Needle and Shunt Procedures
Several fetal treatments are conducted using a thin gauge needle or shunt. These instruments are guided into the womb using ultrasound. Because needles and shunts are generally very thin, there is minimal disturbance of the womb compared to more invasive fetal procedures.
Intrauterine transfusion (IUT) was the first procedure performed to directly treat an underlying fetal problem. IUT is currently used for the treatment of severe fetal anemia, causes of which include alloimmunization (Rh disease being one example), parvovirus infection, and severe fetal-to-maternal hemorrhage. Because of several factors, the number of IUT’s performed in the United States has dropped drastically. Most patients that require IUT are referred to specialized fetal treatment centers.
The early success of IUT led to the development of nonvascular fetal needle and shunt procedures. One example is the work-up and treatment of lower urinary tract obstruction (LUTO). Kidney function in the fetus is assessed in one of two ways. The classic method is by checking urinary electrolytes in the fetal urine via serial vesicocenteses. A needle is inserted into the fetal bladder and the urine is entirely removed. Adequate assessment often requires two or three procedures. Kidney function can also be assessed directly via fetal blood sampling. If renal function is preserved, then urinary diversion to relieve the high pressure to the kidneys and restore normal amniotic fluid volume can be performed, thereby preventing further damage to the fetal kidneys and lungs. The traditional method of urinary diversion is placement of a vesicoamniotic shunt. The vesicoamniotic shunt is a special tube that connects the fetal bladder to the amniotic cavity, thereby bypassing the obstruction.
Another group of disorders that respond well to needle drainage and/or shunting are fetal chest abnormalities. Space-occupying lesions in the fetal thorax, whether fluid or solid, may cause underdevelopment of the lung tissue and lethal pulmonary hypoplasia, as well as compression of cardiovascular structures and eventual fetal hydrops. Examples of fetal chest abnormalities that have been treated with a needle and/or shunt include pleural effusions in the setting of hydrops, congenital cystic adenomatoid malformation (CCAM), and pulmonary sequestrations (PS).
Fetal intervention for select cardiac disease is currently in the investigational stage. These procedures are performed using a needle that is placed into the fetal heart through which the balloon catheter is passed. The balloon catheter in turn is used to open up restricted heart valves.