Retention, stones and obstructed infection

Urological Emergencies, Testicular Torsion & Haematuria Investigation

Urological emergencies require prompt clinical differentiation between conditions that threaten organ viability—such as testicular torsion and obstructed pyelonephritis—and functional retention states requiring structured decompression and systematic investigation. Understanding clear indications for immediate operative intervention versus outpatient evaluation is a key requirement of clinical practice in Australia.

---

Acute Urinary Retention (AUR)

Acute urinary retention is the sudden, painful inability to voluntarily void urine despite a full bladder. Patients present in severe distress with lower abdominal discomfort and a palpable, tender, dull suprapubic mass. Post-void residual (PVR) or catheter drainage volume is typically $500\text{ to }1000\text{ mL}$ or more.

Aetiology

1. Outflow Obstruction: Benign prostatic hyperplasia (BPH; accounts for $> 50\%$ of cases in men over 60 years), urethral stricture, prostate adenocarcinoma, bladder neck contracture, or clot retention from gross haematuria.
2. Pharmacological Triggers: Medications that impair bladder detrusor contractility (anticholinergics, tricyclic antidepressants, first-generation antihistamines, opioids) or increase bladder neck and prostatic tone (sympathomimetic alpha-agonists such as pseudoephedrine).
3. Neurological Disorders: Cauda equina syndrome, acute spinal cord compression, transverse myelitis, multiple sclerosis, or diabetic autonomic cystopathy.
4. Infectious & Inflammatory: Acute bacterial prostatitis, severe urethritis, genital herpes simplex (sacral radiculitis / Elsberg syndrome), or pelvic abscess.

Emergency Catheterisation & Difficult Catheter Protocol

• Immediate Catheterisation: Place a standard 12-French to 14-French Foley silicone catheter under strict aseptic technique, using generous instillation ($10\text{ to }20\text{ mL}$) of sterile lidocaine lubricating gel into the urethra for 3 to 5 minutes prior to insertion.
• Complete Drainage: Draining the entire volume immediately is safe and standard practice. Historical recommendations to clamp the catheter after draining $500\text{ to }750\text{ mL}$ to prevent "decompression haematuria" or hypotension are not supported by modern clinical evidence.
• Management of Difficult Catheterisation: If resistance is met at the prostate or bladder neck, never use force, as this risks creating false passages or tearing the bulbar/membranous urethra. Try a larger bore catheter (16-French to 18-French) which is stiffer and resists buckling, or a Coudé-tip (Tiemann) catheter with the curved tip oriented anteriorly (at 12 o'clock) to navigate the elevated bladder neck. If urethral catheterisation fails or urethral injury is suspected (blood at the meatus following pelvic fracture), consult urology immediately for flexible cystoscopic catheterisation or placement of an emergency suprapubic catheter (SPC) under ultrasound guidance.

High-Pressure Chronic Retention & Post-Obstructive Diuresis (POD)

• High-Pressure Chronic Retention: In contrast to acute retention, patients present with painless, insidious bladder distension, overflow incontinence, bilateral hydronephrosis, and impaired renal function (elevated serum urea and creatinine).
• Post-obstructive diuresis: Output above 200 mL/h for two consecutive hours or over 3 L/day establishes diuresis. Persistence, volume depletion and electrolyte disturbance distinguish clinically dangerous/pathological diuresis; monitor weight, observations, fluid balance and serial blood tests rather than declaring pathology from the first two hours alone.
• Monitoring & Fluid Replacement: Hourly urine output, hemodynamic monitoring, and daily serum electrolytes, urea, and creatinine are mandatory. If the patient develops signs of hypovolaemia, postural hypotension, or progressive electrolyte derangement, administer intravenous fluids (typically $0.45\%$ or $0.9\%$ sodium chloride) matching $50\%\text{ to }75\%$ of the preceding hour's urine output. Replacing $100\%$ of urine volume is avoided, as it creates an ongoing iatrogenic solute diuresis.

Alpha-Blocker Therapy & Trial Without Catheter (TWOC)

Initiate an alpha-1 adrenergic antagonist (such as tamsulosin 0.4 mg daily or prazosin) immediately upon catheterisation for BPH-related retention. Tamsulosin relaxes prostatic smooth muscle and reduces outflow resistance. Maintain therapy for at least 48 to 72 hours prior to removing the catheter for a formal Trial Without Catheter (TWOC), which doubles the rate of successful spontaneous voiding.

---

Urolithiasis & Complicated Renal Colic

Urinary calculus disease classically presents as renal colic: sudden, excruciating, spasmodic loin-to-groin pain radiating along the dermatomal distribution of the ureter to the ipsilateral iliac fossa, scrotum or labia majora, and inner thigh. Patients characteristically writhe in bed and cannot find a comfortable position, accompanied by nausea, vomiting, diaphoresis, and microscopic haematuria ($> 85\%$ of cases).

Diagnostic Imaging

• Non-Contrast CT Kidneys-Ureters-Bladder (CT KUB): The gold standard imaging modality ($> 98\%$ sensitivity and specificity). Accurately defines stone size, anatomical location, stone density in Hounsfield units, and secondary obstructive features (hydroureter, hydronephrosis, perinephric fat stranding).
• Renal Ultrasound: Preferred imaging in pregnant women and children to avoid ionizing radiation.

Indications for Emergency Upper Urinary Tract Decompression

1. Obstructed, infected system: Ureteric calculus with concurrent urinary tract infection, pyelonephritis, fever, rigors, or septic shock. Infected obstructed urine under pressure rapidly causes gram-negative urosepsis and irreversible renal parenchymal loss.
2. Obstructed solitary or functioning solitary kidney.
3. Bilateral ureteric obstruction.
4. Anuria or acute renal failure secondary to obstruction.
5. Intractable pain or persistent vomiting refractory to aggressive parenteral analgesia.

Emergency Decompression Modalities

• Retrograde Ureteric Stent (Double-J Stent): Inserted cystoscopically under fluoroscopy to bypass the obstructing stone.
• Percutaneous Nephrostomy (PCN): Placement of a drainage pigtail catheter directly into the renal pelvis under local anaesthesia and ultrasound guidance. Preferred in critically ill patients in septic shock (avoids general anaesthesia and the lithotomy position) or when retrograde stenting fails.

Axiom: Emergency decompression is purely a drainage procedure to relieve backpressure and control infection. Definitive stone fragmentation (lithotripsy or ureteroscopy) is strictly contraindicated in the setting of acute infection.

Conservative & Medical Expulsive Therapy (MET)

• Stone Size $\le 5\text{ mm}$: Over $70\%\text{ to }80\%$ pass spontaneously. Managed conservatively with oral hydration, antiemetics, and nonsteroidal anti-inflammatory drugs (NSAIDs, such as oral or rectal indomethacin, or oral celecoxib/ibuprofen). NSAIDs are superior to opioids in renal colic because they inhibit prostaglandin-mediated glomerular filtration and decrease renal capsular and ureteric spasm.
• Medical Expulsive Therapy: Tamsulosin 0.4 mg daily inhibits alpha-1D and alpha-1A receptors in the distal ureter, reducing smooth muscle spasm, accelerating stone passage, and lowering analgesic requirements for distal stones measuring $5\text{ to }10\text{ mm}$.
• Elective Surgical Intervention: Indicated for stones $> 10\text{ mm}$, failure of spontaneous passage after 4 to 6 weeks, or recurrent pain. Modalities include Extracorporeal Shock Wave Lithotripsy (ESWL) and Ureteroscopy (URS) with holmium laser lithotripsy.

---

Primary references (checked 7 October 2026): Australian STI guidance.