What is the composition of a staghorn calculus (kidney stone)?

From the Guidelines

Staghorn calculi are most frequently composed of mixtures of magnesium ammonium phosphate (struvite) and/or calcium carbonate apatite. This composition is strongly associated with urinary tract infections caused by urease-producing bacteria, which create an alkaline environment that promotes crystal formation 1. The formation of these stones is often linked to the presence of bacteria that produce the enzyme urease, such as Proteus mirabilis, Klebsiella, and some strains of Pseudomonas and Staphylococcus.

• Key characteristics of staghorn calculi include:
  • Branched stones that occupy a large portion of the collecting system
  • Typically fill the renal pelvis and branch into several or all of the calices
  • Strong association with urinary tract infections caused by urease-producing bacteria
  • Composition of struvite and/or calcium carbonate apatite promotes crystal formation in alkaline urine
• Less common compositions of staghorn calculi include cystine, uric acid, and calcium oxalate, but these are relatively rare 1.
• Understanding the composition of staghorn calculi is crucial for treatment planning, as struvite stones often require complete surgical removal combined with appropriate antibiotic therapy to prevent recurrence, while metabolic stones may respond to medical management targeting the underlying metabolic abnormality 1.

From the Research

Staghorn Calliculus Composition

• Most staghorn renal stones are composed of struvite (magnesium ammonium phosphate) and are linked to urinary tract infection by urease-producing pathogens 2
• Staghorn calculi can also be composed of other materials, including:
  • Struvite and/or carbonate apatite 3
  • Cystine, uric acid, whewellite, and brushite stones 3
  • Calcium phosphate, hydroxyapatite, or brushite stones, which are rare and often associated with hyperparathyroidism, Cushing syndrome, and renal tubular acidosis 3
• Metabolic stones, such as calcium phosphate, uric acid, calcium oxalate, and cystine, can also comprise a large proportion of complete staghorn calculi 4
• The composition of staghorn calculi can vary, with some studies suggesting that metabolic stones are more common than previously thought 4, 5

Importance of Stone Composition

• Knowing the composition and architecture of staghorn calculi is important for stone crushing and treatment 3
• Different stone compositions require different treatment approaches, such as combination therapy of stone crushing and irrigation of alkali solution for cystine stones and uric acid stones 3
• Metabolic evaluation and directed medical management can be an effective treatment approach for staghorn calculi, especially for patients who are unwilling or unable to undergo surgical treatment 5