Urinary calculi are solid particles in the urinary system. They may cause pain, nausea, vomiting, hematuria, and, possibly, chills and fever due to secondary infection. Diagnosis is based on urinalysis and radiologic imaging, usually noncontrast helical CT. Treatment is with analgesics, antibiotics for infection, medical expulsive therapy, and, sometimes, shock wave lithotripsy or endoscopic procedures.
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. How rapidly obstruction develops determines the severity of renal colic. Common areas of lodgment include the following:
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Ureteropelvic junction
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Distal ureter (at the level of the iliac vessels)
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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.
Symptoms and Signs of Urinary Calculi
Large calculi remaining in the renal parenchyma or renal collecting system are often asymptomatic unless they cause obstruction and/or infection. Severe pain, often accompanied by nausea and vomiting, usually occurs when calculi pass into the ureter and cause acute obstruction. Sometimes gross hematuria also occurs.
Pain (renal colic) is of variable intensity but is typically excruciating and intermittent, often occurs cyclically, and lasts 20 to 60 minutes. Nausea and vomiting are common. Pain in the flank or kidney area that radiates across the abdomen suggests upper ureteral or renal pelvic obstruction. Pain that radiates along the course of the ureter into the genital region suggests lower ureteral obstruction. Suprapubic pain along with urinary urgency and frequency suggests a distal ureteral, ureterovesical, or bladder calculus (see Symptoms and Signs of Obstructive Uropathy).
On examination, patients may be in obvious extreme discomfort, often ashen and diaphoretic. Patients with renal colic may be unable to lie still and may pace, writhe, or constantly shift position. The abdomen may be somewhat tender on the affected side as palpation increases pressure in the already-distended kidney (costovertebral angle tenderness), but peritoneal signs (guarding, rebound, rigidity) are lacking.