Staghorn calculi (also sometimes called coral calculi) obtain their characteristic shape by forming a cast of the renal pelvis and calices, thus resembling the horns of a stag.
For a general discussion of renal calculi please refer to nephrolithiasis.
Staghorn calculi are the result of recurrent infection and are thus more commonly encountered in 4:
- spinal cord injury and neurogenic bladder
- ileal ureteral diversion
The majority of staghorn calculi are symptomatic, presenting with fever, haematuria, flank pain and potentially septicaemia and abscess formation.
Staghorn calculi are composed of struvite (magnesium ammonium phosphate) and are usually seen in the setting of infection with urease producing bacteria (e.g. Proteus, Klebsiella, Pseudomonas and Enterobacter). Urease hydrolyses urea to ammonium and increase in the urinary pH 1-3.
The struvite accounts for approximately 70% of these calculi, and is usually mixed with calcium phosphate thus rendering them opaque on both plain films and CT. Uric acid and cystine are the underlying component of a minority of these calculi 3.
The vast majority of staghorn calculi are radiopaque and appear as branching calcific densities overlying the renal outline and may mimic an excretory phase IVP. Lamination within the stone is common.
The collecting system is filled with a densely calcific mass producing intense posterior acoustic shadowing.
Staghorn calculi are radiopaque and conform to the renal pelvis and calyces, which are often to some degree dilated. When viewed on bone window they have a laminated appearance, due to alternating bands of magnesium ammonium phosphate and calcium phosphate 3.
Treatment and prognosis
Staghorn calculi need to be treated surgically (PCNL) +/- ESWL and the entire stone removed, including small fragments, as otherwise these residual fragments act as a reservoir for infection and recurrent stone formation.
If left untreated, staghorn calculi result in chronic infection and eventually may progress to xanthogranulomatous pyelonephritis 3.
There is usually little differential, provided intravenous contrast has not been administered. In the latter situation the opaque collecting system may be attributed to contrast rather than the calculus, especially when staghorn calculi are bilateral.
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- 1. Fishman MC, Hoffman AR. Medicine. Lippincott Williams & Wilkins. (2004) ISBN:0781725437. Read it at Google Books - Find it at Amazon
- 2. Nissenson AR, Berns JS, Lerma E. CURRENT Diagnosis & Treatment Nephrology & Hypertension. McGraw-Hill Professional. (2008) ISBN:0071447873. Read it at Google Books - Find it at Amazon
- 3. Silverman SG, Cohan RH. CT urography, an atlas. Lippincott Williams & Wilkins. (2006) ISBN:0781787548. Read it at Google Books - Find it at Amazon
- 4. Reilly RF, Reilly R, Perazella MA. Nephrology in 30 Days. McGraw-Hill Professional. (2005) ISBN:0071437010. Read it at Google Books - Find it at Amazon
Synonyms & Alternative Spellings
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|Staghorn renal calculi||✗|
|Struvite renal calculi||✗|