RD7.5 | Imaging in Paediatrics — Glossary

Bacterial infection of the renal parenchyma; shows photopenic cortical defects on an acute DMSA scan and is a step on the path to permanent scarring if recurrent.

Dark, branching air-filled bronchi seen against surrounding white consolidated lung; a sign that an opacity is alveolar (lung) rather than pleural fluid.

Failure of an obstructed lung to empty, leaving it abnormally lucent and hyperinflated; exaggerated on expiratory or lateral-decubitus films, with the mediastinum shifting away from the obstructed side on expiration.

'As Low As Reasonably Achievable' — the radiation-protection principle that any ionising imaging dose should be kept as low as possible while still answering the clinical question; especially important in radiosensitive children.

The principle of keeping ionising radiation dose 'As Low As Reasonably Achievable' and using child-sized technique; in paediatric UTI it justifies leading with non-ionising ultrasound and reserving MCUG and DMSA for defined indications.

Continuous low-dose antibiotic given to selected children (e.g. with significant reflux or recurrent infections) to reduce the frequency of UTIs and protect the kidney from further scarring.

Collapse of lung distal to a completely obstructing foreign body, with volume loss, opacity, and shift of the mediastinum TOWARDS the affected side.

A urinary tract infection with features such as serious illness, poor urine flow, abdominal/bladder mass, raised creatinine, septicaemia, failure to respond within 48 hours, or a non-E. coli organism — features that prompt earlier and broader imaging.

Partial bronchial obstruction that allows air in on inspiration but traps it on expiration, producing air-trapping and hyperinflation of the affected lung.

Patchy, often bilateral peribronchial consolidation, common in infants and with staphylococcal or viral-bacterial infection.

Direct endoscopic visualisation of the airway; in foreign body aspiration it is the definitive DIAGNOSTIC and THERAPEUTIC step, allowing both confirmation and removal of the object.

A plain X-ray of the chest; the low-dose, first-line and mainstay imaging investigation when imaging is indicated for a paediatric chest infection.

A sudden bout of coughing, gagging, or transient cyanosis while eating or playing; a convincing history of this is itself an indication for definitive evaluation regardless of imaging.

Pneumonia acquired outside hospital; in children the diagnosis is largely clinical (fever, cough, age-specific tachypnoea, chest signs) and uncomplicated cases do not require routine imaging.

Replacement of alveolar air by inflammatory exudate, producing an area of increased (white) opacity on the chest film, often containing dark branching air bronchograms.

Cross-sectional X-ray imaging of the chest; high-dose relative to a plain film, reserved in children for complications (necrotising pneumonia, abscess, suspected mass, non-resolving disease) using low-dose paediatric protocols.

A nuclear-medicine renal cortical scan using technetium-labelled dimercaptosuccinic acid taken up by functioning tubular cells; damaged cortex appears as a photopenic (cold) defect, detecting acute pyelonephritis and permanent scarring and quantifying differential renal function.

Infected pleural fluid (pus), often septated and loculated; ultrasound is the best tool to characterise it and to guide drainage.

A chest radiograph taken in expiration; the normal lung deflates and becomes denser while an air-trapped lung stays lucent, unmasking unilateral air-trapping.

Real-time X-ray imaging that can show dynamic air-trapping (the obstructed lung failing to deflate and the mediastinum swinging on respiration); used selectively because of continuous radiation exposure.

Inhalation of an object into the airway; a paediatric emergency most common in toddlers, frequently involving radiolucent organic material such as peanuts or seeds.

Dilatation of the renal pelvis and calyces, seen on ultrasound; may reflect obstruction, high-grade vesicoureteric reflux, or a congenital anomaly.

A paediatric radiation-safety campaign promoting child-sized, weight-/size-adjusted imaging technique and avoidance of unnecessary ionising studies in children.

A radiograph taken with the child lying on one side; the dependent normal lung deflates while an air-trapped lung resists deflation — useful in young children who cannot perform a forced expiration.

A localised, thick-walled, often fluid-containing cavity within the lung; a complication of infection confirmed on CT and sometimes requiring drainage.

Micturating (voiding) cystourethrogram; a fluoroscopic study in which the catheterised bladder is filled with contrast and imaged during voiding, used to diagnose and grade vesicoureteric reflux and to show the urethra (e.g. posterior urethral valves). Uses ionising radiation.

Displacement of the mediastinum: AWAY from the affected side in air-trapping/hyperinflation (worst on expiration) and TOWARDS the affected side in collapse.

Breakdown of consolidated lung producing necrotic, non-enhancing areas; a complication best confirmed on contrast-enhanced CT and managed with prolonged intravenous antibiotics.

Infection developing distal to a retained airway foreign body, often presenting as persistent or recurrent consolidation in the same location.

The greater lifetime risk of harm from a given radiation dose in children, due to actively dividing cells and a longer remaining lifespan in which radiation-induced effects can manifest; the rationale for ALARA in paediatric imaging.

An area of reduced or absent tracer uptake on a DMSA scan, indicating damaged or non-functioning renal cortex — acute pyelonephritis on an early scan or permanent scarring on a delayed scan.

Fluid in the pleural space; on an erect chest film it blunts the costophrenic angle. A parapneumonic effusion may be simple or become an infected empyema.

A dense inhaled object (metal, dense plastic, bone) that absorbs X-rays and is therefore directly visible and localisable on a plain radiograph.

An inhaled object (typically organic, e.g. a peanut or seed) that does not absorb X-rays and so is NOT visible on a plain film; detected only by indirect signs — the commonest type in children.

Permanent renal cortical scarring resulting from reflux-associated pyelonephritis; carries a lifelong risk of hypertension and chronic kidney disease and is detected on a delayed DMSA scan.

A well-circumscribed, rounded, mass-like area of consolidation seen in young children (immature collateral ventilation); a benign infection that can mimic a tumour and resolves with treatment.

Radiation-free imaging that is the preferred next step for a suspected pleural collection in a child; it distinguishes simple effusion from septated empyema and guides drainage.

Non-ionising ultrasound of the kidneys, ureters and bladder; the first-line investigation in paediatric UTI, assessing anatomy, hydronephrosis, obstruction, kidney size and structural anomalies.

Retrograde flow of urine from the bladder up the ureters (and into the kidney) due to an incompetent ureterovesical junction; predisposes to pyelonephritis and renal scarring and is graded I–V on MCUG.

Reflux of contrast into the ureter only, without dilatation — the mildest grade.

Gross dilatation and tortuosity of the ureter with severe calyceal blunting (loss of papillary impressions) — the most severe grade, carrying the highest risk of renal scarring.