What Are the Causes of Hydronephrosis?

Hydronephrosis occurs when a kidney becomes distended due to compromised urine flow. Onset is quick and causes severe pain in the area between the ribs and the hips, or progresses gradually with a slight discomfort in the same area. Hydronephrosis is a condition caused by backward pressure on the kidney when the flow of urine becomes blocked, but diseases cause the obstruction to occur.

Structural Abnormalities

• Congenital birth defects of the urinary tract can cause back flow of urine and lead to kidney dilation. A birth defect in which the ureter is inserted too high in the renal pelvis can lead to hydronephrosis. Another structural abnormality linked to kidney dilation is underdeveloped ureteral muscles.

Kidney Stones, Blood Clots and Scar Tissue

• A common cause of hydronephrosis is kidney stones, which develop in the urinary tract and may obstruct the passage of urine. Blood clots and scar tissue are additional causes that potentially block the urinary tract from within, sending back flow to the kidneys.

Tumors

• Both benign and cancerous tumors can form along the urinary tract and in the kidneys, obstructing the passage of urine and causing hydronephrosis. Tumors outside and along the urinary tract or on the cervix, uterus, prostate or other pelvic organs place pressure on the urinary tract and obstruct the flow of urine through it.

Pregnancy

• A pregnant woman's growing uterus places increased pressure on the ureters, which can lead to ureteral obstruction. Hormonal changes during pregnancy reduce normal contractions that move urine through the ureters. Hydronephrosis of pregnancy typically ends when the pregnancy is over, but the ureters and renal pelvis can remain swollen and cause hydronephrosis to linger after pregnancy.

Tips and Warnings

• Hydronephrosis is characterized by pain between the ribs and hips, difficulty urinating and blood in the urine. Consult a doctor immediately if pain, burning, cloudy urine, fevers, sweats and chills are present as these are signs of infection. Kidney damage and failure are complications associated with hydronephrosis and the longer the condition remains untreated, the more kidney function will be lost.