for lying still during the scan. Infants and children may need to be restrained gently to avoid unacceptable motion during the scan. Sedation is normally not required for this study. In case if it is needed then oral tichlofos available as “syp.Pedicloryl” can be given orally (25mg/kg for less than 1yr & 400 – 500 mg for 1-5 yrs). Recommended waiting time is 45 min. to get the sedative effect.

Field of view should be verified with a marker to ensure that both kidneys are included.

Occasionally for special reasons patient may be seated erect on a firm stool with the camera behind vertically as a back rest.

Image Acquisition parameters:
Dynamic multi-phase in 64 X 64 matrix size will suffice.
A rapid first pass for the Vascular phase for 1-2 sec per frame X 30 or 60 seconds
Subsequent frames are usually in 15 sec /20 sec/30 sec for a period of 20 min to 45 min.

Radiotracer administration:
IV Bolus without any extravasation is required. A butter fly needle may be retained for purpose of lasix injection later. Some times in the case of infants, it is more convenient to inject the tracer in the dorsal pedal vein on the patient table outside the camera and position immediately after injection and start the acquisition.
Post inj residual activity in the syringe should be measured and recorded.

Lasix injection:
It is important to monitor the tracer uptake by the kidneys and look for the arrival in the collecting system and the bladder area. There are several possibilities, which decide the use of lasix. The dose is 1.0 mg/kg (max 40 mg). In patients with renal failure higher doses (max 80 mg) may be recommended.

(i) No lasix needed:
Normally activity appears in the bladder area at least from one kidney by 6 minutes. There may not be a need for Lasix inj if both kidneys are draining very well and the acquisition can be completed by 20 minutes. If the bladder is well distended and if the patient feels like voiding, acquisition may be terminated even earlier in the normal studies.

(ii) Early lasix:
When tracer has been accumulated well in one or both kidneys but there is no normal drainage distally IV lasix can be administered as early as 8 minutes to augment the drainage. This is a deviation from the standard protocol acceptable depending on the scan status only and influences the scan interpretation subsequently.

(iii) F+20 protocol:
This protocol is meant for the kidney which is hydronephrotic and most often with impaired function and slow tracer accumulation in the dilated pelvis. It is presumed that by 20 minutes there will be no further tracer coming into the kidney. To push the pooled tracer from behind we attempt to produce a bolus of non-radioactive urine in the kidney itself by injecting the lasix now.

Ideally once the first 20 minutes acquisition is over, the camera should be kept in pause mode the patient should be allowed to go to the toilet to empty the bladder since the activity from one normal kidney would have completely drained into the bladder by this 20 minutes. On returning from the toilet patient should be repositioned and acquisition of the diuretic phase should be resumed. To study the effect of lasix, acquisition should be continued for another 25 minutes for a complete analysis. Special soft ware support is needed if one wants to process the two phases (pre-diuretic and post-diuretic) and merge the curves.
In practice most inject the lasix at 20 min without moving the patient and without interrupting the acquisition since renogram processing is easier. Acquisition might have been set for 45 minutes but optionally terminated earlier by 30/35/40 minutes based on the lasix response seen in the monitor.

(iv) F-15 Protocol:
It is said that maximal urinary flow rate is achieved at 18 minutes post iv injection of lasix. In this protocol such maximal urinary flow is aimed to coincide with the time the radiotracer bolus is arriving at the tubules (i.e. 3 min post injection of tracer) so that the activity is carried faster through the kidney and the PUJ. Here lasix is injected outside the camera room 15 minutes before the scheduled time of tracer injection while hydration is being simultaneously ensured This protocol is preferred in the following conditions:
- when F+20 renogram report was equivocal for obstruction at PUJ
- when the hydronephrosis is huge
- when there is already a nephrostomy drainage tube in situ
- post-pyeloplasty
- when there is dilated ureter or ureters (with or without reflux / bladder outflow abnormality)
- when there is already a stent in the ureter
- post ureteric reimplantation surgery
If venepuncture twice is too much of a difficulty, lasix may be injected intramuscularly also in this protocol.

(v) F+0 Protocol:
In this protocol lasix is injected at the same time of the tracer injection. This protocol is also a deviation for the convenience in infants and children since you can avoid the trouble of another venepuncture. Also injection when the scan is in progress can cause patient motion artifact.

Post dynamic static bladder images
Isotime (about 1 min) static images of KUB area in 256 X 256 matrix are obtained after the dynamic imaging is over.
Pre-void Supine for full bladder image.
Pre-void Erect (optional) to look for gravity assisted drainage in some cases.
Post-void image for residual activity in the bladder. This should be acquired in the same patient position as the pre-void image for comparison.

Post-inj Syringe image may be required in some systems for GFR calculation.
It is better to check the injection site under the camera for extravasation and if necessary even acquire a one minute image which might be useful for correcting the injected activity for GFR calculation.

Delayed image
Isotime static image may be needed after a delay of one to two hours when the dynamic scan shows either no tracer uptake in the kidney region or there is complete retention of accumulated tracer.
Image and Renogram Curve Processing
Background subtracted Time-Activity Curves (Renograms) have to be generated from the dynamic images. For this ROI drawing for the kidneys and background can be critical.

Summed image selection:
The soft ware program normally offers a summed image of your choice to outline the kidneys. When functioning kidneys are well delineated, affected kidneys may not be well delineated and one may have to change the summed image to latter frames to draw the affected kidney.
Different ROI’s for function & drainage:
In normal sized kidneys a single set of ROI’s & curves can be used to assess both uptake phase and excretory phase; but in an enlarged hydronephrotic kidney one may need to process the images first with cortical ROI to assess the uptake function & tubular transit and then again with a new whole kidney or pelvic ROI to assess the excretory phase.

Motion artifact:
It is important to view the cine of the images with the ROI’s to check for any motion. Renogram curves can be totally invalid if there is too much of patient motion and in such cases it is better to discard the curves and calculate the relative function manually from ROI analysis on selected frame from the uptake phase.
Important Quantitative parameters:
Split Function percentage
– this is not applicable when one kidney is not visualized at all.
T max i.e. time to peak
T1/2 - ie time to fall to 50% of activity from Peak or from time of lasix inj. when peak is not reached.
20 min % max & 20 min / 3 min Ratio
This parameter is used to quantify the residual kidney activity when Tc99m EC is used.
GFR ml/min for each kidney when Tc99m DTPA is used.
EC Cl Rate ml/min may be calculated when Tc99m EC is used by either using a suitably modified soft ware for this purpose. If such soft ware is not available one can use the GFR soft ware and then calculate the predicted EC Cl rate values.
Perfusion Curve Parameters
These can be derived and used only if the bolus is rapid & statistically adequate.
Used mostly in transplant kidney study. Counts per pixel need to be used for curve generation. Graft Kidney Curve to be compared with Aorta / Iliac artery curve:
Peak Delay in seconds
Slope Ratio
Graft Perfusion Index from the areas under the curves (until artery peak).

Documentation on Hard copy:
Good quality grouped images of frame per minute should be provided alongwith curves.
Pre- post void images and delayed images should be displayed on same window.
Artifacts and invalid results should be appropriately marked and notified.