Imaging in cystic renal affliction

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  1. R de Bruyn,
  2. I Gordon
  1. Department of Radiology, Great Ormond Street Infirmary for Children NHS Trust, Cracking Ormond Street, London WC1N 3JH, UK
  1. Dr Gordon i.gordon{at}ucl.air-conditioning.united kingdom of great britain and northern ireland

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The term "cystic kidneys" is used to describe a heterogeneous group of conditions characterised either by single/multiple cysts or abnormal kidneys with no obvious cysts as the kidney may appear hyperechoic (solid). Confusion has arisen considering the terminology is imprecise at times and multiple cysts do not necessarily denote a heritable status or specific syndrome. The disorders span all ages in childhood and since the introduction of routine antenatal ultrasound many are identified antenatally.

The ultimate diagnosis of many of the "cystic kidneys" requires clinical, genetic, radiological, and pathological data. Errors arise when insufficient information is gathered and collated. A precise diagnosis is important for prognosis, treatment, and genetic counselling although this may not exist possible at presentation.1-3 Equally the aetiology, histology, and clinical presentation are various, no unmarried classification of "cystic renal illness" is satisfactory; the most widely acceptable classification is genetic and non-genetic (encounter table 1). A morphological nomenclature of "cystic kidneys" however remains useful for the non-genetic disorders. Nomenclature of a detail child's "cystic kidneys" requires information about any relevant family history; parental consanguinity; relevant histopathology if bachelor, and ultrasound of parents and siblings. Full clinical evaluation, evidence of a syndrome or dysmorphic features, assessment of renal part, and whatever antenatal ultrasound findings are all important. Extrarenal manifestations occur and ultrasound examination of liver, pancreas, and spleen is mandatory.

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Table ane

Nomenclature of cystic renal disease

Ultrasound

Ultrasound is the cornerstone of imaging and sequential examinations take described the natural history of many of these disorders (come across tabular array 2). At times ultrasound alone is sufficient for diagnosis, for example, multicystic kidney; however, other weather condition require integration of many imaging modalities when certain conditions are existence considered.

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Table ii

Natural history of cystic renal disease

Ultrasound will identify whether the abnormality is unilateral or bilateral; symmetrical or asymmetrical; the size of the kidneys; and the presence or absence of dilatation of the collecting organization. The exact location within the kidney, size, and number of cysts must exist noted; the echogenicity of the cortex must be compared both to the medulla as well equally to the liver/spleen. As ultrasound equipment improves, anatomic detail of the renal cortex has become improve and information technology is at present possible to detect i–ii mm transonic lesions which are probably tiny cysts. Ultrasound is expected to reach a specific diagnosis yet renal ultrasound cannot distinguish betwixt certain conditions, for case, autosomal dominant polycystic kidney affliction (ADPKD) and tuberose sclerosis in the young kid. Furthermore, other imaging is unremarkably required to expect for associated abnormalities, for example, cystic dysplasia and vesicoureteric reflux; involvement of other systems, for instance, the liver in Caroli'south affliction and autosomal recessive polycystic kidney disease (ARPKD).

Non-genetic "cystic kidney"

The nomenclature is disruptive; "cysts" may be plant yet cysts may merely exist part of another condition, however they must be included in the differential diagnosis of "cystic disease of the kidney".

DYSPLASIA/CYSTIC DYSPLASIA

Renal dysplasia is an aberration of metanephrotic development in which the structure of the kidney is altered and glomerular as well as ductal differentiation are perturbed. There is persistence of "fetal" kidney tissue in the form of nests of metaplastic cartilage associated with primitive ducts. Pathologically, renal cystic illness and renal dysplasia are two distinct entities. This is true even though dysplastic kidneys frequently are cystic and many types of cystic kidneys show some dysplasia. Yet, the term is used without histological confirmation by the clinician. The condition may be unilateral or bilateral; when bilateral the child volition go into renal failure early in life merely finish stage renal failure is variable and may not come near till later in life. All dysplastic kidneys function albeit poorly.5

Imaging

Renal ultrasound appearance includes a small-scale kidney (less than third centile for historic period) with a bright echonephrogram and loss of corticomedullary differentiation. Cysts are variable both in size and number but are usually less than 1 cm. Occasionally the ultrasound appearance is dominated by these small cysts, typically subcortical in position even though the kidney remains modest (fig 1). Dilatation is rarely seen on ultrasound unless associated with obstruction as in posterior urethral valves (PUV) or form 4–v vesicoureteric reflux (VUR).

