Blockage or clogging, e.g., by occlusion or stenosis. [L. obstructio]
closed-loop o. o. of a segment of intestine by rotation on a fixed point (volvulus); frequently impairs venous circulation of the affected bowel segment, resulting in strangulation and gangrene; the segment of intestine contained in a hernia can also become a closed-loop o. when sufficient compression occurs at the neck of the sac.
ureteropelvic junction o. an impediment to drainage of urine from kidney usually to partial or intermittent blockage of renal collecting system of the junction of renal pelvis and ureter.
ureteropelvic o. a blocking or stenosis, usually congenital, at the junction of the renal pelvis and ureter, usually resulting in stasis, pelvocaliectasis, hydronephrosis, or calyceal clubbing.
ureterovesical o. o. of the lower ureter at its entrance into the bladder.
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