Because we synthesized the two most common kidney stones, calcium oxalate and calcium phosphate, we will focus on those two in the discussion of formation, treatment, and prevention. Calcium stones like calcium oxalate and calcium phosphate stones form when urine is “supersaturated with the constituent ions that comprise the stone” (Figge). This means, when urine is supersaturated with calcium and oxalate ion that type of stone is more likely to form. This supersaturation results from the ionic activity of Ca^(2+) and oxalate and Ca^(2+) and PO_4^(2-) is greater than the solubility of product for calcium oxalate and alcium phosphate (Figge).
There can be various reasons for this supersaturation of ions. Concentrations of unbound calcium, oxalate and phosphate ions, urine pH, and other chemical presences can lead to calcium stones (Figge). Though kidney stone formation can be quite complicated, the formation of them is largely a solubility equilibrium problem where Le Chatelier’s Principle comes into play. Consider calcium oxalate stones that form from oxalic acid reacting with calcium ions. CaC_2 [O_4] _((s) ) =Ca_((aq))^(2+)+C_2_[O_4^(2-)I (aq) ) The solubility product of the calcium oxalate salt is K_sp=[Ca^(2+)] [ox^(2-)].
This illustrates that the solubility product of calcium oxalate is solely dependent on the concentration of calcium ions and oxalic acid. If either component’s concentration is increased, the reaction shifts left leading to calcium oxalate formation. If we decrease the amount of oxalic acid or calcium ions, Le Chatelier’s Principle tells us that the reaction will shift to the right to create more Ca^(2+) and oxalic acid to maintain equilibrium and decrease the stress on the system (Uthayakumar). This same idea of shifting in equilibrium applies to calcium phosphate stones. There are ways to prevent calcium stones from forming.
There are several inhibitors of calcium crystallization including citrate, uropontin, pyrophosphate, and nephrocalcin. Citrate “forms soluble complexes with calcium, which then lowers the ionic activity of free calcium ions in the urine and decreases stone formation” (Figge). Dietary adaptations can also help prevent calcium stones from forming. By drinking more fluids, the ions in question become more diluted in urine. Interestingly, decreasing calcium in the diet does not help to prevent calcium stones. In fact, calcium in foods and beverages often bind with oxalate in the intestines and inhibits absorption (Figge).
Thus, a low calcium diet can cause the intestinal tract to absorb more calcium and the kidneys to expel too much oxalate (Figge). As mentioned above, we can use solubility equilibrium concepts to understand prevention of stones. At equilibrium, the rate of dissociation of the Ca^(2+) and oxalic acid is equal to the rate of precipitation of CaC_2 O_4 for calcium oxalate stone reaction. Thus, by decreasing intake of the dissociated ions, we shift the equilibrium so that the precipitate breaks down to form more ions. Numerous studies have shown that increasing fluid intake and increasing urine output to about 2.
L a day can reduce kidney stone recurrence up to 50% (Barnela). For calcium oxalate and uric acid stones, it is important to increase fluids like water, but for the latter stone type, one should moderate consumption of coffee and tea since both contain oxalate (Barnela). One can also reduce oxalate in their diet by omitting food rich in oxalate. These include: cucumbers, peppers, beets, spinach, chocolate, and sweet potatoes (Barnela). An oral potassium citrate has been shows to help prevent stone reformation, but those taking this citrate should ensure that the pH remains less than 7 so that calcium phosphate stones do not orm (Barnela).
Lemon juice has also been shown to increase citrate in urine to prevent stones from reoccurring (Barnela). This supports our findings that lemon juice helps dissolve calcium stones. This is a common natural remedy for prevention and home treatment. It has also been studied and shown that tomato juice had a higher citrate and lower oxalate amount compared to orange, lemon and mandarin juice (Barnela). This would be something we could do further experimentation with. We could compare the dissolving of stones with various juices and compare.
Lastly, those prone to kidney stones should adopt low sodium diet because high salt diets not only decrease urine levels, but also lead to calcium oxalate formation. The treatment of kidney stones is quite different from prevention. In our tests, we found that hydrochloric acid, EDTA, and lemon juice all dissolved the calcium stones. Though dissolution of kidney stones was found to be easy in lab, we cannot directly add these chemicals to the stones in the human body to dissolve them. There have been several attempts at dissolving stones through dissolution methods.
