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MAG3 Renal Scintigraphy & Upper Tract Nuclear Imaging

MAG3 complements anatomical imaging by assessing relative renal uptake and urinary drainage. See the CT urogram companion for anatomical planning and the UPJ obstruction article for disease-specific treatment decisions.

Quick Reference​

Finding or preparation issuePractical interpretation
Prompt collecting-system washout, T½ <10 minStrong evidence against obstruction in a technically adequate study
Prolonged T½, including >20 min—
Low split renal function (SRF)Assess measurement quality, symptoms, anatomy, global renal reserve and trend; no universal nephrectomy cutoff
Adult furosemideUsually 0.5 mg/kg or 40 mg IV; reduced renal function may require more, according to nuclear-medicine assessment[1]
Bladder managementVoid before acquisition; catheterize selectively when emptying is unreliable; include postvoid/gravity-assisted drainage assessment
CTU and MAG3 sequencingOrder according to the clinical question without a routine 48-hour hold; report recent iodinated contrast exposure because it may impair tubular MAG3 clearance.[19]

The adult protocol and interpretation framework below is based on the SNMMI/EANM 2018 obstruction standard.[1]

1. Radiopharmaceutical: Tc-99m MAG3​

Chemistry and Mechanism​

Tc-99m mercaptoacetyltriglycine (MAG3) is predominantly cleared by proximal tubular secretion. Its relatively efficient extraction generally provides better kidney-to-background contrast than a filtration tracer such as DTPA when renal function is impaired. Severe dysfunction can produce an indeterminate MAG3 study.[1]

Tc-99m emits 140 keV photons and has a physical half-life of about 6 hours. For adult obstruction renography, the 2018 SNMMI/EANM standard prefers 37–185 MBq (1–5 mCi), whereas the 2023 US mertiatide label recommends 185–370 MBq (5–10 mCi).[1][10] The 2018 standard considers 370 MBq unnecessarily high for almost all applications; it may be needed for radionuclide angiography or quantitative flow assessment in selected transplant studies.[1] For adults with normal renal function, the estimated effective dose is about 0.007 mSv/MBq without voiding for 3.5 hours and about 0.0017 mSv/MBq with voiding 30 minutes after injection; hydration and voiding at study completion and every 30–60 minutes for the next 3 hours reduce bladder-wall dose.[1] Across the 2018 standard’s 37–185 MBq activity range, the modeled effective dose is roughly 0.06–1.3 mSv for adults with normal renal function, depending on voiding time.[1] Mettler's 2008 catalog estimates 2.6 mSv for a MAG3 renal scan at 370 MBq; its 1.8- and 3.3-mSv renal entries are for DTPA and DMSA, respectively, at the same activity.[11] MAG3 dose varies with administered activity and bladder emptying.[1] For technetium Tc 99m mertiatide, the 2023 US prescribing information directs lactating patients to pump and discard breast milk for at least 24 hours after administration, whereas the 2018 SNMMI/EANM standard does not require interruption.[10][1] A woman who is or may be pregnant is counseled by the nuclear-medicine physician before the study. Adults are imaged supine with the camera behind them, or anterior over the pelvis for a transplant.[1]

A routine MAG3 split-function percentage is relative uptake, not a directly measured GFR. MAG3 clearance can be estimated with a validated camera- or plasma-based method, but that result should not be relabeled as GFR or treated as identical to effective renal plasma flow. The methods, normalization and reference values must be specified.[1][7]

2. The Renogram Curve: Three Phases​

PhaseWhat it contributesImportant limitation
Perfusion / early arrivalTracer delivery and gross asymmetry—
UptakeRelative contribution of each kidney after background correctionTiming, depth, motion, injection infiltration and background activity can distort the percentage
Excretion / drainageParenchymal transit and collecting-system emptying, including response to diuresisRetention can reflect obstruction, weak renal function, a large reservoir or poor bladder emptying

Whole-kidney curves combine parenchymal and pelvic activity. Cortical and collecting-system regions of interest can help separate slow tissue transit from retained urine.[1]

The adult standard acquires images dynamically as serial 10-second frames (some laboratories use 2-second framing for the first few minutes to define time zero more precisely).[1] In hydrated adults with normal function, the renogram typically peaks by 5 minutes and falls to half its peak by 15 minutes; calyceal or pelvic retention of tracer can prolong the apparent time to peak in an otherwise normal kidney.[1]

