12.3 Acute Ureteric Colic & Medical Expulsive Therapy

Acute Ureteric Colic & Medical Expulsive Therapy

Acute ureteric colic is among the most severe pain syndromes encountered in emergency medicine. Successful management requires rapid diagnosis, effective non-opioid analgesia, timely identification of life-threatening obstructive complications requiring emergency surgical decompression, and evidence-based selection between conservative observation, medical expulsive therapy, and endourological intervention.

Clinical Presentation and Pathophysiology of Ureteric Colic

Acute ureteric colic is triggered by sudden acute intraluminal obstruction of the ureter by a migrating calculus.

Pathophysiological Phases of Obstruction

1. Early Phase (Hours 0 to 1.5–2): Acute intraluminal stone impaction impedes urine outflow. Proximal ureteral and renal pelvic pressure surges from physiological baselines of 5–10 mmHg up to 50–70 mmHg. This acute stretching of the pelvicalyceal system stimulates local prostaglandin ($PGE_2$ and $PGI_2$) synthesis. Prostaglandins induce intense afferent arteriolar vasodilation, causing transiently increased renal blood flow (hyperemia). Obstruction raises tubular backpressure and opposes filtration, while pelvic/capsular stretching and hyperperistalsis produce pain.
2. Intermediate Phase (Hours 2 to 5): Intrarenal hydrostatic pressure remains elevated, but renal blood flow begins to decline due to progressive efferent arteriolar and pre-glomerular vasoconstriction mediated by thromboxane $A_2$ and angiotensin II.
3. Late Chronic Phase (Beyond 5 to 24 Hours): Both renal blood flow and intraluminal pressure progressively decline. Glomerular filtration drops markedly. If obstruction remains uncorrected, progressive ischemic parenchymal atrophy and renal injury can become irreversible. Duration, completeness, infection and baseline renal function affect recovery; do not treat 2–4 weeks as a guaranteed safe waiting period.

Pain Characteristics and Radiation Patterns

The agonizing, crescendo-decrescendo flank pain originates from tension mechanoreceptors within the renal pelvis and capsule (innervated by sympathetic fibers via T10–L1 spinal segments):

• Upper Ureteral and Pelviureteric Junction Calculi: Pain localizes to the costovertebral angle and flank, radiating along the subcostal margin to the ipsilateral upper abdomen.
• Mid-Ureteral Calculi (Crossing the Iliac Vessels): Radiates to the lower abdominal quadrant, frequently mimicking acute appendicitis (on the right) or acute diverticulitis (on the left).
• Distal Ureteral and Vesicoureteric Junction (VUJ) Calculi: Radiates along the ilioinguinal and genitofemoral nerves into the ipsilateral groin, testicle, or scrotum in males, and the labium majus in females. Intramural or juxtavesical stones irritate bladder trigone mechanoreceptors, producing marked lower urinary tract symptoms (LUTS): severe frequency, urgency, dysuria, and strangury, frequently misdiagnosed as acute bacterial cystitis.

Diagnostic Imaging Workup

Establishing an accurate diagnosis requires rapid, high-resolution imaging to confirm calculus presence, size, location, and secondary obstructive changes.

Non-Contrast Computed Tomography (NCCT / CT-KUB)

Non-contrast CT (NCCT / CT-KUB) is the confirmatory test for suspected acute ureteric stones in adults after initial ultrasound under EAU guidance. Obtain immediate imaging with fever, a solitary kidney or diagnostic uncertainty; analgesia must not be delayed. Use an appropriate low-dose protocol when suitable.

• Key Diagnostic Parameters Provided by NCCT:
  • Precise Calculus Dimensions: Measured accurately in three orthogonal planes (axial, coronal, and sagittal). Stone size is defined by its greatest diameter.
  • Anatomical Location: Exact level of impaction (PUJ, proximal, mid, distal, or VUJ).
  • Internal Stone Density (Attenuation in Hounsfield Units, HU): Helps estimate composition and SWL suitability, but HU ranges overlap; density alone does not reliably distinguish every stone type. Dual-energy CT can separate uric-acid-containing from calcium stones.
  • Skin-to-Stone Distance (SSD): Measured along the acoustic shock wave path; SSD $> 10$ cm is an independent predictor of SWL failure.
  • Secondary Signs of Obstruction: Perinephric fat stranding (fluid transudation into Gerota's fascia), hydroureteronephrosis, renal enlargement / nephromegaly, and the tissue rim sign (periureteral soft-tissue halo of edema indicating localized inflammatory impaction).
• Low-Dose Protocols: Modern low-dose CT protocols deliver an effective radiation dose $< 1.5 - 3.0$ mSv (comparable to a standard plain abdominal radiograph series) with performance dependent on protocol, body habitus and stone size. EAU cites pooled sensitivity 93.1% and specificity 96.6% for low-dose CT; small stones can be missed.

