(Section Editor: M. G. Zeier) An unusual case of familial cystic kidney disease

A 46-year-old woman with a prior diagnosis of autosomal dominant polycystic kidney disease (ADPKD) was referred to the nephrology clinic with abdominal fullness. She had been diagnosed with ADPKD by ultrasound 10 years previ-ously at a different renal unit and was subsequently lost to follow-up. Her father was diagnosed with polycystic kidney disease at the age of 74 with a normal kidney function. Her sister was also diagnosed with polycystic kidney disease at a different renal unit following this patient’s diagnosis. Her past medical history included severe menorrhagia, iron deficiency anaemia, anxiety, bilateral pleural effusions and polycystic ovaries. She was on perindopril for hyperten-sion though her compliance had been variable. She never suffered from haematuria, back pain or cyst infections. Systemic enquiry did not reveal any significant symptoms. She presented to her general practitioner 2 years prior to this presentation with bilateral swelling of the legs that resolved spontaneously after a month. On examination she was well. Her blood pressure was 130/92 mmHg. Abdominal examination revealed bilateral-ly enlarged kidneys. Examination of other systems was unremarkable apart from minimal peripheral oedema. Urine dipstick revealed +protein and no blood. Renal func-tion was normal with a creatinine of 50 µmol/L. She had a normal MRA and MRI of the head which had been re-quested to rule out berry aneurysms, as there was a family history of death due to ‘stroke’. A repeat ultrasound scan of the abdomen showed bilat-eral polycystic kidneys. There was a small amount of free fluid within the pelvis and as part of the investigation of this a computed tomography (CT) of the abdomen and pelvis was requested. This showed (Figures 1 and 2) bilateral peri-nephric fluid collections and a trace of free fluid. The other organs appeared normal. There was no lymphadenopathy. Question What is the condition causing cystic appearance of the kidneys on the ultrasound and CT