Acquired Cystic Kidney Disease

Acquired cystic kidney disease is the development of multiple cysts (at least three to five per kidney) in the native kidneys of patients with chronic kidney disease or on long term dialysis, without a hereditary cystic disorder.

• Prevalence rises with time on dialysis: about 10 to 20 percent at 3 years, 60 to 90 percent after 10 years; also occurs in advanced chronic kidney disease and after transplantation, where cysts regress with graft function.
• Pathogenesis: tubular obstruction by oxalate crystals and fibrosis, uraemic toxins, growth factors and proliferation of tubular epithelium.
• Risk factors: male sex, longer dialysis duration, African ancestry, younger age at dialysis start, analgesic nephropathy.

Mostly asymptomatic and found on imaging.

• Complications bring symptoms: haematuria, flank pain, retroperitoneal haemorrhage with hypotension, infection, cyst rupture, palpable mass, weight loss.
• Raised haemoglobin in an anaemic dialysis patient suggests erythropoietin production by a tumour.
• Differential diagnosis: autosomal dominant polycystic kidney disease (large kidneys, family history), simple cysts, medullary cystic disease, cystic renal cell carcinoma, tuberous sclerosis, von Hippel-Lindau disease, abscess, tuberculosis.
• Complications: renal cell carcinoma (3 to 7 times population risk; 3 to 7 percent develop tumours), spontaneous retroperitoneal haemorrhage (more frequent with heparin on dialysis), cyst infection, nephrolithiasis, metastatic cancer, hypertension.

Ultrasound shows small or normal-sized shrunken kidneys with multiple cysts of varied size; CT with contrast and magnetic resonance imaging detect tumours (enhancing solid nodules) and haemorrhage; contrast-enhanced ultrasound as an alternative in kidney failure.

• Without family history or enlarged kidneys, polycystic disease is unlikely.
• Haemoglobin, haematuria, urine cytology, and tumour markers are non-specific.
• Screening: annual ultrasound for patients with dialysis duration above 3 to 5 years and life expectancy above 5 years is practised by some centres; all with haematuria, flank pain, mass or unexplained fever need imaging.

Supportive: observation of asymptomatic disease, adequate dialysis, blood pressure control, treat anaemia and mineral bone disease; manage pain with paracetamol (avoid NSAIDs).

Pharmacological

• Cyst infection: ciprofloxacin 500 mg twice daily (renally adjusted to 250 to 500 mg daily on dialysis), trimethoprim-sulfamethoxazole, or chloramphenicol 500 mg every 6 hours, or ceftriaxone 2 g IV daily, for 4 to 6 weeks with drainage if refractory.
• Haemorrhage: rest, fluids and transfusion; heparin-free dialysis or minimal heparin during dialysis for 7 to 14 days; tranexamic acid not routinely advised in dialysis.
• Renal cell carcinoma: systemic therapy for advanced disease (oncology).
• Pain from large cysts: aspiration if needed.

Procedures: arterial embolisation for refractory bleeding; nephrectomy for large symptomatic cysts, uncontrolled haemorrhage or infection; radical or partial nephrectomy for renal cell carcinoma (often bilateral at presentation, and found incidentally); renal transplantation (consider native nephrectomy for suspected tumour first); cyst aspiration and sclerotherapy for symptomatic ones.

Special groups: dialysis patients with prior bleeding (avoid or minimise heparin), kidney transplant candidates (screen for tumours), women (lower risk).

Red flags: haematuria, flank pain, hypotension (retroperitoneal bleed), fever, weight loss, enhancing nodule, new erythrocytosis.

Follow-up: ultrasound or CT annually in high risk dialysis patients (more than 3 to 5 years, male, life expectancy above 5 years); after transplantation, cysts usually regress and tumour risk remains, so surveillance of native kidneys for 1 to 2 years.