Predictors of successful trial without catheter in acute urinary retention

Summary 

Objectives

We aim to identify predictors of successful trial without catheter after an episode of acute urinary retention and to evaluate how serum prostate specific antigen (PSA) and C-reactive protein (CRP) levels behave during an acute urinary retention episode and also whether the PSA level is a useful indicator of undetected prostate cancer.

Patients and methods

335 patients presented to our institution in acute urinary retention from June 2006 to December 2007. After excluding females, patients with known prostate cancer, clot retention due to haematuria and catheter-related problems, 100 patients were entered into this prospective audit. On admission we documented serum PSA and CRP levels, residual urine volumes, urinary tract infection (UTI), digital rectal examination (DRE) and history of urinary tract surgery. The outcome of subsequent trial without catheter (TWOC) was documented. Where indicated, repeat serum PSA and CRP levels, transrectal ultrasound and prostate biopsies were obtained. Parametric and non-parametric tests were used for statistical analysis.

Results

Median residual volume on catheterization was 750mL. Successful TWOC was more likely in smaller sized prostates (Kendall tau-b, p=0.004) and in benign feeling prostates (Fisher Exact Test, p=0.004). TWOC failure was significantly higher in patients diagnosed with new prostate cancer (Fisher Exact Test, p=0.032). Higher initial PSA levels, higher residual volumes and larger prostate size on DRE also resulted in higher TWOC failure rates. However these correlations were not statistically significant. UTI was confirmed in 13 of 100 patients on admission. Presence of UTI on admission had no influence on CRP or PSA levels, residual volumes or outcome of TWOC following treatment of UTI. Nine patients were diagnosed with prostate cancer of whom six had clinically significant cancer. On admission median serum PSA level was 7.0ng/L (range 0.08–4624ng/L) and median serum CRP level 21mmol/L (range normal to 247mmol/L). Serum PSA levels positively correlated with consecutive diagnosis of new prostate cancer. However when using 4ng/L as the upper limit for normal PSA levels, sensitivity for detecting prostate cancer was 89%, specificity only 43% and positive predictive value 18%. Patients with a new diagnosis of prostate cancer had a high TWOC failure rate with eight of nine patients requiring re-catheterization. Neither PSA nor CRP levels were correlated with residual volumes, presence of UTI or prediction of TWOC outcome.

Conclusions

Successful TWOC is more likely in smaller sized and benign feeling prostates. Neither PSA nor CRP levels help to predict TWOC outcome. Residual urinary volumes might be of little value in predicting TWOC outcome. Patients should therefore be given the ‘benefit of the doubt’ and offered TWOC regardless of large residual volumes. Patients presenting in AUR are at risk of harboring clinically significant prostate cancer. A high level of suspicion should remain especially in those with failed TWOC and normal DRE. Serum PSA is an unreliable marker to detect prostate cancer in this patient group. We therefore do not recommend opportunistic PSA screening during an AUR episode. CRP was not a good marker for prostatic infarction or inflammation.

Abbreviations: AUR, acute urinary retention, BPH, benign prostate hyperplasia, CaP, carcinoma of prostate, CRP, C-reactive protein, DRE, digital rectal examination, PSA, prostate specific antigen, RV, residual volume, TWOC, trial without catheter, UTI, urinary tract infection

Keywords: PSA, Acute urinary retention, Trial without catheter, Adenocarcinoma of prostate