CT in the evaluation of complicated autosomal dominant polycystic kidney disease

Purpose: We retrospectively reviewed the CT findings in 24 cases of autosom al dominant polycystic kidney disease (ADPKD) to assess the role of CT in t he 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 w ere retrospectively reviewed for presence of complicated cysts, their morph ological features and associated findings in the perinephric space/retroper itoneum. Results: Cyst haemorrhage was present in all patients, seen as high-density cysts, which were mostly bilateral. Most of these cysts had sharply outlin ed contours, sharp interfaces with adjacent renal parenchyma, imperceptible walls, and homogeneous density, and did not enhance following i.v. contras t administration. However, a few haemorrhagic cysts (9 cysts in 6 patients) showed inhomogeneous density (n=7), dependent layering of high-density blo od 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 increas ed or near water density, and showed wall thickening and enhancement. Other findings included air within the infected cyst (n=1), thickening and enhan cement of peri- and paranephric fasciae (n=5), and abscesses in the posteri or paranephric space and adjoining psoas muscle (n=2). In 2 other patients, although CT suggested cyst infection because of presence of wall enhanceme nt, diagnostic needle aspiration revealed only sterile haemorrhagic fluid. In 1 case, CT revealed a soft tissue density enhancing mass in one of the c ysts; this proved to be a renal cell carcinoma by fine-needle biopsy. Calcu li were observed in 7 patients, and cyst wall calcification in 11 cases. Conclusion: A combination of unenhanced and contrast-enhanced CT allows cor rect diagnosis and differentiation amongst the various complications affect ing patients with ADPKD. However, in a small subgroup of patients, it may n ot be possible to differentiate between haemorrhage and infection; such cas es require diagnostic needle aspiration for diagnosis.