Critical Alerts

• Infected obstructing stone (pyonephrosis) is a urological emergency requiring immediate decompression
• Solitary kidney obstruction risks complete renal failure
• Bilateral obstructing stones rare but can cause acute kidney injury
• Stone size >10mm unlikely to pass spontaneously - early urology referral
• NSAIDs are first-line analgesia - more effective than opioids for renal colic

Key Diagnostics

• Non-contrast CT (NCCT) abdomen/pelvis is gold standard
• Urinalysis (hematuria in 80-90%)
• BUN/Creatinine (renal function, especially if bilateral or single kidney)
• CBC if infection suspected
• Urine culture if fever or UTI symptoms

Emergency Treatments

• Analgesia: Ketorolac 15-30mg IV/IM + Acetaminophen 1g IV
• Opioids: Morphine 0.1mg/kg IV for severe pain or NSAID contraindication
• Antiemetics: Ondansetron 4-8mg IV
• IV fluids: Judicious - aggressive hydration not proven beneficial
• Medical expulsive therapy: Tamsulosin 0.4mg daily for stones 5-10mm

Renal colic refers to the acute pain caused by urinary tract stones (urolithiasis) obstructing the collecting system. The term "colic" describes the intermittent, cramping nature of the pain, though in reality, many patients experience constant severe pain with fluctuating intensity.

Stone Types

Epidemiology

• Lifetime prevalence: 5-15%
• Recurrence rate: 50% within 5-10 years
• Peak incidence: Ages 20-60 years
• Sex ratio: Male > Female (2:1), gap narrowing
• Seasonal variation: More common in summer (dehydration)

Stone Location Terminology

Critical Presentations

Infected Obstructing Stone (Pyonephrosis)

Clinical Features

• Flank pain + fever + rigors
• May progress rapidly to septic shock
• Urology emergency

Management

• Blood cultures, IV antibiotics
• Emergency decompression (ureteral stent or nephrostomy)
• Do NOT attempt lithotripsy until sepsis controlled

By Symptom Pattern

Flank Pain

Lower Abdominal/Groin Pain

Key Mimics to Rule Out

Abdominal Aortic Aneurysm

• Age >60, cardiovascular risk factors
• May have pulsatile mass
• Consider bedside ultrasound
• Pain may radiate to back/flank

Ectopic Pregnancy

• Always check pregnancy test in reproductive-age females
• Shoulder tip pain if ruptured
• May have hematuria

Laboratory Studies

Urinalysis Interpretation

• Hematuria absent in 10-20% of proven stones
• Pyuria without bacteriuria common from inflammation
• WBCs + bacteria + obstruction = emergency

Imaging

Non-Contrast CT Abdomen/Pelvis (Gold Standard)

CT Findings

• Direct visualization of stone
• Hydronephrosis/hydroureter
• Perinephric stranding
• Rim sign around stone
• Measurement of stone size

Ultrasound

When to Use Ultrasound First

• Pregnancy
• Known recurrent stone former
• Pediatric patients
• Young patients with classic presentation

Plain Radiograph (KUB)

• Limited sensitivity (50-60%)
• Cannot detect uric acid or other radiolucent stones
• Useful for follow-up of known calcium stones

Imaging Algorithm

Suspected Renal Colic
        ↓
Pregnancy test (if applicable)
        ↓
Classic presentation + hematuria?
        ↓
    [YES]                        [NO or UNCERTAIN]
        ↓                              ↓
  Low-dose NCCT              Standard NCCT or
  OR Point-of-care           consider alternative
  ultrasound first           diagnoses
        ↓
Stone confirmed?
        ↓
  [YES] → Size assessment → Management
        ↓
  [NO] → Consider alternative diagnoses
         Repeat testing if high suspicion

Discharge Criteria (Safe for Home)

• Pain controlled with oral medications
• Tolerating oral intake
• Afebrile
• No signs of infection
• Stone <10mm with reasonable expectation of passage
• Able to follow up with urology
• Understands return precautions

Admission Criteria

• Intractable pain or vomiting
• Unable to tolerate oral intake
• Signs of infection with obstruction
• Acute kidney injury
• Single functioning kidney with obstruction
• Social factors (unable to access care if deteriorates)

Follow-up Recommendations

Discharge Instructions

• Strain all urine for stone collection
• High fluid intake (2-3L/day)
• Pain medications as prescribed
• Medical expulsive therapy if indicated

Follow-up Timeline

Return Precautions

Return immediately if:

• Fever or chills
• Unable to keep fluids down for >24 hours
• Unable to urinate
• Worsening pain despite medications
• Blood in urine increasing significantly

Understanding Kidney Stones

• Kidney stones form from minerals in urine
• They cause pain as they travel through the urinary tract
• Most small stones (under 5mm) pass on their own
• Larger stones may require procedures

Stone Prevention

General Measures

• Increase fluid intake (goal: 2.5L urine output/day)
• Lemonade and orange juice increase citrate
• Limit sodium intake
• Moderate calcium intake (dietary calcium is protective!)
• Limit animal protein

Stone-Specific Prevention

Medication Instructions

• Take tamsulosin (if prescribed) as directed
• May cause dizziness - rise slowly from sitting/lying
• Continue until stone passes or urology follow-up
• NSAIDs can help with pain - take with food

Pregnancy

Considerations

• Stone incidence same as non-pregnant
• Most common in 2nd and 3rd trimester
• Physiologic hydronephrosis can confuse diagnosis
• Avoid CT if possible

Management

• Ultrasound first-line imaging
• MRI without contrast if needed
• Analgesia: Acetaminophen, opioids (short-term)
• Avoid NSAIDs (especially 3rd trimester)
• Urology involvement for intervention

Pediatric Patients

• Increasing incidence in children
• Consider metabolic/genetic causes
• Ultrasound first-line
• Weight-based analgesia

Patients with Single Kidney

• Any obstruction is potentially critical
• Lower threshold for imaging
• Urgent urology involvement
• Close monitoring of renal function

Recurrent Stone Formers

• May know their typical presentation
• Low-dose CT or ultrasound appropriate
• Metabolic workup essential
• Prevention strategies crucial

Performance Indicators

Documentation Requirements

• Pain scale documentation
• Pregnancy test result (if applicable)
• Stone size and location from imaging
• Presence/absence of hydronephrosis
• Renal function
• Treatment provided
• Disposition rationale
• Clear follow-up plan

Diagnostic Pearls

1. Absence of hematuria doesn't exclude stones - 10-20% have none
2. CT is gold standard but ultrasound first in pregnancy
3. Consider AAA in older patients with first episode
4. Pregnancy test every female of childbearing age
5. Fever + obstruction = emergency

Treatment Pearls

1. NSAIDs are superior to opioids for renal colic
2. Don't push fluids - no benefit, may worsen pain
3. Tamsulosin helps passage for distal stones 5-10mm
4. Stone <5mm = high chance of passing
5. Stone >10mm = needs intervention

Disposition Pearls

1. Discharge most uncomplicated cases with urology follow-up
2. Strain urine - stone analysis guides prevention
3. Infected obstruction = admission and decompression
4. Clear return precautions are essential
5. Know when to call urology emergently