Is transition zone index useful in assessing bladder outflow obstruction due to benign prostatic hyperplasia?: A prospective study

BACKGROUND: Benign prostatic enlargement (BPE) is the commonest cause of bladder outlet obstruction in men above 50 years of age. Though pressure-flow study is the gold standard in establishing outlet obstruction, it is associated with definite morbidity. Several noninvasive parameters are described to diagnose outlet obstruction due to BPE and evaluate treatment efficacy. AIM: We studied the role of transitional zone index (TZI) in assessing bladder outlet obstruction (BOO) due to BPE. SETTING AND DESIGN: Prospective hospital-based cross-sectional diagnostic study. MATERIALS AND METHODS: Thirty-five men aged between 50 and 77 years with untreated lower urinary tract symptoms due to BPE were studied. Patients with prostate cancer, prostatitis, active UTI urethral stricture, neurovesical dysfunction and diabetes mellitus were excluded. All patients underwent a standard assessment using the American Urological Association (AUA) symptom score, uroflow, pressure-flow (PF) study and transrectal ultrasound (TRUS) estimation of TZI. Investigators undertaking PF studies and TRUS were blinded to the investigation of others. From the PF studies, Abrams Griffith (AG) number was calculated. Based on this, patients were grouped into obstructed (AG>40) and unobstructed (AG< 40) groups. STATISTICAL ANALYSIS: TZI was calculated and compared with PF studies using Mann-Whitney U test, logistic regression analysis and receiver operator characteristic curve (ROC). RESULTS: The mean age was 63.2 years (SD). The mean AUA scores and peak flow rate were 16.7 and 7.5 ml/sec, respectively. Of the 35 men, 21 were obstructed and 14 were unobstructed. TZI was not significantly different between the two groups, while the differences in age, AUA symptom score, prostate volume and TZ volume were statistically significant. Logistic regression model did not show any independent effect of TZI in predicting obstruction. ROC curve showed a poor overall accuracy in diagnosing obstruction due to BPE. CONCLUSION: Age, prostate volume and TZ volume are better indicators than TZI in diagnosis of BOO secondary to BPE