Urinary Tract Imaging- Basic Principles Campbell

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Urinary Tract Imaging- Basic PrinciplesCampbell
s Chapter 4
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• Christi Hughart, D.O.

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Plain Films
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• Scout film, primary survey, to follow known
  stones, check placement of catheters/stents/drains
  /foreign bodies
• False vascular calcifications, bowel
  opacities, phleboliths, appendicoliths, GS
• False - stone over sacrum/ilium, radiolucent
  (uric acid)
• If scout before ESWL shows no stone, may need to
  reassess

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Plain Film- Left Distal Ureteral Calculus
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Contrast Films
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• Rapidly concentrated by kidneys and opacifies
  urinary tract
• Low osmolar nonionic contrast material (LOCM)-
  50 less osmolar load- fewer complications than
  high osmolar
• Reactions dose related or idiosyncratic
• Allergic, CV changes, renal toxicity, shock
• Tx- antihistamines, beta agonist, epinephrine
• Renal toxicity risk (average patient)- 1
• Direct toxicity to renal tubules, ischemia,
  altered circulation, precipitation of uric acid
• Prevention- well hydrated, LOCM, small load

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IV Urography
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• Renal parenchyma, collecting system, ureter
• Evaluates- urothelial abnormality, hematuria,
  urolithiasis
• /- bowel prep/npo
• Scout, /- obliques
• Contrast- bolus or drip
• Nephrographic phase- immediate to first minutes-
  parenchyma
• Pyelographic phase- 5 minutes- collecting
  system
• /- compression, oblique- calyces, prone to
  distend ureter, upright- renal ptosis/layering
  in severe hydro, post-void- evaluate
  BOO/diverticulae/filling defect

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Normal Urogram
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Urogram with Prone Film- better visualization of
ureters
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Loopography
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• Imaging of urinary conduit or diversion (always
  order with indication clearly explained)
• Reflux required to see ureters if no IV contrast
  used (constrast sensitivity not contraindication)
• If non-refluxing anastamosis- need IVU,
  antegrade nephrostomy, CT, MRI
• Indications- hematuria, stones, stoma stenosis,
  loop ischemia, urinary fistulae, urine leak,
  stricture at anastamosis, hydro, tansitional cell
  cancer surveillance
• Prep- bowel prep if previous contrast,
  antibiotics, GU irrigant
• Contrast goes in thru catheter
• Scout, supine, conduit distension, drainage film

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Static Cystourethrography
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• Evaluate bladder lesion, rupture, leak, s/p
  trauma/sx- bladder integrity/anast/fistulas
• Scout, fill bladder with 200-400 mL contrast via
  catheter, A/P and obliques (shows extravasation
  posterior to bladder), post-drainage film

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Voiding Cystourethrogram (VCUG)
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• Functional and anatomic evaluation of bladder
• Typically for children with recurrent UTIs
• Dx- reflux, urethral valves, ureterocele,
  dysfunctional voiding, urethral strictures,
  bladder/urethral diverticula
• Scout
• Pediatric 5 or 8 F feeding tube, fill bladder
  with contrast (age 2 x 30)
• Adult standard catheter
• Film during filling- bladder pathology, early
  reflux
• Films during void- reflux, urethral abnormality
• Oblique- evaluate grade 1 reflux, males
• Post-void film

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Normal Male Cystogram
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VCUG
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Retrograde Urethrogram (RUG)
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• Evaluate anterior and posterior urethra-
  strictures, trauma
• 8-16 F foley in fossa navicularis, fill balloon
  with 1-2 mL and inject 30-50 contrast while
  filming obliquely
• Some resistance at membranous urethra and
  sphincter

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Normal RUG
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Retrograde Pyelography
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• Evaluate renal collecting system and ureters
• Indications- hematuria, contrast sensitivity,
  suboptimal IVU, needs cysto
• Pre-op- get sterile urine culture
• IV sedation
• Scout, injection catheter placed in UO, inject
  50 contrast under real time fluoro, drainage
  film at 5-10 minutes
• Backflow- contrast extravasation into
  surrounding tissues due to high injection pressure

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Normal RP
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Nephrostogram
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• Antegrade urogram- inject contrast into
  nephrostomy tube
• Indications- post-sx to evaluate for urine leak,
  post-perc neph to evaluate residual stones,
  evaluate site of ureter obstruction, dx ureteral
  fistulas
• Prep- sterile urine sample, /- antibiotics

