Renal calculi
Although renal calculi (kidney stones) may form anywhere in the urinary tract, they usually develop in the renal pelvis or the calyces of the kidneys. Such formation follows precipitation of substances normally dissolved in the urine (calcium oxalate, calcium phosphate, magnesium ammonium phosphate or, occasionally, urate or cystine).
Renal calculi vary in size and may be solitary or multiple. They may remain in the renal pelvis or enter the ureter and may damage renal parenchyma; large calculi cause pressure necrosis. In certain locations, calculi cause obstruction,
with resultant hydronephrosis, and tend to recur.
with resultant hydronephrosis, and tend to recur.
Among Americans, renal calculi develop in 2 in 1,000 people and are more common in men than in women.
Causes
Although the exact cause of renal calculi is unknown, some patients develop them as a result of genetic factors. Predisposing factors include the following:
Dehydration and resultant decreased urine production causes calculus-forming substances to become concentrated.
Infection in tissue provides a site for calculus development; and pH changes provide a favorable medium for calculus formation (especially for magnesium ammonium phosphate or calcium phosphate calculi). Infected calculi (usually magnesium ammonium phosphate or staghorn calculi) may develop if bacteria serve as the nucleus in calculus formation. Such infections may promote destruction of renal parenchyma.
Obstruction can result from urinary stasis (as in immobility from spinal cord injury), which allows calculi components to collect and adhere, forming calculi. Obstruction also promotes infection, which, in turn, compounds the obstruction.
Metabolic factors that can predispose to renal calculi include hyperparathyroidism, renal tubular acidosis, elevated uric acid levels (usually with gout), defective metabolism of oxalate, genetic defect in metabolism of cystine, and excessive intake of vitamin D or dietary calcium.
Signs and symptoms
Signs and symptoms vary with size, location, and cause of the calculi.
Pain
Pain, the key symptom, usually results from obstruction; large, rough calculi occlude the opening to the ureter and increase the frequency and force of peristaltic contractions. The pain of classic renal colic travels from the costovertebral angle to the flank, to the suprapubic region and external genitalia.
The intensity of this pain fluctuates and may be excruciating at its peak. If calculi are in the renal pelvis and caly-ces, pain may be more constant and dull. Back pain (from calculi that produce an obstruction within a kidney) and severe abdominal pain (from calculi traveling down a ureter) may also occur. Nausea and vomiting usually accompany severe pain.
Accompanying signs and symptoms
Other associated signs and symptoms include fever, chills, hematuria (when calculi abrade a ureter), abdominal distention, pyuria and, rarely, anuria (from bilateral obstruction or unilateral obstruction in the patient with one kidney).
Diagnosis
The complete clinical picture along with the following diagnostic tests allows a diagnosis:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