Figure 1

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Figure 1

Cystic dysplastic kidney. Longitudinal ultrasound scan on a male neonate. The right kidney is small-scale hyperechoeic with loss of the normal corticomedullary differentiation and contains multiple small-scale cysts. The left kidney had like appearance. The float was thickwalled and the infant had posterior urethral valves.

Radiological contrast study—There is an increased incidence of VUR. When the calyces are outlined by contrast on either micturating cystogram (MCU) (fig 2) or intravenous urography (IVU) they are few in number, and bear witness loss of the fornices with blunting; with reflux the renal pelvis may be dilated and rather perpendicular and the ureter is tortuous and dilated.

Figure 2

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Figure 2

Cystic dysplastic kidneys. Micturating cystourethrogram on an infant with dysplastic kidneys on ultrasound showing vesicoureteric reflux into tortuous ureters and abnormal calyces with parenchymal filling and blush.

Radioisotope—The technetium-99m DMSA scan shows reduced function if unilateral, or poor visualisation of the kidneys if bilateral. The normal cool pyramids are not seen and frequently there are focal defects in the kidney which cannot be distinguished from a scar secondary to urinary tract infection (UTI). These focal defects are seen in children with dysplasia who have never had a UTI.

Dysplasia may be seen in association with malformations of the kidney, for case, the upper moiety of a duplex (fig 3), posterior uretheral valves, crossed fused renal ectopia, horseshoe kidney, or the pelvic kidney. In many syndromes and genetic disorders the kidneys are affected with or without cysts; these include Beckwith–Weideman syndrome, Laurence–Moon–Beidel syndrome, Opitz–Lemi syndrome, oto-brachial-digital syndrome, Meckel'due south syndrome, and Zellweger's syndrome among others.5

Figure 3

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Figure iii

Dysplastic upper moeity of a duplex kidney. Longitudinal ultrasound scan of the correct kidney. There are small subcortical cysts in the upper pole (arrow). The collecting system of the lower pole tin can be seen beneath (open arrow).

MULTICYSTIC KIDNEY (MULTICYSTIC DYSPLASTIC KIDNEY)

Multicystic kidney or multicystic dysplastic kidney (MDK) causes confusion with the dysplastic/cystic dysplastic kidney as described in a higher place. In MDK there is loss of lobular organization, although minor islands of renal tissue may be identified. Archaic cartilage and ductules are nowadays, suggesting abnormality of renal differentiation, the hallmark of dysplasia. Some consider MDK and cystic dysplasia every bit ends of the same spectrum; nevertheless, all MDK are not-performance and accept an atretic ureter. In that location are conflicting reports as to the incidence of VUR.

Antenatal ultrasound is the commonest presentation. MDK is commoner in males and has a natural history of involution. In that location are a few example reports of either hypertension or malignancy only this clan is not universally accepted. The of import associated abnormalities (thirty%) include pelvi-ureteric junction obstruction (PUJ), ureteric stenosis of the opposite kidney, and VUR.

Imaging

Ultrasound appearances vary from a pocket-size single cyst to multiple cysts of varying sizes with a big dominant cyst situated peripherally with no identifiable renal parenchyma (fig 4). Sequential ultrasound shows that nearly MDK anfractuous, some during intrauterine life. A few MDK enlarge progressively, generally in those greater than 5–6 cm at birth. Occasionally ultrasound may not distinguish between MDK and PUJ. In such circumstances an isotope report using either 99mTc DMSA or MAG3 is recommended. If function is detected, albeit very poor function, and so one is dealing with PUJ; if at that place is no role so there is little indicate in a drainage procedure as a totally non-performance kidney with PUJ never shows office following drainage; whereas a poorly functioning kidney with PUJ may testify recovery following drainage. Rarely a cyst puncture with instillation of dissimilarity volition distinguish between MDK and PUJ.

Figure 4

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Figure 4

Multicystic kidney. Longitudinal ultrasound browse of the right multicystic kidney showing the classical appearance of multiple cysts of varying sizes with very petty surrounding parenchyma, occupying the whole of the correct kidney.

On 99mTc MAG3 studies in that location is no function of the MDK; the opposite kidney requires assessment for adequate drainage. There is debate every bit to the need for an MCU if the ultrasound scan of the bladder is normal.

SIMPLE CYSTS

Simple cysts in children are rare and ordinarily detected incidentally. In the largest reported paediatric ultrasound series (16 102 cases), cysts were constitute in 0.22%.6 This was not related to historic period. The diagnosis of a unproblematic renal cyst should be one of exclusion, especially if the upper pole is involved when one should doubtable a duplex kidney or a calyceal cyst or part of another "cystic illness". Ultrasound cannot differentiate a elementary cyst from other pathology; this requires an IVU or magnetic resonance urography. Follow up ultrasound into adolescence is suggested to determine whether other cysts develop.

