Scottish National Complex Renal Cyst Surveillance Protocol

Aim to design and test a suitable risk-targeted imaging protocol for follow-up of complex renal cysts categorised IIF.

The Scottish Protocol was designed at a joint meeting with the Scottish Urological and Scottish Radiological societies according to published data on imaging modality, classification criteria and interval progression of Bosniak IIF renal cysts. Patients were listed prospectively to follow this protocol across five NHS health boards within Scotland. Patient data accessed between Aug 21 and Feb 22. All patients with a confirmed Bosniak IIF cyst on computerised tomography or magnetic resonance imaging after multi-disciplinary team review were included. Patients were reviewed according to progression, interval, treatment and histology.

A total of 160 patients were identified with Bosniak IIF cysts. 98 (61%) were male (age range 29-97, median 67, IQR 57-75). Thirty-four patients completed the proposed 4-year follow-up. Seventeen patients advanced to treatment, with 15 patients having confirmed malignancy (9.4% of the total database). The mean time from diagnosis to intervention was 1 year and 2 months (range 34 to 1172 days). No patients developed metastatic disease during follow-up.

The Scottish Complex Renal Cyst Protocol provides a risk-targeted imaging framework that reliably identifies patients with progressive lesions prior to the development of advanced disease. Incidence of progression is consistent with published data of 9.4% most commonly within 2 years, and not beyond 4 years of surveillance.