genitourinary disorders
Urinary Calculi
Pathophysiology of Urinary Calculi
Urinary calculi may remain within the renal parenchyma or renal collecting system or be passed into the ureter and bladder. During passage, calculi may irritate the ureter and may become lodged, obstructing urine flow and causing hydroureter and sometimes hydronephrosis. Common areas of lodgment include the following: Ureteropelvic junction Distal ureter (at the level of the iliac vessels) Ureterovesical junction Larger calculi are more likely to become lodged. Typically, a calculus must have a diameter>5 mm to become lodged. Calculi≤5 mm are more likely to pass spontaneously. Even partial obstruction causes decreased glomerular filtration, which may persist briefly after the calculus has passed. With hydronephrosis and elevated glomerular pressure, renal blood flow declines, further worsening renal function. Generally, however, in the absence of infection, permanent renal dysfunction occurs only after about 28 days of complete obstruction. Secondary infection can occur with long-standing obstruction, but most patients with calcium-containing calculi do not have infected urine. 