Malignant renal obstruction without dilatation

A 61 year old male presented with a one-week history of abdominal pain and loose stools. He had recently received treatment for cellulitis with flucloxacillin. He was anuric on presentation requiring haemodialysis. His ultrasound scan showed patent vessels with no signs of obstruction. A kidney biopsy revealed tubulointerstitial nephritis, attributed to recent treatment with flucloxacillin. A week later he developed lower limb thromboembolic disease triggering further investigations. A FDG PET-CT scan revealed a large FDG-avid retroperitoneal mass causing non-dilated obstruction of both kidneys. Bilateral retrograde stents were inserted which resulted in a 1.6L diuresis and cessation of haemodialysis. Non-dilated obstruction should be considered in anuric AKI, particularly in the context of malignancy, and may require a therapeutic trial of decompression.