Stone is a plain-language clinical term for a hard body concretion, medically called a calculus, that forms when dissolved minerals, salts, proteins, bile components, or cellular debris precipitate and aggregate inside an organ, duct, gland, or hollow viscus. It is distinguished from a foreign body, which enters from outside the body, and from a tumor, which is tissue growth rather than crystallized or inspissated material. The underlying mechanism is usually supersaturation, nucleation, crystal growth, stasis, infection, altered pH, impaired drainage, or abnormal concentration of secretions; examples include calcium oxalate crystallization in urine, cholesterol precipitation in bile, and calcium phosphate deposition in salivary ducts. Stones are generally pathological, although they may be asymptomatic incidental findings; they become clinically significant when they cause obstruction, pain, infection, bleeding, pancreatitis, cholangitis, or organ dysfunction. Common coding-relevant forms include kidney stone or nephrolithiasis (N20.0), ureteral stone or ureterolithiasis (N20.1), bladder stone (N21.0), gallbladder stone or cholelithiasis without cholecystitis or obstruction (K80.20), common bile duct stone or choledocholithiasis without cholangitis/cholecystitis or obstruction (K80.50), salivary stone or sialolithiasis (K11.5), and tonsil stone or tonsillolith coded as other chronic disease of tonsils/adenoids (J35.8). Stone is commonly confused with calcification, but calcification is mineral deposition within tissue, whereas a stone is a discrete concretion within a lumen, duct, cavity, or organ system.
Noun-forming suffix — “pathologic condition or process,” especially a condition characterized by formation or presence of something
The word entered English before the 12th century as stone (noun), inherited from Old English stān, meaning “stone, rock, or hard mineral substance.” Its medical use developed by analogy because urinary, biliary, salivary, and other concretions resemble small stones or pebbles. The Latin root calculus (“small pebble”) connects stone to the calcul- root family: calculus (small pebble → body stone or mathematical reckoning), calculous (pertaining to stones), and calciuria (calcium in urine, a risk factor for urinary stones). The Greek root lith- is highly productive in medical terminology and appears in lithiasis, nephrolithiasis, urolithiasis, cholelithiasis, choledocholithiasis, and lithotripsy.
🔀 ALIASES / ALTERNATE TERMS
Calculus(formal medical term for a stone; plural calculi; used across urology, gastroenterology, otolaryngology, and radiology)
Calculi(plural of calculus; often used in imaging reports, e.g., “nonobstructing renal calculi”)
Calculous(adjective form; appears in phrases such as “calculous cholecystitis,” “calculous obstruction,” and “calculous pyelonephritis”)
Lithiasis(condition of forming or having stones; commonly combined with an anatomic root, such as nephrolithiasis or cholelithiasis)
Nephrolithiasis(kidney stone disease; coded commonly as N20.0 when documented as calculus of kidney)
Ureterolithiasis(ureteral stone; coded commonly as N20.1)
Urolithiasis(general term for stones in the urinary tract; may require site-specific coding such as N20.0, N20.1, N21.0, or N20.9)
Cystolithiasis(bladder stone disease; coded commonly as N21.0)
Cholelithiasis(gallstone disease; uncomplicated gallbladder stone without cholecystitis or obstruction is coded as K80.20)
Choledocholithiasis(common bile duct stone; uncomplicated bile duct stone without cholangitis/cholecystitis or obstruction is coded as K80.50)
Sialolithiasis(salivary gland or salivary duct stone; coded as K11.5)
Tonsillolith(tonsil stone; generally coded under other chronic diseases of tonsils/adenoids as J35.8)
Staghorn calculus(large branching renal collecting-system stone, often infection-related; coded by site, commonly N20.0, with additional infection or obstruction codes when documented)
Obstructing stone(stone causing blockage of urine, bile, saliva, or other drainage; urinary obstruction with hydronephrosis may be coded as N13.2 when documented)
Nonobstructing stone(stone present without documented blockage; commonly coded by anatomic site, such as N20.0 for nonobstructing renal calculus)
🔗 RELATED TERMS
Calculus — the formal medical term for a stone; used when a hard concretion forms inside a duct, cavity, gland, or organ.
