Cross Fused Renal ectopia imaged with Technetium-99m MAG-3 by MikeDurkan

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A review of congenital renal abnormalities and renal scinitigraphy.

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									Crossed-Fused Renal Ectopia
 imaged with Tc99m-MAG₃
            Mike Durkan
        SPRING Term 2008-09
Nuclear Medicine Externship Case Study
                TABLE OF CONTENTS
LIST OF FIGURES------------------------------------------------------------ 3
INTRODUCTION------------------------------------------------------------ 4
DYNAMIC MAG-3 RENOGRAM----------------------------------------- 5-10
CONGENITAL RENAL ABNORMALITES-------------------------------- 11-12
RENAL FUSION CLASSIFICATION---------------------------------------- 13
HORSESHOE KIDNEY ANATOMY----------------------------------------- 14
HORSESHOE KIDNEY VARIATIONS-------------------------------------- 15
ECTOPIC PELVIC KIDNEY--------------------------------------------------- 16
CROSSED-FUSED RENAL ECTOPIA--------------------------------------- 17
PATIENT HISTORY------------------------------------------------------------ 19
IMAGE FINDINGS------------------------------------------------------------ 20
IMAGE FINDINGS: MAG₃ RENOGRAM---------------------------------- 21-22
CONCLUSION------------------------------------------------------------------ 23
REFERENCES------------------------------------------------------------------- 24-26
                                     LIST OF FIGURES
Fig. 1: Mag₃ Renogram 30 min image; [neonatal polycystic kidney]------------------------------------------- 5
Fig. 2: 20 ml emulsion ampoule of Propofol ------------------------------------------------------------------------ 6
Fig. 3: Renal Nephron cut-away---------------------------------------------------------------------------------------- 7
Fig. 4: Detector FOV------------------------------------------------------------------------------------------------------- 8
Fig. 5: Abnormal Left kidney Uptake and Excretion--------------------------------------------------------------- 9
Fig. 6: Left Polycystic kidney with manual ROIs-------------------------------------------------------------------- 10
Fig. 7: Congenital Renal abnormalities------------------------------------------------------------------------------- 11
Fig. 8: ““Redrawn from McDonald and McCellan as reproduced by Abeshouse
        Bhisitkul, 1959”” (Belman et al., 202)----------------------------------------------------------------------- 13
Fig. 9: Horseshoe Kidney------------------------------------------------------------------------------------------------- 14
Fig. 10: Fused Horseshoe kidney--------------------------------------------------------------------------------------- 14
Fig. 11: “Horseshoe kidney and ureter variations” ---------------------------------------------------------------- 15
Fig. 12: Pelvic Kidney------------------------------------------------------------------------------------------------------ 16
Fig. 13: Uncrossed Renal Ectopia-------------------------------------------------------------------------------------- 16
Fig. 14: Cross-Fused Renal Ectopia------------------------------------------------------------------------------------ 17
Fig. 15: Stages of renal development--------------------------------------------------------------------------------- 18
Fig. 16: Left pelvic kidney------------------------------------------------------------------------------------------------ 19
Fig. 17: VCUG; Grade IV vesicoureteral Reflux--------------------------------------------------------------------- 20
Fig. 18 and 19: Crossed-fused renal ectopia?---------------------------------------------------------------------- 21
Fig. 20: Crossed-Fused ROI placement ------------------------------------------------------------------------------- 22
     On November 22, 2008, the PAMC Nuclear medicine department
performed a Tc99m-MAG₃ (Tc-99m-mercaptoacetyltriglycine ) Renal
tubular secretion study on a female 14-20 week old patient. The
patient had a recent urinary tract infection (UTI) and was being
evaluated for obstructive uropathy and comorbid pathology. In addition
to evaluating proximal tubular excretion, the diuretic Lasix (furosemide)
was given to exacerbate any obstructive pathology. Post-acquisition
processing revealed a rare anatomical abnormality called cross-fused
renal ectopia. A VCUG and US revealed similar results, however a CT
scan was never done to confirm the congenital anatomical anomaly.
     This case study will describe the nuclear medicine acquisition and
processing protocol and delineate on renal anatomical anomalies.
•   “Congenital abnormalities in the neonate”
•   Evaluation of Renal perfusion and function
•   Diagnoses of Urinary tract obstructions
      – Ureterovesical/Ureteropelvic junction
         obstruction (UVJ/UPJ obstruction).
•   Renal Infection/Inflammation
      – Acute and chronic pyelonephritis
•   Evaluation of renal transplant
•   Hydronephrosis/Hydroureteronephrosis
•   Renal Vein thrombosis
•   Acute Renal failure
•   Vesicourethral reflux
•   Pelvicaliectasis
•   Hematuria
•   Incontinence
•   Abdominal pain
•   Palpable masses                              Fig. 1: Mag₃ Renogram 30 min image;
                                                 [neonatal polycystic kidney]
•   Hydration                                          •     PRN Sedation per ordering physician
     – Hydration protocols vary from departments              – An outpatient appointment is scheduled
       and institutions                                         with PAMC PICU to assist with pediatric
     – [IV fluids] 5% dextrose in 0.3 normal saline;            sedation.
       15ml/kg over 30 minutes. Maintenance fluid             – Individual institutions may use
       volume for 200ml/kg/24hr. (Christian et al¹)             barbiturates, opiates, Phenothiazines,
     – [no IV fluids] PAMC has patients begin oral              Neuroleptic agents, or combinations.
       hydration 30 min prior to the study.                     See: Society of Nuclear Medicine
•   IV and indwelling Foley catheter placement                  Procedure Guideline for Pediatric
                                                                Sedation in Nuclear Medicine.
     – Outpatient pediatric (neonate-14yrs old)
       patients undergoing renal cortical or tubular
       scans are required to have indwelling Foley
       catheter placement. Outpatient pediatric
       services are provided by the PAMC Pediatric
       Intensive Care Unit (PICU).
     – For infants and neonatal pediatric patients;
       a French 8 (2.6mmØ) or French 6 (1.8mmØ)
       feeding catheter may be used.                       Fig. 2: 20 ml emulsion ampoule of Propofol
• Tc99m-MAG ₃                                            Proximal convoluted tubule
   – Tc-99m-mercaptoacetyltriglycie
   – ERPF (Effective Renal Plasma Flow) and             Glomerulus
     Proximal Tubular excretion
   – 90% protein bound
   – 40% first pass extraction       Afferent Arteriole
   – Compartmental localization
• Radionuclide
   – Technetium-99 metastable
   – T½= 6.02hrs
   – 89% 140 keV gamma photon              Efferent Arteriole