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Ultrasound
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• Grayscale and doppler
• High frequency- high resolution but low
  penetration depth
• Renal- parenchyma, solid vs cystic, hydro
• Use with IVP to evaluate hematuria
• Assess allografts, congenital abnormalities,
  stones
• Cortex vs medulla- pyramids (medulla) less
  echogenic than cortex
• Adrenal- CT/MRI better except in peds (no RP
  fat)
• Nodules, cysts, hemorrhage, location, tumors
• Cortex hypoechoic, medulla echogenic
• Bladder- examine wall, lesions
• Transvaginal, transabdominal, transrectal
• Normal wall gt 6 mm
• Echogenicity in bladder fluid- debri, FB,
  infection
• PVR, bladder volume
• Ureteral jets- should appear in 15 minutes
  unless obstruction exists
• Prostate- transrectal, access for biopsy

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Ultrasound (cont.)
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• Scrotal-
• Use high frequency probe (up to 10 MHz)
• Evaluate- mass, pain, torsion, orchitis,
  epididymitis, hydrocele, hernia, varicoceles
• Testicle- granular, 4 x 3 cm, small anterior
  fluid collection- tunica, epididymis-
  hyperechoic
• Veins- gt2mm varicocele- evaluate in erect
  position with valsalva
• Urethral-
• Male- evaluate stricture- scar length and depth,
  longitudinal along phallus or intraluminal
• Female- diverticulum

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CT
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• Contrast- parenchyma, adrenals
• 3-D or CTA- evaluate vascular abnormality
• 100-150 mL IV bolus injection
• Renal-
• Precontrast- stones, parenchyma, vascular
  calcifications, renal contour
• Corticomedullary- 30 sec- cortex vs medulla
• Nephrographic- 100 sec- uniform enhancement of
  parencyma (masses)
• Pyelographic- excretory- collecting system
• Left renal vein- anterior to aorta, inf/post to
  SMA
• Right renal vein- extends posterolateral from
  IVC

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CT (cont.)
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• Adrenal-
• Malignancy, mets, functional adenoma
• Adenoma- HU lt0
• HU gt20- ? Mets- do perc bx
• MRI if suspect pheo
• Bladder-
• Depends on amount of distension
• Prostate/seminal vesicle-
• To detect abscess or cyst
• If prominent median lobe- appears to extend into
  bladder
• CT urography-
• Enhanced CT of ureters

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CTA
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• Rapid contrast injection with helical CT during
  arterial phase
• Soft tissue and bone reduced
• 3D reconstruction
• Indications- prep for donor nephrectomy, eval
  extra vessels to eval UPJ obstruction, renal
  artery stenosis

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MRI
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• No iodinated contrast
• Soft tissue resolution better than CT
• Contraindications- pacer, aneurysm clips, FB,
  prosthesis
• Allignment of protons in response to external
  magnet- radiofrequency applied causes difference
  in their energy
• T1- fluid dark, fat bright
• T2- fluid bright, fat dark

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MRI (cont.)
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• Renal- do if need cross-sectional images but
  contrast contraindicated, will not evaluate
  stones, determine tumor thrombus in IVC, cortex
  bright on T1
• Adrenal- adenomas contain more fat than
  cancers/pheos, pheo bright on T2, gland seen
  easily on T1, T2- adrenals isodense with liver
• Bladder- to id invasion of wall by transitional
  cell cancer or other pelvic neoplasms (on T2)
• Prostate- evaluate prostate cancer for capsular
  invasion. T1-distinct from surrounding
  fat/seminal vesicles (intermediate intensity),
  T2- peripheral zone (high intensity), central
  (intermediate), neurovascular bundles bright,
  seminal vesicles (high)
• Urethral- intraluminal coil to evaluate
  stricture/diverticulum
• MRU- to id obstruction- ureters/collecting
  system- T2- fluid bright, tissue dark (cant
  distinguish stone from clot/tumor)

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MRA
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• Gadolinium
• Indications- abdominal aorta, ranal artery
  stenosis, pre-donor nephrectomy

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Nuclear Scintigraphy
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• Physiologic and anatomic info
• TC-99 m (t ½ 6 hrs)
• MAG3- cleared by tubular secretion, no
  glomerular infiltration- evaluate renal function
  and renal plasma flow
• DTPA- glomerular filtration- evaluate
  obstruction and renal function
• DMSA- cleared by filtration and secretion- renal
  cortical image

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Diuretic Scintigraphy
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• For hydro not necessarily caused by obstruction
• Done with DTPA or MAG3 (better for renal
  insufficiency)
• When tracer reaches collecting system, diuretic
  given and t ½ calculated based on slope of curve
  given in response to diuretic

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Renal Cortical Scintigraphy
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• DMSA to evaluate for cortical scars or pyelo
• Do 3 months after infection