CALYCEAL CYSTS

This is non a truthful "cystic" status but rather an observation made on ultrasound and confirmed on IVU. The importance of a calyceal cyst is the possibility of a calculus developing within or the theoretical beingness of TB as the cause. In the context of cystic disease, this needs to be identified as distinct.

MULTILOCULAR CYST/MULTILOCULAR CYSTIC WILMS' TUMOUR

Multilocular cystic nephroma is a rare cystic renal mass derived from metanephic blastema seen in children. Histology varies from completely benign (multilocular renal cyst) to malignant (multilocular cystic Wilms' tumour). Clinically the child may present with an abdominal mass. Ultrasound shows a multilocular renal mass with multiple cysts and septations and is not-functioning on isotope. The authentication is the presence of a capsule around the cysts.7Computed tomography (CT) or magnetic resonance imaging (MRI) scanning should exist undertaken in all these children.

LOCALISED CYSTIC Affliction OF THE KIDNEY

This recently recognised condition is genetically, radiologically, and morphologically distinct from autosomal dominant polycystic kidney affliction (ADPKD). The involved segment is enlarged, and contains multiple small cysts that merge into normal renal parenchyma with no abrupt demarcation. There is no surrounding capsule on imaging or histology. This condition differs from ADPKD as it is localised to ane part of one kidney.8 Some of the earlier reported patients with unilateral ADPKD almost certainly had this condition. Clinically the lesions are not progressive in the few reported cases; as the natural history is unclear the kidney should be followed up. Hypertension has been reported.

MEDULLARY SPONGE KIDNEY

Medullary sponge kidney describes an appearance on IVU where dilatation of the collecting ducts causes a medullary blush, in clan with calculi. This may be focal or generalised and the kidney may be enlarged; it is rarely seen in childhood. On IVU, the blush seen is related to the calyces, an appearance seen in ARPKD. The term renal tubular ectasia is used to describe these changes.

ACQUIRED CYSTIC RENAL Affliction

There is no underlying cystic renal disorder, no other organs are involved. Children in chronic renal failure may develop cysts; the frequency increases with length of dialysis with upwardly to ninety% developing cysts if on dialysis for more than than x years. Later transplantation the cysts tend to regress in size. Complications include the potential of renal jail cell carcinoma or haemorrhage. Ultrasound is acceptable for diagnosis and follow up.

Genetic cystic disease

Although conveniently divided into dominant, recessive, and cysts associated with syndromes, the imaging is more circuitous. Similar imaging features may be seen in more than ane condition and furthermore the appearances may change with time; these two factors stress a comprehensive imaging work upwardly at presentation besides every bit at follow up. One cannot rely solely on only ultrasound at diagnosis.

AUTOSOMAL DOMINANT POLYCYSTIC KIDNEY Disease

ADPKD is characterised both past renal and extrarenal manifestations. It usually presents after the tertiary decade of life but presentation in childhood is recorded. At that place is variability in the severity of the renal disease when detected in infancy or antenatally.nine The estimated prevalence is at least 1/1000. Two and possibly three genetic loci have been identified. Ninety per cent of families take the gene located on the short arm of chromosome sixteen (PKD1)10; the 2nd gene is on chromosome four (PKD2). Spontaneous mutation occurs and accounts for lack of family unit history. In PKD1 families, 64% of affected children under 10 years of age volition have cysts; this effigy rises to 90% by the age of 19 years.xi In babyhood, extrarenal manifestations are rare but include cysts in the liver, pancreas, or spleen,12 ,13and subarachnoid haemorrhage caused by intracranial aneurysm. Built hepatic fibrosis is more often than not associated with ARPKD just is reported in association with ADPKD.14

Ultrasound

The prenatal ultrasound may show large hyperechoic kidneys (fig 5) but is not specific (see ARPKD for differential diagnosis). This ascertainment is unexpected and has led to some confusion. In infancy the ultrasonic appearances are variable, from normal to a few isolated cysts, to a kidney packed full of cysts. The more multiple the cysts, the larger the kidneys. The cysts are mostly scattered throughout both the cortex and medulla. Often at that place is unequal interest of the kidneys and the intervening renal tissue appears normal. When found in children (especially very young children) with no family history, the diagnosis of tuberose sclerosis (TS) must be considered.

