TechneScan DMSA (Technetium-99m Succimer Kit)

What Is TechneScan DMSA and What Is It Used For?

TechneScan DMSA belongs to a class of medicines called diagnostic radiopharmaceuticals. Unlike conventional therapeutic drugs, a diagnostic radiopharmaceutical is administered in very small amounts and contains a radioactive atom whose gamma emissions are used to image the structure or function of an organ. TechneScan DMSA is unusual because it is not administered as sold; the vial contains only the non-radioactive “cold” ligand (succimer), which the radiopharmacist labels with fresh technetium-99m immediately before use. The result is 99mTc-succimer, sometimes called 99mTc-DMSA after the chemical name dimercaptosuccinic acid.

The finished injection has a single clinical purpose: to visualize the functioning cortex of the kidneys. After intravenous injection, 99mTc-succimer is extracted from peritubular blood by the proximal tubular epithelial cells, where it binds strongly to sulfhydryl-containing tissue components and remains in place for hours. This slow washout, combined with near-zero background activity in surrounding organs, gives exceptionally clean planar and SPECT images of the kidney parenchyma. Areas of cortex that do not take up the tracer — because they are scarred, dysplastic, infarcted or acutely infected — appear as photopenic (“cold”) defects against bright normal cortex.

The radionuclide used for labeling, technetium-99m, is the workhorse of modern nuclear medicine. It has a short physical half-life of 6.02 hours and emits a 140 keV gamma photon that is almost ideal for external detection with a gamma camera. Because the injected mass of succimer is in the microgram range and the mass of technetium is in the nanogram range, the resulting injection produces no pharmacological effect of its own; it works purely as a visible tracer. Regulatory authorities including the EMA, the UK MHRA, the U.S. FDA and national agencies classify the product under ATC code V09CA02 — technetium (99mTc) dimercaptosuccinic acid.

How Does 99mTc-Succimer Work?

Succimer is a small organic molecule with two adjacent thiol (–SH) groups that readily chelate reduced technetium-99m. When the kit is reconstituted with sterile sodium pertechnetate (99mTc) solution, the stannous chloride present in the vial reduces the pertechnetate anion (TcO₄⁻) to a lower oxidation state, and the reduced technetium-99m forms a stable complex with the succimer ligand. The finished 99mTc-succimer complex circulates briefly in plasma, where it is approximately 75–80% bound to plasma proteins, and is then extracted across the peritubular capillaries into the proximal tubular cells.

Within the proximal tubular cells, 99mTc-succimer binds to cytosolic sulfhydryl-rich proteins and to the outer surface of the cell. Uptake is an active process that depends on peritubular extraction rather than glomerular filtration; only a small fraction of the injected dose is filtered and appears in the urinary bladder. The net result is a striking compartmentalization of the tracer: at 3–6 hours after injection, approximately 40–50% of the administered activity is retained in the renal cortex, 10–20% has been excreted in the urine, and the remainder is distributed in liver, blood and extravascular fluid at very low levels. This ratio is what makes 99mTc-DMSA images look so clean.

Because cortical uptake depends on both perfusion and the mass of functioning tubular cells, the technique measures functioning renal cortical mass directly. The ratio of counts between the left and right kidneys, after correction for background and for soft-tissue attenuation, gives the differential (split) renal function — a key figure in every pediatric nephrology and urology clinic, as well as in the work-up of renovascular hypertension and of potential living kidney donors. SPECT and SPECT/CT imaging further improve the sensitivity and specificity of the examination for detecting small cortical defects, especially in complex anatomy or after partial nephrectomy.

Approved Clinical Indications

TechneScan DMSA (99mTc-succimer injection) has been approved by the EMA, the U.S. FDA, the UK MHRA and other authorities for the following diagnostic uses:

• Detection of renal cortical scarring in children: 99mTc-DMSA scintigraphy is the reference standard for diagnosing renal parenchymal scars after febrile urinary tract infection, as recommended by the European Association of Urology (EAU), the European Society for Paediatric Urology (ESPU) and the National Institute for Health and Care Excellence (NICE).
• Assessment of acute pyelonephritis: Acutely inflamed renal segments show reduced DMSA uptake and appear as cold defects, which is useful in atypical cases or when imaging findings will change management.
• Measurement of differential (split) renal function: Quantitative calculation of the relative contribution of each kidney to overall renal function, with a typical error of less than 5% compared with true glomerular filtration.
• Evaluation of congenital anomalies: Diagnosis and characterization of ectopic kidneys, horseshoe kidneys, crossed fused ectopia, duplex systems, multicystic dysplastic kidney and renal hypoplasia.
• Assessment of renal trauma and infarction: Localization of cortical injury, regions of devascularization and post-traumatic scarring that may not be obvious on computed tomography.
• Follow-up of renal transplantation: Assessment of functioning cortical mass in chronic allograft dysfunction and to differentiate global from segmental cortical loss.
• Investigation of renovascular hypertension: Evaluation of cortical integrity in combination with captopril renography and other modalities.
• Work-up for living kidney donation: Precise quantification of each kidney’s share of cortical function to determine which kidney should be donated.