Ultrasonography (US) and Plain Abdominal Radiography (KUB)

• Ultrasonography: EAU's initial imaging tool for suspected stones, particularly important in pregnancy and children; adult acute-flank-pain evaluation generally proceeds to NCCT confirmation as indicated. Ultrasound has high sensitivity for detecting pelvicalyceal dilatation / hydronephrosis ($> 85\%$), but poor sensitivity for direct ureteral stone visualization ($45 - 60\%$, restricted primarily to the PUJ and the UVJ through a full bladder acoustic window).
• Plain KUB Radiograph: Sensitivity is only $50 - 60\%$; obscured by overlying bowel gas, fecal matter, and bony pelvic architecture. Cannot detect radiolucent calculi. Its primary utility is baseline assessment prior to planned Shock Wave Lithotripsy (to confirm fluoroscopic visibility) and interval surveillance of known radio-opaque stones.

Acute Analgesic Management

Prompt pain relief is the first therapeutic imperative in acute ureteric colic.

First-Line Analgesia: Non-Steroidal Anti-Inflammatory Drugs (NSAIDs)

Per EAU Guidelines, NSAIDs are the first analgesic choice when clinically appropriate, accounting for cardiovascular risk, renal function and other contraindications for acute renal colic:

• Preferred Agents and Dosing: Diclofenac (50–75 mg IV/IM or 100 mg PR), Ketorolac (15–30 mg IV), Indomethacin (50–100 mg PR), or Ibuprofen (600–800 mg PO).
• Pharmacological Mechanism:
  • Inhibit cyclooxygenase (COX-1 and COX-2) enzymes, blocking the synthesis of intrarenal vasodilatory prostaglandins ($PGE_2$ and $PGI_2$).
  • Induce pre-glomerular afferent arteriolar vasoconstriction, dampening renal blood flow and decreasing glomerular filtration rate.
  • Consequently lower intrarenal pelvicalyceal hydrostatic pressure and decrease mechanical stretching of pelvic pain mechanoreceptors.
  • Directly reduce local ureteral edema, inflammation, and hyperperistaltic smooth muscle spasm.
• Clinical Superiority over Opioids: Cochrane meta-analyses and prospective randomized trials demonstrate that NSAIDs achieve faster, more sustained pain reduction, lower requirements for rescue analgesia, and significantly lower rates of adverse events (specifically reducing nausea, vomiting, dizziness, and sedation) compared to opioids.
• Contraindications: Severe chronic kidney disease (eGFR $< 30$ mL/min), acute kidney injury with hypovolemia, active gastrointestinal peptic ulcer disease, severe heart failure, and third-trimester pregnancy.

Second-Line Analgesia: Opioids

• Agents: Morphine, Piritramide, Hydromorphone, or Pethidine.
• Clinical Indications: Reserved strictly for patients with active contraindications to NSAIDs or as rescue analgesia for refractory breakthrough pain.
• Adverse Effects: High incidence of nausea and vomiting (aggravating existing autonomic colic symptoms), respiratory depression, constipation, and physical dependence. Pethidine should be avoided due to neurotoxicity from its active metabolite, norpethidine.

Antispasmodics (Spasmolytics)

• Hyoscine butylbromide (Buscopan) and other anticholinergic spasmolytics are not a substitute for effective colic analgesia; EAU notes that adding antispasmodics to NSAIDs does not improve pain control.

Indications for Urgent Drainage or Stone Intervention

While the majority of acute colic episodes can be managed conservatively, infection with obstruction or anuria requires urgent drainage. With refractory pain or threatened renal function, urgent relief may involve drainage or, when infection is absent, stone removal.

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|                       INDICATIONS FOR URGENT UROLOGICAL INTERVENTION                                  |
|                                                                                                |
|  1. Obstructive Pyelonephritis / Urosepsis (Fever, Rigors, Hemodynamic Instability)           |
|  2. Solitary Kidney with Obstructing Calculus (Imminent Anephric Renal Failure)                |
|  3. Bilateral Obstructing Ureteric Calculi                                                     |
|  4. Intractable Renal Colic Refractory to Maximal Parenteral Analgesia                         |
|  5. Progressive Acute Kidney Injury or Anuria                               |
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1. Obstructive Pyelonephritis and Urosepsis

An obstructing ureteric calculus in the presence of systemic infection (fever $> 38.0^\circ\text{C}$, rigors, tachycardia, hypotension, pyuria, elevated CRP/procalcitonin) is an absolute, life-threatening urological emergency:

• Pathophysiology: High pelvicalyceal pressure forces bacteria and endotoxins across the disrupted renal epithelial barrier into the systemic circulation via pyelovenous and pyelolymphatic backflow, precipitating fulminant septic shock, multi-organ dysfunction and death.
• Decompression Modalities:
  • Retrograde Ureteral Double-J (JJ) Stenting under fluoroscopy, OR
  • Percutaneous Nephrostomy (PCN) tube placement.
  • Both methods are accepted and similarly effective for urgent decompression. Comparative evidence is limited; they do not have identical hospitalization or patient-experience outcomes. Selection depends on institutional availability, surgeon expertise, and patient stability (e.g., coagulopathy favors retrograde stenting; severe hemodynamic instability or retrograde failure favors PCN).

