Percutaneous biopsy is the test of choice for the diagnosis of kidney diseases. Nephrologists make decisions regarding treatment and prognosis by studying the biopsy's histological data.1

This technique is safe and relatively simple to perform. Renal biopsy complications are very limited and when they do occur they are mainly minor.2 Some centres even advocate biopsies in an outpatient setting, without the need for hospital admission.3 Furthermore, practically half of biopsied patients have a potentially treatable disease that tends to include the use of immunosuppressant drugs, thus requiring a certain degree of specificity in the diagnosis due to the adverse effect profile of these treatments.4 Choosing suitable candidates for biopsy is, therefore, a challenge for nephrologists because the benefits of early and treatable diagnosis outweigh the risks if carried out correctly.

Nevertheless, there are no established criteria for performing renal biopsy; the criteria vary according to different centres or countries.1 In general, nephrotic syndrome, nephritic syndrome and acute renal failure tend to be main indications for performing a biopsy.5–7

Spain's largest histopathological data collection is the Spanish Registry of Glomerulonephritis sponsored by the Spanish Society of Nephrology, which has recorded more than 22,000 biopsies to date.8,9 In the region of Castilla-La Mancha, all the biopsies performed between 1994 and 2008 at hospitals in Albacete, Ciudad Real, Cuenca, Guadalajara and Toledo have been recorded.

This study aims to explore the epidemiological and clinical characteristics of biopsied patients with a diagnosis of glomerulonephritis in Castilla-La Mancha (GLOMANCHA) and to analyse renal survival and mortality during follow-up.

The Castilla-La Mancha biopsy registry presents extended follow-up (more than 7 years) and shows that patients undergoing this procedure are predominately men, with a mean age of 48 years, mildly decreased renal function and proteinuria greater than 3g per day. The most common histological diagnoses were lupus nephritis followed by focal segmental glomerulosclerosis and membranous nephropathy. Although these data may initially draw attention, the results must be put into context, as each centre has their own indications for renal biopsy; they do not reflect the total incidence of these diseases, but rather only those which are diagnosed histopathologically. Renal survival is excellent in lupus nephropathy and in minimal change disease, unlike focal segmental glomerulosclerosis and rapidly progressive glomerulonephritis type III. The latter, moreover, has the worst vital prognosis. All these data are consistent with the registries published previously.10,11

In terms of incidence, IgA nephropathy has always remained at the head of the Spanish Registry of Glomerulonephritis, followed by lupus nephritis. According to 2010–2013 data, focal segmental glomerulosclerosis and membranous nephropathy were in third and fourth place respectively. This difference with our series is probably due to the lack of biopsies in the IgA group, if they do not present poor prognosis data and if clinical manifestations are suggestive of this disease.

Regarding the diseases with poor renal prognosis, it was interesting that in our sample GFR at the time of biopsy was the predictor for renal survival, and not proteinuria. Only in IgA nephropathy, proteinuria greater than 2g multiplied the risk for starting RRT by 2.9. In a study that included 141 patients, the Spanish Society of Nephrology Glomerular Disease Study Group (GLOSEN) confirmed the excellent prognosis for patients with IgA nephropathy and minimum or null proteinuria in the long term.12

Rapidly progressive glomerulonephritis type III, which presents the worst prognosis of the diseases studied, has a severely decreased GFR (MDRD 13.6ml/min/1.73m2), with a mean age greater than the other diseases (63 years) at the time of biopsy. These 2 situations are consistent with data recently published by the SEN (Spanish Society of Nephrology) registry and both (GFR and age) are responsible for its poor prognosis.8

Membranous nephropathy is, together with minimal change disease, the disease with the most proteinuria at the time of biopsy (more than 7g per day). Furthermore, both present a GFR greater than 60ml/min/1.73m2. Overall and renal survival are good at 15 years follow-up (greater than 80%). Nevertheless, membranous nephropathy is probably under-diagnosed. More and more authors are advocating for performing biopsy in diabetic patients with proteinuria, as this is often erroneously attributed to diabetic nephropathy.13 In a recent study published by Soleymanian et al., renal biopsy was performed in 46 diabetic patients with proteinuria, haematuria or impaired kidney function and only 34.8% had pure diabetic nephropathy.14

At the time of renal biopsy, the patients with focal segmental glomerulosclerosis presented deterioration of renal function with GFR estimated at 45.1ml/min/1.73m2 and a median proteinuria of 3g per day. These data are consistent with other registries published in the work of Kwon et al., which included 111 Korean adults.15 There was a male predominance (70%) in the sample. Renal function marked the patients’ prognosis, whose renal survival was poor. As in our study, the prognosis factors in the Korean study were renal function and age, but also proteinuria. This is because the final variable of their study was combined, including increased serum creatinine or start of RRT, unlike our study in which we only considered the latter. Moreover, since D’Agati proposed a classification of histological variants in 2003, several studies have aimed to assess renal prognosis in each of these.16 Although there is no clear consensus on whether histological type is a prognostic factor, the collapsing variant seems to be the most aggressive.17,18

In terms of lupus nephritis, previously published data is confirmed regarding the involvement of mainly young women and proteinuria less than 2g per day. For this disease, membranous nephritis has the best renal prognosis compared to the diffuse proliferative variant.19,20

Our study is not exempt of limitations, such as the small amount of data collected from the patients (to facilitate the delivery from the collaborating centres) or its retrospective nature. Moreover, it should be highlighted that only baseline analytical patient data were recorded, which also involves certain limitations. Furthermore, we do not have the treatment data for the patients biopsied and there may be a certain degree of heterogeneity as we looked at diseases from different centres. Nevertheless, the large sample size and follow-up period grant validity to the results presented.

In conclusion, the Castilla-La Mancha Registry of Glomerulonephritis shows the poor prognosis of rapidly progressive glomerulonephritis type III, unlike minimal change disease and lupus nephritis. Renal function is an independent predictor of renal survival and mortality in our population.

This study was funded in part by the Sociedad Castellano-Manchega de Nefrología (Castellano-Manchega Nephrology Society).

None declared.