Because DMSA scintigraphy is the examination that most directly measures functioning renal parenchyma, its findings frequently determine whether a child needs long-term antibiotic prophylaxis, further urological investigation such as voiding cystourethrography, or corrective surgery. Its role is therefore complementary to — not replaced by — ultrasound and MRI.

What Should You Know Before Taking TechneScan DMSA?

Every nuclear medicine examination must be preceded by a careful clinical justification that weighs the anticipated diagnostic benefit against the radiation dose. The referring physician and the nuclear medicine specialist agree that 99mTc-DMSA is the most appropriate tracer for the clinical question (for example, “is there cortical scarring?”), that no recent imaging already answers it, and that alternative non-ionizing techniques such as ultrasound or MRI have been considered. This stepwise approach is known as the ALARA principle (As Low As Reasonably Achievable) and is codified in European and international radiation protection regulations.

Contraindications

TechneScan DMSA must not be used in the following situations:

• Hypersensitivity: Known hypersensitivity to succimer, to technetium, to stannous chloride or to any excipient in the kit (principally sodium chloride and inositol in the lyophilized formulation).
• Pregnancy (elective examinations): 99mTc-succimer is not a recommended examination in pregnancy because it exposes the fetus to ionizing radiation. Non-urgent scans must be postponed until after delivery; urgent examinations require estimation of the fetal dose and use of the lowest achievable activity.
• Severe uncontrolled hypersensitivity history to other radiopharmaceuticals: Requires individual risk–benefit assessment and on-site resuscitation preparedness.

There are no strict age or weight-based contraindications, but each indication is assessed on an individual basis, particularly in very young infants where alternative imaging may be preferred initially.

Warnings and Precautions

Although 99mTc-succimer has an excellent safety profile, several important precautions apply to every examination. Patients and caregivers should be informed about these in advance so that questions can be answered well before the appointment.

Ionizing radiation: Every diagnostic dose of 99mTc-succimer exposes the patient to a small amount of ionizing radiation. The effective dose for a typical adult activity of 80–160 MBq is approximately 0.7–1.4 mSv, comparable to 4–7 months of natural background radiation worldwide (average 2.4 mSv per year). Over a lifetime, repeated radiological examinations contribute cumulatively to the stochastic risk of radiation-induced cancer, so each procedure must be individually justified and imaging repetition minimized.

Pediatric patients: Children are more radiosensitive than adults because their cells divide faster and they have a longer life expectancy during which a radiation-induced cancer might develop. For this reason, pediatric activities are always scaled down from adult activities according to the EANM Paediatric Dosage Card, which uses a body-mass-based multiplier. The minimum administrable activity recommended by the EANM must still be respected to ensure that the image remains diagnostic. Because 99mTc-DMSA is so frequently performed in infants and children, pediatric hospitals are particularly skilled at providing a child-friendly environment and age-appropriate explanations.

Renal function: Because 99mTc-succimer uptake depends on functioning proximal tubules and renal perfusion, severe renal impairment reduces cortical uptake and increases background activity, which can complicate image interpretation. The examination can still be performed, but delayed imaging (up to 24 hours post-injection) may be required to obtain diagnostic images. In anuric patients, the tracer remains in blood and soft tissue for longer, slightly increasing the effective dose.

Hydration and bladder emptying: Patients are usually asked to drink plenty of fluids before and after the examination and to void the bladder frequently. Although only 10–20% of the injected activity is excreted in urine, good hydration accelerates clearance of the unbound fraction, lowers the radiation dose to the bladder wall and improves image quality.

Thyroid blocking (rarely needed): In some centers, patients who will undergo repeated 99mTc-based examinations receive oral potassium iodide or perchlorate to block thyroid uptake of any free pertechnetate from radiochemical impurities in the injection. This is a departmental decision and is not routinely required for a single DMSA scan.