2. Solitary or Transplanted Kidney Obstruction

Acute calculus obstruction of a solitary anatomical or functional kidney, or a renal allograft, can rapidly compromise the remaining renal function and may cause anuria, AKI and hyperkalemia. Obtain urgent specialist assessment and relieve clinically significant obstruction promptly.

3. Bilateral Obstructing Calculi

Produces acute bilateral post-renal failure requiring urgent unilateral or bilateral decompression.

4. Refractory Pain or Intractable Vomiting

Persistent, excruciating pain or intractable vomiting unresponsive to repeated maximal doses of parenteral NSAIDs and opioids requires urgent relief. EAU recommends decompression or ureteroscopic stone removal for analgesia-refractory colic; infection status and patient factors determine the approach.

Medical Expulsive Therapy (MET)

Medical Expulsive Therapy utilizes pharmacological agents to accelerate the spontaneous passage of ureteral calculi, alleviate colic symptoms, and reduce surgical intervention rates.

Pharmacological Mechanism: Alpha-1 Blockers

• The human ureter is densely populated with alpha-1 adrenergic receptors, with the highest receptor concentration located in the distal ureter and intramural ureter (specifically the $\alpha_{1A}$ and $\alpha_{1D}$ receptor subtypes).
• Alpha-1 Blockers (e.g., Tamsulosin 0.4 mg daily, Silodosin 8 mg daily):
  • Antagonize alpha-1 receptors on ureteral smooth muscle cells.
  • Selectively abolish uncoordinated, hyperperistaltic spasms and basal smooth muscle tone.
  • Decrease intraureteral hydrostatic pressure immediately proximal to the stone while preserving coordinated propulsive peristaltic waves.
  • Dilate the distal ureter and ureterovesical junction, facilitating spontaneous passage and reducing pain.

Clinical Efficacy and Guideline Recommendations

Evidence is heterogeneous. SUSPEND found no overall reduction in four-week intervention needs with tamsulosin or nifedipine versus placebo. Other trials and pooled evidence support alpha-blockers particularly for larger distal stones, reflected in current EAU recommendations:

• Distal Ureteral Stones 5–10 mm: Offer an alpha-blocker as one treatment option when active removal is not indicated. Benefit is greatest above 5 mm; do not apply one fixed relative benefit or passage-time reduction to every patient.
• Calculi $< 5$ mm (Any Location): MET provides no statistically significant advantage over placebo. Stones $< 5$ mm exhibit an intrinsically high spontaneous passage rate (75–85%) under simple observation alone.
• Proximal and Mid-Ureteral Calculi: The evidence for MET in the proximal or mid-ureter remains weak and inconclusive; routine MET is not recommended for proximal stones.
• Calcium Channel Blockers (e.g., Nifedipine): Inhibit calcium influx into ureteral smooth muscle. While historically utilized, nifedipine is significantly less effective than tamsulosin and carries systemic hypotension risk; it is largely relegated to historical interest.

Patient Counseling and Adverse Effects

Stop MET and reassess urgently if infection, refractory pain or renal deterioration develops. Patients initiated on tamsulosin must be informed that MET represents an off-label use in many jurisdictions and counseled regarding potential adverse effects: ejaculatory dysfunction, orthostatic hypotension, dizziness, asthenia, and Intraoperative Floppy Iris Syndrome (IFIS) in patients planning cataract surgery.

Expectant Conservative Management & Safety Follow-Up

Conservative expectant management is appropriate for patients who meet all safety criteria:

1. Complete absence of clinical or laboratory signs of sepsis or urinary tract infection.
2. Adequate pain control achieved with oral analgesics.
3. Stable renal function with no indication for urgent relief of obstruction; a solitary kidney or bilateral obstruction warrants particular caution.
4. A stone with a reasonable chance of passage, considering size and location, with informed preference and reliable follow-up. There is no universal<6 mm eligibility cutoff.

Spontaneous Passage Dynamics

Spontaneous stone expulsion depends on two critical anatomical variables:

• Size and Location Matter Together: EAU reports passage in almost 75% of stones<5 mm and 62% of stones≥5 mm overall, with an average expulsion time of about 17 days(range 6–29). These are cohort estimates, not individual guarantees.
• Location: Reported passage is 49–52% for upper,58–70% for mid-ureteral and 68–83% for distal stones. For stones<5 mm, approximately 89% of distal and 71% of upper stones pass.
• Passage becomes less likely as size increases, but >6 mm does not universally mean <15–20% passage. Persistent obstruction, pain, renal impairment or low passage likelihood favors active removal.

Follow-Up and Safety Net

Clinical Triage, Pain Management, and Spontaneous Passage Dynamics