Calicectasis on Renal Imaging: Definition and Clinical Significance
Calicectasis is the dilation of the renal calyces, which are cup-shaped structures that collect urine within the kidney, and is typically seen as a sign of obstruction in the urinary collecting system. This finding can be detected on various imaging modalities including ultrasound, CT, and MRI.
Pathophysiology and Causes
Calicectasis occurs when there is:
- Obstruction to urine flow, causing backpressure and dilation of the collecting system
- May be part of hydronephrosis (dilation of both renal pelvis and calyces)
- Can be unilateral or bilateral depending on the underlying cause
Common causes include:
- Urolithiasis (kidney stones) - most common cause 1
- Ureteropelvic junction obstruction
- Pregnancy (physiologic calicectasis occurs in 70-90% of pregnant patients) 2
- Tumors causing extrinsic compression
- Retroperitoneal fibrosis
- Congenital anomalies
- Post-surgical changes
Imaging Characteristics
Ultrasound Findings
- Dilated, fluid-filled calyces appearing as anechoic (black) areas within the renal parenchyma
- May be associated with increased resistive index (RI ≥0.7) on Doppler ultrasound in obstructive cases (sensitivity 86.7%, specificity 90%) 3
- Grades of caliectasis correlate with increasing resistive indices in most cases 3
CT Findings
- Dilated calyces with low-density (fluid) areas extending from the renal pelvis
- May show the cause of obstruction (e.g., stones, tumor)
- Non-contrast CT is the preferred modality for suspected urolithiasis with sensitivity up to 97% and specificity of 95% 1
- Secondary signs of obstruction may include perinephric stranding or ureteral dilation
MRI Findings
- T2-weighted images show hyperintense (bright) dilated calyces
- Less sensitive than CT for detecting stones but useful for detecting secondary signs of obstruction 1
- Particularly valuable in pregnant patients or those who cannot undergo CT 2
Clinical Significance and Evaluation
Calicectasis may be:
- Obstructive - requiring prompt intervention to prevent kidney damage
- Non-obstructive - as seen in conditions like megacalycosis (congenital enlargement of calyces) 4
- Physiologic - as commonly seen in pregnancy 2
The finding of calicectasis should prompt:
- Assessment for underlying cause
- Evaluation of renal function
- Consideration of the degree of obstruction and need for intervention
Management Considerations
Management depends on the cause, degree of obstruction, and clinical presentation:
- Acute complete obstruction: Requires urgent intervention to prevent permanent renal damage
- Partial obstruction: May be managed conservatively with follow-up imaging
- Physiologic calicectasis (e.g., in pregnancy): Often requires only monitoring
- Congenital calicectasis: May not require intervention unless complicated by infection or stones 4
Special Situations
Pregnancy
- Physiologic calicectasis occurs in 70-90% of pregnant women
- Often asymmetrically prominent on the right side
- Due to mechanical compression from enlarged uterus and smooth muscle relaxation from progesterone 2
- Ultrasound is the imaging modality of choice due to lack of radiation 2, 1
Pediatric Patients
- May indicate congenital anomalies requiring follow-up
- Ultrasound findings of calicectasis in children may warrant further investigation for vesicoureteral reflux or other congenital abnormalities 2
Functional Assessment
- Furosemide-enhanced sonography can help differentiate functional from anatomic obstruction in cases of mild calicectasis 5
- Diuresis renography may be needed to determine the clinical significance of calicectasis 5
Conclusion
When calicectasis is identified on renal imaging, it's important to determine:
- The underlying cause
- Whether it represents true obstruction requiring intervention
- The impact on renal function
The finding should never be ignored, as progressive dilation of the upper urinary tract can lead to acute kidney injury and permanent nephron loss if not properly addressed 2.