Milk of calcium stones: radiological signs and management outcome

Abstract

Milk of calcium (MOC) is a rare type of stone that was first described in 1940 by Ludin and Howald who reported MOC in renal cysts. Milk of calcium is a viscous colloidal suspension of calcium salts. Stasis, obstruction and infection are important predisposing factors. Due to a layering effect, characteristic radiological signs especially in CT can help in diagnosis to avoid unsuccessful shock wave lithotripsy. This is the largest reported case series, in which radiological signs by CT scan to predict renal MOC stones, clinical picture and management outcome are described in detail. Cases with suspected renal milk of calcium stones were studied over 7 years (2008-2015). All cases were diagnosed preoperatively by non-contrast CT. Urine cultures were performed in all patients preoperatively. Intra-operative and postoperative findings were reported. Stones retrieved were sent for chemical analysis using an infrared method. Seven cases of milk of calcium renal stones were included in this study. These stones were faint radio-opaque in two cases and radiolucent in five cases. All cases were diagnosed preoperatively with non-contrast CT. Their Hounsfield units (HU) ranged from 114 to 612. All stones were located in a dependent position (gravitational effect) in the posterior aspect of dilated calyces. Five cases exhibited the typical fluid level and two cases demonstrated semilunar (half moon) pattern in the anterior surface of the stones. All cases underwent PCNL with suction and retrieval of soft stones without the need for disintegration. When stones demonstrate a low Hounsfield unit, are arranged in dependent positions within dilated calyces and exhibit fluid level or semilunar pattern on non-contrast CT, milk of calcium stones should be considered. PCNL is an effective modality for management of renal milk of calcium stones.

A Particular Form of “Urolithiasis” in a Toddler

“…However, in the available reports in which the expelled material was biochemically analyzed, authors described the presence of calcium carbonate in fine colloidal suspension, calcium phosphate, mixed carbonate and oxalate of calcium, carbonate and triple phosphate, calcium monohydrated with uric acid, and triple phosphate. 2,3,5,6 On the basis of our findings (Fig 5), we could hypothesize that a calculogenic matrix composed of urine mucoproteins, urinary solutes, and other secretions could promote precipitation of calcium, carbonate, phosphate (hydroxylapatite), oxalate, etc, determining the formation of milk of calcium.…”

“…To our knowledge (after we conducted research on Medline, PubMed, and relevant specialty journals [all from 1980 to September 2019] and used "milk of calcium," "soft calculi," "children," "urolithiasis," and "nephrolithiasis" as key words), our patient is the first toddler with isolated milk of calcium. The milk of calcium occurrence in calyceal diverticula and renal cysts has been well described, 2 whereas there are few reports associated with hydronephrosis. [3][4][5] Most of the cases reported in literature are unilateral, although rare bilateral cases are described.…”

“…3,6 The etiology is still unclear, but urine stagnation, obstruction, and infection could promote the formation of milk of calcium. 2 We excluded other causes of staghorn stones because of their appearance and consistency. Struvite stones (that occur after UTIs by urease-producing organisms) and cystine stones are harder, and they infrequently shatter and are expelled spontaneously.…”

“…Computed tomography (CT) can reveal a typical crescentshaped dense pattern because of gravitational effect on the colloid suspension of calcium salts. 2 However, general concern over patient radiation exposure has been raised. Low-dose CT, recently introduced in clinical practice, seems to maintain high diagnostic accuracy, sensitivity, and specificity despite significant radiation dose reduction compared to standard-dose CT. 9 It provides information about stone density and localization and urinary tract morphology, and it could be useful when surgical intervention is needed.…”

Diagnostic imaging features of calyceal diverticulum in a cat

“…On the other hand, other diseases do not involve direct communication with the collecting system [3]. The ultrasonographic findings only raise the suspicion of a lesion being a calyceal diverticulum if a diverticulum neck is found, if the cyst contains calculi or milk calcium-liquid, or semisolid calcified materials of the calyceal diverticulum in human medical terms [1][2][3]5,6,8,9]. A confirmed diagnosis of calyceal diver- The pre-contrast image (A) showed hyperattenuated pelvic calculi and calcified materials (arrow) at the ventral part of the right renal cortex.…”