3. Diuretic Renogram Protocol​

Furosemide Timing Protocols​

F0, F−15, F+20/F+30 and other established protocols are legitimate options. There is no universally preferred timing schedule. F0 is convenient and shorter; delayed furosemide permits observation of baseline drainage and lets tracer reach a dilated collecting system before testing washout. Very poor function may require delayed assessment rather than interpreting a rising early curve as obstruction. Consistency is valuable when comparing serial studies.[1]

A published 17-year MAG3-F0 experience used simultaneous administration to measure relative function. The correct uptake window remains important.[4]

Furosemide Dose and Hydration​

  • Adults: 0.5 mg/kg or 40 mg IV is the usual standard.[1] 40 mg is not an absolute ceiling in renal impairment. A higher dose may be needed to obtain an adequate intratubular diuretic concentration; document the actual dose and whether an adequate urine response occurred.
  • Hydration: unless fluid restriction or another contraindication applies, the adult standard suggests an additional oral fluid load of 5–10 mL/kg 30–60 minutes before the examination.[1] Tailor route and volume to the patient; fasting and dehydration can compromise interpretation.
  • Bladder: ask the patient to void before acquisition. Insert a freely draining catheter when anticipated voiding difficulty, a noncompliant bladder or diversion makes it necessary; routine catheterization of every adult is not required. After recent bladder surgery, any indwelling catheter must drain freely during the study to avoid leakage through the surgical incision.[1]

Conditions That Confound Diuretic Renogram Interpretation​

ConfounderWhat to check
Dehydration or insufficient diuretic responsePreparation, renal function, dose and measured urine output
Severely reduced functionWhether enough tracer reached the collecting system to assess drainage reliably
Large compliant renal pelvisReservoir retention despite an unobstructed outlet; assess upright/postvoid emptying
Full bladder, reflux, urinary diversionEmptying and drainage-catheter status; persistent reflux can distort washout
Injection infiltration, motion or inappropriate ROIsRaw images and processing quality before accepting quantitative results
DiclofenacCan delay ureteric transit; discuss withholding or repeating an abnormal study after discontinuation

An indeterminate examination should explain the limiting factor and how a repeat or complementary test could resolve it.[1]

T½ Interpretation​

T½ describes a 50% fall in activity from the relevant maximum, using the laboratory's specified ROI and fitting method. It is not uniformly measured from the furosemide injection time, and results from different acquisition or processing methods are not interchangeable.[1]

ResultInterpretation in context
<10 minPrompt drainage generally excludes obstruction
10–20 minRequires the images, postvoid drainage, renal function and clinical context
>20 min or no measurable half-timeConcerning retention, but also possible with poor function, inadequate diuresis or a large reservoir

An initial downsloping curve followed by a rapid upslope and increased cortical uptake during forced diuresis, sometimes with concurrent flank pain, has been described as the Homsy pattern in a MAG3 case report; with concordant symptoms and anatomical imaging, it may support intermittent, flow-dependent obstruction.[12] The pattern differs from prompt sustained washout or no initial response to furosemide.[1]

4. Split Renal Function (SRF)​

Calculation​

SRF is the relative background-corrected uptake in each kidney, expressed as a fraction of the bilateral total. The uptake interval should precede substantial loss of tracer into the ureter or bladder; a later suitable interval may be needed with severely delayed uptake. Position, depth and background correction matter, particularly with ectopic kidneys and poor function.[1]

Right SRF = corrected right-kidney uptake /
            (corrected right + corrected left uptake) × 100

In subjects with normal renal function, the adult standard reports a 95% confidence interval of 42–58% for relative MAG3 uptake using the integral method with perirenal-background correction.[1] An outlying value identifies asymmetry.[1] A 50:50 split can coexist with severe bilateral dysfunction.[1] The Rutland-Patlak plot is an alternative computational method for differential function.[13] Specify the uptake interval and processing method when reporting or comparing serial results.[1]

Compare like with like: tracer, hydration, furosemide timing, positioning, uptake interval, ROI processing and drainage-device status. Consider whether an apparent change reflects true ipsilateral loss, altered contralateral function or measurement variation.

A prospective repeatability study in 24 men with stable renal function, scanned a mean of 11 days apart, found that a decline of 7 percentage points (for example 50% to 43%) exceeded expected variation under its protocol.[6]

Serum creatinine may remain stable despite unilateral deterioration because it reflects combined renal function. Use the relative study alongside global function and anatomical follow-up.

5. Indications in Reconstructive Urology​

Urethral Stricture — Upper Tract Surveillance​

Order MAG3 when there is a specific unresolved functional or drainage question, such as persistent upper-tract dilation whose significance would change treatment. Ultrasound, renal function, symptoms and outlet evaluation often determine whether functional imaging adds value.

