Calyceal Diverticulum

Calyceal diverticula are outpouchings of renal calyces or even renal pelvis (pelvi-calyceal diverticula) into the renal cortex connected by narrow neck. These are lined by non-secreting urothelium (transitional cell epithelium).

Incidence: 0.2-0.6% of patients undergoing renal imaging.

Usually these are incidental findings and are mostly asymptomatic. Due to stagnation of urine within the diverticulum, these are prone for stone formation. Stones can be found in upto 50% of the calyceal diverticula.

Exact etiology of the formation of calyceal diverticula are not known, may be congenital or acquired due to infections, VUR, or rupture of a cortical cyst.

These are subdivided into two types:¹
Type 1 communicating with a calyx, usually found in upper pole.
Type 2 communicating with renal pelvis, larger, usually found in mid-pole (also called pyelo-calyceal diverticula). Radiopaedia adopts a slightly varied types, with type 1 from minor calyx and type 2 from major calyx or renal pelvis.²

There may be internal calcifications, either in the form of stones or of milk of calcium. In one small ultrasound series, 7 of 11 cases of calyceal diverticula demonstrated mobile echogenic material. It is suggested that the presence of mobile hyperechogenic material within a cystic structure is diagnostic of a calyceal diverticulum. ³

Differential considerations of a calyceal diverticulum would include complex cyst, dilated calyx, cystic renal neoplasm and abscess. Unless an excretory (or urogram) phase is acquired diagnosis of calyceal diverticulum is not possible. Dilated calyx can be due to obstructing stone, tumor or due to infundibular stenosis in TB.



The following plain and contrast CT images are of a 40 year old male patient who was evaluated for left lumbar pain and tenderness.

Plain CT Axial sections showing calcific focus within a subtle hypodense area in the bilateral renal parenchyma. 

Type I Bosniak cyst is noted medially (not marked).

The above three images shows the Plain CT, venous phase and excretory phase axial sections of both kidneys, which shows contrast filling of the cystic appearing area in the venous phase - consistent with the diagnosis of Calyceal Diverticulum of both kidneys. Calculus formation is noted in both these calyceal diverticulum. 

Oblique coronal MIP image showing the contrast filled bilateral calyceal diverticulum (Green arrows). The yellow arrow points to the pathology for which the patient underwent the CT examination (colitis). As in most cases, this case of bilateral calyceal diverticulum was also asymptomatic.  

3D VRT image demonstrating the calyceal diverticula. 

References
1. Mullett, Rebecca et al. “Calyceal diverticulum - a mimic of different pathologies on multiple imaging modalities.” Journal of radiology case reports vol. 6,9 (2012): 10-7. doi:10.3941/jrcr.v6i9.1123

2. Stunell, H et al. “The imaging appearances of calyceal diverticula complicated by uroliathasis.” The British journal of radiology vol. 83,994 (2010): 888-94. doi:10.1259/bjr/22591022

3. Reynard J, Brewster S, Biers S. Oxford Handbook of Urology. Oxford: Oxford University Press; 2006. p. 328.

4. Leveillee RJ, Bird VG. Treatment of Caliceal Diverticula and Infundibular Stenosis. In: Smith AD, Badlani G, Bagley D, et al., editors. Smith’s Textbook of Endourology. 2nd ed. Ontario: BC Decker; 2007. pp. 171–185.

Incisive Canal Cyst (Nasopalatine Duct Cyst, NPDC)

Incisive canal cyst also known as nasopalatine duct cysts (NPDC), is a developmental cyst arising from the epithelial remnants of nasopalatine duct, a duct connecting the nasal cavity with anterior maxilla in fetal life. It is considered the most common non-odontogenic cyst of jaw bone.

Often it presents in 4th to 6th decades, with slight male predilection. Patients may be asymptomatic, or can have pain, discharge and swelling often due to infection.

Incisive canal cyst is often >15mm in size, whereas the normal finding of incisive foramen is not expected to cross 6mm in diameter.  These cyst is seen superior to the roots of the maxillary incisors and usually doesn't result in any root resorption, but can sometimes result in displacement of the incisor roots.


Below are MRI images of incidentally detected Incisive canal cyst in a 50 year old male patient. MRI was done for evaluation of headache. T2 weighted sagittal, coronal and axial images shows a hyperintense cystic lesion in the anterior maxilla with mild displacement of the roots of maxillary incisors. Cyst measured 13.3mm in width.

Cyst was isointense to muscle in T1 WI (not shown), and hyperintense in T2 FLAIR images (not shown).

See another case of Incisive Canal Cyst : CT images HERE.