The growing uterus of a pregnant woman can sometimes impinge on one or both ureters and cause obstruction in the flow of urine. When this happens, urine flows back towards the affected kidney and causes distention of the renal pelvis, which is the part of the kidney that connects with the ureter. This condition is called hydronephrosis of pregnancy. Aside from the compression of the growing womb of the pregnant woman, hormonal changes may also contribute to the occurrence of hydronephrosis of pregnancy.

Hydronephrosis of pregnancy usually affects the right kidney due to the tendancy of the growing uterus to rotate to the right, thus compressing the right ureter. There are cases, however, where both kidneys are affected. When this happens, and hydronephrosis of pregnancy is not treated, kidney failure can occur. Symptoms of kidney failure include weakness, swelling of the feet and hands, and decreased urine output, among many others.

Urine normally flows out of the kidneys under low pressure. When there is an obstruction at a certain area of the ureter, the flow of urine is affected. Urine then tends to go back to the kidney, causing the kidney distention and increasing the pressure in the area. Without proper treatment, this increase in pressure in the affected kidney can sometimes result in renal rupture, which can be a life-threatening situation. Important signs that usually precede a renal rupture include pain between the hips and the ribs, presence of blood in urine, and low blood pressure.

Common complications of hydronephrosis of pregnancy include infection, stone formation, and damage to the affected kidney due to the pooling of urine in the area. Symptoms of infection include fever, abdominal discomfort, and presence of white blood cells in the urine. Patients with hydronephrosis of pregnancy may also experience nausea and vomiting.

An abdominal ultrasound is generally used to diagnosis hydronephrosis of pregnancy because it does not expose the pregnant woman and her fetus to radiation. Treatment usually includes antibiotics and other medications for pain. When these medications do not provide relief to patients, invasive procedures may be done. These include placing a stent in the ureter or using a catheter to drain urine out of the kidneys. Some pregnant women may undergo cesarean operation, or labor induction if the fetus is already at near term.

During treatment of hydronephrosis of pregnancy, pregnant women are frequently advised to drink plenty of fluids. Bed rest is also indicated. They are also often instructed to lie on the side of the kidney that is not affected.