Two major types: Autosomal Dominant Polycystic Kidney Disease (Adult Polycystic Kidney Disease [APKD] and Autosomal Recessive Polycystic Kidney Disease (Infantile Polycystic Kidney Disease) 

Autosomal Dominant Polycystic Kidney Disease

• Is a slowly progressive disease with nearly 100% penetrance

• Potter Type III

• Cause: gene located on short arm of chromosome 16 (in 90%

  • Spontaneous mutation in 10%

• Incidence:1:1,000 people carry the mutant gene

  • 3rd most prevalent cause of chronic renal failure

• Histo: abnormal rate of tubule divisions (Potter Type III) with hypoplasia of portions of tubules left behind as the ureteral bud advances; cystic dilatation of Bowman capsule, loop of Henle, proximal convoluted tubule, coexisting with normal tissue

• Mean age at diagnosis: 43 years (neonatal / infantile onset has been reported)

• M:F = 1:1

• Onset of cyst formation:

  • 54% in 1st decade

  • 72% in 2nd decade

  • 86% in 3rd decade

Associated with:

·     Cysts in: liver (25-50%), pancreas (9%)

·        Aneurysm: saccular "berry" aneurysm of cerebral arteries (3-13%)

·        Mitral valve prolapse

·        Hypertension (50-70%)

·        Azotemia

·        Hematuria, proteinuria

·        Lumbar / abdominal pain

·        Bilaterally large kidneys with multifocal round lesions; unilateral enlargement may be the first manifestation of the disease

·     Cysts may calcify in curvilinear rim- / ringlike irregular amorphous fashion elongated + distorted + attenuated collecting system nodular puddling of contrast material on delayed images

·        "Swiss cheese" nephrogram = multiple lesions of varying size with smooth margins

·        Polycystic kidneys shrink after beginning of renal failure, after renal transplantation, or on chronic hemodialysis

·     NUC: poor renal function on Tc-99m DTPA scan   

US

·     Multiple cysts in cortical region (usually not seen prior to teens)

·        Diffusely echogenic when cysts small (children)

·        Renal contour poorly demarcated

OB-US

·     Large echogenic kidneys similar to infantile PCKD (usually in 3rd trimester, earliest sonographic diagnosis at 14 weeks), can be unilateral

·        Macroscopic cysts (rare)

·        Normal amount of amniotic fluid / oligohydramnios (renal function usually not impaired)

 Complications

·        Death from uremia (59%) / cerebral hemorrhage (secondary to hypertension or ruptured aneurysm [13%]

·        Renal calculi

·        Urinary tract infection

·        Cyst rupture

·        Hemorrhage

·        Renal cell carcinoma (increased risk)

 Differential Diagnosis

·     Multiple simple cysts (less diffuse, no family history)

·        von Hippel-Lindau disease (cerebellar hemangioblastoma, retinal hemangiomas, occasionally pheochromocytomas)

·        Acquired uremic cystic disease (kidneys small, no renal function, transplant)

·     Infantile PCKD (usually microscopic cysts) 

Autosomal Recessive Polycystic Kidney Disease = Polycystic Disease of Childhood

·     Potter Type I

·        Incidence:1: 6,000 to 1:50,000 livebirths

·    F > M; carrier frequency of 1:112
 

Pathology
 

·        Kidney: abnormal proliferation + dilatation of collecting tubules resulting in multiple 1- to 2-mm cysts

·        Liver: periportal fibrosis often with abnormal proliferation + dilatation of bile ducts

·        Pancreas: pancreatic fibrosis

ANTENATAL FORM (most common)
 

·     90% of tubules show cystic changes

·        Onset of renal failure in utero

·        Potter sequence

·        Oligohydramnios and dystocia (large abdominal mass)

·        Prognosis: death from renal failure / respiratory insufficiency (pulmonary hypoplasia) within 24 hours in 75%, within 1 year in 93%; uniformly fatal

NEONATAL FORM

·     60% of tubules show ectasia + minimal hepatic fibrosis + bile duct proliferation

·        Onset of renal failure within 1st month of life

·        Prognosis: death from renal failure / hypertension / left ventricular failure within 1st year of life

INFANTILE FORM

·     20% of renal tubules involved + mild / moderate periportal fibrosis

·        Disease appears by 3-6 months of age

·        Prognosis: death from chronic renal failure / systemic arterial hypertension / portal hypertension

JUVENILE FORM

·     10% of tubules involved + gross hepatic fibrosis + bile duct proliferation

·        Disease appears at 1-5 years of age

·        Prognosis: death from portal hypertension

·        The less severe the renal findings, the more severe the hepatic findings!

·        Severe pulmonary hypoplasia

·        Pneumothorax / pneumomediastinum

          Liver

·        Portal venous hypertension

·        Tubular cystic dilatation of small intrahepatic bile ducts

·        Increase in liver echogenicity (from congenital hepatic fibrosis)

Kidneys

·        Bilateral gross renal enlargement

·        Faint nephrogram + blotchy opacification on initial images

·        Increasingly dense nephrogram

·        Poor visualization of collecting system

·        "Sunburst nephrogram" = striated nephrogram with persistent radiating opaque streaks (collecting ducts) on

·        Delayed images

·        Prominent fetal lobulation
 

 CT
 

·        Prolonged corticomedullary phase
 

 US
 

·        Hyperechoic enlarged kidneys (unresolved 1- to 2-mm cystic / ectatic dilatation of renal tubules increase number of acoustic interfaces)

·        Increased renal through-transmission (high fluid content of cysts)

·        Loss of corticomedullary differentiation, poor visualization of renal sinus + renal borders

·        Occasionally discrete macroscopic cysts <1 cm

·        Compressed / minimally dilated collecting system
 

       OB-US (diagnostic as early as 17 weeks GA):
 

·        Progressive renal enlargement with renal circumference : abdominal circumference ratio >0.30

·        Hyperechoic renal parenchyma

·        Nonvisualization of urine in fetal bladder (in severe cases)

·        Oligohydramnios (33%)

·        Small fetal thorax
 

   OB management
 

·        Chromosome studies to determine if other malformations present (e.g., trisomy 13 / 18)

·        Option of pregnancy termination <24 weeks

·        Nonintervention for fetal distress >24 weeks if severe oligohydramnios present

·        Risk of recurrence:25%

·        DDx: Meckel-Gruber syndrome, adult polycystic kidney disease