Neurogenic Bladder​

MAG3 evaluates the upper tract; urodynamics evaluates storage pressure and compliance. Upper-tract surveillance should follow the patient's risk category, using renal imaging, renal-function assessment and urodynamic reassessment where indicated. The EAU neuro-urology guideline does not prescribe annual MAG3 for every neurogenic patient.[8]

For a poorly emptying or noncompliant bladder or a refluxing reservoir, agree on an appropriate drainage plan with nuclear medicine so bladder back-pressure does not confound the upper-tract study.[1]

Ureteral Reconstruction​

Review the ureteral stricture hub for the clinical decision pathway.

After repair, select ultrasound, laboratory testing and functional imaging according to the procedure, baseline function, symptoms and unresolved concerns. Specify whether a stent or nephrostomy is present.

Urinary Diversion Surveillance​

Conduits, continent pouches and neobladders require ongoing renal and diversion follow-up. Use renography when drainage or relative function needs clarification. For a neobladder or ileal diversion, catheterize before renography to empty residual urine and leave the catheter draining during the study when feasible; this limits reflux-related confounding of washout.[1]

6. MAG3 vs. DTPA​

FeatureMAG3DTPA
Main renal handlingTubular secretionGlomerular filtration
Typical strengthDynamic drainage and relative uptake, especially with impaired functionFiltration-based function measurement with a validated method
Poor renal functionUsually better kidney-to-background contrast; can still be indeterminateLower extraction can limit count statistics and drainage assessment
Meaning of a reported clearanceMAG3 clearance / tubular extraction measureGFR-related measurement, subject to the acquisition and processing method

Choose the tracer and measurement method with nuclear medicine. Avoid claiming that either tracer is interpretable only above a rigid GFR cutoff or that MAG3 is a direct GFR measurement.[1][7]

7. DMSA Renal Cortical Scintigraphy​

DMSA provides static imaging of functioning renal cortex. Its role includes cortical defects or scarring, congenital renal anatomy and relative cortical contribution. A cortical defect is nonspecific: acute inflammatory abnormalities and permanent scar must be distinguished through timing and context. The pediatric SNMMI/EANM standard advises delayed assessment, generally at least six months after acute infection, when the question is persistent scarring.[5]

The pediatric SNMMI/EANM standard obtains posterior, anterior and posterior-oblique planar views with a high- or ultra-high-resolution collimator about 2–3 hours after injection; pinhole views are useful in infants and smaller children, and imaging may be delayed when renal clearance is poor.[5] The pediatric SNMMI/EANM standard suggests SPECT when feasible and pinhole imaging instead of SPECT in infants; equipment and expertise affect local acquisition choices. In a 40-patient comparison (37 children, 3 adults), dual-head SPECT and high-resolution planar imaging detected similar abnormal-segment counts (2.2 versus 2.1; p = 0.84), while other comparisons have favored SPECT.[5][15]

Use DMSA selectively when cortical information changes the clinical decision.

8. Upper Tract Imaging Hierarchy​

QuestionUseful test or combination
Is the collecting system dilated?Ultrasound, interpreted with prior imaging and clinical context
Where is the anatomical lesion?CTU, MRU or targeted retrograde/antegrade imaging as appropriate
Is drainage impaired and what is each kidney's relative contribution?Dynamic renography with an appropriate diuretic protocol
Is there a cortical defect or scar?DMSA when the result would affect management
Is reflux the question?Cystographic evaluation

Retrograde Pyelogram (RGP) vs. MAG3​

RGP defines luminal anatomy and can accompany endoscopic treatment. MAG3 assesses tracer handling and drainage.

CT Urogram and MAG3 Sequencing​

There is no routine 48-hour hold after iodinated CT contrast; recent contrast exposure should be reported because the 2017 Renoscan MAG3 product information warns that contrast media may impair tubular tracer clearance.[18] Choose sequence according to the question and local scheduling.[1] Recent contrast remains relevant if accompanied by acute kidney injury, dehydration or another change in renal function; discuss those clinical issues with nuclear medicine.[1]

9. Intervention Thresholds​

Obstruction with Preserved Function​

Confirm that the study was adequate and integrate symptoms, infections, stones, anatomical progression, parenchymal transit and functional trend. Stable, asymptomatic dilation can justify observation; convincing clinically consequential obstruction can justify intervention without waiting for a preset number of scans.