Figure 5

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Figure 5

Ultrasound browse of both kidneys taken antenatally. Both kidneys (marked by the × and +) are globally hyperechoeic and large. Ultrasound is sensitive in the detection of "brilliant" kidneys but not specific.

Intravenous urography

When the cysts are visible on ultrasound, the IVU will show compression and displacement of calyces (fig 6A) and the renal outlines are lost. The quality of the IVU is usually poor because of the multiplicity of the cysts, and infrequently carried out.

Figure 6

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Figure 6

(A) ADPKD. Intravenous urogram on a child with ADPKD. The correct kidney is large and the left appears normal showing the assymetric nature of the status. The calyces on the correct are displaced around the intrarenal cysts. (B) 99mTc DMSA scan on the same patient showing a normal left kidney. On the correct at that place is a minor amount of functioning renal parenchyma around the not-operation renal cysts.

Radionuclide

A 99mTc DMSA scan will give information regarding the differential function and volition show photon deficient areas occupied by the cysts with uptake in the intervening compressed normal parenchyma (fig 6B).

TUBEROSE SCLEROSIS

Tuberose sclerosis (TS) is an autosomal dominant condition with a reported prevalence of 1 in x 000 and is characterised by multiple hamartomas in the brain, peel, center, kidneys, liver, lung, and os. Genetic linkage has been established to chromosomes 9 and 16; the latter is located in the same region every bit the ADPKD1 factor. The incidence of renal manifestations varies betwixt 47% and 73%. Angiomyolipomas are plant in older patients equally they develop and abound in adolescence. They may occur with or without cysts. Renal cysts are found less oftentimes (18–53%) and in the younger patients. No imaging modality tin currently differentiate the renal TS cysts from ADPKD (fig seven). Echocardiography and cranial CT/MRI should form role of the routine diagnostic work upwardly.xv

Figure 7

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Figure 7

Tuberose sclerosis. Longitudinal and transverse sonogram of the right kidney. The left kidney had similar appearances on ultrasound. The sonogram shows multiple cysts of varying sizes scattered throughout the parenchyma of the kidney. This kid'southward female parent had kidneys which looked very similar and she was initially thought to accept ADPKD until the diagnosis became credible with other clinical manifestations of tuberose sclerosis.

Ultrasound

At that place are two appearances of the kidneys, either multiple cysts or multiple small rounded echogenic foci throughout the parenchyma from angiomyolipomas. Occasionally the cysts and angiomyolipomas may coexist giving a mixed appearance. A rare complexity may exist haemorrhage. There is a higher incidence of renal prison cell carcinoma in later life.

AUTOSOMAL RECESSIVE POLYCYSTIC KIDNEY Illness

This is a rare genetic disorder with an incidence of approximately 1 in 55 000. The inheritance is recessive; the gene has been located on chromosome vi. All children accept hepatic and renal involvement. The liver volition prove hepatic fibrosis in all children by the fourth dimension they accomplish late adolescence; there may likewise be biliary stasis with changes similar to that seen in Caroli'south disease. Splenomegaly is a result of portal hypertension secondary to the hepatic fibrosis. Less severely affected children may present in childhood or fifty-fifty in adolescence.16

Ultrasound

Prenatal diagnosis has been reported every bit early on as 14–17 weeks gestation. The appearance of bilateral echogenic kidneys during the fetal catamenia is not specific to ARPKD. The differential diagnosis of echogenic kidneys detected antenatally includes ARPKD, ADPKD, dysplasia, malformation syndromes associated with dysplasia, and glomerulocystic kidney affliction.

In early infancy both kidneys are equally involved and enlarged (>95th centile). With growth of the child, the kidneys "announced" less enlarged. Typically at that place is a hyperechoic cortex and medulla; variations include the medulla being brighter than the cortex. With high frequency ultrasound probes, small (i–2 mm) cysts may exist detected in the medulla (fig 8A). Occasionally cysts of greater than 2 cm may be found, especially as the child grows. There are well described cases where the imaging is "characteristic" of ARPKD in infancy, all the same past 5 years of age the imaging strongly resembles ADPKD.

