Editing Kidney stone disease (section)

=== Composition ===

{| class="wikitable"
|- style="line-height:133%"
! Kidney<br>stone<br>type
! Relative<br>incidence<br>(adults)<ref name=Frassetto2011>{{cite journal | author= Frassetto L, Kohlstadt I | title= Treatment and prevention of kidney stones: an update. | journal= Am Fam Physician | year= 2011 | volume= 84 | issue= 11 | pages= 1234–42 | pmid= 22150656 | doi=  | pmc=  | url= https://pubmed.ncbi.nlm.nih.gov/22150656 | archive-date= 22 September 2023 | access-date= 28 August 2023 | archive-url= https://web.archive.org/web/20230922163226/https://pubmed.ncbi.nlm.nih.gov/22150656/ | url-status= live }}<br>Including cystine stone incidence of 1%</ref>
! Circumstances
! Color and<br>microscopy<br>appearance
! Radio-density
! Details
|-
| [[Calcium oxalate|Calcium<br>oxalate]]
| 60%
| when urine is acidic (decreased pH)<ref>{{cite book| vauthors = Becker KL |title=Principles and practice of endocrinology and metabolism|date=2001|publisher=Lippincott, Williams & Wilkins|location=Philadelphia, Pa. [u.a.]|isbn=978-0-7817-1750-2|page=684|edition=3|url=https://books.google.com/books?id=FVfzRvaucq8C&pg=PA684|url-status=live|archive-url=https://web.archive.org/web/20170908221053/https://books.google.com/books?id=FVfzRvaucq8C&pg=PA684|archive-date=8 September 2017|df=dmy-all}}</ref>
| Black/dark brown [[File:Calcium oxalate crystal.jpg|center|70 px]]
| Radio-opaque
| Some of the oxalate in urine is produced by the body. Calcium and oxalate in the diet play a part but are not the only factors that affect the formation of calcium oxalate stones. Dietary oxalate is found in many vegetables, fruits, and nuts. Calcium from bone may also play a role in kidney stone formation.
|-
| [[Calcium phosphate|Calcium<br>phosphate]]
| 10–20%
| when urine is alkaline (high pH)
| Dirty white [[File:Calcium phosphate crystal.jpg|center|70 px]]
| Radio-opaque
| Tends to grow in alkaline urine especially when [[Proteus (bacterium)|''Proteus'' bacteria]] are present. The most common type among pregnant women.<ref name=Frassetto2011/>
|-
| [[Uric acid]]
| 10–20%
| when urine is persistently acidic
| Yellow/reddish brown [[File:Uric acid crystal.jpg|center|70 px]]
| Radio-lucent
| Diets rich in animal proteins and purines: substances found naturally in all food but especially in organ meats, fish, and shellfish.
|-
| [[Struvite]]
| {{0}}3%
| infections in the kidney and when urine is alkaline (high pH)
| Dirty white [[File:Struvite crystals.jpg|center|70 px]]
| Radio-opaque
| Prevention of struvite stones depends on staying infection-free. Diet has not been shown to affect struvite stone formation.
|-
| [[Cystine]]
| {{0}}1–2%<ref>{{cite web|title=Cystine stones|url=http://www.uptodate.com/contents/cystine-stones|work=[[UpToDate]]|access-date=20 February 2014|url-status=live|archive-url=https://web.archive.org/web/20140226110022/http://www.uptodate.com/contents/cystine-stones|archive-date=26 February 2014|df=dmy-all}}</ref>
| rare genetic disorder
| Pink/yellow [[File:Cystine crystals.jpg|center|70 px]]
| Radio-opaque
| Cystine, an amino acid (a dimer of cysteine, of the building blocks of protein), leaks through the kidneys and into the urine to form crystals.
|-
| [[Xanthine]]<ref>Bailey & Love's/25th/1296</ref>
|
| extremely rare
| Brick red
| Radio-lucent
|
|}

[[File:Surface of a kidney stone.jpg|thumb|Scanning electron micrograph of the surface of a kidney stone showing tetragonal crystals of [[weddellite]] (calcium oxalate dihydrate) emerging from the amorphous central part of the stone (the horizontal length of the picture represents 0.5 mm of the figured original)]]
[[File:Kidney stones, Uric acid.JPG|thumb|Multiple kidney stones composed of [[uric acid]] and a small amount of [[calcium oxalate]]]]
[[File:Lenticular kidney stone.jpg|thumb|A lenticular kidney stone, excreted in the urine]]

==== Calcium-containing stones ====
By far, the most common type of kidney stones worldwide contains calcium. For example, calcium-containing stones represent about 80% of all cases in the United States; these typically contain [[calcium oxalate]] either alone or in combination with [[calcium phosphate]] in the form of [[apatite]] or [[brushite]].<ref name=Reilly2005Ch13 /><ref name=Coe2005 /> Factors that promote the [[Precipitation (chemistry)|precipitation]] of oxalate crystals in the urine, such as [[primary hyperoxaluria]], are associated with the development of calcium oxalate stones.<ref name=Hoppe2003 /> The formation of calcium phosphate stones is associated with conditions such as [[hyperparathyroidism]]<ref name=NIDDK2006 /> and [[renal tubular acidosis]].<ref name=NIDDK20084696 />

