Mechanism by which shock wave lithotripsy can promote formation of human calcium phosphate stones

Abstract

Human stone calcium phosphate (CaP) content correlates with higher urine CaP supersaturation (SS) and urine pH as well as with the number of shock wave lithotripsy (SWL) treatments. SWL does damage medullary collecting ducts and vasa recta, sites for urine pH regulation. We tested the hypothesis that SWL raises urine pH and therefore Cap SS, resulting in CaP nucleation and tubular plugging. The left kidney (T) of nine farm pigs was treated with SWL, and metabolic studies were performed using bilateral ureteral catheters for up to 70 days post-SWL. Some animals were given an NH4Cl load to sort out effects on urine pH of CD injury vs. increased HCO3 (-) delivery. Histopathological studies were performed at the end of the functional studies. The mean pH of the T kidneys exceeded that of the control (C) kidneys by 0.18 units in 14 experiments on 9 pigs. Increased HCO3 (-) delivery to CD is at least partly responsible for the pH difference because NH4Cl acidosis abolished it. The T kidneys excreted more Na, K, HCO3 (-), water, Ca, Mg, and Cl than C kidneys. A single nephron site that could produce losses of all of these is the thick ascending limb. Extensive injury was noted in medullary thick ascending limbs and collecting ducts. Linear bands showing nephron loss and fibrosis were found in the cortex and extended into the medulla. Thus SWL produces tubule cell injury easily observed histopathologically that leads to functional disturbances across a wide range of electrolyte metabolism including higher than control urine pH.

Intraluminal measurement of papillary duct urine pH, in vivo: a pilot study in the swine kidney

“…This is in keeping with our recent report that treating the entire pig kidney with an overdose of 8,000 SWs leads to alkaline bulk urine compared to the opposite nontreated kidney, i.e. an acidification defect in the SW-treated kidney [25]. We have also recently documented remodeling of nephron structures in SWL-treated regions of the kidney, which could potentially impact tubule acidification processes [25, 26].…”

“…an acidification defect in the SW-treated kidney [25]. We have also recently documented remodeling of nephron structures in SWL-treated regions of the kidney, which could potentially impact tubule acidification processes [25, 26]. With the limitations of this current pilot study (see below) it would be premature to draw firm conclusions linking a change in ductal urine pH to injury caused by SWL.…”

Metabolic diagnosis and medical prevention of calcium nephrolithiasis and its systemic manifestations: a consensus statement

“…Series suggest that idiopathic recurrent CaOx stone formers may switch to hydroxyapatite or brushite stones over time [35]. This is hypothesized to be the consequence of distal nephron damage induced by ESWL or previous obstructive episodes, or of preventive treatment with alkaline citrate [33–36]. In these hydroxyapatite or brushite patients, no investigation for systemic condition is warranted.…”

Discrepancy Between Stone and Tissue Mineral Type in Patients with Idiopathic Uric Acid Stones

“…Using intraoperative microelectrode pH measurements in humans, we have preliminary evidence that dilated BD may in fact contain high pH fluid in ileostomy patients. 15 Shockwave lithotripsy can cause significant transient high urine pH in experimental settings, 16 but only two of the seven patients with apatite plugs had that modality, so the cause of tubule cell injury in the other patients is unclear.…”