Whenever something blocks the flow of urine through a ureter, it is a kidney obstruction. The most common cause of kidney obstruction is a kidney stone. Other causes include structural abnormalities, blood clots, tumors and the shifting of a kidney, which is called kidney ptosis.
Kidney obstruction causes a partial or total blockage of urine drainage. This causes urine to collect in the affected ureter and partially back up into the kidney. This is called hydronephrosis. A urinary tract infection also might occur.
Hydronephrosis that comes on suddenly usually produces severe flank pain, which is pain on one side between the upper abdomen and back. When it comes on gradually, hydronephrosis might cause no pain. In some cases, it will cause dull, intermittent flank pain.
All cases of flank pain should be investigated by a health care provider. If there is no infection present, an ultrasound can be performed to determine the cause. A computerized tomography (CT) scan might be needed if the cause cannot be determined via ultrasound. If a kidney obstruction is found, treatment will depend on the type of obstruction.
Kidney stones account for most cases of obstruction. In addition to flank pain, symptoms of kidney stones include nausea, vomiting, painful urination, blood in the urine and pelvic pain. Kidney stones usually do not require treatment other than pain medication unless there is significant blockage of urine. In this case, surgery probably will take place in an attempt to break up the stone.
Blood clots might sometimes occur in the kidneys or ureters. Blood clots might be caused by injury or clotting disorders. Along with flank pain, symptoms include blood in the urine and low urine output. Blood clots usually are treated with blood thinners, although surgical removal might be necessary. Long-term treatment will depend on the cause of the clot.
Another cause of kidney obstruction is a tumor. The tumor could be in the affected kidney itself, in the ureter or in the abdomen in a place where it puts pressure on the kidney. Symptoms of a tumor include flank pain, a lump in the abdomen, weight loss, fatigue and possibly fever. Treatment of the tumor will depend on its size and location but might include, chemotherapy, radiation or surgical removal.
Sometimes an obstruction is caused by a congenital condition, such as a birth defect. In such cases, it probably will be discovered via ultrasound at a prenatal examination. If only one kidney is affected, the fetus usually will develop well, although the obstructed kidney might be permanently damaged. If both kidneys are affected, however, prenatal surgery might be required.