Nephrolithiasis (renal stones) is a common disorder of the urinary system. Several types of renal stones (calculi) can form, including calcium oxalate (most common), calcium phosphate, uric acid, cystine, and struvite stones.
Staghorn calculi are branched stones that extend into adjoining calyces. Struvite stones can form staghorn calculi.
Calcium oxalate stones often begin as deposits called Randall’s plaques in the loop of Henle. Calcium phosphate stones typically begin in the collecting ducts due to crystal deposition. Patients with cystinuria are predisposed to form cystine stones. Rarely, insoluble drugs such as indinavir, triamterene, and ephedrine can form stones.
It typically presents with renal colic that starts in the flank and moves down toward the genital area as the stone travels from the upper to the lower urinary tract. The pain is not affected by changes in body position.
Other common features include:
Symptoms are relieved once the stone passes into the bladder and is then passed in urine. Renal stones also predispose to urinary tract infection (UTI).
The following conditions are associated with recurrent stones:
Additional associations:
Preferred investigation is CT without contrast.
Other imaging options:
Stones > 10 mm in size do not pass spontaneously, while most stones < 5 mm in size are passed spontaneously in urine.
General measures:
Medical prevention and stone-specific measures:
Medical expulsive therapy (for stones < 10 mm):
Procedures:
In the presence of hydronephrosis, immediate treatment is needed to preserve renal function.
Stones can be studied by X-ray crystallography and infrared spectroscopy to guide preventive measures.
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