What is the medical diagnosis for a patient presenting with symptoms suggestive of a kidney stone, possibly with an underlying urinary tract infection?

Medical Diagnosis: Nephrolithiasis (Kidney Stones) with Possible Complicated Urinary Tract Infection

The medical diagnosis for a patient presenting with symptoms suggestive of kidney stones, possibly with an underlying urinary tract infection, is nephrolithiasis (urolithiasis), which may be complicated by obstructive pyelonephritis or represent infection stones (struvite calculi). 1

Clinical Presentation and Diagnostic Considerations

The typical presentation includes:

• Acute flank pain due to ureteral hyperperistalsis caused by stone passage, often radiating to the groin 1
• Hematuria resulting from irritation and trauma to the ureter 1
• Hydronephrosis as a potential serious complication from ureteral obstruction 1

Critical Distinction: Infection vs. Non-Infection Stones

If urinary tract infection is present with obstruction, this represents a urologic emergency requiring immediate drainage (typically via ureteral stent or percutaneous nephrostomy), as obstructive pyelonephritis can rapidly progress to sepsis and death. 2, 3

The presence of infection suggests two distinct possibilities:

1. Struvite (infection) stones: Caused by urease-producing bacteria (Proteus, Klebsiella, Pseudomonas, Staphylococcus—NOT E. coli) that create alkaline urine promoting magnesium ammonium phosphate crystallization 4, 5
2. Secondarily infected metabolic stones: Calcium oxalate or other stone types that became infected after formation 6, 2

Diagnostic Algorithm

Immediate Assessment Required:

First-line imaging: CT abdomen and pelvis without IV contrast is the reference standard with 97% sensitivity for detecting stones. 1

• Low-dose CT protocols should be used to minimize radiation exposure 1
• This imaging confirms stone presence, size, location, and degree of obstruction 1
• Stone size and location determine likelihood of spontaneous passage (larger and more proximal stones have lower passage rates) 1

Alternative Imaging (Lower Priority):

• Ultrasound with radiography: Sensitivity 90%, specificity 68%, but decreased detection for stones <5 mm 1
• CT urography: Useful for confirming ureteral stone location and distinguishing from phleboliths, but not necessary for initial diagnosis 1

Stone Classification and Implications

Infection Stones (Struvite):

• Bacteria reside within the stone matrix, not just on the surface 4
• Often grow into staghorn configuration filling renal pelvis and calices 4
• Untreated staghorn calculi can destroy kidney function and cause life-threatening sepsis 4
• Complete stone removal is mandatory to eradicate organisms and prevent recurrence 4, 5

Metabolic Stones:

• Calcium oxalate/phosphate stones (most common) 3
• Uric acid stones (form in acidic urine pH <5.5) 4
• Cystine stones (hereditary, associated with higher renal failure risk) 7

Management Priorities Based on Diagnosis

Emergency Situations Requiring Immediate Intervention:

Obstructive pyelonephritis with infection = urologic emergency requiring immediate drainage before definitive stone treatment. 2, 3

Struvite/Infection Stones:

Complete stone removal is the only definitive treatment—medical management alone is inadequate. 6, 2

Treatment options based on stone characteristics 1:

• Percutaneous nephrolithotomy: Primary treatment for staghorn calculi
• Shock wave lithotripsy monotherapy: Only for small volume staghorn calculi (<500 mm²) with normal collecting system anatomy 1
• Open surgery: Reserved for extremely large stones or unfavorable anatomy 1
• Nephrectomy: When kidney has negligible function and serves as source of recurrent infection 1

Non-Infection Stones:

Approximately 90% of stones causing renal colic pass spontaneously. 3

Conservative management includes:

• Hydration and analgesics 3
• Urine straining to recover stone for analysis 3
• Observation for spontaneous passage 3

Critical Pitfalls to Avoid

1. Do not assume E. coli UTI causes struvite stones—E. coli does NOT produce urease and is not associated with infection stone formation 4

2. Do not delay drainage in obstructive pyelonephritis—this is a true emergency that can rapidly progress to sepsis 2, 3

3. Do not leave residual stone fragments in infection stones—fragments will grow and serve as source for recurrent UTI 4, 5

4. Do not use shock wave lithotripsy monotherapy for staghorn cystine stones—poor stone-free rates make this inappropriate 1

5. Recognize high-risk patients for renal failure: hereditary stone diseases (cystinuria, primary hyperoxaluria), primary struvite stones, recurrent obstruction, and frequent urological interventions all increase risk 7

Recurrence Prevention

The bidirectional relationship between stones and infection requires aggressive management: stones promote biofilm formation resistant to antibiotics, while urease-producing bacteria directly cause new stone formation. 5, 6

Essential prevention strategies:

• Complete stone clearance in all infection stone cases 4, 5
• Urine culture monitoring after treatment 5
• Repeated imaging to detect residual fragments 5
• High fluid intake as mainstay of prevention 3