Dr/Ahmed Bahnassy Consultant radiologistRiyadh Military Hospital
Importance of the finding• Most common congenital condition discovered by antenatal US.• ultrasonography enables us to detect the correctable cause of hydronephrosis, such as ureteropelvic junction obstruction.• Failure of recognizing those needing surgical intervention will result in permanent loss of the kidney.
Fetal hydronephrosis Detection• Grignon et al developed a grading system for hydronephrosis in fetuses of 20 weeks gestation or greater in relation to their postnatal findings.• Grade I dilatations (AP renal pelvic diameter up to 1.0 cm) were described as normal and physiologic because none of the affected patients required surgery after birth.• Grade II (>1.0–1.5 cm) and grade III (>1.5 cm with slight dilatation of calices) dilatation was termed intermediate hydronephrosis; 50% required postnatal surgical intervention.• All patients with grade IV dilatation (>1.5-cm pelvis, moderate dilatation of calices, no cortical atrophy) or grade V hydronephrosis (>1.5-cm pelvis, severe caliceal dilatation, atrophic renal cortex) required surgery.• Their work suggests that one should be concerned with pelvic dilatations greater than 10 mm particularly if there is associated calyceal dilatation and loss of cortex.
• Clinically significant disease is more likely if:• (1) a grade 3 or 4 hydronephrosis is present;• (2) the renal pelvis diameter is > 10 mm;• (3) the renal pelvis/kidney ratio is > 0.5.
Incidence:• Pre-natal ultrasound – detects fetal anomaly in 1% of pregnancies, of which 20-30% are genitourinary in origin and 50% manifest as hydronephrosis
Grading of Severity of HydronephrosisGrade Central Renal Renal Complex Parenchymal Thickness 0 Intact Normal 1 Slight splitting Normal 2 Evident splitting Normal 3 Wide splitting Normal 4 Further dilatation Thin
Pathophysiology:• Anatomic and functional processes interrupts the flow of urine.• There is a rise in ureteral pressure causing stretching and dilation; if pressures continue to rise, leads to decline in renal blood flow and GFR.• When significant obstruction is persistent, it affects nephrogenic tissue and results in varying degrees of cystic dysplasia and renal impairment.
I-Mild (Grade II)• These images shows mild dilatation of the pelvis as well as the calyces of the right kidney
II-Moderate (III)• The above ultrasound images show cupping of the calyces with moderate dilation (Right kidney) of the pelvis and calyces. Despite the hydronephrosis the renal parenchyma is still preserved.
III-severe (IV)• The above sonographic images show marked dilatation of the pelvicalyces with sever thinning of the renal parenchyma. note almost total absence of normal renal tissue (cortex).