From the Guidelines
Pyelectasis on an ultrasound refers to the dilation of the renal pelvis, which is a normal variant in many cases, but can also be a marker of underlying renal or urinary tract pathology 1.
Key Points
- Pyelectasis is also known as pelviectasis or hydronephrosis, and it occurs in approximately 1% to 2% of pregnancies 1.
- The condition is often transient and resolves on its own, but it can also be a sign of an underlying issue such as vesicoureteral reflux, ureteropelvic junction obstruction, or multicystic dysplastic kidneys 1.
- The diagnosis of pyelectasis is typically made using ultrasound, which can detect the dilation of the renal pelvis and other abnormalities such as calyceal dilation, parenchymal thickness, and ureteral dilation 1.
- The management of pyelectasis depends on the severity of the condition and the presence of any underlying pathology, and may include regular ultrasound monitoring, antibiotic prophylaxis, or surgical intervention in some cases 1, 2.
Evaluation and Classification
- The evaluation of pyelectasis involves assessing the anterior-posterior renal pelvis diameter, as well as other ultrasound features such as calyceal dilation, parenchymal thickness, and ureteral dilation 1.
- The condition can be classified as A1 (low risk) or A2-3 (increased risk) based on the severity of the dilation and the presence of any underlying pathology 1.
- The classification of pyelectasis guides antenatal management and postnatal follow-up, with A1 cases typically requiring less intensive monitoring and A2-3 cases requiring more frequent ultrasound assessments and potential surgical intervention 1.
From the Research
Definition of Pyelectasis
Pyelectasis is defined as renal pelvicalyceal dilatation, which is caused by urine retention in the upper urinary tract 3. This term does not indicate the cause that leads to the dilatation of and urine retention in the renal pelvicalyceal system.
Causes and Prevalence
Mild pelvicalyceal dilatation during pregnancy is usually considered to be physiological in nature and can occur in up to 90% of pregnant women 3. Retention is more common in the right kidney, in primigravidae, in the second half of pregnancy, and in multiple pregnancies.
Diagnosis and Clinical Implications
Pyelectasis can be diagnosed using ultrasound screening, which allows for the identification of cases with an increased risk of asymptomatic bacteriuria 3. The ultrasound-based evaluation of the kidneys for the presence of pyelectasis and its grade in pregnant women has some clinical implications, including the prevention of asymptomatic bacteriuria from progressing to symptomatic urinary tract infection.
Key Findings
- Pyelectasis is a common finding on fetal ultrasound, with a prevalence of 4.4% in one study 4.
- The criteria for the detection of fetal pyelectasis are still controversial, with different studies using different thresholds for diagnosis 4.
- Pyelectasis can be associated with obstructive urinary tract abnormalities, severe vesicoureteral reflux, or megaureter 4.
- Postnatal evaluation is necessary to confirm the diagnosis and rule out any underlying abnormalities 5, 6, 7.
Diagnostic Thresholds
- A renal pelvis dimension > 5 or 10 mm before or after 28 weeks of gestation, respectively, can be used as a threshold for detection of fetal pyelectasis 4.
- An anteroposterior renal pelvic diameter (APRPD) of 6-9.9 mm can be used to define moderate pyelectasis 6.
- A value of > 10 mm of the renal pelvis mean dimension beyond 28 weeks of gestation can be used as a threshold for detection of fetal upper urinary tract obstruction 4.
Postnatal Outcomes
- Most cases of pyelectasis resolve spontaneously during pregnancy or in the postnatal period 5, 6.
- However, some cases may progress to hydronephrosis or be associated with underlying abnormalities such as vesicoureteral reflux or obstructive uropathies 5, 6, 7.
- Postnatal follow-up is necessary to monitor for any potential complications or underlying abnormalities 5, 6, 7.