Dear Editor,

Urinary tract obstruction can cause a greater or lesser degree of kidney disease depending on its duration and severity. There is a lot of literature on the effects of kidney obstruction from an experimental point of view.1-3 However, there is less experience in humans, although the published works agree that the progressive deterioration of kidney function after removing the blockage is unusual in most patients, especially during the first year.

We present the case of a patient with kidney disease secondary to obstructive prostate adenoma who required regular haemodialysis treatment. After 16 months, he showed partial kidney function recovery, which was sufficient to allow dialysis treatment to be stopped.

A 50 year-old man with a history of prostate syndrome was admitted into emergency due to progressive deterioration of  his general condition.

Physical examination revealed pale skin and mucous membranes and suprapubic dullness. The most relevant laboratory data showed Hb 5.9g/dL, urea/creatinine 425/19mg% and severe metabolic acidosis. The later immunological study (ANA, addition, etc) was normal or negative, proteinuria/24 hours 1.2g, and sediment with haematuria and pyuria with negative culture. An ultrasound showed a severe bilateral hydronephrosis with enlarged prostate, a bladder balloon with significant signs of postvoid residual bladder control. The patient brought an analytical examination performed 5 months earlier in which the only remarkable value was a creatinine of 1.6mg%.

The catheter was inserted and initial humoral regulation measurements were taken. Postobstructive polyuria was observed without improvement of kidney function. 2 packed red blood cell units were transfused and haemodialysis started. At 2 months the patient showed a marked clinical improvement with daily urine output of 1.5-2 litres, but with no evident improvement in the analytical results. A kidney biopsy was performed which showed the presence of 17 glomeruli of normal appearance with minor interstitial lymphocyte inflammatory accumulations, oedema of the tubular epithelium and isolated intratubular hyaline casts with a negative immunofluorescence study, all compatible with chronic moderate interstitial nephritis. Subsequently, retropubic prostate adenectomy was performed with a histological study of fibroadenoma nodular hyperplasia. A new kidney ultrasound was perfectly normal. After 16 months, residual clearances of 18ml per minute were observed in the analytical tests, so it was decided to stop dialysis. These values were stable 9 months after abandoning dialysis.

Obstructive nephropathy is a common cause of chronic kidney disease with a bimodal presentation affecting paediatric and elderly patients.4 There are few studies on the development of obstructive nephropathy in humans, making it difficult to extrapolate experimental effects in clinical practice. In addition, the obstruction in humans is often incomplete and of a subacute or chronic course, and in most occasions it is very difficult to assess from the beginning. Generally the recovery of kidney function is observed between 7 and 10 days after the liberalisation of the urinary tract, although long recovery periods for kidney function have also been found.5 There are few studies relating to the prognosis of obstructive kidney disease that requires dialysis treatment.6,7 Ravanan et al8 has the largest number of patients, with analysis of the behaviour of kidney function after unblocking in an initial group of 104 adult patients with severe and chronic obstruction. 28 of them required treatment with haemodialysis despite the unblocking. After the third year, only 9 patients needed replacement therapy and another patient underwent a transplant. Kidney function improved during the first 3 months, and remained stable in most patients after 3 years. A small number of them observed no improvement after the unblocking treatment and were more likely to require long term haemodialysis.

Thus, despite the fact that obstructive nephropathy can be accompanied by the emergence of an apparent terminal chronic kidney disease, partial improvement in kidney function may be achieved after long periods, even when the patient requires replacement therapy.