• R/P Dosimetry
   – 22mcCi/lb or 10mCi for normal adult
   – Target organ: Kidneys (.014 rads/mCi)
   – Critical organ: Bladder wall and Ovaries
     (.48 and .026 rads/mCi respectively)
   – Lowest dose /m², ideal for pediatrics                Fig. 3: Renal Nephron cut-away
     •  Image posterior. (NOTE: only image anterior if patient has
        renal transplant)
     • (1)“Center the detector’s FOV on the elbows” or (2)“Place
        Xiphoid and pubic symphysis in FOV” or (3)“Center on the
        crux of the iliac crests.”
     • Pediatric patients may need Papoose boards to limit
     • Place Foley catheter out of the FOV.
     (NOTE: some institutions inject 20-100mcCi to improve
        positioning. Pediatrics don’t require this.
•   FLOW
     •   128x128 or 64x64 matrix
     •   2 seconds per frame for 1 minute.
     •   128x128 matrix
     •   60 seconds per frame for
     •   Oldendorf method or modified tubing extensions are used
         during bolus phase.
     •   Extra tubing increases the chance of residual activity in the
         IV. Flush 10cc saline.
•   Lasix (furosemide) INJECTION
     •   Dose: 0.5mg/kg lasix
     •   Lasix is slowly infused over 1 minute at 10 minutes post
         injection of Tc99m-MAG ₃.
                                                                         Fig. 4: Detector FOV
• GE Xeleris  Dynamic Motion Correction Renal Analysis  Mag₃ renal with
  lasix  Ht. and Wt. Pediatric state Initial and residual activity
• Flow images are manually compressed to 8 seconds/frame.
• Dynamic Images are compressed to 2 minutes/frame.

   Fig. 5: Abnormal Left kidney Uptake and Excretion
•   ROI placement, patient motion, dehydration, and
    kidney location are major factors contributing to
    the quality of the study.
•   Depending on the indication, unsatisfactory time-
    activity curves can be produced from partially
    drawn kidney ROIs or fully draw kidney ROIs
    (Christian et al).
•   Some radiologists prefer exclusion of the renal
    pelvis when looking at renal function vs.
•   Images from 4 minutes are used to calculate
    relative renal function.
     – Collecting system is included in kidney ROI
•   Quantitative Dynamic renal images from 2-29
                                                        Fig. 6: Left Polycystic kidney with manual
    minutes are used for renal time-activity curves.    ROIs
     – Collecting system is excluded from kidney ROI
    – Horseshoe kidney
    – Renal ectopia without fusion
         • Crossed Renal Ectopia without fusion
         • Uncrossed Renal Ectopia without fusion

    – Renal Ectopia with fusion
         • Crossed fused renal Ectopia
         • Uncrossed fused renal Ectopia

NOTE: Thoracic kidneys are ectopic but are associated
  with diaphragmatic hernias and won’t be
  discussed because their etiology is much different
  from congenital ectopic kidneys.                      Fig. 7: Congenital Renal abnormalities

