calculus
(kal'kyŭ-lŭs 
)
(kal'kyŭ-lī‵)
(kal'kyŭ-lē‵)
Plural: calculi
[L. calculus, pebble]
A stone, usually composed of mineral salts. Stones can occur in the gallbladder, kidneys, ureters, bladder, or urethra.
SEE: gallstone; kidney stone.
dental c.Mineralized dental plaque, located above or below the gums.
pancreatic c.A calculus in the pancreas, made of calcium carbonate with other salts and inorganic materials.
prostatic c.A stone in the prostate.
urinary c.A stone formed in the urinary tract, usually lodged in the renal pelvis (at the ureteropelvic junction) and /or kidney calyces.
SEE: lithotriptor.
Men in the U.S. have a 13% probability of forming urinary stones sometime during their lives. Women's lifetime incidence of kidney stone disease is approx. 7%.
Stones vary in composition, but most often (80% of the time) contain calcium. Other chemical constituents of stones are oxalates, phosphates, carbonates, cystine, urates, and struvite (ammonium, magnesium, and phosphate).
Struvite calculi, which account for about 15% of all stones, are found primarily in females and are usually related to urinary tract infections. Predisposing factors for stone formation in the urinary tract include dehydration, infection, obstruction, and dietary and metabolic factors (such as dietary supplementation with calcium and vitamin D). In the U.S., geography is also important: more urinary stones are found in southeastern states than in other parts of the country.
Pain related to urinary obstruction or movement of the stone is the primary symptom. Classic renal colic travels from the costovertebral angle to the suprapubic region and external genitalia. Its intensity fluctuates, but it is often excruciating at its peak. Nausea and vomiting usually accompany the most severe pain.
In a patient with renal colic, diagnosis is based on the clinical presentation, urinalysis (which often reveals the presence of blood cells) plus computed tomography (CT) scan or magnetic resonance imaging (MRI), excretory urography, KUB (kidneys, ureters, bladder) x-rays, and stone analysis.
Patients who have urinary stones often have recurrent stone formation or future episodes of renal colic. To prevent stone disease in affected patients, vigorous daily hydration (increased fluid intake) is advisable. The stone patient should aim to excrete 2.5 L or more of urine daily. People who consume high concentrations of dietary calcium have a reduced risk for urinary stones in the future. Soft drink consumers with urinary stones should limit their intake of phosphoric acids, a component of many sodas. Thiazide diuretics and oral citrates have been proven to reduce the risk of repeat stone formation. In people with uric acid stones, allopurinol taken orally reduces stone formation.
The patient suffering renal colic is treated with intravenous fluids, analgesics, and alpha-blocking drugs to relax the lower urinary muscles and facilitate the passage of the stone.
The patient is encouraged to verbalize anxieties and concerns about the severe pain. Pain relief measures are instituted as prescribed: they include analgesics, antispasmodics, and warm, moist heat. All urine is strained for stones, and any calculus is sent for laboratory analysis. Vigorous hydration with oral or intravenous fluids helps in the passage of small stones (90% are smaller than 5 mm in diameter). If an extracorporeal lithotriptor is to be used to shatter a calculus for subsequent removal by suction or natural passage, the duration of the procedure and follow-up care are explained. Procedures for surgical removal depend on the location of the calculus; they include cystoscopy with ureteral manipulation, or a flank or lower abdominal laparoscopic or open approach. All diagnostic and interventional studies are explained, and the patient is encouraged to verbalize fears and concerns. Urine is observed for hematuria, and specimens are tested for specific gravity and pH. Vital signs are monitored. If temperature is elevated, antipyretic measures are instituted as ordered, and antibiotics specific to cultured organisms are prescribed. Fluids are forced (PO/IV) to enhance dilution of urine, and intake and output are monitored. Fruit juices, specifically cranberry juice or cranberry tablets, are often suggested to acidify urine. Evidence for the efficacy of cranberry in renal stones and urinary tract infection is weak. The health care professional stays alert for complications such as infection, stasis, and retention. In patients with struvite stones, to minimize urinary tract infections, the female patient is taught proper perineal hygiene. Antibiotics are also used to enhance the clearance of struvite stones.
After stone-removal surgery, the patient usually has an indwelling catheter or a nephrostomy tube in place. Bloody drainage is expected, and this tube should never be irrigated without a physician's order. If the kidney was removed, the patient should be reassured that the body can adapt well to one kidney. Pulmonary hygiene with an inspirometer is stressed in the presence of flank or abdominal incisions. Dressings are assessed for drainage and are changed per protocol, and signs of hemorrhage or infection are reported promptly.
vesical c.A kidney stone that has formed or lodged in the urinary bladder.