World J Urol (2011) 29:199–204 Table 3 Distribution of patients with or without ‘‘ﬁsh-hook’’ ure- ter(s) in the absence or presence of BPO Fish-hook ureter(s) Benign prostatic obstruction Presentb 44 39 Absentc 28 89 Presenta Absent Two hundred patients were available for evaluation of the test accuracy of this particular radiological sign; 3 patients without BPO did not show contrast media ﬁlling of the distal ureters and were excluded from calculation a Uni- or bilateral b Scha¨fer classes III-VI c Scha¨fer classes 0-II the distal ureter(s) is signiﬁcantly associated with BPO, this radiological sign appears unsuitable for routine evaluation of BPO because its diagnostic value is clearly lower than that of other non-invasive tests, such as ultrasonic mea- surements of IPP [19, 20] or detrusor wall thickness [21, 22]. Nevertheless, the knowledge that the ‘‘ﬁsh-hook’’ sign appears in the presence of BPO might motivate physicians to evaluate for BPO whenever it is visible. The ‘‘ﬁsh-hook’’ shape of the distal ureter seems to be an indirect sign of BPO and might be caused by a prostate median lobe elevating the trigone, displacing the ureteral oriﬁce, and deforming the distal ureter. Prostate median lobe enlargement with intravesical prostatic protrusion (IPP) [10 mm has been described as a signiﬁcant predictor of BPO [19, 20]. The association between IPP and BPO was ﬁrst described in 2003 and, therefore, unknown and not evaluated in 1994. In contrast to IPP, bladder base eleva- tion is not only caused by prostate median lobe but also Table 4 Comparison of clinical data in patients with or without the ‘‘ﬁsh-hook’’ sign of the distal ureter Results are presented as median (interquartile range) Signiﬁcant values are indicated in bold Parameter Age (years) Body mass index(kg/m2) Serum creatinine level (lmol/l) International Prostate Symptom Score, IPSS 1–7 Quality of life score, IPSS 8 Serum prostate speciﬁc antigen (PSA) level (ng/ml) Prostate volume on transrectal ultrasound (ml) Post-void residual urine (ml) Maximum urinary ﬂow rate (ml/sec) Bladder capacity on urodynamic investigation (ml) P value 0.410 0.952 0.234 0.828 0.305 0.028 0.035 0.997 0.086 0.538 123 203 prostate lateral lobe enlargement; this might explain why the radiological sign of the elevated bladder base (seen in 55.7% of our patients) was not an independent predictor of BPO (seen in 40.9% of our patients). Interestingly, we failed to show signiﬁcant associations between BPO and other structural alterations of the urinary tract. Bladder trabeculation showed no association with BPO or detrusor overactivity; these ﬁndings are in accor- dance with previous studies [23]. We also could not dem- onstrate any association between BPO and hydronephrosis; this stands in contrast to others who demonstrated a decreasing bladder compliance with increasing BPO grade [24] and an increasing tendency of upper urinary tract dilation with decreasing compliance [25]. Since IVU was not conducted in patients with creatinine levels [180 lmol/l, the number of patients with bilateral upper urinary tract dilation (n = 16) without impaired renal function might have been insufﬁcient to show this rela- tionship. Bladder stones or diverticula were considered per se as signs of BPO; these patients were treated by prostate surgery without UDI. Although bladder stones or diver- ticula are generally believed to be the result of BPO, only the association between bladder stones and BPO is evi- dence based [18]. Conclusions The ‘‘ﬁsh-hook’’ conﬁguration of the distal ureter(s) is associated with BPO. Whenever this radiological sign is detected in older men, for example during routine assess- ment of urolithiasis or haematuria, the patient should be evaluated for BPO and counselled accordingly. Patients with ‘‘ﬁsh-hook’’ ureter(s) Patients without ‘‘ﬁsh-hook’’ ureter(s) 63.5 (12.0) 25.2 (3.3) 84 (21) 15 (11) 3 (3) 2.8 (5.9) 44 (37) 49 (100) 12.0 (4.7) 349 (302) 62.0 (13.0) 25.5 (4.3) 88 (21) 14 (10) 4 (2) 1.8 (2.8) 36 (22) 48 (116) 13.0 (9.4) 343 (223)