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Acute kidney injury with suspected urinary tract obstruction — MSRA MCQ

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HardNephrologyAcute kidney injury with suspected urinary tract obstructionMSRA

A 76-year-old man has blood tests arranged after reporting 6 weeks of progressive hesitancy, a weak urinary stream, nocturia and a sensation of incomplete bladder emptying. He has no loin pain, fever, rigors, dysuria, vomiting or diarrhoea. His regular medicines are amlodipine and metformin; he has not taken NSAIDs or started any new medicines. Creatinine was 82 micromol/L 1 month ago and is now 174 micromol/L. Potassium is 5.1 mmol/L and bicarbonate is 23 mmol/L. He is afebrile, BP is 136/78 mmHg and he is clinically euvolaemic. Urine dipstick shows blood 1+, protein negative, leucocytes negative and nitrites negative. A urine culture is negative. Which is the most appropriate next investigation?

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Correct answer: E — Arrange an urgent urinary tract ultrasound to be performed within 24 hours

This man has acute kidney injury, with creatinine more than doubling over 1 month, and has a substantial risk of urinary tract obstruction because of progressive lower urinary tract symptoms. There is no clear pre-renal, drug-related or intrinsic renal explanation. NICE recommends urgent urinary tract ultrasound, performed within 24 hours, when the cause of AKI is not identified or the person is at risk of urinary tract obstruction. A routine scan is inappropriate because delaying assessment risks persistent obstructive AKI. Immediate ultrasound within 6 hours is reserved for suspected pyonephrosis: he has no fever, systemic illness, pyuria, nitrituria or other evidence of infected obstruction. CT urogram may be relevant after assessment of persistent haematuria in an appropriate malignancy pathway, but it does not take priority over exclusion of obstruction causing AKI. CT KUB would be appropriate if ureteric colic or stone disease were clinically suspected; his gradual voiding symptoms without colicky pain instead suggest bladder outlet obstruction.

Reference: NICE NG148: Acute kidney injury: prevention, detection and management — Recommendations (Last updated 16 October 2024) — https://www.nice.org.uk/guidance/ng148/chapter/Recommendations