DMSA Cortical Renal Imaging⁹⁹ᵐTc-DMSA

Quick Answer

Tc-99m-DMSA binds and is retained by proximal tubular cells, mapping functioning renal cortex. It is the reference study for acute pyelonephritis (focal cortical photopenia without volume loss), cortical scarring (persistent defects with volume loss, e.g. reflux nephropathy), and differential (split) function, and it confirms pseudotumors (column of Bertin) as normal cortex. It is heavily used in pediatrics (UTI/reflux).

Mechanism

DMSA is taken up and retained by proximal renal tubular cells in proportion to functioning cortical mass and perfusion, with prolonged cortical retention (imaging typically ~2–4 h post-injection). Unlike dynamic agents (MAG3/DTPA), it is a static cortical map, not a drainage study.

Clinical Indications

• Acute pyelonephritis — parenchymal involvement in febrile UTI (especially children).
• Cortical scarring — reflux nephropathy, post-pyelonephritic scars (permanent damage).
• Differential (split) function — each kidney's relative contribution.
• Pseudotumor confirmation — column of Bertin, dromedary hump; and duplex/ectopic/horseshoe anatomy.

Interpretation

• Acute pyelonephritis: focal or multifocal cortical uptake defects without volume loss (may resolve).
• Scar: persistent cortical defects with volume loss/contour deformity — image after ~6 months to confirm permanence.
• Differential function: relative cortical uptake quantifies each kidney's contribution.
• Pseudotumor: a column of Bertin/dromedary hump shows normal cortical uptake, confirming benignity.

Reporting Checklist

• Distinguish acute pyelonephritis (no volume loss) from scar (volume loss) — state timing (re-image scarring at ~6 months).
• Report differential function (%).
• Confirm pseudotumors as normal cortex; correlate photopenic areas with anatomy (cysts, hydronephrosis, duplex).

Common Pitfalls

• Imaging too soon after infection and calling a transient defect a permanent scar (re-image after ~6 months).
• Cysts, hydronephrosis, and duplex anatomy producing photopenic areas mistaken for scars.
• Using DMSA for drainage/obstruction questions (that is MAG3's job).

Board Pearls

DMSA binds and is retained by proximal tubular cells, mapping functioning cortex. The key distinction: acute pyelonephritis = focal cortical uptake defect without volume loss (may resolve); scar = a persistent defect with volume loss/contour deformity. Image scarring only after ~6 months — an early defect can be transient infection, not permanent damage.

DMSA gives differential (split) function from relative cortical uptake and confirms pseudotumors — a column of Bertin or dromedary hump shows normal cortical uptake, establishing benignity. It is central to pediatric UTI/reflux evaluation.

DMSA answers cortical questions dynamic renography cannot (parenchymal infection, permanent scar, cortical mass), but it is not a drainage study — obstruction/hydronephrosis questions need MAG3 ± furosemide. Cysts, hydronephrosis, and duplex anatomy create photopenic areas that mimic scars, so correlate with anatomy.

Related Pages

• Related: Renal scintigraphy (dynamic MAG3/DTPA), radionuclide cystography, pediatric nuclear medicine.
• Calculator: renal split-function tool; pitfalls: Pearls, pitfalls & normal variants.

Figure / Diagram Suggestions

• A pyelonephritis vs scar teaching pair (defect ± volume loss).
• A pseudotumor (column of Bertin) normal-cortex confirmation image.
• A DMSA vs MAG3 role split (cortex vs drainage).

Self-Check (Board-Style)