Although there is no specific treatment for ADPKD as yet, the therapeutic advances to slow down CKD might cause one to expect that, over time, onset of ESRD in ADPKD patients will have been delayed until a later age. Our data, however, show that the age at initiation of RRT in these patients has not varied since 1984. This result is in concordance with other articles , but some publications [16–18] do indicate that the age at initiation of RRT in ADPKD patients has indeed increased. According to Orskov et al. , age at onset of ESRD among their 693 ADPKD patients, followed up for 18 years (divided into three periods), rose from 55.9 (1990–1995) to 60.6 years (2002–2007), though these findings are subject to a potential bias, given the increasing number of patients in each period and especially the rise in the number of women.
The prognosis of CKD patients who start with RRT has improved over the last few years [19, 20]. In the European Registry, the percentage of patients older than 65 who started RRT increased from 22% in 1980 to 55% in 2005 , and this may be attributed to a better control of cardiovascular risk factors. We have not been able to find in the literature any studies comparing the age at onset of ESRD between patients with and patients without ADPKD. Based on our own results, we would stress that while, over the three periods examined, the age at initiation of RRT in non-ADPKD patients rose by more than 9 years, no such change occurred among ADPKD patients.
Epidemiological studies indicate that within the general population, the prevalence of men undergoing RRT is higher than that of women, in accordance with our findings . These data are in agreement with some other publications that associate male gender with earlier initiation of RRT in ADPKD patients [22, 23]. In contrast, and in accordance with other studies [16, 24], we found no significant gender differences in relation to age at initiation of RRT. Our data show that male gender is a risk factor for initiation of RRT among non-ADPKD patients (ratio, 1.6-1.8), but not among ADPKD patients (ratio, 1.1-1.2).
Although most of our ADPKD patients started RRT with haemodialysis, the prevalence study revealed kidney transplantation to be the most widely used method, as expected based on the age at onset of ESRD in this population. The sparse prescription of peritoneal dialysis among ADPKD patients could be due to large kidneys, to the presence of colonic diverticula, to hernias or to massive polycystic liver disease. However, peritoneal dialysis is a first-line technique for this disease, as has been shown by several studies that revealed no differences concerning survival or risk of peritonitis [25, 26]. On the contrary, it was found that ADPKD patients on peritoneal dialysis had a higher survival rate than those on haemodialysis .
The factors related to greater ADPKD severity are primarily carrying a PKD1 mutation, especially if truncating, and hypertension [3, 8, 27]. Other relevant factors include: age at diagnosis [28, 29], increased number and volume of the cysts, left ventricle hypertrophy , proteinuria , haematuria, microalbuminuria, hyperuricaemia , low HDL-cholesterol levels, high urinary sodium and an increase in urinary osmolality . Cardiovascular risk factors increase the rate CKD progression [4, 12], with both entities boosting each other, giving rise to a cardiorenal syndrome. ADPKD is a typical model of type IV cardiorenal syndrome , as the cause of CKD is primary renal failure and secondary cardiovascular involvement. We have observed a lower prevalence of diabetes among patients with ADPKD, but the differences in comparison with non-ADKPD patients have not been found to be significant with regard to hypertension, similarly to other studies [14, 35–37]. The data published on associated diseases in ADPKD and non-ADPKD patients are either incomplete  or have concerned only cardiovascular events . We have observed that cardiovascular diseases, malignancies and respiratory diseases are more frequent among non-ADPKD patients on RRT. This higher rate of co-morbidities in non-ADPKD patients could be explained by the higher prevalence of diabetes and by initiation of RRT at an older age. The lower cardiovascular morbidity among ADPKD patients could be associated with higher haemoglobin levels in this group . In correspondence with Abbott and Agodoa’s results , we found that fewer ADPKD patients on dialysis need erythropoietin compared with the non-ADPKD group (77.9% vs 91.9%). CKD favours a chronic inflammation status with increased inflammatory markers such as C-reactive protein (CRP) . In accordance with other articles, we observed no significant differences between the groups with regard to CRP levels, although they were lower among ADPKD patients on dialysis, probably owing to the lower prevalence of associated diseases .
The hugely significant genetic factor in ADPKD could be related to a fatal renal prognosis that is quite difficult to modify with the currently available therapeutic tools which improve cardiovascular factors. Stimulation of the renin-angiotensin system (RAS) has been associated with a sombre ADPKD prognosis owing to faster growth of the renal cysts . The HALT trial is underway to elucidate the contribution of angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) and the strict control of hypertension to the slowing of decline in renal function . Increased use of RAS-blocking anti-hypertensive drugs could imply that ADPKD patients will start on RRT later and later . However, although ACEIs and ARBs are widely used for ADPKD in our population (specific data not available), this assumption is not in accordance with our findings.
Kidney transplantation is for the moment the best therapeutic choice for ADPKD patients with ESRD. Longer survival of both patient and graft has been observed in recipients of kidney transplants with ADPKD [20, 42], in agreement with our results. This increase in survival could be explained by the ADPKD patients’ younger age, lower rate of diabetes, lower prevalence of dyslipidaemia and anaemia, and also a lower prevalence of co-morbidities, mainly cardiovascular ones. It has not been possible to show that immunological factors may play a role in this survival difference. No explanation for a longer graft survival, other than the own patient’s survival, is available. The relatively low but increasing percentage of pre-emptive living donor transplantation is due to the transplantation policies of Spain, which has a highly successful programme for cadaveric transplantation and is encouraging living donor transplantation to overcome the current relative scarcity of cadaveric donors.
The primary cause of death among ADPKD patients on RRT, in our cohort, is cardiovascular disease, followed by infections, as reported by several other authors [43–45]. Various articles have shown higher survival of ADPKD patients on RRT as compared to non-ADPKD patients, which concurs with our data [46, 47]. We found no differences as to the age of death, even though ADPKD patients started RRT earlier than non-ADPKD patients; this indicates a longer survival of ADPKD patients on RRT. Longer survival of ADPKD patients has been associated with: starting RRT at a younger age, lower prevalence of the cardiovascular risk factors and higher haemoglobin levels, all of which are factors applicable to our results [48, 49]. In another study, ADPKD patients on RRT still showed a higher survival rate than diabetes-free non-ADPKD patients , though such a difference was not observed by other authors .