Struvite Stones: Causes, Treatment & Prevention (Infection Stones Guide)

What are struvite stones? (Infection stones explained)

Struvite stones, also known as infection stones or magnesium ammonium phosphate stones, are a specific type of kidney stone that forms as a result of chronic urinary tract infections (UTIs) caused by certain bacteria. Unlike calcium stones (which form from metabolic abnormalities), struvite stones are a direct consequence of infection. They are more common in women than men (3:1 ratio), and they tend to grow rapidly – often forming large, branched stones called staghorn calculi that fill the entire renal collecting system.

Struvite stones account for about 5‑10% of all kidney stones. However, they are disproportionately dangerous because they can cause recurrent infections, kidney damage, and sepsis if not completely removed.

Causes: UTI bacteria (Proteus, Klebsiella, Pseudomonas)

Struvite stones form when specific bacteria that produce the enzyme urease infect the urinary tract. Urease splits urea into ammonia and carbon dioxide, making the urine highly alkaline (high pH). In alkaline urine, magnesium, ammonium, and phosphate crystallise to form struvite stones.

Common urease‑producing bacteria:

• Proteus mirabilis – the most common cause
• Klebsiella pneumoniae
• Pseudomonas aeruginosa
• Staphylococcus saprophyticus
• Providencia species

Risk factors for struvite stones include:

• Recurrent UTIs, especially in women
• Urinary stasis (conditions that prevent complete bladder emptying – neurogenic bladder, spinal cord injury, benign prostatic hyperplasia)
• Indwelling urinary catheters
• Chronic kidney stones (any type can become infected)
• Anatomical abnormalities (horseshoe kidney, ureteral duplication)

Why struvite stones are dangerous – rapid growth and staghorn formation

Struvite stones are among the most dangerous kidney stones because of their growth pattern and complications:

• Rapid growth: They can grow from small to staghorn size (filling the entire kidney) in 4‑6 weeks.
• Staghorn calculi: These branched stones fill the renal pelvis and extend into the calyces. They cause chronic obstruction, recurrent infections, and progressive kidney damage.
• Permanent kidney damage: Even without complete obstruction, the infection and pressure from the stone can destroy nephrons.
• Sepsis risk: Manipulation of an infected stone (even with antibiotics) can release bacteria into the bloodstream, causing urosepsis – a life‑threatening condition.
• High recurrence rate: If any stone fragments are left behind, they will serve as a nidus for new stone growth and persistent infection.

At Vivekananda Hospital, we treat struvite stones as urological emergencies – they require complete surgical removal as soon as possible after controlling the infection.

Symptoms of struvite stones

Symptoms are often a combination of recurrent UTIs and stone obstruction:

• Recurrent UTIs: Frequent episodes of burning urination, urgency, frequency, foul‑smelling urine, and fever.
• Flank pain: Dull ache or intermittent colic, depending on obstruction.
• Hematuria (blood in urine): Common due to irritation.
• Fever and chills: Sign of active infection – may be persistent or recurrent.
• Chronic fatigue and malaise: From long‑standing infection.
• Asymptomatic (early stage): Small struvite stones may be found incidentally on imaging.

Unlike calcium stones, which cause severe colic, struvite stones often present with vague symptoms until they are large. This leads to delayed diagnosis.

Treatment: Complete surgical removal (PCNL is gold standard)

The treatment of struvite stones has two phases: preoperative antibiotics and complete surgical removal.

Preoperative antibiotics

Before surgery, patients receive targeted antibiotics based on urine culture and sensitivity. This reduces bacterial load and lowers the risk of sepsis during surgery. Common antibiotics include ciprofloxacin, levofloxacin, or third‑generation cephalosporins. Duration is typically 7‑14 days, but complete stone removal is the only cure.

Surgical removal – PCNL is the gold standard

For most struvite stones (which are often large or staghorn), PCNL (percutaneous nephrolithotomy) is the procedure of choice. A 1cm incision is made in the back, and a nephroscope is passed directly into the kidney to fragment and suction out the stone. Success rate for complete stone removal is 85‑95% in one session. For very large staghorn stones, a second PCNL (staged procedure) may be needed.

Alternatives:

• RIRS (flexible ureteroscopy): For small struvite stones (<15mm) that are not staghorn. Less effective for large stones.
• ESWL: Not recommended for struvite stones. Fragments are often not cleared completely, leading to rapid recurrence.
• Open surgery: Rarely used today, reserved for extremely complex staghorn stones or abnormal anatomy.

Post‑surgery care

After PCNL, patients continue antibiotics for 1‑2 weeks. A follow‑up CT scan or KUB X‑ray is performed to confirm no residual fragments. If fragments remain, a second PCNL or RIRS is scheduled.

Prevention: Eradicating the infection and follow‑up

Even after complete stone removal, patients remain at risk for recurrence if the underlying infection is not controlled. Prevention strategies include:

• Complete stone clearance: This is the most important factor. Any residual stone will harbour bacteria.
• Urine culture and sensitivity: Post‑operatively, repeat urine culture to ensure infection is cleared.
• Long‑term antibiotic prophylaxis: Some patients (especially those with neurogenic bladder or recurrent UTIs) may need low‑dose daily antibiotics (e.g., nitrofurantoin, trimethoprim‑sulfamethoxazole) for 3‑6 months.
• Acidification of urine: Struvite stones form in alkaline urine. Some urologists prescribe ammonium chloride or methionine to acidify urine, but this is controversial and not always effective.
• Treat underlying conditions: Correct any anatomical abnormalities (e.g., bladder diverticula, ureteral strictures) that cause urinary stasis.
• Hydration: 2.5‑3 litres of water daily to dilute urine and reduce infection risk.
• Follow‑up imaging: Annual ultrasound or CT scan for 2‑3 years to detect recurrence early.

Interactive FAQ – Struvite stones

Disclaimer: Struvite stones are a serious condition requiring prompt urological care. If you have recurrent UTIs with flank pain or fever, visit Vivekananda Hospital for evaluation. Do not delay – these stones can damage your kidneys rapidly.