7.3 Abdominal Aortic Aneurysm & Urological Emergencies

Section 7.3: Abdominal Aortic Aneurysm & Urological Emergencies

Aorto-vascular and urological conditions frequently present as surgical emergencies. Rapid diagnosis, patient stabilization, and timely intervention are essential to reduce mortality in patients with abdominal aortic aneurysms and prevent permanent organ damage in urological crises.

Abdominal Aortic Aneurysm (AAA)

An abdominal aortic aneurysm (AAA) is defined as a permanent dilatation of the abdominal aorta, typically involving a diameter of 3.0 cm or greater. It is most commonly infrarenal (below the origin of the renal arteries).

Risk Factors

The primary risk factors for AAA include:

• Cigarette smoking (the strongest risk factor for development, expansion, and rupture)
• Male sex
• Age ≥65 years
• Family history of AAA
• Hypertension and cardiovascular disease

Screening Guidelines

The United States Preventive Services Task Force (USPSTF) recommends:

• One-time screening with abdominal ultrasonography for men aged 65 to 75 who have ever smoked (defined as smoking ≥100 cigarettes in a lifetime).
• Screening is not routinely recommended for men who have never smoked, nor for women.

AAA Size and Surveillance Intervals

The risk of AAA rupture is directly proportional to the aneurysm's diameter. Asymptomatic aneurysms are monitored according to size:

• 3.0 – 3.9 cm: Surveillance ultrasound every 3 years
• 4.0 – 4.9 cm: Surveillance ultrasound every 12 months
• 5.0 – 5.4 cm: Surveillance ultrasound every 6 months

Indications for Elective Surgical Intervention

Surgical repair, either via open surgery or Endovascular Aneurysm Repair (EVAR), is indicated when:

1. The AAA diameter reaches ≥5.5 cm in men (or ≥5.0 cm in women).
2. The AAA exhibits rapid expansion: >0.5 cm in 6 months or >1.0 cm in 12 months.
3. The patient becomes symptomatic (e.g., chronic back, flank, or abdominal pain), regardless of size.

Ruptured AAA: Clinical Presentation and Management

Rupture of an AAA is a catastrophic event with an overall mortality rate of >80%.

• Classic Triad:
  1. Severe, acute abdominal, back, or flank pain
  2. Hypotension or hemodynamic instability
  3. Pulsatile abdominal mass (detected in only ~50% of cases)
• Management:
  • Hemodynamically unstable patients with a known AAA and classic symptoms should go directly to the operating room for emergency repair.
  • Hemodynamically stable patients should undergo an immediate contrast-enhanced CT angiography (CTA) of the abdomen and pelvis to confirm rupture and assess suitability for EVAR.
  • Permissive hypotension (maintaining systolic blood pressure between 80–90 mmHg) is employed during resuscitation to limit further bleeding before control is achieved.

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Nephrolithiasis (Kidney Stones)

Nephrolithiasis is the formation of crystalline stones within the urinary tract. The most common type is calcium oxalate, followed by calcium phosphate, struvite (associated with urease-producing bacteria), uric acid, and cystine.

Clinical Presentation

Patients present with acute, severe, colicky flank pain that radiates to the groin or scrotum/labia. The pain is typically accompanied by nausea, vomiting, dysuria, and microscopic or gross hematuria. Patients are characteristically restless and unable to find a comfortable position.

Diagnostic Workup

• Non-contrast Computed Tomography (CT) of the abdomen and pelvis: The diagnostic gold standard (high sensitivity and specificity for almost all stone types).
• Renal Ultrasonography: Preferred in pregnant or pediatric patients to avoid radiation. Shows hydronephrosis and the stone as a hyperechoic focus with acoustic shadowing.

Management

• Conservative Management: Indicated for stones <5 mm in diameter, which have a >90% chance of spontaneous passage. Includes oral hydration, analgesics (NSAIDs are first-line), and medical expulsive therapy with an alpha-1 blocker (e.g., tamsulosin) to relax ureteral smooth muscle.
• Urgent Decompression: Absolute indications for urgent intervention (retrograde ureteral stenting or percutaneous nephrostomy) include:
  1. Obstruction accompanied by infection (fever, pyuria, sepsis) — a urological emergency.
  2. Bilateral obstruction or obstruction of a solitary kidney.
  3. Acute kidney injury (AKI) or intractable pain/vomiting.
• Definitive Stone Clearance: For larger stones (>10 mm) or those failing conservative trial: extracorporeal shock wave lithotripsy (ESWL), ureteroscopy (URS), or percutaneous nephrotomy (PCNL) for staghorn calculi.

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Acute Urinary Retention (AUR)

Acute urinary retention (AUR) is the sudden, painful inability to pass urine voluntarily, leading to rapid bladder distension.

Etiologies

1. Obstructive: Benign Prostatic Hyperplasia (BPH) is the most common cause in men. Other causes include prostate cancer, urethral stricture, and fecal impaction.
2. Infectious/Inflammatory: Prostatitis or vulvovaginitis.
3. Neurologic: Spinal cord injury, cauda equina syndrome, or diabetic neuropathy.
4. Pharmacological: Anticholinergics, sympathomimetics, tricyclic antidepressants, and opioids.

Clinical Presentation

Sudden onset of severe lower abdominal (suprapubic) pain, an inability to void, and a tender, palpable suprapubic mass (distended bladder, typically containing >500 mL of urine).

Workup and Immediate Management

• Diagnostic Confirmation: Bladder ultrasound showing a post-void residual volume (PVR) of >300–500 mL.
• Immediate Decompression: The first-line treatment is immediate bladder catheterization using a urethral Foley catheter. If urethral catheterization fails (e.g., due to severe BPH or urethral strictures), a suprapubic catheter must be placed.
• Post-Decompression Care: Monitor for post-obstructive diuresis (urinary output >200 mL/hour for 2 consecutive hours), which can cause severe dehydration and electrolyte imbalances.