Radiation protection for staff and close contacts: After injection, patients emit small amounts of gamma radiation until the tracer has decayed and been excreted. Staff follow strict radiation protection procedures. Patients are generally advised to avoid prolonged close contact with pregnant women and young infants for the first 12–24 hours after the examination, and to follow any specific instructions given by the nuclear medicine department.

Pregnancy and Breastfeeding

Pregnancy status must be confirmed before any examination in women of childbearing potential. A urine or serum beta-hCG test is commonly performed. The “10-day rule” or pregnancy test should be applied according to local protocol.

• Pregnancy: Elective diagnostic use of 99mTc-succimer is contraindicated. If the examination cannot be avoided, the lowest achievable activity should be used, and the absorbed dose to the fetus should be estimated and documented. A fetal dose of less than 1 mSv is associated with a negligible risk of deterministic effects.
• Breastfeeding: 99mTc-succimer is excreted into breast milk in small amounts. The EANM recommends interrupting breastfeeding for at least 4 hours after a diagnostic injection; some protocols recommend 12 hours. Milk expressed during the interruption should be discarded. Close prolonged contact with the breastfeeding infant outside of feeding should also be limited for the same interval.
• Male fertility: Diagnostic doses do not have clinically significant effects on male fertility, and no specific contraceptive precautions are required.

Children and Adolescents

99mTc-DMSA scintigraphy is one of the most important and most commonly performed nuclear medicine examinations in pediatrics, particularly for the assessment of pyelonephritic scars in children with recurrent urinary tract infections and for work-up of congenital anomalies of the kidney and urinary tract (CAKUT). Pediatric activities must be scaled according to body weight using the EANM Paediatric Dosage Card. The minimum activity required to obtain diagnostic images should be used, never a fixed adult fraction. Age-appropriate preparation (play therapy, parent presence, immobilization aids, oral sedation or general anaesthesia if strictly necessary) should be offered to help children cope with the procedure.

Driving and Operating Machinery

99mTc-succimer does not produce any known pharmacological effect on alertness, vision or psychomotor performance at the tracer doses used. Adult patients are usually fit to drive home after the examination. Individual anxiety, sedation used for pediatric patients, or underlying medical conditions may affect this. Always follow the specific advice of the nuclear medicine department.

How Does TechneScan DMSA Interact with Other Drugs?

Because only microgram amounts of succimer and nanogram amounts of technetium-99m are injected, 99mTc-succimer does not inhibit cytochrome P450 enzymes, does not alter plasma protein binding and does not compete with other drugs for renal transport in a clinically meaningful way. The relevant “interactions” differ from those encountered with pharmacological medicines: they are almost entirely effects of other drugs on how the tracer is distributed, bound, or excreted, which in turn alters the appearance of the scintigraphic images. These are sometimes called imaging interactions or biodistribution interactions.

For this reason it is essential to provide the nuclear medicine department with a complete and up-to-date list of all prescription drugs, over-the-counter products, vitamins and herbal supplements taken in the preceding weeks. In many cases, specific medicines must be paused for a defined interval before the examination, and the referring clinician will give written instructions.

Major Interactions

The following categories of medicines have the most important effects on 99mTc-succimer biodistribution and frequently require timing adjustment, test postponement or selection of a different tracer.

Minor Interactions

Several additional medicines and dietary factors can subtly affect biodistribution or labeling quality. They rarely require discontinuation, but the interpreting physician should be aware of them.

What Is the Correct Dosage of TechneScan DMSA?

TechneScan DMSA is not a patient-administered medicine in the traditional sense. The kit itself is never injected; instead it is reconstituted with a measured activity of sterile sodium pertechnetate (99mTc) in a licensed radiopharmacy, quality-controlled for radiochemical purity and then drawn up into a shielded syringe for intravenous injection. The prescribed quantity is expressed in becquerels (Bq), the SI unit of radioactivity, most commonly with the prefix mega (MBq, one million disintegrations per second). The activity is measured in a calibrated dose calibrator immediately before injection, because technetium-99m decays by 50% every 6.02 hours and the actual activity at injection differs from the calibration time.

Administered activities must always be justified and optimized according to the ALARA principle and to national and international diagnostic reference levels (DRLs). Reference activities vary slightly between the European Association of Nuclear Medicine (EANM), the Society of Nuclear Medicine and Molecular Imaging (SNMMI) and national authorities, but they converge on similar ranges for established indications.

Adults

Children

Pediatric activities are scaled from the adult reference activity of 80 MBq using the EANM Paediatric Dosage Card multiplier based on body weight. A minimum administrable activity of approximately 18–20 MBq is defined to ensure that the images remain diagnostic — below that threshold the signal-to-noise ratio is too poor to answer the clinical question and the child is effectively exposed to radiation for no benefit. Image-quality optimization (optimal collimator, longer acquisition times, pinhole imaging for small kidneys, pediatric-specific SPECT protocols) is essential.

