Diagnostic Ultrasound - Abdomen and Pelvis

Dilated Renal Pelvis
974
Differential Diagnoses: Kidney
DIFFERENTIAL DIAGNOSIS
Common
• Obstructed Renal Pelvis
• Reflux Into Dilated Renal Pelvis
• Extrarenal Pelvis
• Physiologic Distention of Renal Pelvis
• Parapelvic Cyst
• Prominent Renal Vessel
• Urothelial Carcinoma
Less Common
• Pyonephrosis
• Hemonephrosis
• Renal Sinus Hemorrhage
• Pararenal Fluid Collections
• Peripelvic Cyst
• Intrarenal Abscess
• Calyceal Diverticulum
• Acute Renal Vein Thrombosis
Rare but Important
• Pyelogenic Cyst
• Multilocular Cystic Nephroma
• Lucent Sinus Lipomatosis
• Renal Lymphoma
• Retroperitoneal Lymphoma
• Renal Artery Aneurysm
• Arteriovenous Malformation (AVM)
• Intrarenal Varices
• Renal Lymphangiomatosis
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
• Important to differentiate between obstruction and
nonobstruction
○ Follow ureter to level of obstruction to determine cause
• Ultrasound is first-line modality for detection but other
modalities such as CT, MR, VCUG, and retrograde
pyelography may be required for definitive diagnosis
• Nuclear scintigraphy differentiates obstruction from
nonobstructive dilatation
Helpful Clues for Common Diagnoses
• Obstructed Renal Pelvis
○ Isolated dilatation of renal pelvis is uncommon
○ Dilatation elsewhere in GU tract determined by level of
obstruction
– For example, ureteropelvic junction obstruction
manifests with pelvic dilatation and (to lesser degree)
calyceal dilatation
– Ureterovesical junction obstruction presents with
hydroureter as well as pelvicalyceal dilatation
○ Determine if unilateral or bilateral
○ Level of obstruction helps narrow differential diagnosis
○ Most common cause of unilateral obstruction is stone
disease
○ Other causes include bladder, ureteral or other pelvic
mass, retroperitoneal mass or hemorrhage, aortic
aneurysm, retroperitoneal fibrosis, iatrogenic injury
• Reflux Into Dilated Renal Pelvis
○ Hydroureter may be present in addition to renal pelvic
dilatation
○ VCUG essential in determining reflux
– In future, contrast-enhanced voiding urosonography
may be used in place of VCUG to evaluate for reflux
without use of ionizing radiation
• Extrarenal Pelvis
○ Common finding in neonates and often incidentally
noted in other age groups
– Renal pelvis projects medial to renal sinus
○ Appearance may simulate early obstruction but calyces
are not dilated
• Physiologic Distension of Renal Pelvis
○ Commonly noted when bladder is distended
– Frequent in pregnant patients, most commonly in 3rd
trimester; R > L
– Fetal pyelectasis can result in mild pelvic dilatation in
neonates, which subsequently resolves
• Parapelvic Cyst
○ 1-3% of renal parenchymal cysts; usually solitary
○ May be mixed picture, as parapelvic cysts can compress
collecting system resulting in true dilatation
• Prominent Renal Vessel
○ May mimic pelvic dilatation but color Doppler denotes
flow
– Protocol advice: Always remember to use color
Doppler when concerned about pelvic dilatation or
cystic lesion to distinguish from vessel
• Urothelial Carcinoma
○ Hypoechoic mass in dilated pelvis, though usually slightly
hyperechoic to renal parenchyma
○ Can mimic hemorrhage or pus
○ On color Doppler, note internal vascularity within
urothelial carcinoma
Helpful Clues for Less Common Diagnoses
• Pyonephrosis
○ Debris (pus) in dilated pelvicalyceal system
○ Look for presence of urothelial thickening and cause
such as stone
• Hemonephrosis
○ Blood within dilated pelvicalyceal system ± blood in
bladder
○ Echogenicity variable depending upon age of blood
products
• Renal Sinus Hemorrhage
○ In absence of trauma, most often secondary to
anticoagulation, but can be secondary to occult
neoplasm, vasculitis, or blood dyscrasia
○ Cystic lesion of variable echogenicity disrupting normal
central echocomplex, with mass effect upon renal pelvis
and tension upon infundibula
○ Should spontaneously resolve in 3-4 weeks
• Pararenal Fluid Collections
○ May occur in setting of infection, obstruction, or
transplantation; include urinoma, hematoma, abscess,
and lymphocele near renal hilum
• Peripelvic Cyst
○ Lymphatic collection in renal sinus, distinct from
parapelvic cyst, which is intraparenchymal
○ Often multiple and bilateral (unlike parapelvic cyst)