Obstruction with Reduced Function​

Low SRF increases the importance of sound interpretation and counseling. Consider the patient's overall kidney reserve, duration and cause of obstruction, infection, pain, reconstructive feasibility and goals. A decompression trial can be useful in selected uncertain cases, but there is no universal nephrostomy-first algorithm or required recovery to 20% before reconstruction.[16][3]

Very Low Relative Function​

In a retrospective adult UPJO cohort with DRF ≤15%, 19 patients underwent pyeloplasty and 44 nephrectomy. Symptoms improved in both groups; mean DRF in the pyeloplasty group was 9.5% before surgery and 10% after surgery, without significant improvement.[3]

Before nephrectomy, assess absolute or global and contralateral function; a contralateral percentage above 50% merely describes its relative share.[1]

Functional Loss Without Obstruction​

Investigate parenchymal disease, infection, vascular disease and changes in the opposite kidney as appropriate. Correlate with renal-function testing and anatomical imaging; involve nephrology when indicated.

10. Special Protocols and Pearls​

Renal Transplant Protocol​

Allograft scintigraphy can contribute information about perfusion, function, leaks and drainage. A biopsy-correlated study of 181 DTPA examinations in 127 recipients found considerable overlap between graft pathologies. Coordinate the question with the transplant and nuclear-medicine teams, using Doppler, clinical assessment and biopsy when indicated.[9]

For allograft imaging, MAG3 is preferred for functional assessment and is more effective for detecting outflow obstruction and urinary leaks; DTPA better depicts perfusion when vascular compromise or differentiation of acute tubular necrosis from rejection is the question.[17] One described protocol acquires 1 frame per second for the first minute as a first-pass perfusion study, then images every 20 seconds for 30 minutes; its images are used to assess activity in the kidney, collecting system, bladder and any drains for serial comparison.[14] An indwelling bladder catheter should drain freely, especially after recent bladder surgery to avoid leakage through the surgical incision.[1]

Pediatric Protocol Differences​

Use a dedicated pediatric protocol, with weight-based administered activity and age-appropriate hydration. The SNMMI/EANM pediatric standard describes F0 and delayed F+20/F+30 protocols and furosemide 1 mg/kg IV, suggested maximum 40 mg.[2] Routine catheterization is controversial; it is advised for selected conditions such as hydroureteronephrosis, posterior urethral valves, known reflux or neuropathic bladder. Sedation is rarely needed. Infant timing depends on the indication and clinical urgency.[2] The US mertiatide label establishes use from 30 days of age; safety or effectiveness below that age is not established. Earlier neonatal imaging therefore requires a specialist decision that accounts for off-label use and immature renal function.[10]

Post-Nephrostomy Tube Management​

State the clinical question and agree on whether and when to clamp the nephrostomy before the scan. The report must record tube status. A “clamp two hours, then open after uptake” plan depends on the clinical question; opening during excretion can bypass the obstruction being assessed. Do not ask a patient to manipulate or clamp a tube without the treating team's instructions.[1][2]

Drug Interactions​

Provide a current medication list, including chronic diuretics and drugs that may affect renal handling or urinary transit. The adult standard suggests holding a chronic diuretic on the morning of the test to support hydration, with individual instructions from the treating team. Diclofenac can delay transit. Do not automatically stop ACE inhibitors or ARBs for routine obstruction renography; medication withholding for a separate ACE-inhibitor renography protocol is a different question.[1]

11. Ordering Checklist​

  • State the decision the scan should inform: drainage, relative contribution, suspected recurrence or response to treatment.
  • Supply symptoms, relevant infections, recent creatinine or eGFR and prior imaging or scans.
  • Describe surgery, anatomy, stents, nephrostomy tubes, diversion and anticipated voiding difficulty.
  • Agree on hydration, medication instructions, bladder or reservoir drainage and any nephrostomy clamp plan.
  • Ask for comparison with the prior study and identification of technical limitations.

12. Reporting Elements​

Request the tracer and activity, furosemide dose and timing, preparation, patient position and drainage-device status. The interpretation should include relative uptake and processing method, qualitative transit or drainage, the definition of any reported T½, postvoid/gravity-assisted drainage, comparison with prior studies and an explicit explanation of indeterminate findings.[1][2]

Videos​

Pediatric MAG3 Renal Scan
AUA Core Curriculum (2025)

References​

1. Taylor AT, Brandon DC, de Palma D, et al. SNMMI Procedure Standard/EANM Practice Guideline for Diuretic Renal Scintigraphy in Adults With Suspected Upper Urinary Tract Obstruction 1.0. Semin Nucl Med. 2018;48(4):377–390. doi:10.1053/j.semnuclmed.2018.02.010. Full text.

