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Paediatric Surgery
Magnetic Resonance Imaging of the Urinary Tract
Built from Puri — Pediatric Surgery and Pediatric Urology
What’s inside
6 sections · 72 slides
Why MRI for the Urinary Tract?
The gap the other tests leave behind
- What you will be able to explain by the end
- Every existing kidney test has a blind spot
- The core trade-off MRU is designed to break
- So what is magnetic resonance urography (MRU)?
- Why the picture stays good even in a sick kidney
- MRU rests on three pillars
How the Test Is Actually Done
Preparation and timing make or break the study
- Success depends on a standardized protocol
- Hydration: prime the kidney before you image it
- Sedation: holding a child still inside the magnet
- Bladder catheterization: a practical safeguard
- T1 and T2 images: two ways of seeing
- The timed drug sequence: furosemide then gadolinium
- Why gadolinium mirrors the nuclear scan tracer
- A simple trick when the ureter refuses to fill
- The contrast passes through three parenchymal phases
Reading Function and Drainage
Turning bright pixels into surgical decisions
- Calyceal transit time (CTT): the first clock
- Reading the CTT pattern in a swollen kidney
- Renal transit time (RTT): the obstruction flag
- The RTT thresholds you act on
- Differential renal function (DRF): who does the surgery
- How the Patlak number is generated
- Compensated vs decompensated hydronephrosis on MRU
Clinical Applications
One study replacing a stack of tests
- When MRU earns its place
- Congenital malformations: position and rotation
- Horseshoe kidney with hydronephrosis
- Small ectopic, hypoplastic kidney
- Confirming dysplasia and cystic disease
- Segmental multicystic dysplastic kidney
- Ureteroceles and calyceal anomalies
- Ureterocele draining a dilated upper pole
- Polycalycosis with a decompensated junction
- Calyceal diverticulum mimicking a cyst
- Ureteral anomalies and duplicated systems
- Duplex kidney with an ectopic upper-pole ureter
- Finding the ureter even when function is gone
- Mid-ureteric stricture: a previously hidden diagnosis
- Mid-ureteric stricture with an abrupt caliber change
- Hydronephrosis: MRU's most common indication
- Telling obstruction from harmless dilation
- Fetal folds: diagnosed without an operation
- Fetal folds in the ureter
- UPJ obstruction: still no perfect gold standard
- UPJ obstruction with delayed calyceal transit
- Crossing vessels and checking the repair
- Crossing-vessel UPJ obstruction and repair
- Mapping the blood vessels
- Accessory renal arteries with hydronephrosis
- Vesicoureteral reflux: a harder target for MRU
- How good is MRI for reflux, and its limits
- Pyelonephritis and renal scarring
- How infection and scar look on MRU
- Duplex kidney with upper-pole scarring
- Characterizing renal masses
- Large Wilms tumour of the kidney
Limitations and Safety
Real risks that shape who gets the test
- Gadolinium contrast reactions
- Nephrogenic systemic fibrosis (NSF): the serious one
- Sedation, implants, and practical hurdles
- Cost versus value
Summary and Future Directions
From last-resort test to first-line tool
- Numbers worth remembering
- Key takeaways
- Why is a fluid challenge with furosemide given before and during MRU, rather than imaging the resting kidney?
- References (1/3)
- References (2/3)
- References (3/3)
- Pediatric Surgery and Pediatric Urology