Brian M. Benway, MD
Gerald L. Andriole, MD, FACS
BASICS
DESCRIPTION
• Staghorn calculi are branched stones that occupy a large portion of the collecting system. Typically, they fill the renal pelvis and branch into several or all of the calices.
• Partial staghorn: Fills some but not all of the collecting system
• Complete staghorn: Fills nearly the entire collecting system
• Can be comprised of any of the following stone types, with struvite and calcium carbonate apatite the most commonly seen:
– Struvite (magnesium ammonium phosphate)
– Calcium carbonate apatite
– Cystine
– Uric acid
– Calcium oxalate
– Calcium phosphate
• Some literature refers to staghorn calculi as “coral calculi” or “coral nephrolithiasis” based on its characteristic shape.
EPIDEMIOLOGY
Incidence
• Not well-defined, with conflicting studies
• More common in women than in men
Prevalence
N/A
RISK FACTORS
• Chronic indwelling catheter
• Chronic infection
• Dehydration
• Metabolic disorders (hypercalciuria, cystinuria, hyperoxaluria)
• Neurogenic bladder
• Ureteral obstruction or reflux
• Urinary diversion
Genetics
N/A
PATHOPHYSIOLOGY
• Staghorn calculi are most frequently composed of mixtures of magnesium ammonium phosphate (struvite) and/or calcium carbonate apatite
– These are also commonly referred to as “infection stones”
Strong association with urinary tract infection caused by specific organisms that produce the enzyme urease that promotes the generation of ammonia and hydroxide from urea.
• Cystine or uric acid (pure form or mixed) can sometimes grow in a “staghorn” or branched configuration, but calcium oxalate or phosphate stones only rarely grow in this configuration.
• Urinary stasis due to obstruction or smooth muscle paralysis due to endotoxins
• Infection with urea-splitting organisms
– Often harbored inside stones
– Produce urease—hydrolyzes urea into ammonia, bicarbonate, and carbonate
Proteus
Pseudomonas
Klebsiella
Staphylococcus
E. coli
Mycoplasma
Yeast
ASSOCIATED CONDITIONS
• Chronic urinary tract infections
• Urinary tract obstruction
• Urinary diversion
• Neurogenic bladder
GENERAL PREVENTION
• Hydration
• Treatment of urinary tract infections
• Elimination of stones prior to evolution into staghorn calculus
DIAGNOSIS
HISTORY
• Often asymptomatic
• Discovered incidentally on imaging
• Recurrent or persistent urinary tract infection
• Fever, malaise, weight loss
• Renal insufficiency
• Flank pain
• Hematuria
• Neurogenic bladder
• Urinary diversion
• Metabolic disorders
PHYSICAL EXAM
• Costovertebral angle tenderness
• Rarely, palpable mass
DIAGNOSTIC TESTS & INTERPRETATION
Lab
• CBC
• Basic metabolic panel
• PTT/INR
• Urinalysis and culture
– pH >7.0 may indicate urea-splitting infection
– Culture may demonstrate commonly associated bacteria
– Persistence of a species may indicate a stone harboring infection
Imaging
• May be seen on KUB or ultrasound
• CT is gold-standard
– Provides clear information on stone location and configuration
– Evaluates cortical thickness
– Can identify excluded calyces and calyceal diverticula
– Provides information on location of surrounding structures
– Aids selection of access site(s)
Diagnostic Procedures/Surgery
Diagnosis is made based on imaging studies
Pathologic Findings
• Gross pathology—calculus material
• Microscopic evaluation of crystals aids in determination of stone composition
DIFFERENTIAL DIAGNOSIS
• Blood clot
• Fibroepithelial polyp
• Fungus ball
• Granuloma
• Hemangioma
• Malakoplakia
• Renal cell carcinoma and other renal malignancy
• Tuberculosis
• Upper tract carcinoma (urothelial, other)
• Xanthogranulomatous pyelonephritis (XGP)
TREATMENT
GENERAL MEASURES
• Culture-specific antibiotic therapy
• Relief of obstruction in anticipation of later intervention (stent, percutaneous nephrostomy tube)
• Observation is associated with significant morbidity, including renal deterioration and septic events. Only appropriate for patients who would not tolerate definitive intervention
MEDICATION
First Line
Culture-specific antibiotics
Second Line
• Acetohydroxamic acid
– May reduce recurrence of struvite stones
– Inhibits bacterial urease, decreasing urinary ammonia production
– Adult dose: 12 mg/kg/d PO, 3–4 times a day on empty stomach. 1.5 g/d maximum.
