Synopsis
Distinguish CT urography from non-contrast stone CT, recognise hydronephrosis and urgent infected obstruction, and choose urinary imaging according to calculus, haematuria, tumour, pregnancy and renal function.
- For non-pregnant adults with suspected renal colic, NICE recommends urgent low-dose non-contrast CT within twenty-four hours.
- Use ultrasound first in pregnancy and in children or young people; persistent uncertainty in younger patients may justify low-dose CT.
- Non-contrast stone CT and CT urography are different examinations: one detects calculus, while the other characterises renal parenchyma and opacified urothelium.
Key red flags
Sepsis with hydronephrosis, pyonephrosis or an obstructing calculus requires urgent drainage rather than routine follow-up imaging.
Anuria, bilateral obstruction, a solitary obstructed kidney, rapidly worsening acute kidney injury or uncontrolled pain needs immediate urological assessment.
Unexplained visible haematuria from age 45 meets the NICE suspected-cancer referral criterion when there is no UTI or bleeding persists or recurs after treatment.
A normal ultrasound does not exclude a ureteric stone or upper-tract urothelial lesion in a high-risk patient.
Fever, pyuria, sepsis and obstructive imaging indicate a source-control emergency; gas or echogenic debris may heighten concern.
Anuria, bilateral disease, solitary kidney or rising creatinine increases urgency and may alter iodinated-contrast planning.
Investigation priorities
Detect urinary calculi, level of obstruction and important alternative diagnoses in adults.
Management branches
A non-pregnant adult has acute flank-to-groin pain, microscopic haematuria and stable observations.
- Context: assess infection, renal function, solitary kidney, pregnancy possibility, analgesic need and alternative vascular or abdominal diagnoses.
- Reasoning: request urgent low-dose non-contrast CT to identify calculus, level, obstruction and an alternative cause.