Polycystic Kidney Disease

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

· 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%]) /

· cardiac complications (mean age 50 years)

· 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!

Lung

· 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

· Prolonged corticomedullary phase

· 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

From Dahnert, 4^th Edition