LETTER TO THE EDITOR ACuTE REnAL fAILuRE DuE TO bILATERAL uRETERAL sTOnE: A RARE OCCuRREnCE

If urolithiasis is a common disease with a lifetime risk of stone develop­ ment in about 12% of the population, concomitant bilateral obstructing urolithiasis causing acute renal fail­ ure (ARF) is much rarer (1). ARF is defined as an increase of nitrogenous waste products in serum due to deterioration of renal func­ tion. There are three kinds of ARF: prerenal failure due to decreased re­ nal perfusion, intrinsic renal failure due to nephrotoxins and, seldom, postrenal failure due to obstruction of the urinary outflow tract (2). We present such a case of post­ renal ARF due to bilateral obstructive ureteral stone.


Dear Editor,
If urolithiasis is a common disease with a lifetime risk of stone develop ment in about 12% of the population, concomitant bilateral obstructing urolithiasis causing acute renal fail ure (ARF) is much rarer (1).
ARF is defined as an increase of nitrogenous waste products in serum due to deterioration of renal func tion. There are three kinds of ARF: prerenal failure due to decreased re nal perfusion, intrinsic renal failure due to nephrotoxins and, seldom, postrenal failure due to obstruction of the urinary outflow tract (2).
We present such a case of post renal ARF due to bilateral obstructive ureteral stone.

Case report
A 55yearold man presents to the emergency room complaining of total anuria for two days. He has no other urinary symptom such as renal colic, dysuria or hematuria. He had received a flu vaccine one week pre visouly and has a fever (39°C) with little chills, polyarthralgia and nau sea. His medication is diclofenac, a nonsteroidal antiinflammatory drug (NSAID), occasionally completed with paracetamol and aspirin, for re peated tendinitis. Physical examina tion shows some rhonchi at pulmo nary auscultation, the rest being unremarkable. Digital rectal exam fails to show prostate anomaly. Blood pressure is at 160/60 mm Hg with a heart rate at 84 bpm. Urianaly sis cannot be performed because of the total anuria. The laboratory tests reveal increased uremia (67 mg/dL) and creatinemia (7.42 mg/dL), hyper kalemia (5.4 mmol/L), hyponatremia (126 mmol/L) and hypocalcemia (8.4 mg/dL). Macrocytic anemia and thrombocytopenia are also found.
JBR-BTR, 2014, 97: 319-320.   only to the segments of the abdo men where the stones are detected.

ACuTE REnAL fAILuRE DuE TO bILATERAL uRETERAL sTOnE: A RARE OCCuRREnCE
Given the rising stone prevalence due to dietary risks factors (6), ARF secondary to bilateral stone occlu sion will probably become more fre quent, so that we must attentively track it with US examination. Unen hanced CT must be performed in complex cases. the majority of the cases, bilateral ureteral obstruction resulting in ARF is due to malignant disorders such as prostate and cervix cancers or be nign disorders like retroperitoneal fi brosis and prostatic hypertrophy (3, 4). Rarer causes are neurogenic blad der and bilateral clots, papillary ne croses or ureteral calculi (2). Our patient has been initially diag nosed with intrinsic ARF because of the nearly normal US and of the known link between NSAID and acute interstitial nephritis (4). Based on a second US and an unenhanced CT, final diagnosis is a rare occur rence of bilateral obstructing ureter al stone in a patient without any pain or history of kidney lithiasis.

References
Ultrasonography is a non irradiat ing technique required in ARF since it can detect stones or signs of ob struction as pyelocalyceal dilation but mid ureters remain hard to ac cess and hydronephrosis can be missing at an early stage. Unen hanced CT of the abdomen has a high sensitivity in the diagnosis of urolithiasis (96%) and is the refer encestandard examination when li thiasic obstructive uropathy is sus pected (5). Moreover, Dual Energy CT is able to characterize the compo sition of urinary tract stones, which may have an impact for treatment. Since it remains more irradiating, we apply Dual Energy, in our Institution, Prostate specific antigen level re mains normal (0.26 ng/mL).
A renal ultrasonography (US) is performed and shows a slight right pyelocaliectasis with no other anom aly.
Given the chronic intake of NSAID, the ARF with total anuria without re nal colic as well as the anemia and the thrombocytopenia, the patient is diagnosed with acute tubulointersti tial nephritis and likely medullar aplasia secondary to NSAID. A treat ment by dialysis and corticosteroids is started.
Two days later, considering the lack of sustained improvement, a second US is done and reveals major bilateral pyelocalyceal dilation. An unenhanced computed tomography (CT) is immediately performed and displays bilateral mid ureteric stone with bilateral hydronephrosis.
The patient is then successfully treated by bilateral double J cathe ter.

Discussion
There are very few publications about bilateral urolithiasis causing ARF in the urological or radiological literatures. Whereas prerenal and in trinsic renal failures are responsible for most episodes of ARF (respec tively 85 and 10%), ARF has a postre nal origin in only 5% of cases (2). In bayer n.v./s.a.