CT in the evaluation of complicated autosomal dominant polycystic kidney disease

Purpose: We retrospectively reviewed the CT findings in 24 cases of autosomal dominant polycystic kidney disease (ADPKD) to assess the role of CT in the diagnostic work-up of patients with complicated ADPKD. Material and Methods: Twenty-four patients with ADPKD underwent unenhanced and contrast-enhanced CT for flank pain, haematuria, or fever. The images were retrospectively reviewed for presence of complicated cysts, their morphological features and associated findings in the perinephric space/retroperitoneum. Results: Cyst haemorrhage was present in all patients, seen as high-density cysts, which were mostly bilateral. Most of these cysts had sharply outlined contours, sharp interfaces with adjacent renal parenchyma, imperceptible walls, and homogeneous density, and did not enhance following i.v. contrast administration. However, a few haemorrhagic cysts (9 cysts in 6 patients) showed inhomogeneous density (n=7), dependent layering of high-density blood leading to fluid-fluid level (n=2), and contour irregularity (n=3). CT revealed presence of cyst infection in 6 cases; the involved cysts were larger (average size 4.2 cm) than adjacent cysts, had only a mildly increased or near water density, and showed wall thickening and enhancement. Other findings included air within the infected cyst (n=1), thickening and enhancement of peri- and paranephric fasciae (n=5), and abscesses in the posterior paranephric space and adjoining psoas muscle (n=2). In 2 other patients, although CT suggested cyst infection because of presence of wall enhancement, diagnostic needle aspiration revealed only sterile haemorrhagic fluid. In 1 case, CT revealed a soft tissue density enhancing mass in one of the cysts; this proved to be a renal cell carcinoma by fine-needle biopsy. Calculi were observed in 7 patients, and cyst wall calcification in 11 cases. Conclusion: A combination of unenhanced and contrast-enhanced CT allows correct diagnosis and differentiation amongst the various complications affecting patients with ADPKD. However, in a small subgroup of patients, it may not be possible to differentiate between haemorrhage and infection; such cases require diagnostic needle aspiration for diagnosis.