What is the appropriate acute and early definitive management for a 70-year-old man with a three-month history of obstructive voiding symptoms who now has acute urinary retention, a distended tender hypogastric region, impaired renal function, and severe hypertension while on amlodipine and losartan?

Acute Management of Urinary Retention with Post-Renal Acute Kidney Injury

Immediately catheterize the bladder via urethral catheter for complete decompression, start tamsulosin 0.4 mg or alfuzosin 10 mg once daily at the time of catheter insertion, and temporarily discontinue the ARB (losartan) given the acute kidney injury with creatinine of 3 mg/dL. 1, 2

Immediate Bladder Decompression

• Perform urgent urethral catheterization to achieve complete bladder decompression for this patient presenting with acute urinary retention and a distended, tender hypogastric region 1, 2
• If urethral catheterization fails, place a suprapubic catheter for drainage 1
• The bladder scan or post-catheterization volume will confirm retention and quantify the residual volume 1

Management of Acute Kidney Injury

• Temporarily discontinue losartan (ARB) in the setting of acute kidney injury with creatinine elevated to 3 mg/dL, as ACE inhibitors and ARBs can cause or exacerbate AKI through decreased filtration fraction, particularly with volume depletion 3
• The acute kidney injury is post-renal (obstructive uropathy) from urinary retention, and bladder decompression should lead to improvement in renal function 4
• Order renal ultrasound to assess for hydronephrosis, which has >90% sensitivity for detecting upper tract obstruction 1
• Monitor renal function closely after catheterization; creatinine should improve within 24-48 hours if the obstruction was the primary cause 1

Alpha Blocker Therapy

• Start tamsulosin 0.4 mg or alfuzosin 10 mg once daily immediately at the time of catheter insertion to improve trial without catheter (TWOC) success rates 1, 2
• Alpha blockers significantly improve TWOC success: alfuzosin achieves 60% success versus 39% with placebo, and tamsulosin achieves 47% versus 29% with placebo 1
• Continue alpha blocker therapy for at least 3 days before attempting catheter removal 1
• Tamsulosin may be preferable in this elderly patient as it has a lower probability of orthostatic hypotension compared to doxazosin or terazosin 1

Important Caveat on Alpha Blockers

• Exercise caution with alpha blockers given his severe hypertension (BP 170/90) and age, as these medications can cause dizziness and postural hypotension 1
• However, the benefit of improved voiding trial success outweighs this risk, and tamsulosin is less likely to cause orthostatic hypotension 1

Hypertension Management

• Continue amlodipine as calcium channel blockers do not worsen renal function in AKI 3
• The severe hypertension (170/90) may be partially related to pain from bladder distension and should improve after catheterization 5
• Plan to restart losartan only after renal function stabilizes (creatinine returns toward baseline) and volume status is optimized 3
• Two studies demonstrated increased 30-day mortality when ACE inhibitors/ARBs were not restarted after acute illness, possibly from hypertensive rebound leading to acute cardiac decompensation 3

Diagnostic Evaluation

• Perform urinalysis and urine culture on the post-catheterization specimen to rule out infection 5, 2
• Do not check PSA at this time, as it will be falsely elevated due to bladder distension and catheter insertion 5
• Perform digital rectal examination to assess prostate size and consistency, which will guide definitive management 5, 2
• Consider renal ultrasound if creatinine does not improve within 24-48 hours after decompression 1

Trial Without Catheter (TWOC)

• Keep the catheter in place for 3 days of alpha blocker therapy before attempting removal 1
• There is no evidence that catheterization longer than 72 hours improves outcomes, and prolonged catheterization increases infection risk 1
• The voiding trial is more likely to succeed if the retention was precipitated by temporary factors (medications, constipation), but this patient's 3-month history of obstructive symptoms suggests underlying BPH 1

If TWOC Fails

• Surgical intervention (TURP) is recommended for patients with refractory retention who have failed at least one attempt at catheter removal 1, 4
• Surgery is also indicated given his renal insufficiency as a result of obstructive uropathy 4
• For patients who are not surgical candidates, treatment with intermittent catheterization or an indwelling catheter is recommended 1

Additional Considerations

• Assess for and treat constipation, which can contribute to urinary retention in elderly patients 1
• The patient should be counseled that he remains at increased risk for recurrent urinary retention even after successful catheter removal 1
• Consider adding a 5-alpha reductase inhibitor (finasteride or dutasteride) if prostate is enlarged (>30cc), as combination therapy with alpha blockers reduces acute urinary retention risk by 79% and need for surgery by 67% 1

Critical Pitfalls to Avoid

• Do not use doxazosin or terazosin as first-line agents, as these require titration and doxazosin has been associated with increased congestive heart failure in men with cardiac risk factors 1
• Do not delay restarting the ARB indefinitely once renal function stabilizes, as this increases risk of hypertensive complications 3
• Remove the indwelling catheter as soon as medically possible (ideally within 24-48 hours after starting alpha blocker) to minimize infection risk, though 3 days is acceptable for alpha blocker optimization 1
• Do not assume alpha blocker therapy alone will manage his hypertension; the losartan should be restarted once renal function improves 1