Diagnostic Ultrasound - Abdomen and Pelvis

Cystic Disease of Dialysis
TERMINOLOGY
Abbreviations
• Acquired cystic kidney disease (ACKD)
Synonyms
• Acquired cystic disease of uremia
Definitions
• Presence of 3 or more renal cysts per kidney in patients
with chronic kidney disease (CKD) who do not have
hereditary cystic disease
• Occurs predominantly in patients on long-term dialysis
(peritoneal or hemodialysis)
IMAGING
General Features
• Best diagnostic clue
○ Small kidneys with multiple small cysts bilaterally
○ Advanced stage: Large kidneys as cysts increase in size
and number
• Location
○ Bilateral; in areas of scarring throughout cortex and
medulla
• Size
○ Usually < 1 cm, up to 3 cm
• Morphology
○ Simple cyst: Round, fluid-filled lesion with imperceptible
walls
○ Complex cyst: Internal debris, septations, calcifications,
wall thickening
Ultrasonographic Findings
• Grayscale ultrasound
○ Multiple bilateral small cysts in normal size or atrophic,
echogenic kidneys
○ Cysts scattered in both renal cortex and medulla
○ Renal size may be enlarged due to increase in size and
number of cysts
– In advanced stage, appearance may resemble adult
polycystic kidney disease (ADPKD)
○ Simple cysts:Well-defined round lesions with posterior
acoustic enhancement, distinct echogenic posterior wall,
lack of internal echoes
○ Hemorrhagic cysts: May contain internal echoes or
nodular debris
– Distinction from neoplasm not always possible
○ Cyst rupture: May bleed into renal pelvis or
retroperitoneum resulting in hematuria or
retroperitoneal hematoma, respectively
○ Malignant transformation of cysts typically manifests as
papillary growth within the cyst
• Color Doppler
○ Presence of internal flow signal distinguishes tumor
from hemorrhagic cyst
○ Power Doppler more sensitive than color Doppler to
detect slow flow
• Contrast enhanced ultrasound (CEUS)
○ Increased sensitivity for detecting malignancy compared
to unenhanced US and CECT
○ Not nephrotoxic, can be used in end-stage renal disease
○ No internal enhancement in simple and complex cysts
(other than thin smooth septa)
○ Contrast uptake within cystic lesion is suspicious for
malignancy
CT Findings
• Well-defined, thin-walled, nonenhancing lesions, < 20 HU
• ± cyst wall calcifications, ± luminal high density from crystal
deposition
• Superior to ultrasound for detection of small tumors
○ Neoplasms enhance with contrast, typically more
heterogeneous
○ Hyperdense cysts may be difficult to distinguish from
solid lesions unless contrast is administered
MR Findings
• Best imaging test to evaluate for enhancing lesions, but
contrast use may be limited secondary to risk of
nephrogenic systemic fibrosis (NSF)
• Simple cyst:T1 hypointense, T2 hyperintense,
homogeneous
• Hemorrhagic cyst: Variable T1 and T2 signal dependent
upon age of hemorrhage
• CEMR: No enhancement
Imaging Recommendations
• Best imaging tool
○ Ultrasound as initial investigation for establishing
diagnosis in patients on dialysis
○ CEUS, CECT, or CEMR to evaluate complex cysts and
distinguish from renal cell carcinoma (RCC)
• Protocol advice
○ No widely accepted guidelines for screening of dialysis
patients for ACKD or RCC
DIFFERENTIAL DIAGNOSIS
Multiple Simple Cysts
• Rarely as numerous as in ACKD
• Normal size kidneys with normal echogenicity
• Renal function not impaired
• Incidence increases with increasing age
Adult Polycystic Kidney Disease (ADPKD)
• Hereditary disorder characterized by multiple renal cysts
and various systemic manifestations
• Cysts and kidneys are larger in size than in ACKD
• Differential features favoring ADPKD
○ Family history; presence of renal failure
○ Cysts in other organs: Liver (75%), pancreas (10%),
spleen, ovaries
○ Intracranial aneurysms
von Hippel-Lindau Disease
• Autosomal dominant multisystemic disorder
• Multiple renal cysts, cysts in other organs
• Kidneys are normal in size and functional
• Hemangioblastomas: Cerebellar, spinal, and retinal
• Multifocal renal cell carcinomas, pheochromocytomas
Tuberous Sclerosis (TS)
• Multiple bilateral renal cysts
• Multiple small fat-containing renal angiomyolipomas
Diagnoses: Urinary Tract
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