Lithiasis — the condition of having or forming stones; shares the lith- root and is usually paired with an organ-specific prefix.
Nephrolithiasis — kidney stone disease; usually coded as calculus of kidney (N20.0) when the stone is in the kidney.
Ureterolithiasis — stone in the ureter; coded as calculus of ureter (N20.1) and clinically important because it commonly causes renal colic and hydronephrosis.
Renal colic — acute flank pain caused by ureteral spasm or obstruction from a stone; coded as unspecified renal colic (N23) when no more specific stone or obstruction diagnosis is documented.
Hydronephrosis — dilation of the renal collecting system due to impaired urine drainage; stone-related hydronephrosis is coded specifically as hydronephrosis with renal and ureteral calculous obstruction (N13.2).
Cholelithiasis — gallstone disease; may be uncomplicated (K80.20) or complicated by obstruction, cholecystitis, cholangitis, or pancreatitis.
Choledocholithiasis — stone in the common bile duct; uncomplicated bile duct calculus without obstruction is coded as K80.50, while obstruction changes code selection.
Cholangitis — infection/inflammation of the bile ducts, often triggered by an obstructing common bile duct stone; when due to bile duct calculus, combination codes in the K80 series are used.
Cholecystitis — inflammation of the gallbladder; when caused by gallstones, calculous cholecystitis is coded with K80 combination codes such as K80.00 or K80.10 depending on acuity and obstruction.
Sialolithiasis — salivary stone disease; coded as K11.5 and often presents with painful swelling during meals.
Tonsillolith — calcified or inspissated debris in tonsillar crypts; generally coded as J35.8 when clinically significant.
Calcification — mineral deposition within tissue; differs from a stone because it is embedded in tissue rather than a free or obstructing concretion in a lumen or duct.
Crystal — microscopic precipitated mineral or chemical structure; crystals may be precursors to stones but are not the same as macroscopic calculi.
Lithotripsy — procedure that fragments stones, commonly used for renal, ureteral, bladder, biliary, or pancreatic duct calculi depending on site and approach.
Cystoscopy — endoscopic evaluation of the bladder and urethra; commonly used to diagnose or treat bladder stones and distal ureteral stones.
Ureteroscopy — endoscopic approach to ureteral or renal collecting-system stones, often with laser lithotripsy, basket extraction, and/or ureteral stent placement.
ERCP — endoscopic retrograde cholangiopancreatography; primary endoscopic procedure for common bile duct stone removal or biliary sphincterotomy.
Increased procedural services; may be supported for unusually complex stone burden, impacted stone, distorted anatomy, or prolonged operative work when documented
Unplanned return to operating/procedure room for related procedure during postoperative period
⚠️ Coding Note: For inpatient professional-fee coding, stone diagnoses should be coded to the most specific documented anatomic site and complication status: kidney versus ureter versus bladder for urinary stones, and gallbladder versus bile duct with or without obstruction, cholecystitis, cholangitis, or pancreatitis for biliary stones. Do not code a nonspecific stone diagnosis when the imaging, operative note, or discharge diagnosis identifies the exact site, such as renal calculus (N20.0), ureteral calculus (N20.1), bladder calculus (N21.0), or bile duct calculus with obstruction (K80.51). Sequence the acute complication first when coding guidelines require it, especially sepsis, acute cholangitis, acute cholecystitis, pyonephrosis, or biliary pancreatitis, and use combination K80 codes when gallstone disease includes cholecystitis, cholangitis, or obstruction. A common undercoding issue is missing stone-related obstruction: documentation triggers such as “obstructing ureteral stone,” “hydronephrosis due to calculus,” “infected obstructing stone,” “septic stone,” “CBD stone with obstruction,” or “impacted stone” should prompt review for codes such as [[N13.2]], K80.51, or the appropriate obstructed K80 combination code. For procedures, verify whether the operative note supports stone extraction, lithotripsy, stent placement, access, bilateral work, staged treatment, or return to the OR; modifiers such as -LT, -RT, -50, -22, -58, -78, -59, and -XS should be used only when payer policy and documentation support them.
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