Diagnostic Ultrasound - Abdomen and Pelvis

Perigraft Fluid Collections
TERMINOLOGY
Abbreviations
• Perigraft fluid collections (PFC)
Definitions
• Not uncommon in early postoperative period and usually
asymptomatic
• PFC include hematomas, seromas, urinomas, lymphoceles,
and abscesses
• Depending on size and location, PFC may cause mass effect
on allograft resulting in hydronephrosis or graft
dysfunction
• Hematomas/seromas: Normal sequela of surgery often
small, seen immediately after transplantation
• Lymphoceles, most common PFC, occur in 5-15% patients,
usually after 4 weeks
○ Frequently cause hydronephrosis due to extrinsic
ureteral compression
• Urinomas occur in 2-5% of patients secondary to
anastomotic leak or ureteric ischemia within first 2 weeks
• Abscesses occur later in postoperative period with clinical
evidence of infection
○ Bacterial or fungal infection not uncommon in renal
transplant patients due to immunosuppression
IMAGING
General Features
• Best diagnostic clue
○ Collection of simple or complex fluid around renal
allograft, typically walled off
○ Appearance and complications of PFC depend on
composition and location
○ Definitive diagnosis established by ultrasound-guided
needle aspiration
• Location
○ Variable
• Size
○ Variable
• Morphology
○ Depends on composition of PFC
Ultrasonographic Findings
• Grayscale ultrasound
○ Fluid characteristics when simple: Anechoic or
hypoechoic with posterior enhancement
○ Internal echoes when complex
○ Seromas: Typically anechoic and small
– May contain low-level echoes if infected
○ Hematomas: Echogenicity depends on age of collections
– Acute hematomas appear as echogenic
heterogeneous collection
– Crescentic perigraft fluid collection or ovoid collection
– Upon maturation, hematomas become cystic
containing low-level internal echoes and thin or thick
fibrin strands with retracting clot
○ Lymphoceles: Well defined and anechoic but may be
septated
– Located near renal vascular pedicle
○ Urinomas: Usually localized anechoic collection
– Undetectable when small, may produce urinary ascites
as they enlarge
– Typically adjacent to ureter and separate from bladder
– Rarely septated unless infected
○ Abscesses: Typically complex thick-walled cystic
structures with irregular outline and echogenic internal
debris
– Can form adjacent to, or remote from, graft
• Color Doppler
○ Useful to differentiate complex PFC from complex cystic
masses by demonstrating vascularity within masses
Ultrasound-Guided Aspiration
• Aspiration to drain collection and exclude infection
• Aspirate should be tested for creatinine, markedly elevated
in urine leak
• Aspirate from hematoma or lymphocele has creatinine level
comparable to serum
Nonvascular Interventions
• Percutaneous sclerosis
○ Therapeutic option for recurrent lymphoceles
Fluoroscopic Findings
• Contrast cystography can demonstrate ureterovesical
anastomotic leak
• After percutaneous access, antegrade pyelography (AP) can
be used to detect more proximal leaks
CT Findings
• Collection with CT attenuation between 10-24 HU
suggestive of lymphoceles or seromas
• Collection with high CT attenuation (> 28 HU) most likely
hematoma
• Abscesses or chronic hematomas have variable HU values
• CT superior for larger collections, local consequences, as
well as other abdominopelvic complications
○ Wider FOV, less limited by body habitus and acoustic
window
• Multidetector CT urography (CTU) superior to intravenous
pyelogram in detecting urine leaks and ureteral obstruction
• CT cystography or CT nephrostography have high sensitivity
for ureteral leaks
Nuclear Medicine Findings
• Technetium-99m mercaptoacetyltriglycine (Tc-99m MAG)
study
○ Progressive radiotracer activity in abnormal collection is
diagnostic of urinoma
○ Large photopenic defect compressing graft kidney is
suggestive of PFC
Imaging Recommendations
• Best imaging tool
○ US is first-line modality for evaluating graft dysfunction,
excellent for PFC
○ US guidance for aspiration (CT guided if US is not
feasible)
• Protocol advice
○ CT may be performed as general survey for abscess or
complications
Diagnoses: Kidney Transplant
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