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Renal & Urinary Tract Imaging in Obstructive Uropathy. Dr Omolola Mojisola Atalabi FWACS,FMCR , MBA ( Ib ) Senior Lecturer Consultant Radiologist College of Medicine/ University College Hospital Ibadan, Nigeria. Declaration. No conflict of interest Nothing to declare. Objective.
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Renal & Urinary Tract Imaging in Obstructive Uropathy Dr Omolola Mojisola Atalabi FWACS,FMCR, MBA (Ib) Senior Lecturer Consultant Radiologist College of Medicine/ University College Hospital Ibadan, Nigeria
Declaration • No conflict of interest • Nothing to declare
Objective • To refresh the common causes of renal obstructive uropathy in children • To know the common imaging modalities including modalities like MAG-3, DMSA & DTPA scan • Indications for each modality • Advantages and disadvantages of each modality • To understand the rationale behind the usage of the different imaging modalities
Introduction • Obstructive uropathy (OU) is a structural or functional hindrance of normal urine flow. It can cause renal impairment in all age groups. • urinary tract obstruction can lead to permanent damage to the urinary tract. • Infravesical obstruction can lead to changes in the bladder, such as trabeculation, cellule formation, diverticula, bladder wall thickening, and, ultimately, detrusor muscle decompensation. • Progressive back pressure on the ureters and kidneys can occur and can cause hydroureter and hydronephrosis. The ureter can then become dilated and tortuous, with the inability to adequately propel urine forward.
Introduction II • Hydronephrosis can cause permanent nephron damage and renal failure. • Urinary stasis along any portion of the urinary tract increases the risk of stone formation and infection, and, ultimately, upper urinary tract injury. • Urinary tract obstruction can cause long-lasting effects to the physiology of the kidney, including its ability to concentrate urine. • The causes in children may be congenital or acquired.
Congenital Causes • Pelvi-ureteric junction obstructions (PUJ) • Posterior urethral valves (PUV), • Urethral atresia, • Phimosis • Meatalstenosis. • Associated anomalies include • imperforate anus • vertebral malformations. N Eke, SN Elenwo. Obstructive uropathy in children: A review Port Harcourt Medical Journal Vol. 1 (3) 2007: pp. 137-144
Acquired causes • Calculi, • Post-traumatic and • Post-inflammatory strictures and • Meatal stenosis.
Causes of urinary tract obstruction Site of obstruction /Possible causes • Within the lumen • Blood clot. • Calculi. • Sloughed papillae. • Tumour of renal pelvis or ureter.
Causes of urinary tract obstruction cont... • Within the wall • Ureteric, urethral or ureterovesical stricture. • Congenital megaureter. • Bladder neck obstruction • Congenital urethral valves. • Pinhole meatus. • Neurogenic bladder • Functional failure due to denervation (e.g. following spinal trauma, multiple sclerosis.
Consideration • Imaging should be tailored to confirm clinical impressions and should either guide in the initial management of urologic conditions or help to modify the therapeutic plan. • Use imaging modalities that are devoid of ionising radiation where possible. • When the use of ionising radiation is unavoidable, the ‘ALARA’ principle must be obeyed
Imaging Modalities • Plain X ray • Ultrasonography ( Prenatal and postnatal) • Intravenous pyelography or urography • Retrograde urethrography • Micturatingcystourethrography (MCU) • Computerized tomography scan • Radionucleotide studies • Retrograde pyelography • Nephrostography • Magnetic resonance imaging
USS Attributes • USS of the kidneys and bladder is a useful imaging modality as an initial study. • It is a noninvasive, inexpensive study that does not involve radiation exposure or depend on renal function. • It is the initial study of choice in pregnant women. • USS is a very useful source of imaging in patients with intravenous pyelography (IVP) dye allergies or elevated creatinine levels, • In children, this is often part of the initial workup for obstructive processes. • It is sensitive in revealing renal parenchymal masses, hydronephrosis, a distended bladder, and renal calculi. • The accuracy of this imaging modality depends heavily on the experience of the sonologist / sonographer.
USS • Dilatation of the upper urinary tract is often detected using prenatal ultrasonography performed at or after 20 weeks' gestation (approximately 1% of pregnancies). • Such findings may require sequential ultrasonography of the fetus. • Depending on the degree of dilation, bilaterality, and presence of other anomalies, prenatal consultation by a pediatric urologist may be indicated. • Follow-up renal and bladder ultrasonography should be performed after the first day of life if anomalies are detected prenatally. • Newborns have a physiologic oliguria on the first day of life that can lead to false-negative ultrasonography findings. • If the findings are normal at this point, ultrasonography should be repeated 4-6 weeks later.
