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
- 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)
- 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.
- 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.
- 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.
- 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.