In 1939, one of the first attempts was to dissolve calcium phosphate stones sing isotonic citrate solutions having a pH of 4 (Gonzalez). This did not yield good results due to patient bleeding from the acidity levels of the solution. Another attempt at dissolution of kidney stones was performed in 1957 using Renacidin, a solution containing malonic and gluconic acids (Gonzalez). Though Renacidin did successfully dissolve calcium phosphate and struvic stones, there were many safety issues of Renacidin irrigation that resulted in some patient deaths and other controversies in later years (Gonzalez).
In our dissolution of calcium oxalate and calcium phosphate stones, we found EDTA elped prevent the formation of the stones. EDTA is a weak acid that acts as a ligand or chelating agent to metal ions like Ca^(2+) and Mg^(2+). EDTA binds with the metal ions forcing them to remain in solution. Though direct dissolution of stones is not done in the real world, there is a controversial treatment method called EDTA chelation therapy. This is where an EDTA solution is injected directly into the bloodstream to help bind with metal ions like calcium, iron and lead to be removed (“Chelation Therapy”).
Though EDTA chelation therapy has been effective in some cases, it can remove good calcium from uscles and bones and can cause kidney damage and other serious consequences (“Chelation Therapy”). Shock wave therapy is often used to break up a large kidney stone so that it can be passed through the urine (“Kidney Stones Causes”). Surgery can also be performed if necessary or removal using a ureteroscope (“Kidney Stones Causes”). Strong acids like hydrochloric acid dissociate completely in water and have a high K_a.
A large equilibrium constant means that the reaction will be driven toward the products or in other words, the acid will contribute more H^+. Because strong acids donate more protons, when added to a kidney stone, the stone ill become a positive molecule which bonds with the negative part of the water molecule to dissolve in solution. Consider the equilibrium reaction of calcium phosphate dissociating to its respective ions and the addition of a strong acid like HCI.
Ca_3 [(PO_4)_21 _(s) )=3Ca_((aq))^(2+)+2P [O_4^(3-)] _((aq) ) Addition of strong acid: 2P [0_4^(3-)] _((aq) )+2H_((aq))^nt=2HP [O_4^(2-)1 _((aq)) 2HP [0_4^(2-)] _((aq) )+2H_((aq))^+=2H_2 P [O_4^(1-)] _((aq)) 2H_2 P [O_4^(1-)) _((aq) )+2H_aq^+=2H_3 P [0_41 _((aq)) The reaction of the protons and the phosphate molecules in the last three equations consume the phosphate produced in the first eaction (“Descriptive Chemistry”). By Le Chatelier’s Principle, this will shift equilibrium toward the products, and consequently, more Ca_3 (PO_4)_2 dissolves.
This supports our findings when we dissolved the kidney stones in hydrochloric acid. See Table 3. 0. We found that it took less drops of HCl to dissolve each precipitate than it did using EDTA and lemon juice. The higher the concentration (3. 0 M HCI), the less amount was needed. We also found in our prevention of precipitation, that HCl and EDTA prevented the formation of the calcium phosphate stone and HCI prevented the formation of only alcium oxalate. As discussed in our errors, theoretically, if enough EDTA was present, calcium oxalate should not have formed.
Hydrochloric acid and EDTA are reagents that interact with the anion and cation of the synthesized stones. That is, HCI reacted with the phosphate anion PO_4^(3-)in reaction 1 and C_2 0_4^(2-) in reaction 2. The EDTA interacted with the calcium cation in both reactions to bind to the metal cation and prevent precipitation. Ligands or chelates “which are formed by EDTA with metal cations are extraordinarily strong, due to the fact that they have many complex-forming functional ends and hese complexes are formed by O and N atoms and also the formed rings are 5 membered” (Gulensoy).
Thus, if there is enough EDTA present in the solution with Ca^(2+)cations, it becomes “impossible to precipitate [this ion] in the form of CaCO_3, CasO_4, Ca_3 (PO_4 )_2, CaC_2 O_4 ” (Gulensoy). We found in our tests to prevent formation of these stones using EDTA, that there was no calcium phosphate formation, but we did have some cloudiness when performing our reaction of calcium nitrate and sodium oxalate. According to our findings, if we use enough EDTA, we should expect no formation of calcium oxalate.