Elderly

No specific dose reduction is required for elderly patients on the basis of age alone. However, elderly patients often have reduced renal function, which can prolong the biological half-life of the tracer and slightly increase the effective dose to the bladder wall and to soft tissues. Good hydration and encouragement of frequent voiding mitigate this effect. SPECT imaging may be particularly useful in older adults because cortical thinning makes small defects harder to see on planar views alone.

Renal Impairment

99mTc-succimer is excreted primarily via tubular retention and, to a lesser extent, via glomerular filtration. Severe renal impairment does not contraindicate the scan but reduces cortical uptake and increases background activity. In these patients:

• Use the upper end of the recommended activity range when body size allows.
• Delay imaging to 6 hours or even 24 hours post-injection.
• Interpret the scan qualitatively rather than relying on absolute differential percentages when uptake is globally reduced.
• In anuric dialysis patients the concept of “split function” may not be clinically useful; clarify the referral question first.

Missed Dose

Because 99mTc-succimer is administered as a single intravenous dose on the day of examination in a hospital setting, the concept of a “missed dose” does not apply in the usual sense. If an appointment is missed, it should be rescheduled as soon as practical. The radiopharmacy will need sufficient notice to plan the labeling and dispensing on the new date, because the isotope decays quickly and each prepared vial is valid only for a few hours.

Overdose

Because the administered activity is calibrated immediately before injection, accidental overdosing is extremely rare. In the unlikely event that a substantially greater activity is administered than intended, patient radiation dose can be reduced by forced diuresis and frequent voiding of the bladder, together with good hydration. There is no specific pharmacological antidote; symptomatic management is based on the radiation dose absorbed rather than on the trace chemical mass involved. Because succimer binds to heavy metals, chelation therapy is not indicated in the context of a DMSA imaging overdose — the concentrations are far too low to have any therapeutic or toxic effect.

What Are the Side Effects of TechneScan DMSA?

Because only microgram amounts of succimer and nanogram amounts of technetium-99m are injected, 99mTc-succimer does not produce classical pharmacological side effects. The side effects that have been reported are almost exclusively injection-site reactions, vasovagal responses and very rare hypersensitivity reactions. Large post-marketing surveillance databases and pediatric cohort studies consistently show adverse event rates well below 1 in 10,000 examinations.

Side Effect Frequency Overview

Radiation-Related Stochastic Effects

Even at the low activities used for diagnostic examinations, ionizing radiation carries a small theoretical long-term risk of stochastic effects — primarily a slightly increased lifetime probability of radiation-induced cancer. The risk from a single 99mTc-DMSA scan is estimated to be in the range of approximately 1 in 10,000 to 1 in 100,000, depending on age and organ dose. This must be compared with the benefit of obtaining a diagnosis that could materially change clinical management — for example, identifying renal scarring that warrants long-term follow-up or antibiotic prophylaxis, or confirming that differential function is preserved well enough for a kidney to remain in situ. Deterministic effects such as skin burns or hair loss do not occur at diagnostic doses; these are associated only with interventional fluoroscopy or therapeutic radionuclide administration.

Managing Side Effects

If a reaction occurs, it is treated symptomatically. Nuclear medicine departments are equipped with resuscitation equipment and are staffed by personnel trained to recognize and treat rare hypersensitivity reactions, following the same anaphylaxis algorithms used for iodinated contrast media. Mild infusion reactions usually resolve spontaneously within minutes and do not require specific therapy. Extravasation is prevented by careful intravenous technique; if it occurs, elevation and warm compresses generally suffice. Any reaction, however mild, should be reported to the nuclear medicine staff and documented in the patient’s medical notes.

National pharmacovigilance reporting systems such as the UK Yellow Card scheme, EudraVigilance in the European Union and MedWatch in the United States accept reports for radiopharmaceuticals as for any other medicine. Reporting even mild reactions helps build a more accurate long-term safety profile.

How Should You Store TechneScan DMSA?

TechneScan DMSA is classified, after reconstitution, as a Class 7 dangerous good (radioactive material) and is therefore subject to a double layer of regulation: pharmaceutical regulation (as a medicine) and radiation protection regulation (as a radioactive source). It is delivered directly from the manufacturer to the nuclear medicine department in validated cold-chain packaging, accompanied by a Certificate of Analysis documenting kit composition and batch specifications.

