Calculus (medicine)

A calculus is a stone (a concretion of material, usually mineral salts) that forms in an organ or duct of the body. Stones cause a number of important medical conditions.

A number of important medical conditions are caused by stones:

• Nephrolithiasis (kidney stones)
  • Can cause hydronephrosis (swollen kidneys) and renal failure
  • Can predispose to pyelonephritis (kidney infections)
  • Can progress to bladder stones and bladder outlet obstruction
• Cholelithiasis (gallstones)
  • Can predispose to cholecystitis (gall bladder infections) and ascending cholangitis (biliary tree infection)
  • Can progress to choledocholithiasis (gallstones in the bile duct) and gallstone pancreatitis (inflammation of the pancreas)
• Rhinolith (nasal calculus)

Stones can also be asymptomatic.

Some common principles (below) apply to stones at any location, but for specifics see the particular stone type in question.

• From an underlying abnormal excess of the mineral, eg. with elevated levels of calcium (hypercalcaemia) that may cause kidney stones, dietary factors for gallstones.
• Local conditions at the site in question that promote their formation, e.g. local bacteria action (in kidney stones) or slower fluid flow rates, a possible explanation of the majority of salivary duct calculus occurring in the submandibular salivary gland.
• Bezoars are a type of calculus found in the intestines of mostly ruminant animals and may be composed of inorganic or organic constituents.

Stones can cause disease by several mechanisms:

• Irritation of nearby tissues, causing pain, swelling, and inflammation.
• Obstruction of an opening or duct, interfering with normal flow and disrupting the function of the organ in question.
• Predisposition to infection (often due to disruption of normal flow).

Diagnostic workup varies by the stone type, but in general:

• Clinical history and physical examination can be sufficient in some cases.
• Imaging studies are often needed.
  • Some stone types (mainly those with substantial calcium content) can be detected on X-ray and CT scan.
  • Many stone types can be detected by ultrasound.
• Factors contributing to stone formation (as in #Aetiology) are often tested:
  • Laboratory testing can give levels of relevant substances in blood or urine.
  • Some stones can be directly recovered (at surgery, or when they leave the body spontaneously) and sent to a laboratory for analysis of content.

Again, treatment varies by stone type, but in general:

• Modification of predisposing factors can sometimes slow or reverse stone formation.
  • Medications can sometimes be used.
  • Surgery is sometimes needed.
• Infections due to stones have to be treated with antibiotics and/or surgery.
• Pain is managed with medication.

• Rhinolith (nasal calculus)
• Salivary duct calculus

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