2. Majd M, Bar-Sever Z, Santos AI, De Palma D. The SNMMI and EANM Procedural Guidelines for Diuresis Renography in Infants and Children. J Nucl Med. 2018;59(10):1636–1640. doi:10.2967/jnumed.118.215921.

3. Freitas PFS, Barbosa JABA, Cho DH, et al. Short-term outcomes of pyeloplasty vs. nephrectomy in adult patients with ureteropelvic junction obstruction and differential renal function ≤15%. Scand J Urol. 2021;55(3):192–196. doi:10.1080/21681805.2021.1879929.

4. Sfakianakis GN, Sfakianaki E, Georgiou M, et al. A renal protocol for all ages and all indications: mercapto-acetyl-triglycine (MAG3) with simultaneous injection of furosemide (MAG3-F0): a 17-year experience. Semin Nucl Med. 2009;39(3):156–173. doi:10.1053/j.semnuclmed.2008.11.001.

5. Vali R, Armstrong IS, Bar-Sever Z, et al. SNMMI procedure standard/EANM practice guideline on pediatric Tc-99m DMSA renal cortical scintigraphy: an update. Clin Transl Imaging. 2022. doi:10.1007/s40336-022-00484-x. Society guideline text.

6. Taylor A, Manatunga A, Halkar R, Issa MM, Shenvi NV. A 7% decrease in the differential renal uptake of MAG3 implies a loss in renal function. Urology. 2010;76(6):1512–1516. doi:10.1016/j.urology.2010.03.066.

7. Taylor A Jr, Corrigan PL, Galt J, et al. Measuring technetium-99m-MAG3 clearance with an improved camera-based method. J Nucl Med. 1995;36(9):1689–1695. PubMed.

8. European Association of Urology. EAU Guidelines on Neuro-urology. 2026. The guideline.

9. Gupta SK, Lewis G, Rogers KM, et al. Quantitative Tc-99m DTPA renal transplant scintigraphic parameters: assessment of interobserver agreement and correlation with graft pathologies. Am J Nucl Med Mol Imaging. 2014;4(3):213–224. PubMed.

10. Jubilant DraxImage Inc. Kit for the Preparation of Technetium Tc 99m Mertiatide Injection: US prescribing information. Revised January 2023. DailyMed label.

11. Mettler FA Jr, Huda W, Yoshizumi TT, Mahesh M. Effective doses in radiology and diagnostic nuclear medicine: a catalog. Radiology. 2008;248(1):254–263. doi:10.1148/radiol.2481071451

12. Cuda T, Thapa C, Pattison DA, et al. Diagnosis of intermittent hydronephrosis on multiphase CT intravenous pyelogram and Tc-99m-MAG3 study — Homsy sign. Radiol Case Rep. 2026;21(8):3419–3421. doi:10.1016/j.radcr.2026.04.093

13. Piepsz A, Ham H. Estimation of differential renal function by means of 99mTc-MAG3: integral method or Rutland-Patlak plot? Eur J Nucl Med. 1999;26(12):1627–1628. PubMed.

14. Goldfarb CR, Srivastava NC, Grotas AB, Ongseng F, Nagler HM. Radionuclide imaging in urology. Urol Clin North Am. 2006;33(3):319–328. doi:10.1016/j.ucl.2006.03.006

15. Brenner M, Bonta D, Eslamy H, Ziessman HA. Comparison of 99mTc-DMSA dual-head SPECT versus high-resolution parallel-hole planar imaging for the detection of renal cortical defects. AJR Am J Roentgenol. 2009;193(2):333–337. doi:10.2214/AJR.08.1788

16. Kalra S, Mehra K, Muruganandham K, et al. "Does Diversion in Poorly Functioning Obstructed Kidneys in Adults Favors Reconstructive Surgeries Over Ablative Procedures? A Prospective Study." Cureus. 2020;12(8):e10124. doi:10.7759/cureus.10124

17. Blaufox MD, De Palma D, Taylor A, et al. "The SNMMI and EANM practice guideline for renal scintigraphy in adults." Eur J Nucl Med Mol Imaging. 2018;45(12):2218–2228. doi:10.1007/s00259-018-4129-6

18. Medi-Radiopharma Ltd. Renoscan MAG3 1 mg kit for radiopharmaceutical preparation: Summary of Product Characteristics. Revised October 24, 2017. Product information

19. Medi-Radiopharma Ltd. Renoscan MAG3 1 mg kit for radiopharmaceutical preparation: Summary of Product Characteristics. Revised October 24, 2017. Product information