Kit Storage (Before Labeling)

• Temperature: Store in a refrigerator at 2–8 °C. Do not freeze. Freezing can damage the lyophilized cake and compromise labeling yield.
• Light: Protect from direct sunlight and strong artificial light by keeping the vials in their original carton.
• Packaging: Keep the vials in the outer carton until immediately before use. The rubber stopper must not be pierced except to add sodium pertechnetate (99mTc) for reconstitution.
• Shelf life: Typically 12–24 months from manufacture (see the expiry date printed on the vial label). Do not use beyond the expiry date, even if the vial appears intact.
• Access: Keep in a dedicated, locked radiopharmacy refrigerator accessible only to authorized personnel. Never store in a domestic refrigerator or with food products.

Reconstituted Injection Storage

• Lead shielding: Once labeled with 99mTc pertechnetate, the vial must be placed in a lead shielded pot to reduce external dose rates to staff and patients.
• Temperature: Store at controlled room temperature, below 25 °C. Do not refrigerate or freeze the radiolabeled injection.
• In-use shelf life: The radiolabeled 99mTc-succimer injection should be used within 4 hours of preparation, and in any case not later than the activity drop below the minimum required for diagnostic imaging.
• Single use: The vial is for single-patient or multi-patient use only as specified in the local Summary of Product Characteristics and must never be used after the stated in-use shelf life.

Quality Control Before Use

Every reconstituted batch of 99mTc-succimer must undergo radiochemical purity testing before release to the clinical area. The accepted specification is typically not less than 95% bound as 99mTc-succimer, with free pertechnetate and hydrolyzed reduced technetium each contributing less than 5%. Acceptable methods include instant thin-layer chromatography (ITLC-SG) with saline and methyl ethyl ketone (MEK), or high-performance liquid chromatography (HPLC). Batches that fail purity specifications must be rejected and reprocessed or discarded as radioactive waste.

Disposal of Waste

Unused radiolabeled material, syringes, needles, vials and other contaminated waste must be managed according to national regulations for radioactive waste. In practice this usually means storing items in a dedicated decay area until the residual activity has fallen below clearance limits (typically 10 half-lives, i.e. around 60 hours for 99mTc). After decay, items may be disposed of as conventional infectious clinical waste or as non-radioactive waste if local rules permit. Never dispose of radioactive materials via ordinary wastewater, household waste or landfill. These rules protect both public health and the environment.

Keep all medicines and radioactive sources out of the sight and reach of children. Patients and visitors must not be allowed unsupervised access to stored kits or to prepared radiolabeled injections.

What Does TechneScan DMSA Contain?

The kit is designed to convert sodium pertechnetate (99mTc) — a simple inorganic radionuclide — into a stable, tissue-targeted radiopharmaceutical suitable for safe intravenous injection. Understanding the composition of the vial helps explain why the finished injection is essentially a dilute saline solution containing only a microgram-level concentration of the 99mTc-succimer complex.

Active Substance and Excipients

• Active ligand: Succimer (meso-2,3-dimercaptosuccinic acid), typically 1.0–1.2 mg per vial; chelates reduced technetium-99m to form 99mTc-succimer.
• Reducing agent: Stannous chloride dihydrate (SnCl₂·2H₂O) or a tin fluoride derivative, at microgram level, reduces the pertechnetate anion (7+) to a lower oxidation state suitable for ligand binding.
• Stabilizer / antioxidant: Ascorbic acid, at trace amounts, protects the tin from re-oxidation during storage and ensures radiochemical purity.
• Bulking agent: Inositol or similar sugar alcohol, to maintain the lyophilized cake.
• pH adjustment: Hydrochloric acid or sodium hydroxide, as needed, to obtain the specified pH range after reconstitution.
• Atmosphere: The vial is sealed under nitrogen to exclude oxygen during storage.
• Radionuclide (added at labeling): Sodium pertechnetate (99mTc) injection, eluted from a licensed 99Mo/99mTc generator on the day of use.
• Final diluent: Sterile 0.9% sodium chloride solution may be used to adjust the final volume or activity concentration.

Physical and Radiochemical Characteristics

Packaging and Manufacturer

TechneScan DMSA is supplied as a carton containing several sterile single-dose glass vials of lyophilized powder, each sealed with a rubber stopper and aluminium overseal. The rubber stoppers are latex-free. The carton is labeled with the batch number, expiry date, storage conditions and radioactive material handling information. The product is manufactured by Curium Pharma, a global leader in nuclear medicine radiopharmaceuticals, with production sites in Europe and North America.