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IMAGE INTERPRETATION · RENAL AND GENITOURINARY

Differential Renal Function on MAG3

Tc-99m MAG3 renal scan — composite image, flow curve, renogram curves, and quantitative results showing bilateral abnormal drainage with asymmetric differential function
Tc-99m MAG3 renal scan — composite image, flow curve, renogram curves, and quantitative results showing bilateral abnormal drainage with asymmetric differential function

Provided clinical image

Question

The results table on this MAG3 renal scan shows 'Diff perfusion (%)' of 79.21% for the left kidney and 20.79% for the right. What does differential perfusion (split renal function) represent?

  1. AThe percentage of the injected dose retained in each kidney at 20 minutes post-injection
  2. BThe percentage of total renal function contributed by each kidney, calculated from tracer uptake during the 2–3 minute phase
  3. CThe ratio of each kidney's blood flow to the aortic flow during the first minute of the study
  4. DThe percentage of tracer excreted into each kidney's collecting system by the time of peak activity
Show the answer and explanation

B. The percentage of total renal function contributed by each kidney, calculated from tracer uptake during the 2–3 minute phase

Differential renal function (split function) represents the percentage of total kidney work performed by each kidney. It is calculated from tracer uptake during the 2–3 minute phase — early enough that the counts reflect cortical extraction rather than collecting system drainage. Normal split function is approximately 45–55% per kidney. In this scan, the left kidney is contributing 79% and the right only 21%, indicating that the right kidney is significantly underperforming relative to the left.

More renal and genitourinary images

Tc-99m MAG3 renogram curves — both kidneys show a continuously rising pattern throughout the 45-minute study; Left T½ = 80.65 min, Right T½ = 51.73 minBilateral Impaired Drainage on MAG3 Renogram Tc-99m MAG3 renal scan acquired with motion correction (MoCo) applied — noted in the window title 'Cine FLOW FUNCTION MoCo MoCo'Motion Correction in MAG3 Renal Scans Tc-99m MAG3 diuretic renogram with Lasix at 21 min — right kidney shows prolonged T½ (85.53 min) with persistent tracer retention and rising renogram curve post-furosemide, indicating UPJ obstructionUPJ Obstruction on MAG3 Diuretic Renogram Tc-99m DMSA renal cortical scan at 30 min and 3 hours (POST, RAO, LAO views) showing focal cortical defect — renal scarring post-pyelonephritisRenal Cortical Scar on DMSA Scan Tc-99m MAG3 qualitative renal scan (0–30 min sequential images) with renogram curves and quantitative parameters for both kidneysNormal Renal Drainage Half-Time on MAG3 Tc-99m MAG3 qualitative renal scan — renogram function curves: left kidney (red dashed), right kidney (green), bladder (purple dotted)Why MAG3 for Renal Imaging: Tubular Secretion
← Why Post-Void Images on a Radionuclide CystogramBilateral Impaired Drainage on MAG3 Renogram →

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