Diagnosis: Staghorn Calculus with Urinary Tract Infection
The diagnosis for a patient presenting with staghorn calculi, flank pain, and hematuria is a large branched renal stone (staghorn calculus) that occupies the renal pelvis and extends into multiple calices, most commonly composed of struvite/calcium carbonate apatite (infection stone) associated with urease-producing bacterial infection. 1
Clinical Presentation and Diagnostic Features
The classic triad you describe represents the typical presentation of staghorn calculi:
- Flank pain occurs due to collecting system distension, obstruction, and associated inflammation from chronic infection 1
- Hematuria (either gross or microscopic) results from mucosal irritation and inflammation caused by the stone and infection 1
- Staghorn configuration indicates a branched stone occupying the renal pelvis with extensions into one or more calices 1
Symptomatic gross hematuria with flank pain is the classic presentation of urinary stone disease, distinguishing it from painless gross hematuria which has stronger cancer association 1. However, the presence of staghorn calculi makes stone disease the clear diagnosis.
Stone Composition and Pathophysiology
Staghorn calculi are most frequently composed of struvite (magnesium ammonium phosphate) and/or calcium carbonate apatite, termed "infection stones" due to their strong association with urease-producing organisms 1. The pathophysiology involves:
- Urease-producing bacteria (typically Proteus, Klebsiella, or Pseudomonas) generate ammonia and hydroxide from urea 1
- The resultant alkaline urine (pH >7.2) and high ammonia concentration promote struvite crystallization 1
- Bacteria reside within the stone matrix itself, making the stone inherently infected 1
- Recurrent urinary tract infections perpetuate stone growth and can lead to life-threatening sepsis 1
Critical Diagnostic Considerations
Only 1% of staghorn calculi are truly "silent" - the vast majority cause clinical complications in 53% of patients 2. Pathologic complications include:
- Pyonephrosis (20% of cases) 2
- Xanthogranulomatous pyelonephritis (8% of cases) 2
- End-stage pyelonephritic kidney (6% of cases) 2
- Severe hydronephrosis (7% of cases) 2
- Perinephric abscess (5% of cases) 2
Imaging and Confirmation
Non-contrast CT scan is the gold standard for confirming staghorn calculi, demonstrating the branched stone configuration filling the renal pelvis and caliceal system 3. The imaging will show:
- Stone burden and precise anatomic configuration 3
- Degree of collecting system involvement (partial vs. complete staghorn) 1
- Presence of hydronephrosis or other complications 3
- Renal function assessment of the affected kidney 4
Essential Workup Before Treatment
Obtain urine culture before initiating antibiotics if infection is suspected, as ADPKD patients with staghorn calculi often harbor complicated UTIs with resistant organisms 4. Additional necessary studies include:
- Stone analysis when material is available to guide preventive strategies 3
- Serum creatinine to assess renal function 4
- Assessment of contralateral kidney function if nephrectomy is being considered 1, 4
Natural History Without Treatment
Conservative management of staghorn calculi leads to unacceptably high morbidity and mortality 5. Long-term follow-up of conservatively managed patients shows:
- Chronic renal failure develops in 36% of patients (22 of 61) 5
- Death from uremia occurs in 11% of patients (7 of 61) 5
- Progressive kidney destruction occurs over time 5
- Complete removal of the stone is essential to eradicate causative organisms, relieve obstruction, prevent stone growth, and preserve renal function 1
Common Diagnostic Pitfalls
Do not assume flank pain and hematuria always equals simple nephrolithiasis - while staghorn calculi are the diagnosis here, other differentials include Page kidney (subcapsular hematoma causing secondary hypertension), loin pain hematuria syndrome, or even malignancy 6, 7. The presence of staghorn configuration on imaging confirms the diagnosis.
Do not delay obtaining urine culture - prompt identification of urease-producing organisms is essential for appropriate antibiotic selection and confirms the infection stone etiology 4.