Staghorn

Staghorn Calculi

Staghorn calculi, also known as staghorn kidney stones, are large, branched stones that occupy a large portion of the renal pelvis and extend into at least one of the calyces. These stones are composed of various materials, with struvite (magnesium ammonium phosphate) and calcium phosphate being the most common components. Staghorn calculi are associated with urinary tract infections caused by urease-producing bacteria, such as Proteus mirabilis, Klebsiella, Pseudomonas, and Enterobacter species. The presence of these stones can lead to significant morbidity, including recurrent urinary tract infections, obstructive uropathy, and renal failure if not properly managed.

Etiology and Pathogenesis

The formation of staghorn calculi is closely linked to urinary tract infections (UTIs) with urease-producing bacteria. Urease splits urea into ammonia and carbon dioxide, increasing the pH of urine and leading to the precipitation of magnesium ammonium phosphate and calcium phosphate. Over time, these precipitates form the characteristic branched stones that can fill the renal pelvis and extend into the calyces.

Clinical Presentation

Patients with staghorn calculi may present with a variety of symptoms, including flank pain, hematuria (blood in the urine), recurrent UTIs, and sometimes fever if an infection is present. However, some patients may be asymptomatic, with the stones discovered incidentally during imaging studies for unrelated reasons.

Diagnosis

The diagnosis of staghorn calculi involves a combination of clinical history, physical examination, and imaging studies. Non-contrast computed tomography (CT) scan is the gold standard for imaging, as it can clearly delineate the size and shape of the stones, as well as their relationship to the renal anatomy. Ultrasound and intravenous pyelography (IVP) are other diagnostic tools that may be used.

Treatment

The treatment of staghorn calculi typically involves a combination of surgical intervention and antibiotic therapy. The primary goal is to completely remove the stone and eradicate any associated infections. Percutaneous nephrolithotomy (PCNL) is the preferred surgical method for most staghorn calculi, as it allows for the direct removal of the stone through a small incision in the back. In some cases, extracorporeal shock wave lithotripsy (ESWL) may be used, but its effectiveness is limited for large or complex stones. Antibiotic therapy is tailored based on urine culture and sensitivity tests to ensure the eradication of the underlying bacterial infection.

Prevention

Preventive measures for staghorn calculi focus on the management of risk factors, such as chronic UTIs and urinary tract obstructions. Long-term antibiotic prophylaxis may be recommended for patients with recurrent UTIs. Additionally, maintaining adequate hydration and addressing any anatomical abnormalities of the urinary tract can help reduce the risk of stone formation.

Prognosis

The prognosis for patients with staghorn calculi is generally good with appropriate treatment. However, the risk of recurrence is significant, and long-term follow-up is necessary to monitor for new stone formation and manage any recurrent infections.