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1、CYSTIC KIDNEYS Cystic disease of the kidneys in childhood isa confusing and complicated subject. Also thecomplex and often contradictory nomenclatureused to describe cystic kidneys is not an aid tounderstanding the subject. This section aims toprovide the sonographer with a simpleapproach to cystic
2、kidneys in children. Multicystic kidney or multicystic dysplastic kidneythis refers to many cysts in one kidney often containing some dysplastic elements. Not all multicystic kidneys are dysplastic. The condition is still considered to be non-hereditary. If the multicystic kidney is unilateral, the
3、other kidney may be normal, hydronephrotic or dysplastic. If bilateral, it is incompatible with life, and infants die soon after birth with hypoplastic lungs and/or renal failure.Terminology Cystic dysplasiadysplastic kidneys can be Cystic dysplasiadysplastic kidneys can be unilateralunilateral or b
4、ilateral, usually contain cysts and are or bilateral, usually contain cysts and are disorganized,disorganized, containing ectopic tissue such ascontaining ectopic tissue such as cartilage and muscle. They may function.Ultrasonically cartilage and muscle. They may function.Ultrasonically they usually
5、 appear small andthey usually appear small and echogenic with small echogenic with small peripheral cortical cysts.peripheral cortical cysts. While dysplastic kidneys are While dysplastic kidneys are often hypoplastic, notoften hypoplastic, not all small kidneys are dysplastic. all small kidneys are
6、 dysplastic. The clinical featuresThe clinical features are very variable from a normal are very variable from a normal appearingappearing neonate to a very dysmorphic infant. neonate to a very dysmorphic infant. DysplasticDysplastic kidneys are associated with urinary tract kidneys are associated w
7、ith urinary tract obstruction,obstruction, and many syndromes are associated with and many syndromes are associated with cysticcystic dysplastic kidneys. Bilateral renal dysplasia willdysplastic kidneys. Bilateral renal dysplasia will result in progressive renal failure.result in progressive renal f
8、ailure. Polycystic kidney disease refers to Polycystic kidney disease refers to twotwo conditions:conditions: autosomal recessive autosomal recessive polycystic kidney diseasepolycystic kidney disease and and autosomal dominant renal disease.autosomal dominant renal disease. Autosomal recessive poly
9、cystic kidneys were previously known as infantile polycystic kidneys. Confusingly these kidneys appear highly echogenic on ultrasound. There is generalized dilation of the collecting tubules.Autosomal dominant renal disease was previously known as adult polycystic kidney disease. Cysts develop anywh
10、ere along the nephron. The ultimate diagnosis of the cysticrenal disorder is not dependent on anyone imaging modality and will depend onmany factors. Sources of information whentrying to come to the diagnosis should becollated from many areas, such as: obstetric history of the mother prenatal histor
11、y and fetal ultrasonography family history information clinical examination of the child radiology of patient and parents laboratory data, for example DNA pathology if a biopsy is taken or fromany other family members that may havehad a biopsy or nephrectomy in the past. Ultrasound is still the imag
12、ing modalityof choice in children, and the findings onultrasound will direct further imaging asrequired. The ultrasound approach to anycystic renal disease in children mustinclude observations about the following,which should be carefully stated in theultrasound report. unilateral or bilateral renal
13、 cysts (bilateralinvolvement is more common in the geneticallyinherited conditions) size of the kidneysare they large or small? localization to one part of the kidney or diffuseinvolvement of the whole kidney. Is there acapsule around the cysts? extrarenal cysts, in particular in the liver orpancrea
14、s liver size and hepatic parenchyma appearance presence of a large spleen and portalhypertension. Renal cysts are common and may behereditary,developmental or acquired. Theclassification of cystic renal disease variesaccording to the perspective from which it iswritten, and despite a vast amount ofl
15、iterature on the subject, there is still nogenerally accepted classification in existence.The early Potter classification is of limitedvalue for clinical practice because not all typesrepresent clinical entities. The following classification is by nomeans all inclusive but aims to emphasizethe impor
16、tant clinical cystic disorders likelyto be encountered by the sonographer.Broadly speaking, cystic disease of thekidneys can be divided into two groupsgenetic disease and non-genetic disease: Genetic diseaseautosomal recessive polycystic kidneydisease (ARPKD)autosomal dominant polycystic kidneydisea
17、se (ADPKD)juvenile nephronophthisis and medullarycystic disease complexglomerulocystic kidney diseasecysts with multiple malformation syndromes; Non-genetic diseasesimple cystsmulticystic dysplastic kidneymultilocular cystsacquired renal cystic disease (chronicrenal failure)caliceal diverticulummedu
18、llary sponge kidney.Genetic diseaseAutosomal recessive polycystic kidney disease(ARPKD) This is a generalized cystic dilation of the renalcollecting tubules so that the kidneys are packedto a greater or lesser degree with tiny little cysts(Fig. 3.31). It is much rarer than the autosomaldominant form
19、 and occurs in 1 in 50 000 people.Prenatal diagnosis can be made but there arefalse positive and false negative diagnoses.Congenital hepatic fibrosis is a prerequisite forthe diagnosis of ARPKD.Figure 3.31 Autosomal recessive polycystic kidney disease (ARPKD).(A) Cut section of a postmortem specimen
