What investigations are recommended for a patient with proteinuria and normal renal function?

For a patient presenting with proteinuria with normal renal function (eGFR ≥ 60 ml/min/1.73 m²), the recommended investigations are:

• Measure proteinuria using urine albumin:creatinine ratio (ACR) rather than protein:creatinine ratio (PCR) due to greater sensitivity for low levels of proteinuria.
• If the initial ACR is between 3 mg/mmol and 70 mg/mmol, confirm the result with a repeat early morning urine ACR sample; if the initial ACR is 70 mg/mmol or more, a repeat sample is not required.
• Assess renal function by estimating glomerular filtration rate (eGFR) using serum creatinine, interpreting values ≥ 60 ml/min/1.73 m² with caution.
• Test for haematuria using reagent strips and evaluate further if 1+ or higher is detected.
• Consider renal ultrasound if there is persistent proteinuria, haematuria, or other clinical indications such as symptoms of urinary tract obstruction or family history of hereditary kidney disease.

These investigations help confirm the presence and quantify the degree of proteinuria, exclude other urinary abnormalities, and assess for underlying kidney pathology despite normal renal function NICE NG203.