• Wilmer (1974):                    • McDonald and
  – 1) Horseshoe kidney
                                      McClellan (1957)
  – 2) L-shaped kidney that is a      – 1) crossed renal with fusion
    transitional form between
                                      – 2) crossed renal ectopia
    horseshoe kidney and
                                        without fusion
    unilateral fused kidney. (the
    ureter does not cross the         – 3) Solitary crossed renal
    midline).                           ectopia
  – 3) Unilateral fused ectopic       – 4) Bilaterally crossed renal
    kidney where the ureter             ectopia
  – 4) Miscellaneous
               McDonald and McClellan (1957)

Fig. 8: ““Redrawn from McDonald and McCellan as reproduced by Abeshouse Bhisitkul,
•   Horseshoe kidney is the most common congenital renal ectopia. (1 in 450 people).
•   90% are fused in the lower moieties.
•   Kidney stones and Ureteropelvic junction (UPJ) obstruction are common in Horseshoe
    kidney .
•   This kidney is the only ectopic anomaly that remains in the ipsilateral retroperitoneal

         Fig. 9: Horseshoe Kidney                      Fig. 10: Fused Horseshoe kidney

Fig. 11: “Horseshoe kidney and ureter variations”
                    ECTOPIC PELVIC KIDNEY
•   Pelvic kidneys’ have a similar occurrence rate as horseshoe
    kidney (1 in 500).
•   Frequent problems associated with pelvic kidneys are UTIs
    and vesicourethral reflux.
•   Unlike Horseshoe kidney, ectopic pelvic kidneys “lay” outside
    the ipsilateral retroperitoneal space and renal fossa.
•   Pelvic kidney’s are classified as Uncrossed/Solitary Ectopic
    kidneys without fusion.

                                                           Fig. 13: Uncrossed Renal Ectopia
     Fig. 12: Pelvic Kidney

• Depending on the source,
  crossed-fused renal ectopia
  has an incidence of 1 in
  14,000 pediatric admissions
  and 1 in 7,500 autopsies.
   – Incidence of VUR
     (Vesicoureteral reflux) is
     estimated at 70%
   – Hydronephrosis is reported at

                                     Fig. 14: Cross-Fused Renal Ectopia
                                       •   The exact cause of renal ectopia is still
                                       •   “Normal morphogenesis requires the
                                           coexistence of competent inducible
                                           constituents which are under strict
                                           temporal control.
                                       •   Teratogenic agents like thalidomide increase
                                           the risk of developing ectopic kidneys.
                                       •   Congenital abnormalities like: spinal
                                           deformities and anorectal anomalies are
                                           associated with renal ectopia.
                                       •   Studies and research show inhibition of
                                           embryological development in the early
                                           stages decreases renal blastema growth and
                                           retards the growth of ureteric buds.
                                       •   Time-lag theory: A genetic error causes the
                                           metanephric blastema to develop out of
                                           sync with the ureteric bud.
Fig. 15: Stages of renal development
                PATIENT HISTORY
• The female 14 week old pediatric patient with crossed-
  fused renal ectopia had a history of UTI.
• An abdominal Ultrasound (US), voiding cystourethrogram
  (VCUG), and MAG₃ renogram w/ lasix were ordered
• The US showed an small ectopic pelvic kidney. A VCUG
  showed reflux into the left ureter.

                                      Fig. 16: Left pelvic kidney
                    IMAGE FINDINGS

• Ultrasound:
  – Pelvic kidney
• Voiding Cystourethrogram
  – Grade II vesicoureteral Reflux
• MAG₃ renogram
  – Ectopic pelvic kidney with
    decreased size and function.

                                     Fig. 17: VCUG; Grade IV vesicoureteral
• MAG₃ and lasix dose:
   – 1mCi Tc99m-MAG3 (22mcCi/lb)                5 MIN
       • Minimum 1mCi
   – 6mg lasix @10 minutes
• Crossed-fused Renal ectopia was
  never diagnosed because a
  corresponding CT was not
   – However, the possibility of crossed-   25 MIN
     fused ectopia was very high.
• MAG₃ renography showed no                  Ectopic
  obstruction but decreased
  “left”/ “pelvic” kidney function.                                           Bladder

• Obvious ectopic kidney with
  possible fusion.                          Fig. 18 and 19: Crossed-fused renal ectopia?
• Processing the images were
                                        5 MIN
  difficult and required accurate
  placement of the ROIs.
• The anatomical anomaly caused
  the left and right kidney ROIs to
• In addition to overlapping
  structures; the RT renal pelvis     25 MIN
  was very difficult to mask from
  renal parenchyma.
• The time-activity curve revealed
  slight variations from patient         Fig. 20: Crossed-Fused ROI placement
  motion and the above
  mentioned artifacts.

    Crossed fused renal ectopia is a very rare
congenital abnormality. Positioning, ROI
placement, and other imaging considerations
should be discussed with the radiologist or ordering
physician. The case presented was not confirmed
as “crossed fused renal ectopia” because CT
imaging was not done. After consulting with the
Radiologist, he recommended a Tc99m-DMSA renal
SPECT to assess renal cortical function.
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