20、 in a patient with ARPKD. There are multiple small cysts throughout the whole of the renal substance. It is these multiple cysts with their posterior acoustic enhancement which give the hyperechogenic appearances on ultrasound. (BD)Sonograms of the kidney in three patients with ARPKD to demonstrate
21、the wide variation in appearance. The kidneys are all large, over the 95th centile, and are globally hyperechoic. The visible cysts are generally small, rarely exceeding 2 cm. Sometimes the increase in echogenicity is primarily medullary.ABCD There are two types of presentation of ARPKDdepending on
22、the age of the patient and the dominance of the renal or the hepatic disease. In those children who present at birth or during the neonatal period the renal disease dominates, while in those who present later in childhood or adolescence the liver disease dominates, with much milder renal manifestati
23、ons. The hepatic disease in these children is called congenital hepatic fibrosis with renal tubular ectasia and comes to medical attention because of theproblems associated with hepatic fibrosis, such as splenomegaly, portal hypertension, varices and bleeding. Gross cystic dilation of the intrahepat
24、icbiliary tree is usually called Caroli syndrome.The original description was purely of thehepatic disease, but dilation of the bile ductsis seen in early presenting ARPKD and in themilder end of the renal spectrum of renal tubularectasia. The risk for a sibling of having thiscondition is 25%, and t
25、he parents kidneysshould be normal.Sonographic Appearances There is a wide spectrum of appearances frombirth and with increasing age throughout childhood. There is bilateral equal involvement of the kidneys,and the reniform shape is usually maintained. The kidneys must be big and are generally overt
26、he 90th centile for age in the young. With increasingage and progression of the renal disease,fibrosis mayresult in stabilization and comparative decrease inthe renal size. The inhomogeneous global increase inecho texture is due to the myriad ofmicrocysts presenting multiple acousticinterfaces. In s
27、ome a subcapsular rim of normalhypoechoic cortex is diagnostic. Medullary pyramids may be hypoechoic atbirth in some less severely affected but overtime become hyperechoic. In older childrenthe corticomedullary differentiation is usuallylost. Visible macrocysts are uncommon butcan be seen, and they
28、are generally nomore than 12 cm in diameter. Theybecome more common with age. Hepatic fibrosis is always present. Thehepatic echo texture may be normalbut,with increasing fibrosis, will becomecoarse and increased particularly in theperiportal region.Figure 3.32 Dilated bile ducts in autosomal recess
29、ive polycystic kidney disease (ARPKD). Longitudinal sonogram of the liver showing the dilated cystic spaces.These are not cysts but dilations of the bile ducts. The liver should always be carefully examined in all children suspected of having ARPKD. The liver must be carefully examined for lesions w
30、hich are cystic dilations of the biliary tree. The hepatic cystic lesions are not true cysts but rather out-pouchings of the bile ducts (Fig.3.32). In older children, because of the hepatic In older children, because of the hepaticfibrosis and liver disease, portalfibrosis and liver disease, portalh
31、ypertension may be present. Evidence ofhypertension may be present. Evidence ofportal hypertension with an enlargedportal hypertension with an enlargedspleen and varices must be sought.spleen and varices must be sought. Doppler examination of the liver, spleen Doppler examination of the liver, splee
32、nand portal system is an essential part ofand portal system is an essential part ofthe examination in these children.the examination in these children.Further imaging When the child is older and over theneonatal period,an IVU is performed.This willdemonstrate the streaky radiating pattern ofcontrast
33、 which is almost pathognomonic ofARPKD (Fig. 3.33). The importance of doingthis examination is that in showing thecaliceal pattern it will help exclude othercauses of large echogenic kidneys in theneonatal period, such as dysplasia.ABFigure 3.33 Intravenous urogram (IVU) in autosomal recessive polyc
34、ystic kidney disease (ARPKD). (A) & (B) Two examples of the IVU appearances of ARPKD. The urogram should always be performed to demonstrate the caliceal pattern. This will demonstrate the typical radiating appearance of the contrast as it passes through the collecting system and help differentiate t
35、he dysplastic bright kidneys. A hepatic iminodiacetic acid (HIDA) scanshould be performed at about 1 year of age.If performed too early the HIDA scan will benormal but, if delayed, the effects of thehepatic fibrosis will have had time to manifest.This involves a radioisotope tracer excreted inthe bi
36、le and will demonstrate accumulation andstasis of isotope in the cystic areas and delayedclearance from the abnormal liver. A large leftlobe of liver may also be seen. CT and MRI are rarely needed exceptin uncertain cases (Fig. 3.34). DMSAscan is not always performed but mayshow focal defects in the
37、 kidney.Figure 3.34 MRI examination in autosomal recessive polycystic kidney disease (ARPKD). This infant with ARPKD had an MRI because of apnoeic attacks. The examination was done to exclude a pulmonary artery sling, which was not present. The kidneys are huge,filling the abdomen and compressing the lungs. Note also the cystic areas in the liver, which are areas of bile duct dilation as seen in Figure 3.32.
