Milk of Calcium Kidney: Initial Management
Percutaneous nephrolithotomy (PCNL) with suction is the definitive treatment for milk of calcium kidney stones, as these soft, viscous calcium suspensions cannot be effectively treated with shock wave lithotripsy and require direct extraction without fragmentation. 1
Diagnostic Confirmation
Before proceeding with treatment, confirm the diagnosis using the following imaging characteristics:
- Obtain non-contrast CT scan to identify pathognomonic features: low Hounsfield units (114-612 HU), gravity-dependent layering in dilated calyces (posterior aspect when supine), and either a fluid level or semilunar (half-moon) pattern 1, 2
- Perform imaging in both supine and prone positions to demonstrate the characteristic horizontal layering that shifts with gravity, confirming the colloidal suspension rather than solid calculi 2, 3
- Ultrasound findings show a sonolucent "leveled" image with posterior acoustic shadow inside hydro-calyceal dilation or calyceal diverticulum, with the level persisting in both positions 4
Critical Pitfall to Avoid
Never attempt shock wave lithotripsy (SWL) for milk of calcium stones - the viscous colloidal suspension of calcium salts will not fragment with SWL, making this modality completely ineffective and resulting in unnecessary procedures 1, 4, 2
Definitive Surgical Management
- PCNL with suction is the treatment of choice for renal milk of calcium stones, allowing retrieval of the soft material without need for disintegration 1
- All seven cases in the largest reported series were successfully managed with PCNL and suction alone 1
- For ureteral milk of calcium, ureteric stent insertion may allow partial drainage, followed by ureteroscopy and LASER lithotripsy if needed 5
Preoperative Workup
- Obtain urine culture preoperatively in all patients, as infection is an important predisposing factor along with stasis and obstruction 1
- Send retrieved material for chemical analysis using infrared spectroscopy to confirm calcium carbonate, calcium phosphate, or calcium oxalate composition 1, 2
Clinical Context
- Milk of calcium accounts for approximately 0.6% of all urinary lithiasis diagnosed by ultrasound 4
- Patients typically present with urinary tract infections, renal pain, or hematuria 4
- Plain radiographs are often misleading: stones appear faintly radio-opaque in only 29% of cases and radiolucent in 71% 1, 2
- Intravenous pyelography is unreliable, showing no abnormality or misleading findings in the majority of cases 4
Special Population Considerations
Patients with spinal cord injury and prolonged immobilization are at particular risk for developing bilateral renal milk of calcium due to hypercalciuria and urinary stasis 5, 2