A 68-year-old man presents with progressive lower urinary tract symptoms including nocturia (×4 per night), weak urinary stream, and incomplete emptying for the past 8 months. Digital rectal examination reveals a smooth, enlarged prostate. Serum PSA is 2.8 ng/mL. Which investigation is most appropriate to confirm the diagnosis and assess the degree of bladder outlet obstruction?

## Diagnostic Approach to BPH **Key Point:** Uroflowmetry with post-void residual (PVR) measurement is the gold standard non-invasive investigation to confirm bladder outlet obstruction (BOO) and assess severity in suspected BPH. ### Why Uroflowmetry? Uroflowmetry objectively measures: 1. **Peak flow rate (Qmax)** — reduced (<15 mL/s suggests obstruction) 2. **Flow pattern** — plateau or interrupted curve indicates obstruction 3. **Post-void residual** — measured by ultrasound immediately after micturition (>100 mL suggests significant obstruction) **Clinical Pearl:** A normal Qmax (>15 mL/s) with normal PVR (<50 mL) effectively excludes significant BOO and suggests symptoms are functional or due to overactive bladder rather than BPH. ### Diagnostic Algorithm for BPH ```mermaid flowchart TD A[LUTS + DRE findings suggestive of BPH]:::outcome --> B[Symptom score IPSS]:::action B --> C{Mild symptoms?}:::decision C -->|Yes| D[Conservative management]:::action C -->|No| E[Uroflowmetry + PVR]:::action E --> F{Qmax reduced<br/>PVR elevated?}:::decision F -->|Yes| G[Confirm BOO<br/>Consider treatment]:::outcome F -->|No| H[Reassess diagnosis<br/>Consider OAB]:::outcome G --> I{Refractory to<br/>medical therapy?}:::decision I -->|Yes| J[Urodynamics if<br/>considering surgery]:::action ``` **High-Yield:** IPSS score alone does NOT confirm BPH — it quantifies symptoms only. Objective evidence of BOO via uroflowmetry is essential before committing to invasive treatment. ### Role of Other Investigations | Investigation | Indication | Role in BPH | |---|---|---| | Transrectal ultrasound | Prostate biopsy guidance, cancer screening | NOT diagnostic for BPH; measures volume only | | Cystoscopy | Hematuria, suspected bladder pathology | Invasive; reserved for failed TURP or complications | | MRI pelvis | Staging prostate cancer, complex anatomy | Unnecessary for routine BPH diagnosis | | Urodynamics | Neurogenic LUTS, failed surgery | Reserved for complex cases or pre-operative planning | **Mnemonic: "BOO-Flow"** — **B**ladder **O**utlet **O**bstruction confirmed by **Flow**metry + PVR.