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IMAGE INTERPRETATION · RENAL AND GENITOURINARY

Why MAG3 for Renal Imaging: Tubular Secretion

Tc-99m MAG3 qualitative renal scan — renogram function curves: left kidney (red dashed), right kidney (green), bladder (purple dotted)
Tc-99m MAG3 qualitative renal scan — renogram function curves: left kidney (red dashed), right kidney (green), bladder (purple dotted)

Provided clinical image

Question

The sequential images shown are from a qualitative renal scan used to evaluate kidney drainage. Looking at the renogram curves, the left kidney (red dashed line) peaks early and clears normally, while the right kidney (green line) peaks later and retains tracer through 30 minutes. Which radiopharmaceutical is MOST COMMONLY used for this type of renal drainage study?

  1. ATc-99m DMSA (dimercaptosuccinic acid) — binds to renal cortical tubular cells and provides static images of cortical function
  2. BTc-99m MDP (methylene diphosphonate) — taken up by osteoblasts and used primarily for renal cortical scanning due to urinary excretion
  3. CTc-99m MAG3 (mercaptoacetyltriglycine) — excreted by tubular secretion, providing dynamic images ideal for evaluating renal blood flow and drainage
  4. DTc-99m sulfur colloid — taken up by the reticuloendothelial system and used for renal drainage studies when MAG3 is unavailable
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C. Tc-99m MAG3 (mercaptoacetyltriglycine) — excreted by tubular secretion, providing dynamic images ideal for evaluating renal blood flow and drainage

Tc-99m MAG3 (mercaptoacetyltriglycine) is the most commonly used radiopharmaceutical for dynamic renal studies (renography). It is excreted primarily by tubular secretion (not glomerular filtration), giving it a high extraction efficiency — especially useful in patients with reduced renal function. MAG3 produces high-quality renogram curves that allow evaluation of renal perfusion, cortical transit, and collecting system drainage. Tc-99m DMSA is used for static cortical imaging (scarring, pyelonephritis) and does not evaluate drainage.

More renal and genitourinary images

Tc-99m MAG3 qualitative renal scan with quantitative parameters: Right T½ = 22.2 min, residual 30 min = 49.4%; Left T½ = 8.1 min, residual 30 min = 15.9%; equal bilateral differential function (51%/49%)Furosemide Dose for Diuretic Renography Direct radionuclide cystogram — sequential bladder filling frames, post-flow total, post-voiding views, and anterior/posterior bladder prevoid imagesDirect Radionuclide Cystogram Technique Direct radionuclide cystogram — sequential frames during bladder filling and voiding phasesVesicoureteral Reflux on Radionuclide Cystogram Direct radionuclide cystogram — post-flow total image and post-voiding views showing the bladder before and after urinationWhy Post-Void Images on a Radionuclide Cystogram Tc-99m MAG3 renal scan — composite image, flow curve, renogram curves, and quantitative results showing bilateral abnormal drainage with asymmetric differential functionDifferential Renal Function on MAG3 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
← Normal Renal Drainage Half-Time on MAG3Furosemide Dose for Diuretic Renography →

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