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Acquired Cystic Kidney Disease

Definition:

Acquired cystic kidney disease (ACKD) is characterized by the development of multiple bilateral renal cysts in patients with advanced chronic kidney disease or end-stage kidney disease without a hereditary cystic kidney disease.

Epidemiology:

The prevalence of acquired cystic kidney disease depends strongly on the duration of end-stage kidney disease, the imaging modality used, and the diagnostic criteria: 10 % (less than 1 year on dialysis) to more than 90 % (more than 10 years on dialysis).

Etiology of Acquired Cystic Kidney Disease

Renal cysts arise partly from tubular obstruction caused by fibrosis, oxalate crystals, or vascular occlusions. In addition, cystogenic and carcinogenic substances in uremia (e.g., impaired elimination of growth factors) promote cyst formation. The development of renal cysts correlates with the duration of end-stage kidney disease; kidney transplantation improves the condition. After graft failure, cyst formation increases again and may also occur in the transplant. There is an increased risk of malignant transformation; up to 1 % develop renal cell carcinoma.

Pathology of Acquired Cystic Kidney Disease

Gross pathology:

Bilateral cortical cysts, on average 0.5 to 1 cm in size. Calcium oxalate crystals are frequently found in the cysts.

Risk of malignancy:

Adenomas, atypical epithelial proliferations, and renal cell carcinomas may arise in the shrunken kidneys. Findings suspicious for a tumor include newly appearing solid or contrast-enhancing lesions, interval growth, hemorrhage, or complex cystic morphology.

Renal cell carcinoma arising in acquired cystic kidney disease is regarded as a distinct subtype in the WHO classification (acquired cystic disease-associated renal cell carcinoma, ACD-RCC). In contrast to classic RCC subtypes, ACD-RCC typically shows a mixed microcystic-cribriform, tubular, and papillary morphology with eosinophilic tumor cells and intratumoral calcium oxalate crystals in patients with ACKD.

Clinical Presentation and Diagnosis of Acquired Cystic Kidney Disease

Signs and symptoms:

Acquired cystic kidney disease is often asymptomatic and detected incidentally on imaging. Clinically relevant manifestations include flank pain, hematuria, cyst hemorrhage, rarely retroperitoneal hemorrhage, cyst infection, and a suspicious renal mass.

Diagnosis:

Laboratory tests:

Depending on the clinical question, complete blood count, inflammatory markers, coagulation studies, urine sediment, and urine culture.

Renal ultrasound imaging:

Renal ultrasound imaging shows small echogenic kidneys with multiple cysts. Signs of infection are a thickened cyst wall and internal echoes. A renal mass may be detected.

Abdominal CT or MRI:

MRI offers advantages for assessing small structures because of its higher soft-tissue contrast; furthermore, nephrotoxic contrast agents can be avoided.

Differential diagnosis:

Important differential diagnoses include autosomal dominant polycystic kidney disease (ADPKD), other hereditary cystic kidney diseases, simple renal cysts in chronic kidney disease, and cystic renal tumors. Findings arguing against ADPKD include the typically small rather than enlarged kidneys, the absence of a corresponding family history, and the lack of typical extrarenal manifestations.

Treatment of Acquired Cystic Kidney Disease

Asymptomatic acquired cystic kidney disease does not require causal therapy. Complications such as hemorrhage, infection, or suspected malignancy are treated.

Infected cyst:

Initial treatment is with antibiotics. If antibiotic therapy fails, percutaneous drainage or, rarely, nephrectomy may be indicated in cases of a large infected cyst, abscess formation, or a severe septic course.

Bleeding or hematuria:

In addition to supportive measures and adjustment of anticoagulation, angiographic embolization or, in exceptional cases, nephrectomy may be required in the setting of significant bleeding.

Screening for renal tumors:

There is no uniformly accepted screening protocol for asymptomatic dialysis patients with acquired cystic kidney disease or renal tumors. In clinical practice, serial ultrasonographic follow-up of the native kidneys is performed as a minimal recommendation in patients on long-term dialysis. Alternatively, annual CT or MRI may be considered in patients with a good life expectancy or those on the waiting list for kidney transplantation.

Suspected malignancy:

The standard treatment for nonfunctioning native kidneys is radical nephrectomy. Active surveillance may be considered in selected individual cases with a small lesion, high surgical risk, or limited life expectancy. Nephron-sparing approaches are an option only in patients with compensated chronic kidney disease.

References

Choyke 2000 CHOYKE, P. L.: Acquired cystic kidney disease.
In: Eur Radiol
10 (2000), Nr. 11, S. 1716–21

  German version: Erworbene zystische Nierenerkrankung

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