Calculus (medicine)

Overview
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.

Common stone diseases
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.

Aetiology

 * 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.

Pathophysiology & Symptoms
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).

Diagnosis
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 ) 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.

Treatment
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.