– Pediatric dose: 10 mg/kg/day titrated
– May have severe side effects including deep venous thrombosis, myelosuppression, hepatotoxicity, palpitations, edema, nausea, vomiting, diarrhea, headache, loss of taste sensation, hallucinations, rash, abdominal discomfort
– Must follow CBC and liver functions
– Contraindicated in patients with severe renal insufficiency (serum creatinine >2.5 mg/dL)
SURGERY/OTHER PROCEDURES
• Goal is complete elimination of stone burden
• Percutaneous nephrolithotomy (PCNL) is gold-standard (1)
• Shockwave lithotripsy (SWL) is not recommended as monotherapy for most staghorn calculi
• If combination SWL and PCNL or “sandwich” therapy is performed, PCNL should be the last intervention
• SWL monotherapy can be considered for small stones (<500 mm2), provided a ureteral stent or nephrostomy tube is placed. May also be used in pediatric patients.
• Open surgery is not commonly performed. May be used in extraordinary cases where clearance is not expected within a reasonable number of less-invasive procedures
• Nephrectomy for kidneys with negligible function or Xanthogranulomatous pyelonephritis (XGP)
• Dissolution may be effective in carefully selected patients, but has the potential for significant side effects. It is not presently included in the guidelines for staghorn management.
ADDITIONAL TREATMENT
Radiation Therapy
N/A
Additional Therapies
Prophylactic antibiotics to suppress UTI
Complementary & Alternative Therapies
N/A
ONGOING CARE
PROGNOSIS
• Observation associated with significant risk of renal deterioration (28–48%) (2,3)
• Good prognosis for patients who are rendered stone-free
COMPLICATIONS
• Observation
– Death
– Functional renal loss
– Pyelonephritis
– Sepsis
• Intervention
– Anesthesia complications
– Death
– Hematoma
– Hemorrhage
– Injury to colon, liver, spleen
– Pneumothorax/hydrothorax
– Upper tract injury
– Urinary fistula
– Urinoma
FOLLOW-UP
Patient Monitoring
• KUB and ultrasound at regular intervals
• Urinalysis and culture
• Consider metabolic evaluation (serum studies, 24-hr urine study)
Patient Resources
N/A
REFERENCES
1. Preminger GM, Assimos DG, Lingeman JE, et al. Chapter 1: AUA guideline on management of staghorn calculi: diagnosis and treatment recommendations. J Urol. 2005;173:1991–2000.
2. Koga S, Arakaki Y, Matsuoka M, et al. Staghorn calculi—long-term results of management. Br J Urol. 1991;68:122–124.
3. Teichman JM, Long RD, Hulbert JC, et al. Long-term renal fate and prognosis after staghorn calculus management. J Urol. 1995;153:1403–1407.
ADDITIONAL READING
• Healy KA, Ogan K. Pathophysiology and management of infectious staghorn calculi. Urol Clin N Am. 2007;34:363–374.
• (AUA) Report on the Management of Staghorn Calculi (2005). https://www.auanet.org/education/guidelines/staghorn-calculi.cfm. Accessed January 25, 2014.
• Segura, JW. Staghorn calculi. Urol Clin N Am. 1997;24:71–80.
See Also (Topic, Algorithm, Media)
• Pyelonephritis, Xanthogranulomatous
• Urinary Tract Infection (UTI), Complicated, Adult
• Urinary Tract Infection (UTI), Complicated, Pediatric
• Urolithiasis, Adult, General
• Urolithiasis, Pediatric, General
• Urolithiasis, Staghorn Image 
CODES
ICD9
• 274.11 Uric acid nephrolithiasis
• 592.0 Calculus of kidney
• 599.0 Urinary tract infection, site not specified
ICD10
• N12 Tubulo-interstitial nephritis, not spcf as acute or chronic
• N20.0 Calculus of kidney
• N39.0 Urinary tract infection, site not specified
CLINICAL/SURGICAL PEARLS
• Staghorn calculi are large branching renal calculi most often associated with urinary tract infections.
• Observation carries a high risk of morbidity, including renal deterioration and sepsis.
• Percutaneous nephrolithotomy is the gold-standard for treatment.