Figure 8

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Figure eight

(A) ARPKD—ultrasound browse. Longitudinal supine sonogram of the right kidney. This shows a considerably enlarged kidney (between the + and +) with a globally echogenic echonephrogram. The medullae show a number of echogenic foci (pointer) which is the acoustic enhancement behind the small medullary cysts. (B) ARPKD—intravenous urogram. Two considerably enlarged kidneys with the typical streaky radiating pattern of contrast excretion. (C) ARPKD—ultrasound and99mTc DMSA scans. Left image shows the typical large hyperechoic kidney of ARPKD. Right image shows the 99mTc DMSA browse on the same patient, indicating the focal defects in mainly the polar regions of the kidney. The defects are not related to large cysts equally can exist seen from the ultrasound browse. This child had non suffered from urinary tract infections. (D) ARPKD—liver ultrasound browse. This longitudinal scan of the liver of the infant in (A) shows multiple cystic dilatations of the bile ducts in the liver. The gall bladder is arrowed. (Due east) ARPKD—liver ultrasound and Hida scans. Left epitome is a longitudinal scan of the liver, showing a "cyst" loftier in the right lobe of the liver. Right image is a Hida scan on the same patient. Hida is a radiopharmaceutical which is excreted in the bile. The image shows accumulation of tracer inside the "cyst" seen on ultrasound (pointer). Annotation likewise the big left lobe of the liver.

Most affected children accept some degree of hepatosplenomegaly equally they grow. The spectrum of hepatic abnormalities may exist subtle on ultrasound. In the young child the liver may exist normal or enlarged with increased echogenicity in the periportal region from the bile duct proliferation and fibrosis. Unmarried or multiple cysts communicating and closely related to the biliary tree together with biliary ectasia may be nowadays. A big spleen and bear witness of portal hypertension and varices may be shown with ultrasound and Doppler examination.17

Intravenous urography

The IVU is even so considered mandatory to confirm the diagnosis ARPKD. This will show bilateral and symmetrical enlargement of the kidneys and a streaky nephrogram as contrast clears in the ectatic collecting ducts. This may crave delayed images up to 24 hours. The IVU should be undertaken at nigh iii–6 months of age as renal immaturity with or without associated renal damage before this age may result in not-visualisation of the kidneys (fig 8B). However, infants with ADPKD presenting with big hyperechoic kidneys in the neonatal catamenia may bear witness "puddling" of contrast to differentiate from ARPKD.18

Radioisotopes

Renal

99mTc DMSA studies in ARPKD prove patchy uptake of isotope, in item at the poles. The defects noted are relatively large and do non relate to any focal abnormality seen on ultrasound. These changes were seen in all children from this establishment. The changes on 99mTc DMSA are non-specific; notwithstanding, in this clinical setting with no history of UTI these defects are specific to ARPKD (fig 8C).

Liver—99mTc HIDA is a hepatobiliary amanuensis which, following hepatocyte uptake, is secreted into the bile. After i year of age, the 99mTc HIDA scan shows an enlarged left lobe of the liver with delayed passage of isotope through the liver, sometimes with areas of pooling and prominence of the duct system, even when ultrasound fails to show dilatation of the bile ducts (fig 8D). This provides a valuable non-invasive method for the sit-in of subclinical biliary ectasia which is invariable in ARPKD. This appearance has been described in Caroli's disease (fig 8E).

JUVENILE NEPHRONOPHTISIS

Juvenile nephronophtisis has an autosomal recessive inheritance and presents in childhood as chronic renal failure. Information technology is characterised past an early concentrating defect, polyuria, polydipsia with growth retardation, and anaemia.

MEDULLARY CYSTIC Affliction

Medullary cystic illness shows an autosomal dominant inheritance and presents up to the fourth decade of life.

Imaging in juvenile nephronophtisis and medullary cystic disease

As the ultrasound appearances are similar they will exist described together. Ultrasound volition reveal two normal sized kidneys with a globally hyperechoic appearance. Cysts are not a feature till late in the affliction and are then typically corticomedullary. An IVU is of footling help because of very poor opacification of the kidneys. In the early stages of the disease when the tubules are affected to a greater degree than the glomeruli, the 99mTc DMSA scan may fail to bear witness the kidneys, nonetheless the 99mTc DTPA scan (a glomerular amanuensis) may be about normal.

Extrarenal manifestations reported in juvenile nephronophtisis include skeletal abnormalities, congenital hepatic fibrosis, and mental retardation.

Conclusion

Cystic renal disease is a broad spectrum of conditions; imaging forms a crucial attribute in the evaluation of the child. The primary imaging modality is ultrasound. Even so in almost all cases other imaging is required to ensure that the suggested diagnosis or differential diagnosis is as accurate as possible at presentation. Follow up of these children is essential and includes imaging. The screening of family unit members with ultrasound is a useful procedure and could be undertaken in relevant families. Each patient is unique; imaging should be comprehensive and collation of all the information is essential to have the best adventure of reaching a diagnosis.

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