Intravenous Urography • IVP involves the injection of contrast into the venous system and a series of KUB radiographs over time. • It can be performed in patients with a normal creatinine value (< 1.5 mg/dL) for visualization of the urinary tract. • It provides both anatomical and functional information. • Delayed calyceal filling, delayed contrast excretion, prolonged nephrography results, and dilatation of the urinary tract proximal to the point of obstruction characterize obstruction. • IVU is superior to CT scan in revealing small urothelial upper tract lesions. • If IVU is inadequate, retrograde pyelography can be performed to completely visualize the renal pelvis or ureter. • Contraindication: Known contrast allergy
Micystourethrogram (MCUG)/ Voiding cystourethrogram (VCUG) • A MCUG or VCUG, is a fluoroscopic technique for watching a person's urethra and urinary bladder while the person voids. • The technique consists of catheterizing the person in order to fill the bladder with a radiocontrast agent, • Under fluoroscopy the radiologist watches the contrast enter the bladder and looks at the anatomy of the patient • If the contrast moves into the ureters and back into the kidneys, the radiologist makes the diagnosis of vesicoureteral reflux, and gives the degree of severity a score.
Retrograde Urethrography/ Cystography : • Radiographic contrast is injected into the urethral meatus via Foley catheter at the distal urethra. • Ideally Fluoroscopy is used to visualize the entire urethra for stricture or any abnormalities.
Cystoscopy with retrograde pyelography • Retrograde pyelography is performed in the operating room with a cystoscope in the bladder. Radiographic dye is injected into each ureteral orifice. • Then, with the use of fluoroscopy, any ureteral or renal pelvis filling defects or abnormalities can be visualized. • The contrast load does not interfere with renal function and can be used in patients with elevated creatinine levels. • It can also be used in patients with an IVP dye allergy because the contrast remains extravascular.
Nuclear Renogram • Radioisotope renography is a form of kidney imaging involving radioisotopes that allows a nuclear medicine physician or radiologist to visualize the kidneys and learn more about how they are functioning. • After injection into the venous system, the compound is excreted by the kidneys and its progress through the renal system can be tracked with a gamma camera. • If the kidney is getting blood, but there is an obstruction lower down, the contrast will not pass beyond the level of the obstruction, whereas if there is a partial obstruction then there is a delayed transit time for the radioisotope to pass. • If the kidney is not getting blood for example, it will not be viewed at all, even if it looks structurally normal on medical ultrasonography or magnetic resonance imaging.
Nuclear Renogram • A renal scan can be performed to determine the differential function of the kidneys, as well as to demonstrate the concentrating ability, excretion, and drainage of the urinary tract. Lasix can be administered with the renal scan to verify delayed excretion and the presence of obstruction. • More information can be gathered by calculating time activity curves; with normal kidney perfusion, peak activity should be observed after 3–5 minutes. The relative quantitative information gives the differential function between each kidney's filtration activity.
Nuclear Renogram • NR is the best imaging study to differentiate a multi-cystic kidney from hydronephrotic kidney. A CAT scan would require sedation, it exposes the child to more radiation and it is more expensive. • Notice that, unlike x-rays, nuclear renogram images show the right kidney on the viewer's right. Multi-cystic kidneys do not function.
CT • A CT scan is very useful in providing anatomic details • It provides information regarding the urinary tract, as well as any possible retroperitoneal or pelvic pathologic condition that can affect the urinary tract via direct extension or external compression. • A noncontrast CT scan should be obtained to assess for calculi. If calculi are found, flat-plate radiography of the abdomen (KUB) should be obtained to help determine calcium content and stone shape and to assist in monitoring the progress of the stone. Its progress can be observed with periodic simple radiography. • A contrasted CT scan is needed to provide information on renal pathology. • If delayed contrast images are obtained, CT urography with 3-dimensional reconstruction can provide excellent visualization of the entire upper urinary tracts.
Magnetic resonance imaging • MRI is not a first-line test used to evaluate the urinary tract. • In patients who cannot tolerate a CT scan with contrast, an MRI with gadolinium can be performed to reveal any enhancing renal lesions. • MRI is useful in delineating specific tissue planes for surgical planning, as well as in evaluating the presence or extent of a renal vein or inferior vena cava thrombus in cases of renal tumors. • MRI does not reveal urinary stones well so is not often used.
Cystoscopy • Cystoscopy is the placement of a small camera called a cystoscope through the urethral meatus and passing through the urethra into the bladder. Any abnormalities in the urethra, prostatic urethra, bladder neck, and bladder can be visualized. This can be performed in the office or in the operating room.
Obstructive Uropathy • In children, obstruction may be more commonly due to UPJ or UVJ obstruction, ectopic ureter, ureterocele, megaureter, or posterior urethral valves. • Prenatal screening with ultrasonography is important in early identification of obstruction. • In addition, children with incontinence or urinary tract infection need a workup because they may also have some type of urinary tract obstruction.
Share History with the managing team • The clinical presentation of urinary tract obstruction varies with the location, duration, and degree of obstruction. Thus, a thorough history and physical examination are key in the patient evaluation. • Share the clinical findings!!!!
Ureteropelvic junction (UPJ) obstruction • Ureteropelvic junction (UPJ) obstruction is defined as an obstruction of the flow of urine from the renal pelvis to the proximal ureter • UPJO is one of the most common birth defects of the ureteroccurring in 1 per 1000-2000 newborn and far the most common cause of pediatric hydronephrosiss. • It is more common in males and affects the left kidney more than the right. A blockage in both kidneys occurs in about 10-15% of the cases. • Widespread use of antenatal ultrasonography and the advent of modern imaging techniques have resulted in earlier and more common diagnosis of hydronephrosis
Urolithiasis & Ureteric calculus • Note echogenic area with shadowing
