Renal · Year 2 · from Renal
Case 1: Calcium Oxalate Stone with Acute Renal Colic
Patient Presentation
Demographics: 38-year-old male
Chief Complaint: Sudden onset severe left flank pain for 6 hours
History of Present Illness: The patient developed sudden severe left flank pain that woke him from sleep. The pain is colicky, radiating to the left groin and testicle. He has been nauseated with one episode of vomiting. He noticed pink-tinged urine. He has never had a kidney stone before but his father had multiple stones.
Social History:
- Low fluid intake (mainly coffee and soda)
- High protein diet
- No regular exercise (sedentary job)
Physical Examination:
- Blood pressure: 148/92 mmHg
- Heart rate: 98 bpm
- General: Writhing in pain, unable to find comfortable position
- Abdomen: Soft, mild left CVA tenderness
- GU: Normal external genitalia, mild left testicular tenderness (referred)
Workup and Results
Laboratory Studies:
- Creatinine: 1.0 mg/dL
- BUN: 14 mg/dL
- Calcium: 9.6 mg/dL
- Uric acid: 7.2 mg/dL
- Urinalysis: 2+ blood, pH 6.0, no WBC, no bacteria
CT Abdomen/Pelvis (Non-contrast):
- 6 mm stone in left distal ureter at ureterovesical junction
- Mild left hydronephrosis
- No other stones
- Hounsfield units: 1,200 (consistent with calcium stone)
Clinical Image
Non-contrast CT demonstrating a 6 mm calculus at the left ureterovesical junction (arrow) with associated proximal hydroureter and mild hydronephrosis.
Diagnosis
Acute Renal Colic due to Calcium Oxalate Nephrolithiasis
Supporting features:
- Classic colicky flank pain radiating to groin
- Hematuria
- High-density stone on CT (calcium)
- No infection
Discussion
This case illustrates typical calcium stone presentation:
- Most Common Stone Type: The lecture notes that calcium oxalate stones account for 70-80% of all kidney stones, making this the classic presentation.
- Renal Colic Characteristics: The lecture describes colicky pain that radiates from flank to groin as the stone moves distally. Pain at the ureterovesical junction often radiates to the testicle/labia due to shared innervation.
- CT is Gold Standard: Non-contrast CT is the gold standard imaging modality with sensitivity >95%. Hounsfield units help determine stone composition - calcium stones typically >400 HU.
- Stone Size and Passage: The lecture states that stones <5 mm have >90% spontaneous passage rate, while 5-10 mm stones have ~50% passage rate. This 6 mm stone has reasonable chance of passage with conservative management.
Treatment Plan
- Pain Control:
- NSAIDs first-line (ketorolac, ibuprofen)
- Opioids for refractory pain
- IV fluids for hydration
- Medical Expulsive Therapy:
- Tamsulosin 0.4 mg daily (alpha-blocker relaxes ureteral smooth muscle)
- Expected passage within 4-6 weeks
- Follow-up:
- Strain urine to capture stone for analysis
- Repeat imaging in 2-4 weeks if no passage
- Urology referral if stone not passed by 4-6 weeks
- 24-hour Urine Metabolic Evaluation:
- Perform 6-8 weeks after stone passage
- Assess for hypercalciuria, hyperoxaluria, hypocitraturia
Teaching Points
- Non-contrast CT is the gold standard for kidney stone diagnosis
- Stones <5 mm have >90% spontaneous passage rate
- NSAIDs are first-line analgesia for renal colic
- Alpha-blockers (tamsulosin) facilitate stone passage
- Stone analysis guides prevention strategies