Staghorn calculi, also sometimes called coral calculi, are renal calculi that obtain their characteristic shape by forming a cast of the renal pelvis and calyces, 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 women 6, those with renal tract anomalies, reflux, spinal cord injuries, neurogenic bladder or 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 (MAP, magnesium ammonium phosphate) and are usually seen in the setting of recurrent urinary tract infection with urease producing bacteria (e.g. Proteus, Klebsiella, Pseudomonas and Enterobacter). Urease hydrolyses urea to ammonium and increase in the urinary pH 3-5.
Struvite accounts for approximately 70% of the composition 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 5.
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 calcified mass, producing marked 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 windows they have a laminated appearance, due to alternating bands of magnesium ammonium phosphate and calcium phosphate 5.
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 5.
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.
inanimate object inspired
- champagne glass pelvis
- Coca-cola bottle sign
- coin lesion
- corduroy sign
- dinner fork deformity
- fishhook ureters
- goblet sign
- leather bottle stomach
- Lincoln log vertebra
- napkin ring sign
- polka-dot sign
- rugger-jersey spine
- scalpel sign
- string of pearls sign
- tam o' shanter sign
- water bottle sign
- white pyramid sign
- wine bottle sign
vegetable and plant inspired
- aubergine sign
- celery stalk metaphysis
- celery stalk anterior cruciate ligament
- chocolate cyst
- coconut left atrium
- coffee bean sign (sigmoid colon)
- cottage loaf sign
- cotton wool appearance (bone)
- doughnut sign
- drooping lily sign
- ivy sign
- linguine sign
- macaroni sign
- miliary opacities
- omental cake
- onion skin periosteal reaction
- pancake brain
- pancake vertebra
- popcorn calcification
- rice bodies
- rice grain calcification
- salt and pepper skull
- tree in bud
- waterlily sign
- fruit inspired
animal and animal produce inspired
- fish and seafood
- poultry and fowl
- domesticated and wild animals
- insects and bugs
- mythical creatures
- food inspired
- weapon and munition inspired signs
- 1. Dyer RB, Chen MY, Zagoria RJ. Classic signs in uroradiology. Radiographics. 2004;24 Suppl 1 (suppl 1): S247-80. Radiographics (full text) - doi:10.1148/rg.24si045509 - Pubmed citation
- 2. Dyer RB, Chen MY, Zagoria RJ. Abnormal calcifications in the urinary tract. Radiographics. 1998;18 (6): 1405-24. doi:10.1148/radiographics.18.6.9821191 - Pubmed citation
- 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. Fishman MC, Hoffman AR. Medicine. Lippincott Williams & Wilkins. (2004) ISBN:0781725437. Read it at Google Books - Find it at Amazon
- 5. 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
- 6. 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