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Renal ultrasound, CT and nuclear imaging

Essential points for quick revision.

2 min synopsisUK scopeSources checked 27 Aug 2026Clinical review pending
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Escalate

Suspected pyonephrosis in acute kidney injury needs immediate urinary-tract ultrasound, targeted within six hours by NICE, and urgent urological drainage if obstruction is confirmed. An infected obstructed system, anuria, bilateral obstruction, obstruction of a solitary functioning kidney, renal trauma with instability or a leaking abdominal aortic aneurysm mimic requires immediate senior action rather than routine outpatient imaging.

Synopsis

Select renal imaging by the clinical question, recognise modality limitations and escalate obstructed infection, stones, masses and contrast-related risk without delaying necessary diagnosis.

  • Name the question before naming the scan: retention, hydronephrosis, calculus, renal mass, urothelial lesion, vascular event, differential function and cortical scarring require different techniques.
  • Ultrasound is radiation-free and shows kidney size, parenchymal appearance, gross masses, cysts, collecting-system dilatation and bladder residual, but a normal study does not exclude early or intermittent obstruction.
  • For adults with suspected renal colic, NICE recommends urgent low-dose non-contrast CT within 24 hours; pregnancy changes the first-line investigation to ultrasound.

Key red flags

Infected obstructed system

Fever or hypothermia, rigors, flank pain, pyuria and AKI with hydronephrosis suggest pyonephrosis or an infected obstructed kidney. Antibiotics do not penetrate or drain a pressurised system reliably; decompression is source control.

Investigation priorities

01
Renal tract ultrasoundFirst step

Assess kidney size and symmetry, echogenicity, cysts, larger masses, collecting-system dilatation and bladder volume without ionising radiation.

Management branches

Septic obstructionImage and drain without delay

Sepsis or systemic illness with flank pain, AKI, anuria, stone history or suspected upper-tract blockage.

  1. Begin sepsis assessment, cultures, renal-adjusted antimicrobials, lactate and haemodynamic care while alerting urology; do not wait for imaging to start resuscitation.
  2. Arrange immediate ultrasound within the NICE six-hour target when pyonephrosis is suspected, or the fastest locally agreed cross-sectional imaging if ultrasound will not answer the urgent question.

Key medicines

Iodinated intravascular contrast mediumUse the radiologist-selected agent and protocol only when it materially answers the question; volume and route are examination-specific rather than a bedside prescription.
Furosemide during MAG3 renographyAdminister only within the local nuclear-medicine diuretic renogram protocol at its specified timing and dose.
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Sources and review status4 sources · checked 27 Aug 2026 · clinical review pending
Sources

Sources and review status

National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.

Authoring stateRapid draftClinical stateAwaiting reviewJurisdictionUnited Kingdom