A 62-year-old man with a 2-year history of BPH managed with tamsulosin reports persistent nocturia (×5 per night) and recurrent urinary tract infections. Serum creatinine is 1.2 mg/dL (baseline 0.9 mg/dL). DRE shows a large, smooth prostate. Before considering surgical intervention, which investigation is most appropriate to assess upper urinary tract involvement and guide management?

## Assessment of Upper Urinary Tract in BPH **Key Point:** Renal ultrasound combined with post-void residual (PVR) measurement is the most appropriate initial investigation to detect upper urinary tract complications (hydronephrosis, renal insufficiency) in BPH with rising creatinine and recurrent UTIs. ### Clinical Context: Why Upper Tract Imaging? This patient has **red flags** suggesting obstructive uropathy: - Rising serum creatinine (1.2 from baseline 0.9 mg/dL) - Recurrent UTIs (sign of residual urine and stasis) - Large prostate on DRE - Persistent symptoms despite alpha-blocker therapy These findings warrant assessment of: 1. **Hydronephrosis** — indicates upper tract obstruction 2. **Renal function deterioration** — suggests chronic obstruction 3. **Post-void residual** — quantifies degree of lower tract obstruction ### Investigation Comparison for BPH Complications | Investigation | Sensitivity for Hydronephrosis | Radiation | Cost | Role in BPH | |---|---|---|---|---| | **Renal ultrasound** | 85–90% | None | Low | **First-line for upper tract screening** | | Non-contrast CT | 95–98% | High | High | Reserved for stone disease, hematuria | | IVU | 85–90% | Moderate | Moderate | Outdated; replaced by ultrasound + CT | | Retrograde pyelography | 100% | Moderate | High | Invasive; reserved for therapeutic intervention | **Clinical Pearl:** In a patient with BPH and rising creatinine, **ultrasound is the safest, most cost-effective first-line test** to screen for hydronephrosis. If hydronephrosis is confirmed, further imaging (CT, urodynamics) guides surgical planning. ### Diagnostic Pathway ```mermaid flowchart TD A[BPH + rising creatinine<br/>+ recurrent UTIs]:::outcome --> B[Renal ultrasound<br/>+ PVR measurement]:::action B --> C{Hydronephrosis?}:::decision C -->|Yes| D[Confirm obstructive<br/>uropathy]:::outcome D --> E{Surgical candidate?}:::decision E -->|Yes| F[Urodynamics ±<br/>CT for staging]:::action E -->|No| G[Percutaneous nephrostomy<br/>or ureteral stent]:::action C -->|No| H[Elevated PVR?]:::decision H -->|Yes| I[Proceed with<br/>BPH treatment]:::action H -->|No| J[Reassess diagnosis<br/>Nephrology referral]:::action ``` **High-Yield:** **Renal ultrasound is non-invasive, radiation-free, and has >85% sensitivity for hydronephrosis** — ideal for screening in BPH with renal dysfunction. It should be the first imaging modality in this clinical scenario. **Mnemonic: "RUSH-PVR"** — **R**enal **U**ltrasound + **S**erum creatinine + **H**ydronephrosis screening, plus **PVR** measurement.