The Prevalence of Simple Renal and Hepatic Cysts Detected by Spiral Computed Tomography
Introduction
The increasing use of ultrasonography and computed tomography (CT) over the last three decades has led to the identification of benign lesions whose aetiology and clinical significance are as yet unclear. Simple renal cysts and simple hepatic cysts are such lesions. While some are part of defined clinical syndromes such as polycystic kidney disease, most remain largely asymptomatic and of no apparent clinical importance.
Knowledge of the prevalence and characteristics of both hepatic and renal cysts provides a useful background for the interpretation of both ultrasound and CT. Renal cysts have been consistently reported as being increasingly common with age, although prevalence data vary considerably. Prevalence data on hepatic cysts, as determined by in-vivo imaging, is scarce. To our knowledge there has been no published study looking at the association between renal and hepatic cysts.
The purpose of this paper is to report the prevalence of both renal and hepatic cysts among patients attending for abdominal CT. The last such report, based on third-generation CT of kidneys, dates back to 1983 [1]. Advances in CT technology over the last two decades justify a re-evaluation of CT in the detection of simple cysts.
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Patients and methods
Six hundred and seventeen patients who underwent abdominal CT at the Department of Clinical Radiology between January 1998 and December 2001, for reasons other than the detection of kidney or liver disease, were included in the study. Examinations were performed on a GE Hi-speed Advantage CT machine (Milwaukee, WI, USA) using a collimation of either 7 or 10 mm. Two hundred and ninety-five of these were women aged 17–91 years (mean 62.8 years) and 322 were men aged 19–92 years (mean 65.5 years).
Results
Simple renal cysts were found in 254 patients (41%) while simple hepatic cysts were found in 110 patients (18%). The prevalence of renal cysts was found to increase steadily with age (Table 1) and was significantly higher at all ages in men than women (p=0.001). The ratio of combined prevalence in males:females was 1.4:1. Statistical analysis revealed a significant positive correlation between total number of renal cysts and age (p<0.05). The total number of renal cysts per patient in our study
Discussion
Renal cysts are largely accepted as being acquired lesions that are thought to evolve from diverticula in distal convoluted and collecting tubules 2, 3. The progression of diverticula into cystic masses is thought to occur mainly as an age-related process associated with weakening of the tubular basement membrane [4]. In support of this, diverticula have been shown to be more common in the older population and in patients with a known history of urinary obstruction where increased back pressure
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