Abstract
Higher blood pressures (mean systolic difference 16.8 mmHg) when compared to matched individuals are already reported in patients with calcium urolithiasis. We present the prevalence of hypertension and renal impairment in patients with cystinuria from our specialist single centre. We analysed our prospective database of adult patients with cystinuria who attend our cystinuria service. This included details of the medical and operative management of their disease. Descriptive statistics were used to analyse and present the data. 120 patients were included with a median age of 40 (19–76) years, 66 were male (55%) and 54 were female (45%). 54/120 patients (45%) were taking medications to prevent stone formation. 78% (94/120) patients reported having undergone one or more stone-related procedure. 59% (55/94) of these having required at least one PCNL or open procedure during their lifetime. Prevalence of hypertension was 50.8% (61/120), and double in males compared to females (62.1% vs. 37.0%, P = 0.0063). Mean baseline creatinine was 88.2 (49–153) µmol/l and eGFR was 77.6 (32–127) ml/min/1.73 m2. When categorized by CKD stage, only 24.6% (27% vs. 21%, M vs. F) patients had normal renal function (being an eGFR > 89 ml/min/1.73 m2). 57.6% patients were CKD stage 2 and 17.8% CKD stage 3. Females had a slightly greater incidence of renal impairment. All patients who have previously undergone a nephrectomy (n = 10) or have a poorly functioning kidney (n = 19) have renal impairment (CKD stage 2 or 3). Incidence of hypertension in patients with cystinuria is 51%, with a male preponderance. Only 25% of patients with cystinuria have normal renal function. This highlights the long-term cardiovascular and renal risks that the metabolic effects of cystinuria pose, in addition to the challenges of managing recurrent urolithiasis in a young population.
Highlights
Cystinuria is a genetic disorder, which results in dysfunctional transport of cystine and three dibasic amino acids, namely; ornithine, arginine and lysine [1]
We present the prevalence of hypertension and renal impairment in a large single-centre cohort of cystinuric patients who are managed in a standardised specialist clinic
Patients attending the service routinely have their blood pressure and renal function checked at each follow-up episode, in addition to urinalysis for urinary pH, body weight measurements and relevant imaging to assess stone burden
Summary
Cystinuria is a genetic disorder, which results in dysfunctional transport of cystine and three dibasic amino acids, namely; ornithine, arginine and lysine [1] Failure to reabsorb these amino acids from the proximal convoluted tubule results in high urinary concentrations, with subsequent precipitation of cystine as renal calculi. The two key gene mutations which are thought to be responsible for the disorder are SLC3A1 and SLC7A9 [2, 3]. This rare condition affects around 1:2000 people in UK, presenting with recurrent urolithiasis and long-term renal complications [4]. Previous research reports varying ages at which patients present with their first calculus; most studies report a young age, with peak age of presentation with their first urinary calculus being between 11 and 20 years of age and estimated 25% develop their first calculus prior to the age of
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