What Is Antenatal Hydronephrosis?
Antenatal hydronephrosis is the condition that occurs in the fetus during pregnancy. The condition is characterized by enlargement of the kidney due to the accumulation of fluid. Antenatal hydronephrosis indicates various renal disorders in the fetus. found more in males as compared to females. The condition is It is found in 0.5 percent of females and 1 percent in males. Fortunately, in almost all the case, other organs are not affected due to antenatal hydronephrosis.
How Is Antenatal Hydronephrosis Diagnosed?
Antenatal hydronephrosis is diagnosed through various methods. Some diagnostic techniques involve advanced equipment and may not be available at al the centers for diagnosing this condition. Most cases of antenatal hydronephrosis are found during a routine ultrasound at around 20 weeks gestation period.
Following are the methods to diagnose antenatal hydronephrosis:
Laboratory testing: Evaluating the urine sample of the fetus may help in identifying kidney dysfunction or renal dysplasia. Through the ultrasound-guided technique, the urine sample of the fetus is obtained. In the case of a healthy fetus, the urine so formed is hypotonic. However, in a diseased condition, the urine obtained is isotonic. Increased level of calcium, sodium, Microglobulin, and chloride indicates possible renal dysplasia.
Ultrasonography: Ultrasonography was the first diagnostic method that helped in identifying hydronephrosis in the fetus. It also helps in identifying the possible cause of accumulation of fluid in the kidney.
Magnetic Resonance Imaging: Magnetic resonance imaging during pregnancy provides more detailed condition and provide important insight into the severity of the disease. Once the severity is identified, optimum medical interventions can be designed.
Other additional procedures: The procedures that can help in diagnosis include amniocentesis, chromosomal analysis, maternal serum biochemistry, and chorionic villus sampling.
What Are The Various Grades Of Antenatal Hydronephrosis?
The grades of antenatal hydronephrosis are determined by the Antero-posterior diameter (APD) of the renal pelvis. The diameter is evaluated through ultrasonography. The grades or classification of antenatal hydronephrosisis done as mild, moderate and severe.
Following are the various grades for antenatal hydronephrosis:
| GRADING OF ANH | II TRIMESTER | III TRIMESTER |
| Mild | 4-< 7 mm | 7 – < 9 mm |
| Moderate | 7 – ≤ 10 mm | 9 – ≤ 15 mm |
| Severe | >10 mm | >15 mm |
Almost 57 – 88% of the antenatal hydronephrosis is mild while 10 to 30 % of the cases are of moderate grade. 2-13% of the cases of antenatal hydronephrosis are severe.
Antenatal hydronephrosis is caused due to the following conditions:
Ureteral obstruction or blockage: This obstruction may be either Ureteropelvic junction obstruction (UPJ) or ureterovesical junction obstruction (UVJ) or megaureter. The UPJ obstruction is indicated when there is a dilation of the pelvic-calyceal system without any ureteral dilation.
Renal anomalies: Generally, only a single ureter drains the urine from a kidney. However, in almost 1 % of the humans, there are two ureters originated from a kidney. This duplication does not cause any complications in the majority of patients. In approximately 1 in 1500 infants, there is an obstruction in the upper tube.
Urethral obstruction: Urethral obstruction in the fetus may also lead to antenatal hydronephrosis.
Vesicoureteral reflux: When there is the backflow of urine from the ureter and bladder towards the kidney, the urine does not flow properly and gets accumulated.
Polycystic Kidney: Due to the complete obstruction of the ureter, one of the kidneys is not normally developed. The other kidney functions normally and the baby usually born with a multicyclic kidney.
If there is a prolonged obstruction of urine and increased pressure, this may cause a progressive reduction in kidney function. Medical interventions may reduce the pressure and allow the kidney to function but may not be able to regain the lost function.
No intervention is required in antennal hydronephrosis due to various reasons such as lack of technology for accurate diagnosis, non-identification of the definite reason for the fluid accumulation, and no strong data corresponding to safety and efficacy of medical/surgical interventions. However, a follow-up is required during the post-natal period in infants with varying degrees of antenatal hydronephrosis.
Post-natal management of infants with moderate to severe hydronephrosis is done by identifying the cause of the condition and designing a treatment strategy. KUB ultrasound is done usually 48-72 hours after birth. Antibiotics are administered as prophylactic therapy. Before discharge, complete diagnosis, evaluation, and treatment should be provided to the infant.
Most fetuses with antenatal hydronephrosis have an excellent prognosis. The condition resolves on its own in many cases. The morbidity and mortality depend upon various factors such as underlying cause, or whether one or both the kidneys are affected.
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