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  Disease summary:

  
  
  
  
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    Cystic diseases of the kidney are a heterogeneous group of hereditary, developmental, or acquired disorders that have in common the presence of renal cysts.

    
    
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    A renal cyst is a fluid-filled cavity lined by epithelial cells that derives primarily from the renal tubules, loosing its connection with their origin tubule once developed.

    
    
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    Polycystic kidney disease (PKD) is a group of monogenic disorders that result in renal cyst development, being autosomal dominant polycystic kidney disease (ADPKD) and autosomal recessive polycystic kidney disease (ARPKD) the most common forms.

    
    
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    ADPKD, caused by mutation in PKD1 or PKD2, is generally a late-onset multisystem disorder characterized predominantly by bilateral renal cysts and variable extra renal manifestations (extrarenal cysts, cardiac valvular defects, arterial aneurysms, colonic diverticulosis, abdominal wall hernias)

    
    
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    ARPKD, most commonly affecting newborns and young children, is caused by mutation in PKHD1 and is characterized by enlarged echogenic kidneys and congenital hepatic fibrosis.

  
  
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  Hereditary basis:

  
  
  
  
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    ADPKD is the most frequent inherited renal disorder (1 in 400-1000) and follows an autosomal dominant inheritance pattern with complete penetrance and high intrafamilial variability.

    
    
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    ARPKD follows an autosomal recessive inheritance with an incidence of approximately 1:20.000; the frequency of heterozygosity is approximately 1:70.

  
  
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  Differential diagnosis:

  
  
  
  
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    Cystic diseases in the differential diagnosis of ADPKD: ARPKD, other systemic diseases associated with renal cysts such as tuberous sclerosis complex (TSC), von Hippel-Lindau disease (VHL), and orofacial digital syndrome type 1 (OFDS), acquired renal cystic disease (ARCD) in patients with end-stage renal disease (ESRD), medullary sponge kidney, and simple cysts (Table 144-1).

    
    
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    Cystic diseases in the differential diagnosis of ARPKD: early-manifesting ADPKD, a group of inherited pleiotropic disorders causing polycystic kidneys (nephronophthisis [NPHP], Joubert syndrome and related disorders [JSRD], Meckel syndrome [MKS], Bardet-Biedl syndrome [BBS]), glomerulocystic kidney disease, and diffuse cystic dysplasia.

Diagnostic Criteria for ADPKD

At least one of the following when there is a family history of ADPKD

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  Unified diagnostic criteria based on ultrasound findings in individuals at risk for ADPKD

  
  
  
  
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    Three or more (unilateral or bilateral) renal cysts if between 15 and 39 years and genotype unknown

    
    
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    Two or more cysts per kidney if between 40 and 59 years

    
    
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    Four or more cysts per kidney if patient is more than or equal to 60 years

  
  
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  No established diagnostic criteria exist based on computed tomography (CT) or magnetic resonance imaging (MRI). Ultrasound criteria could reasonably be applied to CT or MRI if restricted to cysts measuring greater than or equal to 1 cm in diameter (MRI and contrast-enhanced CT are more sensitive than ultrasound to detect smaller cysts).

  
  
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  Identification of a known PKD1 or PKD2 mutation by sequence analysis or genetic diagnosis based on linkage analysis.

In the absence of a family history of ADPKD

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  More than 10 cysts per kidney in the absence of manifestations, suggestive of a different renal cystic disease (presumptive diagnosis)

  
  
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  Identification of a PKD1 or PKD2 mutation by sequence analysis

Diagnostic Criteria for ARPKD

At least two of the following

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  Kidney involvement

  
  
  
  
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    Infants or early childhood: bilateral renal enlargement with loss of corticomedullary differentiation

    
    
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    Older patients: precalyceal tubular ectasia or bilateral renal cysts

  
  
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  Evidence of ductal plate malformation

  
  
  
  
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    Diagnosis of congenital hepatic fibrosis (CHF) on liver biopsy or

    
    
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    Radiologic findings consistent with intrahepatic bile duct dilatation

  
  
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  Detection of PKHD1 mutation by direct sequencing

  
  
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  Definite diagnosis of ARPKD, CHF, or Caroli disease in a sibling

And the absence of

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  Renal cysts in both parents demonstrated by ultrasound (US)

  
  
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  Manifestations suggesting a different renal cystic disease in the child

Clinical Characteristics