Posterior urethral valves a cause of fetal ascites
urinary ascites in fetus subsequent to obstructive uropathy due to posterior urethral valves
A 27 year old primi( Gravida 1, para 0, live 0, abortion 0) with non consanguineous marriage presented to department of Radio diagnosis for TIFFA at 22 weeks amenorrhea with prior antenatal check ups and ultrasonograms with no significant abnormalities. A prenatal diagnosis of Obstructive uropathy due to posterior urethral valves is made. The parents were counseled in detail about the condition. In view of poor prognosis of fetus, the parents opted medical termination of pregnancy. This was done by labor induction using misoprostol at 23 weeks gestation. The patient delivered still born male child weighing 450 grams with gross distension of abdomen.
The scan showed gross ascites outlining liver, spleen and bowel loops. There is grossly distended urinary bladder with craniocaudal length of urinary bladder 29mm, Bilateral hydroureteronephrosis with AP diameter of pelvis10 mm on right and 33mm on left and small right perinephric collection with mild oligohydramnios and thickened placenta with placenta thickness 5.2 cm and associated mild pulmonary hypoplasia. MRI of fetus is done consequent to this ultrasonogram confirmed the diagnosis of Posterior urethral valves with bilateral hydroureteronephrosis and right perinephric collection and gross ascites.T2w and T1w axial, coronal, Sagittal images were obtained. Mild thinning of dome of urinary bladder noted.
Possible etiopathogenesis in this case:- Posterior urethral valves in this fetus led to progressive megacystis and bilateral gross hydroureteronephrosis. (Renal Pelvic Diamater)RPD measures 33mm on left side, while 10mm on right side. This apparent resolution on right side is due to pop off into perirenal urinoma subsequent to rupture of pelvicalyceal system. Mild thinning of dome of urinary bladder could possibly have created a way/rent for passive intraperitoneal seepage of urine forming urinary ascites Obstructive uropathy in fetus is as a result of upper and lower urinary tract obstruction. Hydronephrosis refers to abnormal dilation of renal pelvis and calyces. The term pyelectasis implies milder form of hydronephrosis. Measurement of anteroposterior diameter of renal pelvis(RPD) is the simplest way to evaluate renal pelvic dilation although RPD can greatly vary over 2 hours of ultrasound observation. Renal pelvic dilation can be transient and physiologic. However calyceal dilation is an important finding and always pathologic, independent of pelvic size. Detection of fetal pyelectasis is important for two reasons: aneuploidy and postnatal uropathy. Society for fetal urology(SFU) proposed a different classification based on degree of renal pelvic dilation( mild, moderate, marked ), calyceal dilation and parenchymal atrophy. In general cut off values of AP diameter of renal pelvis (RPD) are 5 mm at 18 -23 weeks and 7 mm in third trimester. Grade 0 - No hydronephrosis Grade 1- Only dilated renal pelvis, some fluid in renal pelvis Grade 2- Dilation of renal pelvis and few calyces. Grade 3 -Dilation of renal pelvis and all calyces. Grade 4 -Dilation of renal pelvis and calyces with thinning of renal parenchyma. Renal pelvic dilation may be the first manifestation of any urinary tract abnormality pelviureteric or vesicoureteric junction obstruction, VUR, duplex kidney and urethral obstruction. Severity of hydronephrosis: Second trimester: Mild- RPD <7 mm Moderate- RPD 7 - 10 mm Severe -RPD > 10mm Third trimester: Mild- RPD < 9 mm Moderate -RPD (9-15 )mm Severe RPD > 15 mm The risk for any post natal pathology was 12% for mild, 45% for moderate, 88% for severe hydronephrosis. A prospective study done by Sairam et al reported natural history of hydronephrosis.96% of fetuses with mild hydronephrosis had complete resolution in either third trimester or in early neonatal period. 67% of fetuses with moderate and severe hydronephrosis had resolution in third trimester, 21% had postnatal resolution. An over view of it shows resolution, improvement in 98 % of patients in SFU grade 1 & 2, while stabilization of hydronephrosis in 51% of those with SFU grades 3 & 4. URINARY TRACT OBSTRUCTION: Posterior urethral valves are the most common cause of lower urinary tract obstruction. Now a days this condition is called Congenital Obstructive Posterior Urethral Membrane(COP
Posterior urethral valves may be diagnosed in ultrasound by a keyhole bladder and bilateral hydroureteronephrosis. However it may sometimes result in severe obstructive uropathy and urinary ascites. SFU grading of renal obstruction should be done and prioritize into correctable and non correctable conditions thus providing scope for termination or in utero or postnatal management further.