[[Oxaluria]] is increased in patients with certain gastrointestinal disorders including inflammatory bowel disease such as [[Crohn's disease]] or in patients who have undergone resection of the small bowel or small-bowel bypass procedures. Oxaluria is also increased in patients who consume increased amounts of oxalate (found in vegetables and nuts). Primary hyperoxaluria is a rare autosomal recessive condition that usually presents in childhood.<ref name="De Mais">{{cite book | vauthors = De Mais D |title= ASCP Quick Compendium of Clinical Pathology |edition= 2nd |publisher= ASCP Press |location= Chicago |year= 2009 }}</ref>

Calcium oxalate crystals can come in two varieties. Calcium oxalate monohydrate can appear as 'dumbbells' or as long ovals that resemble the individual posts in a picket fence. Calcium oxalate dihydrate have a tetragonal "envelope" appearance.<ref name="De Mais" />

==== Struvite stones ====
About 10–15% of urinary calculi are composed of [[struvite]] (hexa-hydrated [[ammonium magnesium phosphate]], NH<sub>4</sub>MgPO<sub>4</sub>·6H<sub>2</sub>O).<ref name=Heptinstall2007 /> Struvite stones (also known as "infection stones," [[urease]], or triple-phosphate stones) form most often in the presence of infection by urea-splitting [[bacteria]]. Using the enzyme urease, these organisms [[Metabolism|metabolize]] [[urea]] into [[ammonia]] and [[carbon dioxide]]. This [[alkalinity|alkalinizes]] the urine, resulting in favorable conditions for the formation of struvite stones. ''[[Proteus mirabilis]]'', ''[[Proteus vulgaris]]'', and ''[[Morganella morganii]]'' are the most common organisms isolated; less common organisms include ''[[Ureaplasma urealyticum]]'' and some species of ''[[Providencia (bacterium)|Providencia]]'', ''[[Klebsiella]]'', ''[[Serratia]]'', and ''[[Enterobacter]]''. These infection stones are commonly observed in people who have factors that predispose them to [[urinary tract infection]]s, such as those with [[spinal cord injury]] and other forms of [[neurogenic bladder]], [[ileal conduit urinary diversion]], [[vesicoureteral reflux]], and [[Obstructive uropathy|obstructive uropathies]]. They are also commonly seen in people with underlying metabolic disorders, such as [[idiopathic]] [[hypercalciuria]], [[hyperparathyroidism]], and [[gout]]. Infection stones can grow rapidly, forming large calyceal staghorn ([[antler]]-shaped) calculi requiring invasive surgery such as percutaneous nephrolithotomy for definitive treatment.<ref name=Heptinstall2007 />

Struvite stones (triple-phosphate/magnesium ammonium phosphate) have a 'coffin lid' morphology by microscopy.<ref name="De Mais" />

==== Uric acid stones ====
About 5–10% of all stones are formed from [[uric acid]].<ref name=Moe2006 /> People with certain metabolic abnormalities, including [[obesity]],<ref name=Johri2010 /> may produce uric acid stones. They also may form in association with conditions that cause [[hyperuricosuria]] (an excessive amount of uric acid in the urine) with or without [[hyperuricemia]] (an excessive amount of uric acid in the [[blood serum|serum]]). They may also form in association with disorders of acid/base metabolism where the urine is excessively acidic (low [[pH]]), resulting in precipitation of uric acid crystals. A diagnosis of uric acid [[urolithiasis]] is supported by the presence of a [[Radiodensity|radiolucent]] stone in the face of persistent urine acidity, in conjunction with the finding of uric acid crystals in fresh urine samples.<ref name=Halabe1994 />

As noted above (section on calcium oxalate stones), people with [[inflammatory bowel disease]] ([[Crohn's disease]], [[ulcerative colitis]]) tend to have [[hyperoxaluria]] and form oxalate stones. They also have a tendency to form urate stones. Urate stones are especially common after [[Colectomy|colon resection]].

Uric acid stones appear as [[Pleomorphism (cytology)|pleomorphic]] crystals, usually diamond-shaped.  They may also look like squares or rods which are polarizable.<ref name="De Mais" />

==== Other types ====
[[File:Cystine Crystals in Canine Urine Sediment.jpg|alt=Translucent, hexagon-shaped crystals seen through a microscope|thumb|Microscopic [[cystine]] crystals have a distinctive hexagonal shape and are present in the urine of people with kidney stones composed of cystine]]
People with certain rare [[Inborn error of metabolism|inborn errors of metabolism]] have a propensity to accumulate crystal-forming substances in their urine. For example, those with [[cystinuria]], [[cystinosis]], and [[Fanconi syndrome]] may form stones composed of [[cystine]]. Cystine stone formation can be treated with urine alkalinization and dietary protein restriction.  People affected by [[xanthinuria]] often produce stones composed of [[xanthine]]. People affected by [[adenine phosphoribosyltransferase deficiency]] may produce [[2,8-dihydroxyadenine]] stones,<ref name=Kamatani1996 /> [[Alkaptonuria|alkaptonurics]] produce [[homogentisic acid]] stones, and [[Iminoglycinuria|iminoglycinurics]] produce stones of [[glycine]], [[proline]], and [[hydroxyproline]].<ref name=Rosenberg1968 /><ref name=Coskun1993 /> Urolithiasis has also been noted to occur in the setting of therapeutic drug use, with crystals of drug forming within the renal tract in some people currently being treated with agents such as [[indinavir]],<ref name=Crixivan2010 /> [[sulfadiazine]],<ref name=Schlossberg2011 /> and [[triamterene]].<ref name=Carr1990 />