Patients with a chronic disease may develop new, but often related, symptoms. The assumption, however, that all symptoms are related and need no further investigation, may result in the misdiagnosis of a serious disease. Autosomal dominant polycystic kidney disease is a common inherited condition, occurring in between 1 in 200 and 1 in 1000 of the population.1 After diagnosis patients are followed up by nephrologists because of the risk of progression to end stage renal failure. Renal function may be preserved, however, and outpatient attendance is often infrequent. If complications develop, affected individuals may present to primary care providers or a wide range of hospital and surgical specialties, where staff should be aware of possible diagnostic difficulties. Macroscopic haematuria is a common complication that is usually related to the polycystic kidney disease.2 We present two cases where subsequent investigations discovered bladder carcinoma and suggest possible screening methods.