Renal Scintigraphy

What it does

Renal Scintigraphy reads the two renal nuclear-medicine studies. Dynamic Tc-99m MAG3 or DTPA renography, usually with a diuretic, measures how each kidney takes up tracer and how well it drains in suspected urinary tract obstruction. Static Tc-99m DMSA imaging shows the functioning renal cortex and its scars, mainly in children after urinary tract infection.

For a renogram, the run draws kidney and background regions, builds the time-activity curves and returns split function, time to peak (Tmax), drainage half-time (T½) and output efficiency, with the drainage pattern behind the obstruction call. For a DMSA scan, it maps cortical defects and scars and gives the differential renal function.

Intended use

Decision support for studies that are quantitative by nature but sensitive to how regions are drawn: a reproducible set of curves and numbers traced to their regions, and a consistent drainage assessment for the urologist deciding between observation and surgery. Poor hydration, a full bladder and a dilated, compliant collecting system can all slow drainage without obstruction, so the drainage pattern is returned with the curve behind it.

Who it is for

Nuclear-medicine physicians and radiologists reporting renal studies, paediatric urologists and nephrologists following hydronephrosis and urinary tract infection, and adult urologists assessing obstruction and planning surgery.

Accepted input

• Dynamic renogram: DICOM NM dynamic series of a MAG3 or DTPA study, with the diuretic phase when performed.
• DMSA scan: DICOM NM static images, planar views or SPECT, of the renal cortex.
• A study is one or the other; the run selects the matching section from the tracer and acquisition type.

Requirements

Requirement	Why
Dynamic frames with frame timing from injection onward	Time-activity curves, Tmax and split function in the uptake window
Both kidneys and the bladder in the field of view	Regions for each kidney and assessment of drainage
Time of diuretic administration (renogram)	Drainage half-time is measured after the diuretic
Posterior or both posterior and anterior views (DMSA)	Differential function and cortical defects per kidney
Original DICOM NM images, not screenshots	Region-based counts need the source data

Optional context

Age, hydration, bladder catheterisation, the diuretic timing protocol and prior pyeloplasty or reimplantation can be passed in clinical_context; they are used in the guidance.

The result

Section	Content
Diuretic renogram	Kidney regions, time-activity curves, split function, Tmax, drainage half-time, output efficiency and drainage pattern
DMSA cortical scan	Cortical defects and scars per kidney and differential renal function
Draft report	Opt-in (options.report): an English narrative that interprets the result for the reader (findings, impression, limitations); every number is checked against the findings

The regions of interest and curves are returned with the numbers, so every value can be traced back to the counts it was computed from.

Standards

• Guideline: SNMMI/EANM practice guideline on diuretic renal scintigraphy (2018) for renogram acquisition and quantification.
• DMSA: EANM guideline for cortical renal scintigraphy with DMSA.
• Units: UCUM units (minutes, percent).
• Terminology: SNOMED CT and RadLex for findings and anatomy.
• DICOM: SR TID 1500 Measurement Report for split function and curve parameters; Key Object Selection; Encapsulated PDF.

Reading the renogram numbers

Split function is the share of total renal uptake contributed by each kidney in the early uptake phase. Tmax and the drainage half-time describe the curve shape; output efficiency expresses how much of the tracer taken up by the kidney has left it by a given time, which is less dependent on renal function than the half-time alone.