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Paediatric · Renal

Paediatric Renal Imaging

Snapshot

Renal studies dominate paediatric nuclear medicine. ⁹⁹ᵐTc-DMSA is the reference standard for cortical scarring after urinary tract infection and for differential function; ⁹⁹ᵐTc-MAG3 diuretic renography separates obstruction from dilatation; and radionuclide cystography (direct or MAG3 indirect) detects vesicoureteric reflux at low radiation dose.

Childhood UTIs can scar the developing kidney, so accurate cortical and drainage assessment guides management. Radionuclide cystography gives far lower gonadal dose than fluoroscopic studies for reflux detection.

DMSAScarring reference
MAG3Obstruction & reflux
Low doseCystography

When to image

  • Assessing scarring after febrile/recurrent UTI (DMSA).
  • Antenatal or postnatal hydronephrosis — obstruction vs dilatation (MAG3).
  • Detecting and monitoring vesicoureteric reflux (cystography).
  • Differential function before intervention.

How to read it

  • DMSA: cortical photopenia = acute pyelonephritis or scar; report split function.
  • MAG3: judge drainage from images, curve shape, cortical clearance and gravity-assisted/post-void drainage — T½ must not be interpreted in isolation; the aim is to find kidneys at risk of losing function.
  • Cystography: tracer in the ureters/renal pelvis indicates reflux (graded); indirect (MAG3) cystography needs a toilet-trained, cooperative child.

Protocol

  • Weight-based administered activity (EANM dosage card or 2024 North American consensus); adequate oral or IV hydration; a bladder catheter is optional — always assess gravity-assisted and post-void drainage.
  • DMSA static imaging; MAG3 dynamic (± indirect cystogram); direct cystography for reflux.
  • Comfort/immobilisation and family-centred care.

Pitfalls

  • Image for scars at least 6 months after the most recent acute infection.
  • Dehydration blunts diuretic response.
  • Movement degrades quantification — attention to positioning.
Evidence & guidelines
  • SNMMI/EANM guidelines: diuresis renography in children (Majd et al., J Nucl Med 2018;59:1636–1640) and paediatric DMSA (Vali et al., Clin Transl Imaging 2022;10:173–184); EANM direct cystography (Fettich et al., 2003); EANM dosage card / 2024 North American consensus.
  • DMSA is the cortical reference standard; radionuclide cystography minimises reflux-study dose.
In depth
  • ⁹⁹ᵐTc-DMSA is bound by proximal tubular cells, with 40–65% of the injected dose in the renal cortex at 2 h and little urinary excretion; the paediatric activity is 1.85 MBq/kg (minimum 18.5 MBq, maximum 100 MBq).
  • In piglet models with histology as reference, DMSA SPECT detected acute pyelonephritis with about 92% sensitivity and 94% specificity per kidney; normal differential uptake is about 45–55%.
  • Acute pyelonephritis appears as focal or multifocal reduced cortical uptake with indistinct margins and no volume loss (the kidney may be swollen); a mature scar shows volume loss, cortical thinning or a wedge-shaped defect with sharper edges.
  • Pinhole and SPECT both improve defect detection over parallel-hole planar imaging; SPECT is slightly more sensitive than pinhole but less specific, with similar overall accuracy. EANM finds no consensus on SPECT and warns of false positives, and pinhole views are often used instead of SPECT in infants.
  • Reassess for scarring with DMSA at least 6 months after acute pyelonephritis, since many acute defects resolve.
  • ⁹⁹ᵐTc-glucoheptonate is an alternative cortical agent (10–20% of the dose in the proximal tubules at 2 h), but because 40–65% is filtered, pelvicalyceal activity can interfere with cortical assessment.
  • For transplant and dynamic renal imaging MAG3 is preferred, at 3.7 MBq/kg (5.55 MBq/kg if a flow study is needed), minimum 37 MBq and maximum 148 MBq.
  • In the 'top-down' approach, DMSA is done first after febrile UTI and cystography is reserved for abnormal scans, because renal damage rather than reflux itself is the main concern. Ultrasound is insensitive for focal scarring (5% sensitivity against DMSA in one large series).

Sources: SNM procedure guideline for renal cortical scintigraphy in children 1997 (PMID 9379207) · North American consensus guidelines 2016/2024 update (PMID 27909182 · PMID 40664486) · PMID 11152787 (Majd, Radiology 2001) · EANM DMSA guideline 2009 (Piepsz et al.) · PMID 8862320 (Majd, J Nucl Med 1996) · PMID 15311040 (Hansson, J Urol 2004) · PMID 14669099 (Moorthy, Pediatr Nephrol 2004)

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