Lower urinary tract obstructions (LUTO) with massive bladder distension affect a variety of developing organ systems with consequent morbidity and mortality. Yet, the impact of LUTO on the fetal cardiovascular system has not previously been investigated.
Jack Rychik, MD, director of CHOP’s Fetal Heart Program, recently led a study investigating the cardiovascular consequences of LUTO in the fetus (Rychik J, McCann M, Tian Z, Bebbington M, Johnson MP. Fetal cardiovascular effects of lower urinary tract obstruction with giant bladder. Ultrasound Obstet Gynecol 2010; 36(6): 682-6). The study specifically examines the impact of a giant bladder on flow characteristics in the descending abdominal aorta to determine if a giant, distended bladder within the pelvis causes vascular compression with observable consequences.
Fetal echocardiography was performed in 42 fetuses with LUTO and a distended bladder and was compared to 35 normal controls matched for gestational age. Parameters investigated were cardiothoracic ratio, presence or absence of ventricular hypertrophy, and pericardial effusion. Doppler echocardiographic examination of mitral and tricuspid valve inflow and the ductus venosus was performed. To assess arterial vascular impedance, pulsatility indices (PIs) were calculated for segments of the descending aorta and right and left iliac arteries (RIA and LIA). The study yielded subtle, but potentially important, cardiovascular findings in the LUTO group. An increased cardiothoracic ratio was seen in nine (21%), ventricular hypertrophy in 12 (29%) and small pericardial effusion in 15 (36%). Filling characteristics of the right ventricle in the LUTO group demonstrated greater dependency upon atrial contraction and ductus venosus flow demonstrated higher downstream impedance to filling than in controls, suggesting diminished right ventricle compliance. The LUTO group also had lower distal descending aorta, lower RIA-PI and lower LIA-PI than controls, suggesting vascular compression and increased impedance to flow.
These findings show LUTO with giant urinary bladder compresses the iliac arteries, which may lead to increased afterload on the fetal heart, with consequences for the right ventricle. It reinforces CHOP’s use of fetal echocardiography, with attention to flow in the lower descending aortic arterial tree, in the evaluation of fetuses with LUTO. Rychik hopes to further study the impact of fetal treatment such as bladder drainage on these cardiovascular parameters.